CN100442400C

CN100442400C - Thyrite ceramic, manufacturing method and thyrite apparatus

Info

Publication number: CN100442400C
Application number: CNB011376961A
Authority: CN
Inventors: 人见笃志; 松岡大; 千田直树; 小笠原稔; 竹岛勉; 直井克夫
Original assignee: TDK Corp
Current assignee: TDK Corp
Priority date: 2000-11-15
Filing date: 2001-11-15
Publication date: 2008-12-10
Anticipated expiration: 2021-11-15
Also published as: MY127329A; TW535174B; CN1353097A; SG104950A1

Abstract

A composite perovskite-based semiconductor varistor ceramic and a varistor may contain a first component consisting of oxides of Sr, Ba, Ca and Ti, at least one component of a second component consisting of at least one kind of oxide selected from oxides of R (Y and lanthanoids) and a third component consisting of at least one kind of oxide selected from oxide of M (Nb and Ta), and a fourth component consisting of an oxide of Si. The ceramic substantially containing no Mg. A composition of the ceramic is 0.10 <= a/(a+b+c) <= 0.40, 0.30 <= b/(a+b+c) <= 0.50, 0.20 < c/(a+b+c) <= 0.50, 0.84 <= (a+b+c+e)/(d+f) <= 1.16, 1.0 <= (e+f)/dx100 <= 10.0, and g/dx100 <= 0.6. A composite perovskite-based semiconductor varistor ceramic and a varistor may consist of at least one kind of Sr, Ba and Ca, and Ti, and have a surface provided with a compressive stress.

Description

Thyrite device pottery, manufacture method and thyrite device

Technical field

The present invention relates to be used for the pottery of thyrite device (varistor), and be particularly related to and have (Sr, Ba, Ca) TiO ₃The composite perofskite base pottery of composition relates to the varistor with this pottery preparation, and relates to the manufacture method of this pottery.

Background technology

Varistor be its resistance with alive variation and a kind of resistive element of non-linear change, and particularly, the resistor that its resistance reduces rapidly when the voltage that applies above certain voltage value.

The compound of the various potteries of existing main composition varistor.Owing to have the nonlinear functions and the electrostatic capacitance characteristic of resistance simultaneously, have (Sr, Ba, Ca) TiO ₃The composite perofskite base pottery of composition is well suited for being used for absorbing the surge voltage that electronic equipment produces, or is used to remove noise.For example, this pottery is used for DC electrical micro-machine annular voltage-sensitive resistor etc.

In the varistor of making by this composite perofskite base pottery, can be by selecting Sr, the mole ratios of Ba and Ca is controlled the temperature dependency of varistor voltage (voltage that the resistance of varistor reduces rapidly).That is, for the overcurrent inflow varistor that prevents to cause owing to the varistor voltage reduction that is associated with the operating temperature increase, or thermal runaway taking place, can regulate temperature dependency.At Japanese patent gazette No.0828287B (Japanese patent gazette No.02146702A), Japanese patent gazette No.03045559A, and the varistor that the temperature dependency of varistor voltage is regulated is in such a way disclosed among the Japanese patent gazette No.2944697C (Japanese patent gazette No.03237057A).

In recent years, owing to when installing, require the acceleration of welding job speed such as electronic units such as varistors, and used high-temperature soldering and pb-free solder, so improved welding temperature.Therefore, because varistor is exposed in the abominable welding condition, so the heat cracks that caused by the localized heat impact usually takes place.As for the electrode of varistor, then use Ag (silver) electrode usually.Yet, owing to the raising of welding temperature causes the Ag composition of kind electrode to dissolve in the scolder, because all or part of disappearance of electrode, might be destroyed as the function of varistor.

For the varistor that can effectively prevent this thermal shock is provided, in Japanese patent gazette No.63276201A, discloses and had TiO ₂The annular voltage-sensitive resistor of base pottery.Yet, in communique, do not mention concrete data fully.And, this TiO ₂The base voltage sensitive resistor pottery is with regard to the electrology characteristic and varistor voltage controlled of electrostatic capacitance, and the performance of composite perofskite base voltage sensitive resistor pottery is on duty mutually, thereby this pottery is inapplicable.

So,, the demand of composite perofskite base voltage sensitive resistor pottery is constantly increased even because its electrology characteristic superior and carry out the characteristic that its function of thermal weld also can not be destroyed.And, in order to improve operating efficiency, for example, need the better based varistor of flexural stress intensity.

Summary of the invention

So the objective of the invention is to provide composite perofskite base voltage sensitive resistor pottery and varistor, its electrology characteristic is good, even and carry out its function of thermal weld can be not destroyed yet.

Another object of the present invention is that based varistor will be provided, and its electrology characteristic, bending strength and thermal shock resistance are good, and the manufacture method of this based varistor is provided.

According to the present invention, a kind of composite perofskite base semiconductor based varistor and varistor comprise first composition of being made up of Sr, Ba, Ca and Ti; Second composition and ternary at least one composition, the oxide that second composition is selected from the oxide of R (Y and lanthanide series) by at least one class is formed, and the oxide that the 3rd composition is selected from the oxide of M (Nb and Ta) by at least one class is formed; And the four-component of forming by the oxide of Si.This pottery does not contain Mg substantially.This pottery consist of 0.10≤a/ (a+b+c)≤0.40,0.30≤b/ (a+b+c)≤0.50,0.20≤c/ (a+b+c)≤0.50,0.84≤(a+b+c+e)/(d+f)≤1.16,1.0≤(e+f)/d * 100≤10.0, and g/d * 100≤0.6, wherein a is the mole number that the Sr of first composition is calculated as SrO, b is the mole number that the Ba of first composition is calculated as BaO, c is the mole number that the Ca of first composition is calculated as CaO, d is the mole number that the Ti of first composition is calculated as TiO, and e is that R to second composition is respectively as YO _3/2, CeO ₂, PrO _11/6, TbO _7/4And RO _3/2The mole number that (other lanthanide series) calculates, f is as NbO to ternary M _5/2And TaO _5/2The mole number of Ji Suaning respectively, g are that Si to four-component is as SiO ₂The mole number that calculates.

The present invention has not only improved the resistance to sudden heating of varistor, by reducing the SiO that is used as sinter additives as far as possible ₂Amount, suppressed because the generation of the heat cracks that the caused localized heat of abominable welding condition impacts, and (total mole number of A part composition is to the ratio of total mole number of B part composition to pass through to regulate total amount A/B, A part composition comprises other composition that can enter the lattice of A part composition with respect to ionic radius, and B part composition comprises other composition of the lattice that can enter B part composition) and compensate owing to reduce SiO ₂The deterioration of the caused sintering degree of amount, A/B represents with (a+b+c+e)/(d+f).In addition, the present invention further suppresses localized heat and impacts by not comprising Mg basically, and then has improved the resistance to sudden heating of varistor.In addition, by suitable selection A part mole ratios, and the amount of semiconductor transformation agent and type, can improve the electrology characteristic of varistor.

In addition, the parameter that the present invention is suitable for is not simple A/B ratio, this is the ratio of the mole number of the A part composition only be made up of Sr, Ba, Ca and the B that only is made up of the Ti mole number that partly becomes to be grouped into, but synthesizes perovskite structure and comprise the total value A/B of mole ratios of the ion of additive.That is, this is because be not simple A/B to the real contribution of sintering degree, but this total A/B.Specifically, because the semiconductor transformation agent is a solid-state solution ion important in the additive, under situation of the present invention, the dosage of semiconductor transformation agent is big, so if use simple A/B ratio, then error becomes very big.Yet, because by using total A/B can obtain accurate control for the first time, so the varistor that does not almost have characteristic drift can be provided.

The composition of first composition is 0.30≤a/ (a+b+c)≤0.40,0.30≤b/ (a+b+c)≤0.40 preferably, and 0.25≤c/ (a+b+c)≤0.35.And first composition and second and third composition composition one of at least is preferably 0.96≤(a+b+c+e)/(d+f)≤1.01.And the composition of the second and the 3rd at least one composition of composition is preferably 1.0≤(e+f)/d * 100≤4.0.And then the composition of four-component is preferably g/d * 100≤0.3.

This pottery preferably also comprises the fifty percentth minute that is made up of at least one type oxide of selecting from the oxide of following various element: Li, Na, Mn, Co, Ni, Cu, Zn, Sc, Fe, Ga, In, Mo and W.Preferably also have 0＜h/d * 100≤1.000, wherein h is the content Li for the fifty percentth minute, Na, and Mn, Co, Ni, Cu, Zn, Sc, Fe, Ga, In, Mo and W are as LiO _1/2, NaO _1/2, MnO, CoO _4/3, NiO, CuO, ZnO, ScO _3/2, FeO _3/2, GaO _3/2, InO _3/2, MoO ₃And WO ₃And the mole number that calculates.

The fifty percentth minute improving electrology characteristic, such as the raising of non linear coefficient α, etc. the aspect be effective.

This varistor preferably has the electrode that forms at least one surface of pottery, and the electrode of being made up of Cu or the material mainly made by Cu.Under one situation of back, electrode is preferably made by Cu alloy or the Cu that comprises frit.

In addition, according to the present invention, based varistor comprises the oxide of being made up of following at least one dvielement: Sr, Ba, and Ca and Ti, and have compression stress on its surface.

Since there is very big compression stress at ceramic surface, the bending strength when this not only can improve welding, and can obtain very high heat shock resistance characteristic, prevent the generation of be full of cracks when the temperature part raises when welding.Here it is, when welding, owing to differential expansion takes place localized heating, and becomes the tension force that causes be full of cracks at ceramic surface.As long as the compression stress that formation in advance can this tension force of balance on based varistor surface just can obtain to be enough to resist the based varistor of localized heat impact.In addition, if having residual compressive stresses on the based varistor surface, bending strength will increase.This is identical with the principle of tempered glass.

If X-ray stress constant is-the 100MPa/ degree that then compression stress preferably is not less than 15MPa.Be more preferably and be not less than 25MPa, be more preferably again and be not less than 40MPa.

Under this situation, this pottery preferably comprises by Sr, Ba, first composition that the oxide of Ca and Ti is formed; Second composition and the 3rd composition one of at least, the oxide that second composition is selected from the oxide of R (Y and lanthanide series) by at least one class is formed, the 3rd composition is made up of from the oxide of the oxide selection of M (Nb and Ta) at least one class; And the four-component of forming by the oxide of Si, the a/ in trilinear coordinates (a+b+c) wherein, the value of b/ (a+b+c) and c/ (a+b+c) is in tie point (0.2,0.0,0.8) and point (0.0,0.4,0.6) line segment on, or in a/ (a+b+c) and the scope of b/ (a+b+c) greater than this line segment, and they consist of 0.84≤(a+b+c+e)/(d+f)≤1.16,0.75≤(e+f)/d * 100≤10.0, and g/d * 100≤0.6, wherein a is the mole number that the Sr of first composition is calculated as SrO, b is the mole number that the Ba of first composition is calculated as BaO, and c is the mole number that the Ca to first composition calculates as CaO, and d is that Ti to first composition is as TiO ₂The mole number that calculates, e are that R to second composition is respectively as YO _3/2, CeO ₂, PrO _11/6, TbO _7/4And RO _3/2The mole number that (other lanthanide series) calculates, f is as NbO to ternary M _5/2And TaO _5/2The mole number of Ji Suaning respectively, g are that Si to four-component is as SiO ₂The mole number that calculates.

Like this, the present invention has not only improved the resistance to sudden heating of varistor, by reducing the SiO that is used as sinter additives as far as possible ₂Amount, suppressed because the generation of the heat cracks that the caused localized heat of abominable welding condition impacts, and (total mole number of A part composition is to the ratio of total mole number of B part composition to pass through to regulate total amount A/B, A part composition comprises other composition that can enter the lattice of A part composition with respect to ionic radius, and B part composition comprises other composition of the lattice that can enter B part composition) and compensate owing to reduce SiO ₂The deterioration of the caused sintering degree of amount, A/B represents with (a+b+c+e)/(d+f).In addition, by suitable selection A part mole ratios, and the amount of semiconductor transformation agent and type, can improve the intensity and the electrology characteristic of varistor.

In addition, the parameter that the present invention is suitable for is not simple A/B ratio, this is the ratio of the mole number of the A part composition only be made up of Sr, Ba, Ca and the B that only is made up of the Ti mole number that partly becomes to be grouped into, but synthesizes perovskite structure and comprise the total value A/B of mole ratios of the ion of additive.That is, this is because think that the real contribution to the sintering degree is not simple A/B, but this total A/B.Specifically, because the semiconductor transformation agent is a solid-state solution ion important in the additive, under situation of the present invention, the dosage of semiconductor transformation agent is many, so if use simple A/B ratio, then error becomes very big.Yet, because by using total A/B can obtain accurate control for the first time, so the varistor that does not almost have characteristic drift can be provided.

A/ in trilinear coordinates (a+b+c), the value of b/ (a+b+c) and c/ (a+b+c) is preferably in tie point (0.5,0.0,0.5) and first line segment of point (0.2,0.2,0.6), tie point (0.2,0.2,0.6) and point (0.1,0.4,0.5) second line segment, tie point (0.1,0.4,0.5) and point (0.1,0.5,0.4) the 3rd line segment, or tie point (0.1,0.5,0.4) and point (0.2,0.8,0.0) the 4th line segment, perhaps a/ (a+b+c) is in the zone greater than these first to the 4th line segments.

A/ (a+b+c) in the trilinear coordinates again, the value of b/ (a+b+c) and c/ (a+b+c) preferably is in tie point (0.4,0.2,0.4) and the 5th line segment of point (0.2,0.4,0.4), tie point (0.2,0.4,0.4) and point (0.2,0.5,0.3) the 6th line segment, tie point (0.2,0.5,0.3) and point (0.3,0.5,0.2) the 7th line segment, tie point (0.3,0.5,0.2) and the 8th line segment of point (0.6,0.2,0.2), or tie point (0.6,0.2,0.2) and point (0.4,0.2,0.4) the 9th line segment, or be in by in the 5th to the 9th these line segment institute area surrounded.

First composition and second and third composition one of at least composition of composition preferably are in 0.96≤(a+b+c+e)/(d+f)≤1.01.

Second and third composition one of at least combination of composition preferably is in 0.75≤(e+f)/d * 100≤4.0

The combination of four-component preferably is in g/d * 100≤0.3

This pottery preferably also comprises the fifty percentth minute that is made up of at least one type oxide of selecting from following all oxides: Li, Na, Mn, Co, Ni, Cu, Zn, Sc, Fe, Ga, In, Mo and W.Preferably also have 0＜h/d * 100≤1.000, wherein h is the content Li for the fifty percentth minute, Na, and Mn, Co, Ni, Cu, Zn, Sc, Fe, Ga, In, Mo and W are as LiO _1/2, NaO _1/2, MnO, CoO _4/3, NiO, CuO, ZnO, ScO _3/2, FeO _3/2, GaO _3/2, InO _3/2, MoO ₃And WO ₃And the mole number that calculates.

In addition, according to the present invention, a kind of manufacture method of based varistor comprises reduces the step that sintering step and carrying out reoxidizes the pottery that is obtained, the reduction sintering step is in order to obtain to comprise Sr, Ba, the oxide that Ca and Ti are at least a, re-oxidation step are in order to produce compression stress at ceramic surface.

Because the processing that reoxidizes that exists by reduction sintering and ceramic surface has produced big compression stress, so not only can improve the bending strength when welding, and can obtain high heat shock resistance characteristic, even, also can prevent heat cracks in when welding local temperature rise.From the amount of oxygen defective of reduction the sintering and the relation that compensates by the oxygen that reoxidizes processing between the oxygen defective, can carry out analogy analysis, produce resistance to sudden heating and residual compressive stresses by reduction sintering and the combination that reoxidizes processing.

When welding, cause differential expansion by localized heating, and become the tension force that makes ceramic surface that be full of cracks take place.As long as in advance in the compression stress of enough this tension force of balance of based varistor surface formation energy, just can obtain to be enough to resist the based varistor that localized heat impacts.In addition, if there is residual compressive stresses in the based varistor surface, then bending strength increases.The principle of this and tempered glass is similar.

Preferably material powder is weighed and mix,, after roasting, grind and form powder, and the object of such formation is reduced sintering and reoxidizing so that powder can have predetermined composition.

Suppose that X-ray stress constant is-100MPa/ ℃, then compression stress is preferably and is not less than 15MPa.More preferably be not less than 25MPa, more preferably be not less than 40MPa again.

The temperature that reoxidizes processing is preferably between 850 ℃ and the 1050 ℃ of scopes, comprises two ends.This temperature better between 900 ℃ and 1000 ℃, comprises two ends.Like this, the temperature rather than the change composition that reoxidize processing by change are controlled the piezo-resistance magnitude of voltage, can guarantee the scope of broad piezo-resistance magnitude of voltage and enough non linear coefficient α, keep big surperficial residual compressive stresses simultaneously

Thereby, because broad piezo-resistance voltage range is to obtain at identical composition with practical α, simultaneously owing to big surperficial residual compressive stresses keeps high intensity and high thermal resistance character, thereby needn't prepares multiple material, and be easy to control material.

Reoxidizing the processing time preferably is not more than 32 hours, and this time was more preferably between 0.25 and 16 hour again, comprised two ends, and should the time better between 0.5 and 8 hour, comprise two ends.

Reoxidizing oxygen partial pressure in the processing is preferably by force and is not less than 0.1 atmospheric pressure.

This pottery preferably comprises by Sr, Ba, first composition that the oxide of Ca and Ti is formed; Second composition and the ternary one of at least composition, the oxide that second composition is selected from the oxide of R (Y and lanthanide series) by at least one class is formed, and the 3rd composition is made up of from the oxide of the oxide selection of M (Nb and Ta) at least one class; And the four-component of forming by the oxide of Si, the a/ in trilinear coordinates (a+b+c) wherein, the value of b/ (a+b+c) and c/ (a+b+c) is in tie point (0.2,0.0,0.8) and point (0.0,0.4,0.6) line segment on, or at a/ (a+b+c), in the scope of b/ (a+b+c) greater than this line segment, and they consist of 0.84≤(a+b+c+e)/(d+f)≤1.16,0.75≤(e+f)/d * 100≤10.0, and g/d * 100≤0.6, wherein a is the mole number that the Sr of first composition is calculated as SrO, b is the mole number that the Ba of first composition is calculated as BaO, and c is the mole number that the Ca to first composition calculates as CaO, and d is that Ti to first composition is as TiO ₂The mole number that calculates, e are that R to second composition is respectively as YO _3/2, CeO ₂, PrO _11/6, TbO _7/4And RO _3/2The mole number that (other lanthanide series) calculates, f is as NbO to ternary M _5/2And TaO _5/2The mole number of Ji Suaning respectively, g are that Si to four-component is as SiO ₂The mole number that calculates.

A/ in trilinear coordinates (a+b+c), the value of b/ (a+b+c) and c/ (a+b+c) is preferably in tie point (0.5,0.0,0.5) and first line segment of point (0.2,0.2,0.6), tie point (0.2,0.2,0.6) and point (0.1,0.4,0.5) second line segment, tie point (0.1,0.4,0.5) and point (0.1,0.5,0.4) the 3rd line segment, or tie point (0.1,0.5,0.4) and point (0.2,0.8,0.0) the 4th line segment, perhaps a/ (a+b+c) is in the zone greater than first to the 4th these line segments.

A/ (a+b+c) in the trilinear coordinates again, the value of b/ (a+b+c) and c/ (a+b+c) preferably is in tie point (0.4,0.2,0.4) and the 5th line segment of point (0.2,0.4,0.4), tie point (0.2,0.4,0.4) and point (0.2,0.5,0.3) the 6th line segment, tie point (0.2,0.5,0.3) and point (0.3,0.5,0.2) the 7th line segment, tie point (0.3,0.5,0.2) and the 8th line segment of point (0.6,0.2,0.2), tie point (0.6,0.2,0.2) and point (0.4,0.2,0.4) the 9th line segment, or be in by in the 5th to the 9th these line segment institute area surrounded.

Second and third composition one of at least composition of composition preferably is in 0.75≤(e+f)/d * 100≤4.0

The composition of four-component preferably is in g/d * 100≤0.3

In addition, according to the present invention, a kind of manufacture method of based varistor has reduces the step that the step and carrying out of sintering reoxidizes the pottery that is obtained, and the reduction sintering step is in order to obtain to comprise Sr, Ba, the oxide that Ca and Ti are at least a.Reoxidize carry out step temperature between 850 ℃ and 900 ℃, comprise two ends, reoxidizing the time of carrying out step was preferably between 0.25 and 32 hour, comprise two ends, perhaps reoxidize carry out step temperature between 900 ℃ and 1050 ℃, comprise two ends, reoxidize the time of carrying out step to be preferably between 0.1 and 32 hour, comprise two ends.

Again, according to the present invention, a kind of manufacture method of based varistor has reduces the step that the step and carrying out of sintering reoxidizes the pottery that is obtained, and the reduction sintering step is in order to obtain to comprise Sr, Ba, the oxide that Ca and Ti are at least a.Reoxidize carry out step temperature between 900 ℃ and 950 ℃, comprise two ends, reoxidizing the time of carrying out step was preferably between 0.5 and 16 hour, comprise two ends, perhaps reoxidize carry out step temperature between 950 ℃ and 1000 ℃, comprise two ends, reoxidize the time of carrying out step to be preferably between 0.25 and 16 hour, comprise two ends.

Reoxidize the temperature and time in the processing and do not change composition by adjusting, so that control piezo-resistance voltage, can keep the intensity of pottery own in very high level, and can obtain, and overcome enough tolerances of local thermal shock when welding the enough bending strengths of bending stress.Certainly, can guarantee enough non linear coefficient α in very broad piezo-resistance voltage range, and reduce the dependence of quick resistance voltage heat treatment temperature.Like this, owing in the scope of piezo-resistance voltage broadness, obtain practical non linear coefficient α and enough intensity, just needn't prepare multiple material, and be easy to control material.

Preferably regulate and reoxidize the processing time and control the varistor magnitude of voltage.If consider to reoxidize the influence of the variation of treatment conditions to varistor voltage, the time that reoxidizes processing is littler than the Temperature Influence of oxidation processes.Thereby, the time that reoxidizes processing by last adjusting is controlled the varistor magnitude of voltage, become very little because of the influence that reoxidizes treatment conditions causes the drift to the varistor magnitude of voltage, thereby product is improved, and the control that reoxidizes treatment conditions becomes easy.

Preferably material powder is weighed and mix,, after carrying out roasting, grind and form powder, and the object of such formation is reduced sintering and reoxidizing so that powder can have predetermined composition.

Preferably material powder is weighed again and mix, after carrying out roasting, add a part of composition, make powder can have predetermined composition, grind and form powder, and the object of such formation is reduced sintering and reoxidizing so that regulate composition.

As shown in Figure 5, reoxidizing processing preferably follows the single heat treatment process of a circulation of temperature rising and decline to carry out.In addition, as shown in Figure 6, reoxidize to handle and preferably carry out with the heat treatment process of following a plurality of independent temperature to rise and to descend.

Under this situation, this pottery preferably comprises by Sr, Ba, first composition that the oxide of Ca and Ti is formed; Second composition and the 3rd composition one of at least, the oxide that second composition is selected from the oxide of R (Y and lanthanide series) by at least one class is formed, the 3rd composition is made up of from the oxide of the oxide selection of M (Nb and Ta) at least one class; And the four-component of forming by the oxide of Si, and pottery consist of 0.30≤a/ (a+b+c)≤0.40,0.30≤b/ (a+b+c)≤0.40,0.25≤c/ (a+b+c)≤0.35,0.84≤(a+b+c+e)/(d+f)≤1.16,0.75≤(e+f)/d * 100≤10.0, and g/d * 100≤0.6, wherein a is the mole number that the Sr of first composition is calculated as SrO, b is the mole number that the Ba of first composition is calculated as BaO, c is the mole number that the Ca of first composition is calculated as CaO, and d is that Ti to first composition is as TiO ₂The mole number that calculates, e are that R to second composition is respectively as YO _3/2, CeO ₂, PrO _11/6, TbO _7/4And RO _3/2The mole number that (other lanthanide series) calculates, f is as NbO to ternary M _5/2And TaO _5/2The mole number of Ji Suaning respectively, g are that Si to four-component is as SiO ₂The mole number that calculates.

The present invention has not only improved the resistance to sudden heating of varistor, by reducing the SiO that is used as sinter additives as far as possible ₂Amount, suppressed because the generation of the heat cracks that the caused localized heat of abominable welding condition impacts, and (total mole number of A part composition is to the ratio of total mole number of B part composition to pass through to regulate total amount A/B, A part composition comprises other composition that can enter the lattice of A part composition with respect to ionic radius, and B part composition comprises other composition of the lattice that can enter B part composition) and compensate owing to reduce SiO ₂The deterioration of the caused sintering degree of amount, A/B represents with (a+b+c+e)/(d+f).In addition, by suitable selection A part mole ratios, and the amount of semiconductor transformation agent and type, can improve the intensity and the electrology characteristic of varistor.

In addition, the parameter that the present invention is suitable for is not simple A/B ratio, this is the ratio of the mole number of the A part composition only be made up of Sr, Ba, Ca and the B that only is made up of the Ti mole number that partly becomes to be grouped into, but synthesizes perovskite structure and comprise the total value A/B of mole ratios of the ion of additive.That is, because think that this is that the real contribution to the sintering degree is not simple A/B, but this total A/B.Specifically, because the semiconductor transformation agent is a solid-state solution ion important in the additive, under situation of the present invention, the dosage of semiconductor transformation agent is many, so if use simple A/B ratio, then error becomes very big.Yet, because by using total A/B can obtain accurate control for the first time, so the varistor that does not almost have characteristic drift can be provided.

The combination of first composition and the second and the 3rd at least one composition of composition is preferably 0.96≤(a+b+c+e)/(d+f)≤1.01.The combination of the second and the 3rd at least one composition of composition is preferably 0.75≤(e+f)/d * 100≤4.0 again.And the combination of four-component is preferably g/d * 100≤0.3.

This pottery preferably also comprises the fifty percentth minute that is made up of at least one type oxide of selecting from the oxide of following various element: Li, Na, Mn, Co, Ni, Cu, Zn, Sc, Fe, Ga, In, Mo and W.Preferably also have 0＜h/d * 100≤1.000, wherein h is the content Li for the fifty percentth minute, Na, and Mn, Co, Ni, Cu, Zn, Sc, Fe, Ga, In, Mo and W are as LiO _1/2, NaO _1/2, MnO, CoO _4/3, NiO, CuO, ZnO, ScO _3/2, FeO _3/2, GaO _3/2, InO _3/2, MoO ₃And WO ₃And the mole number that calculates.This fifty percentth minute is effectively improving on the electrology characteristic, such as improving non linear coefficient α.

In addition, according to the present invention, a kind of manufacture method of based varistor has following steps: to comprising Sr, and Ba, the step of at least a oxide raw material powder weighing of Ca and Ti makes the powder of being weighed have predetermined composition; The step of mixing the powder of having weighed; The step that the powder that mixes is carried out roasting; The step that the object of roasting is ground; Make the step of the object shaping of grinding; The object that is shaped is reduced the step of sintering; And to the step that reoxidizes of object of reduction sintering.Grinding steps carries out like this, makes after grinding the specific area of each particle become 0.5 and 5.0m ²Between/the g, comprise two ends; And forming step is carried out like this, make the density of shaped-article become 2.80 and 3.40g/cm ³Between, comprise two ends.

And then according to the present invention, a kind of manufacture method of based varistor has following steps: to comprising Sr, and Ba, the step of at least a oxide raw material powder weighing of Ca and Ti makes the powder of being weighed have predetermined composition; The step of mixing the powder of having weighed; The step that the powder that mixes is carried out roasting; Add the step of a part of composition, be predetermined composition so that regulate the object of roasting; The step that the object of regulating is ground; Make the step of the object shaping of grinding; The object that is shaped is reduced the step of sintering; And to the step that reoxidizes of object of reduction sintering.Grinding steps carries out like this, makes after grinding the specific area of each particle become 0.5 and 5.0m ²Between/the g, comprise two ends; And forming step is carried out like this, make the density of shaped-article become 2.80 and 3.40g/cm ³Between, comprise two ends.

So far, the composition and the normal sintering of based varistor various researchs have been carried out.Yet, for the grinding size that changes with degree of grinding in the manufacture process, because the change of the density of the variation agglomerate bodies of molding condition, and follow these bending strength and thermal-shock resistance also not to inquire into.As the treatment conditions in the process of lapping of one of process for making, be the key factor of influence by the sintered ceramic characteristic that follow-up normal sintering obtained.Like this, when determining such as the strontium titanium base material, the treatment conditions in the process of lapping are to preventing that the inhomogeneities that material is formed and the concentrated gradient of composition from being very important.Find that in addition the treatment conditions in the forming process influence the bending strength and the resistance to sudden heating of sintered ceramic strongly.

That is to say, if the specific area of each particle is greater than 0.5m after grinding in the process of lapping ²/ g, the inhomogeneities of then can generating material not forming or the concentrated gradient of composition.Thereby, can obtain enough bending strengths of sintered ceramic and resistance to sudden heating.If specific area surpasses 5.0m ²/ g then milling time becomes oversize.Thereby this not only makes and makes is inefficient, and because its activity is easy to produce the liquid phase of rich Ti, causes being easy to the inhomogeneities that occurs forming.Thereby, wish that specific area is no more than 5.0m ²/ g.

If the density of the object that is shaped is for being not less than 2.80g/cm ³,, in manufacture process, never appear problem because the intensity of the object that is shaped is enough.On the other hand, surpass 3.40g/cm owing to work as the density of shaped-article ³The time, the life time of former and shaping dies will shorten, thus maintenance cost increases, thereby this is inefficient in the mill.So the density of wishing shaped-article is for being not more than 3.40g/cm ³

Make that by grinding raw material specific area after the grinding is 0.5 and 5.0m ²Between/the g, comprise two ends, and make the density of shaped-article become 2.80 and 3.40g/cm shaping particles ³Between, comprising two ends, the intensity that can keep pottery itself is at high level, and acquisition reaches anti-localized heat impact enough when welding to the enough bending strengths of bending stress.

Under this situation, this pottery preferably comprises by Sr, Ba, first composition that the oxide of Ca and Ti is formed; One of at least composition in second composition and the 3rd composition, the oxide that second composition is selected from the oxide of R (Y and lanthanide series) by at least one class is formed, and the 3rd composition is made up of from the oxide of the oxide selection of M (Nb and Ta) at least one class; And the four-component of forming by the oxide of Si, and pottery consist of 0.10≤a/ (a+b+c)≤0.40,0.30≤b/ (a+b+c)≤0.50,0.20≤c/ (a+b+c)≤0.50,0.84≤(a+b+c+e)/(d+f)≤1.16,0.75≤(e+f)/d * 100≤10.0, and g/d * 100≤0.6, wherein a is the mole number that the Sr of first composition is calculated as SrO, b is the mole number that the Ba of first composition is calculated as BaO, c is the mole number that the Ca of first composition is calculated as CaO, and d is that Ti to first composition is as TiO ₂The mole number that calculates, e are that R to second composition is respectively as YO _3/2, CeO ₂, PrO _11/6, TbO _7/4And RO _3/2The mole number that (other lanthanide series) calculates, f is as NbO to ternary M _5/2And TaO _5/2The mole number of Ji Suaning respectively, g are that Si to four-component is as SiO ₂The mole number that calculates.

The composition of first composition is preferably 0.30≤a/ (a+b+c)≤0.40,0.30≤b/ (a+b+c)≤0.40, reaches 0.25≤c/ (a+b+c)≤0.35.First composition and the second and the 3rd composition one of at least composition of composition are preferably 0.96≤(a+b+c+e)/(d+f)≤1.01.The second and the 3rd composition composition one of at least is preferably 0.75≤(e+f)/d * 100≤4.0.And the composition of four-component is preferably g/d * 100≤0.3.

This pottery preferably also comprises the fifty percentth minute that is made up of at least one type oxide of selecting from following all oxides: Li, Na, Mn, Co, Ni, Cu, Zn, Sc, Fe, Ga, In, Mo and W.Preferably also have 0＜h/d * 100≤1.000, wherein h is the content Li for the fifty percentth minute, Na, and Mn, Co, Ni, Cu, Zn, Sc, Fe, Ga, In, Mo and W are as LiO _1/2, NaO _1/2, MnO, CoO _4/3, NiO, CuO, ZnO, ScO _3/2, FeO _3/2, GaO _3/2, InO _3/2, MoO ₃And WO ₃And the mole number that calculates.This fifty percentth minute is effectively improving on the electrology characteristic, such as improving non linear coefficient α.

Description of drawings

From below in conjunction with the explanation of accompanying drawing, will understand other purpose of the present invention and advantage to the preferred embodiments of the present invention.

Fig. 1 a is the plan view of expression as the annular voltage-sensitive resistor structure of one embodiment of the present of invention;

Fig. 1 b is the cutaway view of being got along A-A line shown in Fig. 1 a;

Fig. 2 is illustrated in when using Cu and Ag as electrode material respectively, and the residue electrode area is to the performance plot of the ratio of welding temperature;

Fig. 3 is expression E ₁And E ₁₀The circuit diagram of measuring circuit;

Fig. 4 is the better performance plot in zone of expression A part mole ratios;

Fig. 5 is the diagram that is used for illustrating heat treatment step one example that reoxidizes processing;

Fig. 6 is the diagram that is used for illustrating another example of heat treatment step that reoxidizes processing.

Embodiment

First embodiment

In Fig. 1 a, the based

varistor

10,11 that 10 expressions form with annular is illustrated in the electrode of the surface formation of based varistor 10.In the present embodiment, five electrodes 11 have been formed by equi-angularly space.Shown in Fig. 1 b, based varistor 10 is formed by internal semiconductor part 10a and at the formed insulating barrier 10b of its whole near surface.

Below will the composition of the based varistor 10 of this first embodiment be described.

This based varistor 10 comprises first composition of the composite perofskite of being made up of the oxide of Sr, Ba, Ca and Ti; Second composition and ternary at least one composition, second composition by at least one class from R (Y and lanthanide series (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu)) oxide that oxide is selected is formed, and the oxide that the 3rd composition is selected from the oxide of M (Nb and Ta) by at least one class is formed; And the four-component of forming by the oxide of Si.In the present embodiment, this based varistor does not contain Mg substantially.If a is the mole number that the Sr of first composition is calculated as SrO, b is the mole number that the Ba of first composition is calculated as BaO, c is the mole number that the Ca of first composition is calculated as CaO, d is the mole number that the Ti of first composition is calculated as TiO, and e is that R to second composition is respectively as YO _3/2, CeO ₂, PrO _11/6, TbO _7/4And RO _3/2The mole number that (other lanthanide series) calculates, f is as NbO to ternary M _5/2And TaO _5/2The mole number of Ji Suaning, and g respectively is that Si to four-component is as SiO ₂The mole number that calculates.So, this based varistor consists of 0.10≤a/ (a+b+c)≤0.40,0.30≤b/ (a+b+c)≤0.50,0.20≤c/ (a+b+c)≤0.50,0.84≤(a+b+c+e)/(d+f)≤1.16,1.0≤(e+f)/d * 100≤10.0, and g/d * 100≤0.6.This composition 0.30≤a/ (a+b+c)≤0.40 preferably again, 0.30≤b/ (a+b+c)≤0.40,0.25≤c/ (a+b+c)≤0.35 and 0.96≤(a+b+c+e)/(d+f)≤1.01,1.0≤(e+f)/d * 100≤4.0, and g/d * 100≤0.3.

First composition is the main component of based varistor 10.In synthetic perovskite, this first composition is by the A part composition of Sr, Ba, Ca, and the B of Ti partly becomes branch to form.The second and the 3rd composition is a metal oxide, and their effect is to make its semiconductor transformation, mainly is in order to improve the sintering degree and add four-component.

As the electrology characteristic of varistor mainly by varistor voltage E ₁₀Temperature characterisitic and non linear coefficient α represent.Varistor voltage E ₁₀Be illustrated in the magnitude of voltage that is applied when the 10-mA electric current flows through varistor, and non linear coefficient α is generally with α=1/log (E ₁₀/ E ₁) expression.E wherein ₁It is the magnitude of voltage that when the 1-mA electric current flows through varistor, is applied.

As for content Sr, the Ba of A part composition, the mole ratios of Ca, preferably Sr is no less than 0.10 and no more than 0.40, and Ba is no less than 0.30 and no more than 0.50, and Ca is no less than 0.20 and no more than 0.50.Be more preferably Sr and be no less than 0.30 and no more than 0.40, Ba is no less than 0.30 and no more than 0.40, and Ca is no less than 0.25 and no more than 0.30.At this moment, just can improve its electrology characteristic, such as varistor voltage E ₁₀Controllability, varistor voltage E ₁₀Temperature characterisitic, and non linear coefficient α, and improve the resistance to sudden heating of varistor.In other words, if Sr is too many, E then ₁₀Temperature characterisitic will become negatively, if very little, then intensity will descend.In addition, if Ba is too many, E then ₁₀The positive trend of temperature characterisitic will be too strong, and if very little, E then ₁₀Temperature characterisitic become negative.In addition, if Ca too much or very little, for varistor voltage E ₁₀Non linear coefficient α will diminish.If Ca is too many, varistor voltage E ₁₀To become very big so that be difficult to control, and base is by reoxidizing the formation insulator.

Semiconductor transformation agent (the second and/or the 3rd composition) is to principal component (TiO ₂) molar percent (this is that mole number by metal ion calculates) be preferably between 0.1 and 10.0, comprise two ends.In addition, this molar percent is preferably between 0.1 and 4.0, comprises two ends.Like this, can improve the resistance to sudden heating of sensitive resistor.In other words, if the semiconductor transformation agent too much or very little, then becoming is easy to take place heat cracks.

In addition, total A/B is preferably between 0.84 and 1.16, comprises two ends.And A/B is more preferably between 0.96 and 1.01, comprises two ends.At this moment, as described below, if four-component (SiO- ₂) amount reduce, then can improve the sintering degree.In other words, this is because if A/B is too big or too little, then sintering is hindered, thereby base forms insulator owing to reoxidizing.In addition, this is also because if A/B is too big or too little, then be easy to the occurrence temperature be full of cracks.As mentioned above, at SiO ₂Amount less and add in the scope of a large amount of semiconductor transformation agent, in order to keep resistance to sudden heating, must limit to be limited on total A/B being not more than 1.16, or more preferably be not more than 1.01.

By four-component (SiO is set ₂) to principal component (TiO ₂) molar percent for being not more than 0.6, perhaps be more preferably and be not more than 0.3, can obviously improve the resistance to sudden heating of varistor.In other words, SiO ₂Add as sinter additives, even and under the situation of forming fluctuation, also can stably carry out sintering, and if SiO ₂Amount increase, then becoming is easy to take place heat cracks.Should be noted that and be not more than 0.6 or be not more than 0.3 SiO ₂Content (molar percent) comprise that also its dosage is zero situation.

By not comprising the resistance to sudden heating that Mg can improve varistor substantially.That is, this be because, if MG is included in the pottery, then pottery becomes and is easy to take place heat cracks.Substantially the meaning that does not comprise the sort of material is that the content of this material is general about less than 0.001 molar percent.

Varistor pottery 10 also can comprise the fifty percentth minute (additive): Li, Na, Mn, Co, Ni, Cu, Zn, Sc, Fe, Ga, In, Mo and the W that is made up of at least one type oxide of selecting from the oxide of following various element.If think that content is by conversion Li, Na, Mn, Co, Ni, Cu, Zn, Sc, Fe, Ga, In, Mo and W are to LiO _1/2, NaO _1/2, MnO, CoO _4/3, NiO, CuO, ZnO, ScO _3/2, FeO _3/2, GaO _3/2, InO _3/2, MoO ₃And WO ₃The mole number that obtains, it is formed so preferably 0＜h/d * 100≤1.000.Thereby, the effect of improving non linear coefficient α is arranged.

In addition, except these additives, varistor pottery 10 also can comprise other element as unavoidable impurities, as P, and S, K, Al, Zr.This element exists as oxide usually.

As mentioned above, the polycrystal formed by the Ca-Ti ore type crystal of varistor pottery 10.The part of each composition is included in the Ca-Ti ore type crystal, is dissolved in the particle with solid-state, and other parts then are present in the border of crystal grain as oxide or composite oxides.For example, Ba, Ca, Sr, Ti, Nb, Ta, Y, major parts such as lanthanide series are present in the particle, and Mo, W, Mn, Si, major parts such as Co are present in the crystal grain border.

The average particulate diameter of varistor pottery 10 is typically about 0.5 to 10 μ m, and is 1 to 6 μ m specifically.

Electrode 11 is formed by Cu or the main material of being made by Cu.If electrode is made by AG, because the rising of welding temperature causes the Ag composition of kind electrode to be dissolved in the scolder, thereby, will disappear to the electrode of small part.Yet, by the electrode 11 that Cu makes or the main material of being made by Cu is made, even also be difficult at elevated temperatures be etched, thereby can be durable in thermal weld work.

The main material of being made by Cu is meant Cr, Zr, and Ag, Ti, Be, Zn, Sn, Ni, Al, Si, the alloy that waits, or comprise by Li Na, K, Sr, Ba, Mn, Cu, Zn, Bi, Si, Al, Bi, the Cu of the frit that the oxide of Pb etc. is made.

Fig. 2 illustrates, and when using Cu and Ag as electrode material respectively, the residue electrode area is to the ratio of welding temperature.

After coating solder flux and preheating annular voltage-sensitive resistor as an example, annular voltage-sensitive resistor is immersed in the solder bath of the quick solder that comprises each temperature and reached for 5 seconds.

Obviously as seen, when solder temperature is 400 ℃, in the Ag electrode residue electrode zone is corroded from figure, it is original 55.5% that electrode becomes, and but then, the Cu electrode is not etched, and remains electrode area and be original 100%.

Below with the manufacture method of this varistor pottery 10 of simple declaration.

Obtain varistor pottery 10 by handling material powder in the following order: mix, roasting is ground, and is shaped, and adhesive is removed, the reduction sintering, and reoxidize.

The powder that each of pottery constitutes the compound of element is used as material powder usually.Oxide or become the compound of oxide by sintering can be used as material powder such as carbonate and hydroxide.For example, if provide example with regard to Ba, then at least one class barium compound is such as BaCO ₃, BaSiO ₃, BaO, BaCl ₂, Ba (OH) ₂, and Ba (NO ₃) ₂And alkoxide (for example, (CH ₃O) ₂Ba), can be used as raw material.The average particulate diameter of material powder is typically about 0.2 to 5 μ m.

At first, material powder is weighed, make final composition can become above-mentioned composition, and carry out wet mixing usually and close.Then, after carrying out processed, material powder is carried out drying, and with about 1080 to 1250 ℃ of roastings of carrying out 2 to 4 hours.Then, after grinding the object of roasting, add organic bond, and and then add water, the pH conditioning agent, wetting agents etc. also mix.Afterwards, mixture is shaped, and carry out adhesive remove handle after, in reducing atmosphere with about 2 to 4 hours of 1250-1400 ℃ of sintering, to obtain semiconductive ceramic.

Each material powder, such as Ti, Nb, Ta, Y, lanthanide series, Mo, W, Mn can add when Si, Co etc. mix after roasting.

Semiconductive ceramic to such acquisition is heat-treated (reoxidizing processing), for example, 800 to 1000 ℃ temperature, in oxidizing atmosphere, as carrying out in the air, enables to obtain and the suitable varistor voltage of this object.Form insulating barrier 10b by this heat treatment at surface portion.Owing to the existence of this insulating barrier shows the varistor characteristic.Because if this insulating barrier thickening, then non linear coefficient α and varistor voltage become big, and if attenuation, then non linear coefficient α and varistor voltage decreases, so must select heat-treat condition, make insulating barrier to become suitable thickness by the required characteristic of product.

After reoxidizing processing,, form electrode on a surface of based varistor, thereby obtain varistor with Cu or the main material of making by Cu.

Below, with reference to the example according to first embodiment of the invention, the present invention is described in more detail.

Example 1-1

What will carry out in example 1-1 is, to by fixing the molar percent and the type of other parameter such as semiconductor transformation agent, total A/B, and SiO ₂Molar percent, and the sample that mole ratios obtained that changes A part composition compares.

At first, by respectively to SrCO as raw material ₃, BaCO ₃, CaCO ₃, TiO ₂, NbO _5/2, and SiO ₂After conversion is weighed and prepared burden, make it to have the composition shown in the table 1-1, use the humid medium mill to mix these raw materials and reach 10 to 20 hours, dewater and drying.

After the mixture that the use tunnel cave obtains with 1150 ℃ of roastings, mixture is carried out rough lapping, after the mixing of use humid medium mill reaches 10 to 20 hours, dewater and drying then.Afterwards, mix 1.0 to 1.5wt% polyvinyl alcohol as organic bond, make it granulation, and the mixture that makes granulation is at 2t/cm to mixture ²Forming pressure under be shaped, become the shaped-article of external diameter 12mm, internal diameter 9mm, thickness 1.0mm.

Under 1000 ℃ in air, to such shaping object carry out after binder remove to handle, at N ₂(95 percent by volume)+H ₂Carry out sintering with about 1350 ℃ in the reducing atmosphere of (5 percent by volume) and reach 2 hours, to obtain semiconductive ceramic.Afterwards, in air, this semiconductive ceramic is carried out two hours the processing that reoxidizes, obtain based varistor with 950 ℃.

Afterwards, in neutral atmosphere,,, form five Cu electrodes 11 shown in these figure, obtain specimen for the varistor of measuring by at 750 ℃ of roasting Cu thickeners to a surface applied Cu thickener of the based varistor 10 shown in Fig. 1 a and the 1b.

Then, at 20 ℃ of voltage E that measure each sample ₁₀And E ₁Afterwards, use the voltage E that records ₁₀And E ₁By α=1/log (E ₁₀/ E ₁) acquisition non linear coefficient α.And then, obtained varistor voltage E ₁₀Temperature characterisitic (temperature coefficient).And, each sample is carried out the heat cracks test.

Use measuring circuit measuring voltage E as shown in Figure 3 ₁₀And E ₁In this measuring circuit, ammeter 30 is connected between varistor 31 and the DC constant-current source 32, and voltmeter 33 is in parallel with varistor 31.Use ammeter 30 and voltmeter 33, when 1mA and 10mA electric current flow through varistor 31 respectively,, record voltage E by measuring the magnitude of voltage between varistor 31 two ends ₁₀And E ₁

By Δ E _10T={ E ₁₀(85)-E ₁₀(20) }/{ E ₁₀(20) * (85-20) } * 100[%/℃], obtain varistor voltage E to each sample ₁₀Temperature characterisitic (temperature coefficient) Δ E _10TVoltage E ₁₀(85) and E ₁₀(20) be respectively at 20 ℃ of temperature varistor E with 85 ℃ ₁₀Voltage.These temperature are to use constant temperature oven to record.

By using solder, the electrode side that makes the soldering iron that has preestablished temperature touch the sample that is in room temperature reached for 3 seconds, carried out the heat cracks test.As the temperature of soldering iron, two class temperature have been used, promptly 360 ℃ and 400 ℃.Use ethanol that visual observation has been carried out in the be full of cracks that becomes hundred samples.It the results are shown among the table 1-1.

The gram molecule rate of A part composition is for the electrology characteristic of varistor, and particularly for varistor voltage E ₁₀Temperature characterisitic, have a significant impact.As varistor voltage E ₁₀Temperature characterisitic when negative, the voltage of varistor rises with working temperature and descends, thereby excessive electric current will flow through varistor, maybe might cause thermal runaway.Thereby sample 1-15 is to 1-17, and 1-26 is the scope that can not be used as varistor at sample to 1-29 and 1-31.

If voltage E ₁₀Temperature characterisitic be zero or positive, do not wish that so it surpasses 0.06, thus sample 1-18 to 1-23 and 1-30 preferably not as varistor.

Sample 1-25 is owing to handle and by integral insulation by reoxidizing, and can not be as varistor work.In addition, because 1-24 and 1-26 comprise too much Ca, their varistor voltage E ₁₀High especially, thereby be difficult to control.

Though the E of sample 1-13,1-14 and 1-32 ₁₀Characteristic be not higher than 0.06, but since contained Ca too much or very little, they are to varistor voltage E ₁₀Non linear coefficient α low, thereby also bad.

So we can say, because varistor voltage E ₁₀Temperature characterisitic be not higher than 0.06, and to varistor voltage E ₁₀Factor alpha not low, so sample 1-1 is preferred to 1-12.This is corresponding to the mole ratios of determined A part in the claim 1.In this scope, in being 360 ℃ thermal shock test, the soldering iron temperature do not have heat cracks to take place, and and then, in being 400 ℃ thermal shock test, the soldering iron temperature do not have heat cracks to take place yet.

In addition, its voltage E ₁₀Temperature characterisitic not to be higher than 0.02 sample 1-1 be better to 1-7 in the present invention.This is corresponding to the mole ratios of determined A part in the claim 2.Particularly, sample 1-4 has voltage E ₁₀Temperature characterisitic and the balance of non linear coefficient α the best, so near the mole ratios of A part composition this sample is best in the present invention.

Example 1-2

What will carry out among the example 1-2 is, relatively by changing the sample that amount obtained of semiconductor transformation agent.

Fix other parameter, such as the mole ratios of A part, a based semiconductor agent, total A/B, and SiO ₂Molar percent, carry out with example 1-1 in similarly be provided with, different is the molar percent of setting the semiconductor transformation agent as shown in table 1-2, produces sample, its measurement is similar to the measurement among the example 1-1.The results are shown in table 1-2.

The amount of semiconductor transformation agent influences the heat-resisting cracking of varistor pottery.Because the semiconductor transformation agent of sample 1-33 and 1-38 is respectively very little and too many, in the soldering iron temperature is 360 ℃ test, heat cracks has taken place, thereby these not preferred.Thereby in the soldering iron temperature was 360 ℃ test, sample 1-4 and 1-34 that heat cracks does not take place were preferred among the present invention to 1-37.This is corresponding to the molar percent of determined semiconductor transformation agent in the claim 1.

In addition, because sample 1-37 in the soldering iron temperature is 400 ℃ test heat cracks has taken place, and sample 1-4 and 1-34 that be full of cracks takes place in this heat cracks of 400 ℃ test are more preferred among the present invention to 1-36.This is corresponding to the molar percent of determined semiconductor transformation agent in the claim 4.In addition, near the molar percent the molar percent of the semiconductor transformation agent of sample 1-4 is best in the present invention.

Example 1-3

What will carry out among the example 1-3 is relatively to change the sample of the type of semiconductor transformation agent.

Fix other parameter, such as the mole ratios of A part, the molar percent of semiconductor transformation agent, total A/B, and SiO ₂Molar percent, and carry out with example 1-1 in similarly be provided with, different is the type that changes the semiconductor transformation agent as shown in table 1-3, produces sample, its measurement is similar to the measurement among the example 1-1.The results are shown in table 1-3.

Because all samples 1-4 and 1-39 be to 1-55, be in the test of 360 ℃ and 400 ℃ in the soldering iron temperature, there is not the heat cracks generation, use NbO _5/2, TaO _5/2, YO _3/2, LaO _3/2, CeO ₂, PrO _11/6, NdO _3/2, SmO _3/2, EuO _3/2, GdO _3/2, TbO _7/4, DyO _3/2, HoO _3/2, ErO _3/2, TmO _3/2, YbO _3/2, LuO _3/2Or NbO _5/2+ YO _3/2As semiconductor transformation agent (equimolal) is preferred person among the present invention.

Example 1-4

What will carry out among the example 1-4 is relatively to change total sample that A/B obtained.

Fix other parameter, such as the mole ratios of A part, the molar percent of semiconductor transformation agent and type, total A/B, and SiO ₂Molar percent, and carry out with example 1-1 in similarly be provided with, different is to change total A/B as shown in table 1-4, produces sample, its measurement is similar to example 1-1.The results are shown in table 1-4.

The sintering degree of total A/B value influence pottery.Total A/B of sample 1-56 and 1-62 is respectively too little and too big because they can not sintering pottery accurately, and reoxidize to handle and make it integral insulation, so they can not be as varistor work.And, heat cracks when being 360 ℃, the soldering iron temperature takes place.

As show shown in the 1-4, at SiO ₂Amount less and when adding a large amount of semiconductor transformation agent, in order to keep heat-resisting cracking, the upper limit of must special control total A/B.If total A/B surpasses 1.16, heat cracks just takes place at 360 ℃, and if total A/B surpass 1.01, at 400 ℃ heat cracks take place then.

In other words, sample 1-4 and 1-57 be to 1-61, because the soldering iron temperature is in 360 ℃ the test heat cracks not to take place, is preferred among the present invention.This is corresponding to determined total A/B in the claim 1.

In addition, sample 1-4 and 1-58 be to 1-60, because the soldering iron temperature is in 400 ℃ the test heat cracks not to take place, is preferred among the present invention.This is corresponding to determined total A/B in the claim 3.As among the sample 1-4, near total A/B that the composition of its B part is many slightly the optimum range among the present invention.

Example 1-5

What will carry out among the example 1-5 is relatively to change SiO ₂The sample that molar percent obtained.

Fix other parameter, such as the mole ratios of A part, the molar percent of semiconductor transformation agent and type, and total A/B, and carry out with example 1-1 in similarly be provided with, different is to change SiO as shown in table 1-5 ₂Molar percent, produce sample, its measurement is similar to example 1-1.Soldering iron temperature in the heat cracks test is three types a temperature, promptly 360 ℃, 400 ℃ and 450 ℃.The results are shown in table 1-5.

SiO ₂Add as sinter additives.If comprise SiO ₂Even, form fluctuation to some extent, also can carry out stable sintering.If yet its amount increase, it becomes and is easy to take place heat cracks.

Sample 1-67 and 1-68 are owing to there is too many SiO ₂, in the soldering iron temperature is 360 ℃ test heat cracks takes place promptly, so be not preferred.So sample 1-4 and 1-63 be to 1-66, in the soldering iron temperature is the test of 360 ℃ and 400 ℃ heat cracks does not take place, so be preferred among the present invention.This is corresponding to the determined SiO in the claim 1 ₂Molar percent.Though SiO among the sample 1-63 ₂Nominally batching be zero, in fact, SiO ₂Be included in each raw material as impurity, thereby SiO among the sample 1-63 ₂Actual content do not have vanishing.

In the soldering iron temperature is among the sample 1-66 heat cracks to take place in 450 ℃ the test.So sample 1-4 and 1-63 be to 1-65, heat cracks does not take place in it in the soldering iron temperature is 450 ℃ test, so become preferred among the present invention.This is corresponding to the determined SiO in the claim 5 ₂Molar percent.In addition, near the SiO sample 1-4 ₂Molar percent be the best among the present invention.

Example 1-6

What will carry out among the example 1-6 is relatively to have changed the sample of the kind and the amount of additive.

Fix other parameter, such as the mole ratios of A part, the molar percent of semiconductor transformation agent and type, total A/B, and SiO ₂Molar percent, and carry out with example 1-1 in similarly be provided with, different is kind and the amount that changes additive as shown in table 1-6, produces sample, its measurement is similar to example 1-1.The results are shown in table 1-6.

Additive has the voltage E of adjusting such as varistor ₁₀And the effect of these electrology characteristics of non linear coefficient α.Mn has amplified the voltage E of varistor ₁₀And non linear coefficient α, and Co has amplified the voltage E of varistor ₁₀Find that in addition Mo and W have the effect of amplifying non linear coefficient α.Though do not illustrate among the table 1-6, find other element, such as Li, Na, Ni, Cu, Zn, Sc, Fe, Ga, In also has similar effect.

Owing to the dosage of sample 1-73 and 1-77 is too big, the sintering degree is hindered, and pottery is reoxidized processing and insulate.Thereby each additive is not more than 1.00 sample 1-69 to 1-72 to the molar percent of principal component, and 1-74 to 1-79, is the preferred person among the present invention to 1-76 and 1-78.This is included in the kind and molar percent of the additive of defined in the claim 6.

Example 1-7

What will carry out among the example 1-7 is more not add the sample of Mg, and change the sample that Mg obtained.

Fix other parameter, such as the mole ratios of A part, the molar percent of semiconductor transformation agent and type, total A/B, and SiO ₂Molar percent, and carry out with example 1-1 in similarly be provided with, different is the dosage that changes Mg as shown in table 1-7, produces sample, its measurement is similar to example 1-1.The results are shown in table 1-7.

If contain Mg, then becoming is easy to take place heat cracks.Sample 1-80 is to 1-82, and each content that has principal component is higher than 0.001 Mg content, even also heat cracks will take place in the soldering iron temperature is 360 ℃ test, so be not preferred.

Thereby, preferably, do not contain Mg fully among the present invention as sample 1-4, perhaps the content of Mg generally is not more than 0.001 molar percent (should be substantially free of Mg).This is corresponding to the content described in the claim 1.

Second embodiment

Below will the composition of the based varistor 10 of this second embodiment be described.

Based varistor 10 comprises first composition of the composite perofskite of being made up of the oxide of Sr, Ba, Ca and Ti; Second composition and ternary at least one composition, second composition by at least one class from R (Y and lanthanide series (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu)) oxide that oxide is selected is formed, and the oxide that the 3rd composition is selected from the oxide of M (Nb and Ta) by at least one class is formed; And the four-component of forming by the oxide of Si.If a is the mole number that the Sr of first composition is calculated as SrO, b is the mole number that the Ba of first composition is calculated as BaO, c is the mole number that the Ca of first composition is calculated as CaO, d is the mole number that the Ti of first composition is calculated as TiO, and e is that R to second composition is respectively as YO _3/2, CeO ₂, PrO _11/6, TbO _7/4And RO _3/2The mole number that (other lanthanide series) calculates, f is as NbO to ternary M _5/2And TaO _5/2The mole number of Ji Suaning, and g respectively is that Si to four-component is as SiO ₂The mole number that calculates.As for this based varistor at a/ (a+b+c), composition in the trilinear coordinates of b/ (a+b+c) and c/ (a+b+c), as shown in Figure 4, Sr, Ba and Ca, i.e. a/ (a+b+c), b/ (a+b+c) and c/ (a+b+c) are in tie point (0.2,0.0,0.8) and point (0.0,0.4,0.6) line segment on, or in a/ (a+b+c) and the scope of b/ (a+b+c) (hereinafter referred to as first scope) greater than this line segment.And composition is 0.84≤(a+b+c+e)/(d+f)≤1.16,0.75≤(e+f)/d * 100≤10.0, and g/d * 100≤0.6.

As for the mole ratios of A part composition, the a/ in the trilinear coordinates (a+b+c), the value of b/ (a+b+c) and c/ (a+b+c) is preferably in tie point (0.5,0.0,0.5) and point (0.2,0.2,0.6) first line segment, tie point (0.2,0.2,0.6) and point (0.1,0.4,0.5) second line segment, tie point (0.1,0.4,0.5) and the 3rd line segment of point (0.1,0.5,0.4), or tie point (0.1,0.5,0.4) and point (0.2,0.8,0.0) the 4th line segment, perhaps a/ (a+b+c) is in the scope greater than first to the 4th these line segments (hereinafter referred to as second scope).

In addition, as for the mole ratios of A part composition, a/ in the trilinear coordinates (a+b+c), the value of b/ (a+b+c) and c/ (a+b+c) preferably is in tie point (0.4,0.2,0.4) and point (0.2,0.4,0.4) the 5th line segment, tie point (0.2,0.4,0.4) and point (0.2,0.5,0.3) the 6th line segment, tie point (0.2,0.5,0.3) and the 7th line segment of point (0.3,0.5,0.2), tie point (0.3,0.5,0.2) and point (0.6,0.2,0.2) the 8th line segment, tie point (0.6,0.2,0.2) and point (0.4,0.2,0.4) the 9th line segment, or be in the scope of being surrounded (hereinafter referred to as the 3rd scope) by the 5th to the 9th these line segments.

Total A/B more preferably 0.96≤(a+b+c+e)/(d+f)≤1.01.

The amount of semiconductor transformation agent is 0.75≤(e+f)/d * 100≤4.0 more preferably

SiO ₂Amount g/d * 100≤0.3 more preferably

First composition is the principal component of varistor pottery 10.This first composition is partly become to be grouped into by the A part composition of Sr, Ba and Ca and the B of Ti in composite perofskite.The second and the 3rd composition is the metal oxide that helps semiconductor transformation, and four-component mainly adds for improving the sintering degree.

Sr, the Ba that comprises in the A part composition, the mole ratios of Ca are preferably in first scope.This is more preferably and is in second scope, and is more preferably and is in the 3rd scope.At this moment, just can improve its electrology characteristic, such as varistor voltage E ₁₀Controllability, varistor voltage E ₁₀Temperature characterisitic, and non linear coefficient α, and improve the resistance to sudden heating of varistor.In other words, if Sr is too many, E then ₁₀Temperature characterisitic will become negatively, if very little, then intensity will descend.In addition, if Ba is too many, E then ₁₀The positive trend of temperature characterisitic will be too strong, and if very little, E then ₁₀Temperature characterisitic become negative.In addition, if Ca too much or very little, for varistor voltage E ₁₀Non linear coefficient α will diminish.If Ca is too many, varistor voltage E ₁₀To become very big so that be difficult to control, and base forms insulator by reoxidizing.

Semiconductor transformation agent (the second and/or the 3rd composition) is to principal component (TiO ₂) molar percent (this is that mole number by metal ion calculates) be preferably between 0.75 and 10.0, comprise two ends.In addition, this molar percent is preferably between 0.75 and 4.0, comprises two ends.Like this, can improve the intensity and the resistance to sudden heating of sensitive resistor.In other words, if the semiconductor transformation agent too much or very little, then becoming is easy to take place heat cracks.

In addition, total A/B is preferably between 0.84 and 1.16, comprises two ends.And A/B is more preferably between 0.96 and 1.01, comprises two ends.At this moment, as described below, if four-component (SiO- ₂) amount reduce, then can improve the sintering degree.In other words, this is because if A/B is too big or too little, then sintering is hindered, thereby base forms insulator owing to reoxidizing.In addition, this is also because if A/B is too big or too little, then be easy to the occurrence temperature be full of cracks.At SiO ₂Amount add less and as mentioned above in the scope of a large amount of semiconductor transformation agent, in order to keep resistance to sudden heating, must limit to be limited on total A/B being not more than 1.16, or more preferably be not more than 1.01.

By four-component (SiO is set ₂) to principal component (TiO ₂) molar percent for being not more than 0.6, perhaps be more preferably and be not more than 0.3, can obviously improve the intensity and the resistance to sudden heating of varistor.In other words, SiO ₂Add as sinter additives, even and under the situation of forming fluctuation, also can stably carry out sintering, and if SiO ₂Amount increase, then becoming is easy to take place heat cracks.Should be noted that and be not more than 0.6 or be not more than 0.3 SiO ₂Content (molar percent) comprise that also its dosage is zero situation.

Varistor pottery 10 also can comprise the additive of being made up of at least one type oxide of selecting from the oxide of following various element: Li, Na, Mn, Co, Ni, Cu, Zn, Sc, Fe, Ga, In, Mo and W.If think that content is by conversion Li, Na, Mn, Co, Ni, Cu, Zn, Sc, Fe, Ga, In, Mo and W are to LiO _1/2, NaO _1/2, MnO, CoO _4/3, NiO, CuO, ZnO, ScO _3/2, FeO _3/2, GaO _3/2, InO _3/2, MoO ₃And WO ₃The mole number that obtains, it is formed so preferably 0＜h/d * 100≤1.000.Thereby, the effect of improving non linear coefficient α is arranged.

Semiconductive ceramic to such acquisition is heat-treated (reoxidizing processing), for example, 800 to 1000 ℃ temperature, in oxidizing atmosphere, as carrying out in the air, enables to obtain and the suitable varistor voltage of this object.Reoxidize in the processing at this, the speed that temperature rises and descends is typically about 100 ℃/h to 600 ℃/h.In addition, this preferred temperature that reoxidizes processing comprises two ends, or is more preferably between 900 ℃ to 1000 ℃ between 850 ℃ to 1050 ℃, comprises two ends.In addition, its preferable time is to be not more than 32 hours, and is more preferably between 0.25 and 16 hour, comprises two ends.In addition, the partial pressure of its oxygen is not less than 0.1 atmospheric pressure.

Reoxidize processing by this and form insulating barrier 10b at surface portion.Owing to the existence of this insulating barrier shows the varistor characteristic.Because if this insulating barrier thickening, then non linear coefficient α and varistor voltage become big, and if attenuation, then non linear coefficient α and varistor voltage decreases, so must select treatment conditions, make insulating barrier to become suitable thickness by the required characteristic of product.

Suppose that X-ray stress constant for-100MPa/ ℃, then reoxidizes in the processing at this according to embodiment according to this, the compression stress on varistor surface preferably is not less than 15MPa.More preferably be not less than 25MPa, more preferably be not less than 40MPa again.

Since there is compression stress at ceramic surface, the bending strength when this not only can improve welding, and can obtain very high heat shock resistance characteristic, prevent the generation of be full of cracks when the temperature part raises when welding.

After reoxidizing processing,, form electrode 11 on a surface of based varistor, thereby obtain varistor with Cu or the main material of making by Cu.Mainly identical among the material of making by Cu and first embodiment.

In the second above-mentioned embodiment, though electrode forms at the varistor ceramic surface, electrode also can be in top and the back side or the side formation of varistor.

Below, according to the example of second embodiment of the invention, the present invention is described in more detail.

Example 2-1

What will carry out in example 2-1 is, to by fixing the molar percent and the type of other parameter such as semiconductor transformation agent, total A/B, and SiO ₂Molar percent, and the sample that molar percent obtained that changes A part composition compares.

At first, by to SrCO as raw material ₃, BaCO ₃, CaCO ₃, TiO ₂, NbO _5/2, and SiO ₂After conversion is weighed and prepared burden respectively, make it to have the composition shown in the table 1-1, use the humid medium mill to mix these raw materials and reach 10 to 20 hours, dewater and drying.

After the mixture that obtains with 1150 ℃ of roastings, mixture is carried out rough lapping, after the mixing of use humid medium mill reaches 10 to 20 hours, dewater and drying then.Afterwards, mix 1.0 polyvinyl alcohol that arrive 1.5wt% as organic bond, make it granulation, and the mixture of granulation is shaped under the forming pressure of 2t/cm, become the object of external diameter 12mm, internal diameter 9mm, thickness 1.0mm to mixture.

Under 600 ℃ in air, to such shaping object carry out after binder remove to handle, at N ₂(95 percent by volume)+H ₂Carry out sintering with about 1350 ℃ in the reducing atmosphere of (5 percent by volume) and reach 2 hours, to obtain semiconductive ceramic.Afterwards, in air, this semiconductive ceramic is carried out two hours the processing that reoxidizes, obtain based varistor with 950 ℃.

Then, at 20 ℃ of voltage E that measure each sample ₁₀And E ₁Afterwards, use the voltage E that records ₁₀And E ₁By α=1/log (E ₁₀/ E ₁) acquisition non linear coefficient α.And then, obtained varistor voltage E ₁₀Temperature characterisitic (temperature coefficient).And, when each sample being carried out the heat cracks test, measure the residual compressive stresses on each sample surfaces.

Use measuring circuit measuring voltage E as shown in Figure 3 ₁And E ₁₀In this measuring circuit, ammeter 30 is connected between varistor 31 and the DC constant-current source 32, and voltmeter 33 is in parallel with varistor 31.Use ammeter 30 and voltmeter 33, when 1mA and 10mA electric current flow through varistor 31 respectively,, record voltage E by measuring the magnitude of voltage between varistor 31 two ends ₁And E ₁₀

By Δ E _10T={ (E ₁₀(85)-E ₁₀(20) }/{ E ₁₀(20) * (85-20) * 100}[%/℃], obtain varistor voltage E to each sample ₁₀Temperature characterisitic (temperature coefficient) Δ E _10TVoltage E ₁₀(85) and E ₁₀(20) be respectively at 20 ℃ of temperature varistor E with 85 ℃ ₁₀Voltage.These temperature are to use constant temperature oven to record.

By using solder, the electrode side that makes the soldering iron that has preestablished temperature touch the sample that is in room temperature reached for 3 seconds, carried out the heat cracks test.As the temperature of soldering iron, three class temperature have been used, promptly 360 ℃ and 400 ℃ and 450 ℃.Use ethanol that visual observation has been carried out in the be full of cracks that becomes hundred samples.

Use the X-ray diffraction method for measuring stress that the residual stress on each sample surfaces is measured.Because the perovskite structure as each sample principal phase belongs to cubic system, so the surface stress that produces at in-plane can promptly calculate with the ratio that is parallel to the perovskite surface gap of surface direction from the perovskite surface gap perpendicular to surface direction by the diffraction of X-ray on ceramic surface.Here, use the collimated light beam that produces by the Cr ball, carry out stress measurement by the side gradient method.In addition, interpolation is waved for twice when measuring.The diffracted ray that is used to measure is near 134 degree (310).

It is known using this method of measurement of this X-ray diffraction.For example, in B.D.Cullity (by Gentaro Matsumura translation), " Newly-edited summary of X-raydiffraction ", Agune Co., Ltd., pp.412-442, June, 1980, and " X-raydiffraction handbook ", Rigaku Denki Co., Ltd., pp.103-105, February has detailed description in 2000.

Employed formula is as follows when calculating surperficial residual stress in this example:

σ = - \frac{E}{2 (1 + v)} \cdot \cot θ_{0} \cdot \frac{π}{180} \cdot \frac{Δ (2 θ)}{Δ (\sin^{2} ψ)} = K \cdot \frac{Δ (2 θ)}{Δ (\sin^{2} ψ)}

Wherein, σ residual stress (MPa), E are Young's modulus (MPa), and ν is the Poisson rate, θ ₀Be standard Bragg angle (degree) (θ here ₀=134 (degree)/2).In addition, ψ be sample surfaces normal direction and mensuration between angle (degree), 2 θ are the angle of diffraction (degree), K is the Stress Constants (MPa/ degree) that is determined by the material and the angle of diffraction.

From the angle of diffraction 2 θ that measure and the sin that can obtain by the angle ψ that sample surfaces normal direction and material normal direction form ²Relation between the ψ is used least square method to find its gradient, and this gradient be multiply by Stress Constants K, can obtain the measuring and calculating to residual stress.

In this example, suppose Stress Constants K=-100MPa/ degree.This be because, from above-mentioned formula obviously as seen, can use by its former state with the Grad that least square method finds from the result of the measurement that obtains, because stress value can freely be set according to the value of K.In other words, this is owing to there is Grad just enough, in other words, because the absolute value of Stress Constants K is unessential, so represent that the index to the cube shaped range degree of perovskite in mutually is given.

2-1 is shown in the results are shown in of example 2-1.

About the mark of forming, the content of SrO is expressed as a gram molecule, and the content of BaO is expressed as the b gram molecule, and the content of CaO is expressed as c gram molecule, TiO ₂Content be expressed as d gram molecule, NbO _5/2Content be expressed as the f gram molecule, and SiO ₂Content be expressed as the g gram molecule.Composition is fixed as f/d * 100=3.00, g/d * 100=0.2, and (a+b+c)/(d+f)=0.98.

The mole ratios of A part composition is to the varistor characteristic, particularly to varistor voltage E ₁₀The influence of temperature characterisitic very big.

Removing sample 2-1 outside sample 2-24 and the 2-25 to 2-23, and 2-26 (mole ratios of A part composition is a/ (a+b+c)=0.00 in 2-32, b/ (a+b+c)=0.20, c/ (a+b+c)=0.80, and a/ (a+b+c)=0.00, b/ (a+b+c)=0.00, c/ (a+b+c)=1.00), in the soldering iron temperature is 360 ℃ test heat cracks does not take place.At this moment, to 2-23, and the residual compressive stresses of 2-26 in the compositing range of 2-32 is unlimitedly for being not less than 15MPa at the sample 2-1 that heat cracks does not take place.

So, first scope is as the compositing range of sample 2-1 to 2-23 and 2-26 to 2-32, the scope that value wherein is fit to following condition is a preferred range of the present invention, i.e. a/ in trilinear coordinates shown in Figure 4 (a+b+c), b/ (a+b+c) and c/ (a+b+c), be in the point (0.2 of connection corresponding to the 2-28 sample, 0.0,0.8) and corresponding to the point (0.0,0.4 of 2-23 sample, 0.6) line segment on, perhaps make a/ (a+b+c) and b/ (a+b+c) greater than this line segment.These scopes are corresponding to the A part mole ratios of determining in claim 15 and 32.In addition, if residual compressive stresses is not less than 15MPa, owing in the soldering iron temperature is 360 ℃ test heat cracks does not take place, this scope also is preferred range in the present invention.This is corresponding to the residual compressive stresses of determining in claim 12 and 24.

Except other sample 2-1 of sample 2-20 to 2-25,2-27 and the 2-28 to 2-19,2-26 and 2-29 in 2-32, heat cracks does not take place in the soldering iron temperature is 400 ℃ test.At this moment, the sample 2-1 that heat cracks does not take place to 2-19,2-26 and 2-29 in the compositing range of 2-32, residual compressive stresses is unlimitedly for being not less than 25MPa.

So, second scope is to 2-19 as sample 2-1,2-26 and 2-29 be to the compositing range of 2-32, and the scope that value wherein is fit to following condition is more preferred range, i.e. a/ in trilinear coordinates shown in Figure 4 (a+b+c) among the present invention, b/ (a+b+c) is in the point (0.5 that is connected corresponding to sample 2-27 with c/ (a+b+c), 0.0,0.5) and corresponding to the point (0.2,0.2 of sample 2-37,0.6) first line segment on, connect this point (0.2,0.2,0.6) and corresponding to the point (0.1 of sample 2-8,0.4,0.5) second line segment on, connect this point (0.1,0.4,0.5) and corresponding to the point (0.1 of sample 2-9,0.5,0.4) the 3rd line segment on, perhaps connect this point (0.1,0.5,0.4) and the 4th line segment corresponding to the point (0.2,0.8,0.0) of sample 2-19 on, perhaps make a/ (a+b+c) greater than these first to the 4th line segments, and do not comprise point (0.5,0.0,0.5) corresponding to 2-27.In addition, as long as residual compressive stresses is not less than 25MPa, owing in the soldering iron temperature is 400 ℃ test, heat cracks does not take place, so these scopes also are preferred range more in the present invention.These are corresponding to the residual compressive stresses of determining in claim 13 and 25.

Except sample 2-8 to 2-10,2-16 to 2-28, heat cracks to 2-15, among 2-29 and the 2-31, does not take place to 2-7,2-11 in other sample 2-1 outside 2-30 and the 2-32 in the soldering iron temperature is 450 ℃ test.At this moment, at the sample 2-1 that heat cracks does not take place to 2-7,2-11 to 2-15, in the compositing range of 2-29 and 2-31, residual compressive stresses is unlimitedly for being not less than 40MPa.

So the 3rd scope is to 2-7 as sample 2-1,2-11 is to 2-15, the compositing range of 2-29 and 2-31, the scope that value wherein is fit to following condition is a preferred range more among the present invention, i.e. a/ in trilinear coordinates shown in Figure 4 (a+b+c), and b/ (a+b+c) is in the point (0.4 that is connected corresponding to sample 2-31 with c/ (a+b+c), 0.2,0.4) and corresponding to the point (0.2,0.4 of sample 2-11,0.4) the 5th line segment on, connect this point (0.2,0.4,0.4) and corresponding to the point (0.2 of sample 2-12,0.5,0.3) the 6th line segment on, connect this point (0.2,0.5,0.3) and corresponding to the point (0.3 of sample 2-13,0.5,0.2) the 7th line segment on, connect this point (0.3,0.5,0.2) and the 8th line segment corresponding to the point (0.6,0.2,0.2) of sample 2-29 on, perhaps connect this point (0.6,0.2,0.2) and corresponding to the point (0.4,0.2 of sample 2-31,0.4) the 9th line segment on, perhaps by these the 5th to the 9th line segments around scope.These are corresponding to the mole ratios of the A part of determining in claim 17 and 34.In addition, if residual compressive stresses is not less than 40MPa, owing in the soldering iron temperature is 450 ℃ test, heat cracks does not take place, so this scope also is preferred range more in the present invention.This is corresponding to the residual compressive stresses of determining in claim 14 and 26.

Example 2-2

What will carry out among the example 2-2 is, relatively by changing the sample that amount obtained of semiconductor transformation agent.

Fix other parameter, such as the mole ratios of A part, a based semiconductor agent, total A/B, and SiO ₂Molar percent, carry out with example 2-1 in similarly be provided with, different is the molar percent that changes the semiconductor transformation agent as shown in table 2-2, produces sample, its measurement is similar to the measurement among the example 2-1.Yet, do not measure varistor voltage E ₁₀Temperature characterisitic.The results are shown in table 2-2.

About the mark of forming, the content of SrO is expressed as a gram molecule, and the content of BaO is expressed as the b gram molecule, and the content of CaO is expressed as c gram molecule, TiO ₂Content be expressed as d gram molecule, NbO _5/2Content be expressed as the f gram molecule, and SiO ₂Content be expressed as the g gram molecule.Composition is fixed as a/ (a+b+c)=0.35, b/ (a+b+c)=0.35 and c/ (a+b+c)=0.30, and g/d * 100=0.2, and (a+b+c)/(d+f)=0.98, but f/d * 100th changes.

The amount of semiconductor transformation agent influences the heat-resisting cracking of varistor pottery.At sample 2-33 semiconductor transformation dosage in the 2-39 is respectively too many and very little, except other sample 2-4 of these samples and 2-34 in the soldering iron temperature is 360 ℃ test heat cracks do not take place to 2-38.At this moment, the sample 2-4 of heat cracks and 2-34 residual compressive stresses in the compositing range of 2-38 not taking place is not less than 24MPa unlimitedly.

Thereby, in sample 2-4 and 2-34 range of mole fractions, be preferred range among the present invention to 0.75≤f/d * 100≤10.00 of 2-38.This is corresponding to the amount of determined semiconductor transformation agent in claim 15 and 32.In addition since in residual compressive stresses when being not less than 15MPa, in the soldering iron temperature is 360 ℃ test heat cracks does not take place, so this scope also is a preferred range among the present invention.This is corresponding to determined residual compressive stresses in claim 12 and 24.

In 2-37, in the soldering iron temperature is the test of 400 ℃ and 450 ℃ heat cracks does not take place at other sample 2-4 except sample 2-33,2-38 and 2-39 and 2-34.At this moment, the sample 2-4 of heat cracks and the 2-34 residual compressive stresses in the compositing range of 2-37 not taking place, is not less than 40MPa unlimitedly.

Thereby, in sample 2-4 and 2-34 range of mole fractions, be preferred range more among the present invention to 0.75≤f/d * 100≤4.00 of 2-37.This is corresponding to the amount of determined semiconductor transformation agent in claim 19 and 36.In addition since in residual compressive stresses when being not less than 40MPa, in the soldering iron temperature is the test of 400 ℃ and 450 ℃ heat cracks does not take place, so this scope also is a preferred range more among the present invention.This is corresponding to determined residual compressive stresses in claim 14 and 26.

Example 2-3

What will carry out among the example 2-3 is relatively to have changed the sample of the type of semiconductor transformation agent.Fix other parameter, such as the mole ratios of A part, the molar percent of semiconductor transformation agent, total A/B, and SiO ₂Molar percent, carry out with example 2-1 in similarly be provided with, different is the type that changes the semiconductor transformation agent as shown in table 2-3, produces sample, its measurement is similar to the measurement among the example 2-1.Yet, do not measure varistor voltage E ₁₀Temperature characterisitic.The results are shown in table 2-3.

About the mark of forming, the content of SrO is expressed as a gram molecule, and the content of BaO is the b gram molecule, and the content of CaO is the c gram molecule, TiO ₂Content be the d gram molecule, YO _3/2, LaO _3/2, CeO ₂, PrO _11/6, NdO _3/2, SmO _3/2, EuO _3/2, GdO _3/2, TbO _7/4, DyO _3/2, HoO _3/2, ErO _3/2, TmO _3/2, YbO _3/2, LuO _3/2Or NbO _5/2+ YO _3/2The content of (waiting mole number) is the e gram molecule, TaO _5/2Or NbO _5/2Content be the f gram molecule, and SiO ₂Content be the g gram molecule.Composition is fixed as a/ (a+b+c)=0.35, b/ (a+b+c)=0.35 and c/ (a+b+c)=0.30, and g/d * 100=0.2, and (a+b+c)/(d+f)=0.98.

Because all samples 2-4 and 2-40 be to 2-56, in the soldering iron temperature is the test of 360 ℃ and 400 ℃ heat cracks does not take place, so preferably use NbO among the present invention _5/2, TaO _5/2, YO _3/2, LaO _3/2, CeO ₂, PrO _11/6, NdO _3/2, SmO _3/2, EuO _3/2, GdO _3/2, TbO _7/4, DyO _3/2, HoO _3/2, ErO _3/2, TmO _3/2, YbO _3/2, LuO _3/2Or NbO _5/2+ YO _3/2(waiting mole number) is as the semiconductor transformation agent.At this moment, the sample 2-4 of heat cracks and the 2-40 residual compressive stresses in the compositing range of 2-56 not taking place, is not less than 37MPa unlimitedly.

Example 2-4

What will carry out among the example 2-4 is relatively to change total sample that A/B obtained.

Fix other parameter, such as the mole ratios of A part, the molar percent of semiconductor transformation agent and type, total A/B, and SiO ₂Molar percent, and carry out with example 2-1 in similarly be provided with, different is to change total A/B as shown in table 2-4, produces sample, its measurement is similar to example 2-1.Yet, do not measure varistor voltage E ₁₀Temperature characterisitic.The results are shown in table 2-4.

About the mark of forming, the content of SrO is expressed as a gram molecule, and the content of BaO is expressed as the b gram molecule, and the content of CaO is expressed as c gram molecule, TiO ₂Content be expressed as d gram molecule, NbO _5/2Content be expressed as the f gram molecule, and SiO ₂Content be expressed as the g gram molecule.Composition is fixed as a/ (a+b+c)=0.35, b/ (a+b+c)=0.35 and c/ (a+b+c)=0.30, and f/d * 100=3.00, and g/d * 100=0.2, but (a+b+c)/(d+f) change.

Except sample 2-57 and 2-63, in 2-62, in the soldering iron temperature is 360 ℃ test heat cracks does not take place at other sample 2-4 and 2-58.At this moment, the sample 2-4 of heat cracks and the 2-57 residual compressive stresses in the compositing range of 2-63 not taking place, is not less than 21MPa unlimitedly.

So sample 2-4 and 2-58 are preferred range to 0.84≤(a+b+c)/(d+f)≤1.16 number ranges among the 2-62 in the present invention.This is corresponding to determined total A/B in claim 15 and 32.In addition, if residual compressive stresses is not less than 15MPa, owing in the soldering iron temperature is 360 ℃ test heat cracks does not take place, this scope also is preferred range in the present invention.This is corresponding to the residual compressive stresses of determining in claim 12 and 24.

In 2-61, in the soldering iron temperature is the test of 400 ℃ and 450 ℃ heat cracks does not take place at other sample 2-4 except sample 2-57,2-58,2-62 and 2-63 and 2-59.At this moment, the sample 2-4 of heat cracks and the 2-59 residual compressive stresses in the compositing range of 2-61 not taking place, is not less than 40MPa unlimitedly.

So sample 2-4 and 2-59 are preferred range more to 0.96≤(a+b+c)/(d+f)≤1.01 number ranges among the 2-61 in the present invention.This is corresponding to determined total A/B in claim 18 and 35.In addition, if residual compressive stresses is not less than 15MPa, owing in the soldering iron temperature is the test of 400 ℃ and 450 ℃ heat cracks does not take place, this scope also is preferred range more in the present invention.This is corresponding to the residual compressive stresses of determining in claim 14 and 26.

From table 2-4 as seen, at SiO ₂Amount little and added in the scope of a large amount of semiconductor transformation agent, in order to keep heat-resisting cracking, to control the upper limit of total A/B inevitably especially.If total A/B surpasses 1.16, then heat cracks begins to take place at 360 ℃.If total A/B surpasses 1.01, then heat cracks begins to take place at 400 ℃.

Example 2-5

What will carry out among the example 2-5 is relatively to change SiO ₂The sample that molar percent obtained.

Fix other parameter, such as the mole ratios of A part, the molar percent of semiconductor transformation agent and type, and total A/B, and carry out with example 2-1 in similarly be provided with, different is to change SiO as shown in table 2-5 ₂Molar percent, produce sample, its measurement is similar to example 2-1.Yet, do not measure varistor voltage E ₁₀Temperature characterisitic.The results are shown in table 2-5.

About the mark of forming, the content of SrO is expressed as a gram molecule, and the content of BaO is expressed as the b gram molecule, and the content of CaO is expressed as c gram molecule, TiO ₂Content be expressed as d gram molecule, NbO _5/2Content be expressed as the f gram molecule, and SiO ₂Content be expressed as the g gram molecule.Composition is fixed as a/ (a+b+c)=0.35, b/ (a+b+c)=0.35 and c/ (a+b+c)=0.30, and f/d * 100=3.00, and (a+b+c)/(d+f)=0.98, but g/d * 100th changes.

Sample 2-68 and 2-69 are owing to there is too many SiO ₂, in the soldering iron temperature is 360 ℃ test heat cracks takes place promptly, so be not preferred.So sample 2-4 and 2-64 be to 2-67, in the soldering iron temperature is the test of 360 ℃ and 400 ℃ heat cracks does not take place, so be preferred among the present invention.This is corresponding to the determined SiO in claim 15 and 32 ₂Molar percent.At this moment, the sample 2-4 of heat cracks and the 2-64 residual compressive stresses in the compositing range of 2-67 not taking place, is not less than 32MPa unlimitedly.Though SiO among the sample 2-64 ₂Nominally batching be zero, in fact, SiO ₂Be included in each raw material as impurity, thereby SiO among the sample 2-64 ₂Content do not have vanishing.

In the soldering iron temperature is among the sample 2-67 heat cracks to have taken place in 450 ℃ the test.So sample 2-4 and 1-64 be to 2-66, heat cracks does not take place in it in the soldering iron temperature is 450 ℃ test, so become among the present invention better preferred.This is corresponding to the determined SiO in claim 20 and 37 ₂Molar percent.In addition, if residual compressive stresses is not less than 40MPa, owing in the soldering iron temperature is 450 ℃ test heat cracks does not take place, this scope also is preferred range more in the present invention.This is corresponding to the residual compressive stresses of determining in claim 14 and 26.Near sample 2-4 SiO ₂Molar percent be the best among the present invention.

Example 2-6

What will carry out among the example 2-6 is relatively to have changed the sample of the kind and the amount of additive.

Fix other parameter, such as the mole ratios of A part, the molar percent of semiconductor transformation agent and type, total A/B, and SiO ₂Molar percent, and carry out with example 2-1 in similarly be provided with, different is kind and the amount that changes additive as shown in table 2-6, produces sample, its measurement is similar to example 2-1.Yet, do not measure varistor voltage E ₁₀Temperature characterisitic.The results are shown in table 2-6.

About the mark of forming, the content of SrO is expressed as a gram molecule, and the content of BaO is expressed as the b gram molecule, and the content of CaO is expressed as c gram molecule, TiO ₂Content be expressed as d gram molecule, NbO _5/2Content be expressed as f gram molecule, SiO ₂Content be expressed as the g gram molecule, and content of additive is expressed as the h gram molecule.Composition is fixed as a/ (a+b+c)=0.35, b/ (a+b+c)=0.35 and c/ (a+b+c)=0.30, and f/d * 100=3.00, (a+b+c)/(d+f)=0.98, and g/d * 100=0.20, but h/d * 100th changes.

Additive has the voltage E of adjusting such as varistor ₁₀And the effect of these electrology characteristics of non linear coefficient α.Mn has amplified the voltage E of varistor ₁₀And non linear coefficient α, and Co has amplified the voltage E of varistor ₁₀Find that in addition Mo and W have the effect of amplifying non linear coefficient α.Though do not illustrate among the table 2-6, find other element, such as Li, Na, Ni, Cu, Zn, Sc, Fe, Ga, In also has similar effect.

Because the dosage of sample 2-74 and 2-78 is too big, the sintering degree is hindered, and makes ceramic insulation and reoxidize to handle.Except sample 2-74 and 2-78, other sample 2-70 is to 2-73, and 2-75 to 2-80, in the soldering iron temperature is 360 ℃ test heat cracks does not take place to 2-77 and 2-79.At this moment, the sample 2-70 that heat cracks does not take place is to 2-73, the residual compressive stresses of 2-75 to 2-77 and 2-79 to the compositing range of 2-80, the 29MPa that all is not less than without exception.

Thereby each molar percent that has to principal component is to be not more than 1.00 sample 2-70 to 2-73, and 2-75 is preferred among the present invention to 2-77 and 2-79 to 2-80.This is included in the kind and molar percent of the additive of defined in claim 21 and 38.

Example 2-7

What will carry out among the example 2-7 is, relatively reoxidizes the sample that temperature obtained in the treatment conditions by change.

Fix other parameter, such as the mole ratios of A part, the molar percent of semiconductor transformation agent and type, total A/B, and SiO ₂Molar percent, and carry out with example 2-1 in similarly be provided with, different is to change to become to reoxidize treatment conditions as shown in table 2-7, produces sample, its measurement is similar to example 2-1.Yet, do not measure varistor voltage E ₁₀Temperature characterisitic.The results are shown in table 2-7.

About the mark of forming, the content of SrO is expressed as a gram molecule, and the content of BaO is expressed as the b gram molecule, and the content of CaO is expressed as c gram molecule, TiO ₂Content be expressed as d gram molecule, NbO _5/2Content be expressed as f gram molecule, SiO ₂Content be expressed as the g gram molecule.Composition is fixed as a/ (a+b+c)=0.35, b/ (a+b+c)=0.35 and c/ (a+b+c)=0.30, and f/d * 100=3.00, (a+b+c)/(d+f)=0.98, and g/d * 100=0.20.

The condition that produces sample is: the time that reoxidizes processing is 2 hours, and processing procedure is carried out (partial pressure of oxygen is 0.2 atmospheric pressure) in air.

With the increase that reoxidizes temperature in the processing procedure, the voltage E of varistor ₁₀Wide variation.

Except sample 2-81,2-82, beyond 2-87 and the 2-88, heat cracks does not take place in other sample 2-4 and 2-83 in the soldering iron temperature is 360 ℃ test in 2-86.At this moment, the residual compressive stresses 20MPa that is not less than without exception in the sample compositing range of heat cracks does not take place.

Thereby it reoxidizes treatment temperature be 850 ℃ to 1050 ℃ sample 2-4 and 2-83 to 2-86 is preferred among the present invention.This is corresponding to claim 27.In addition, if residual compressive stresses is not less than 15MPa, because heat cracks does not take place in the soldering iron temperature is 360 ℃ test, so this scope also can be described as preferable range among the present invention.This is corresponding to the residual compressive stresses in claim 12 and 24.

Heat cracks among 2-84 and the 2-85, does not take place in sample 2-4 in the soldering iron temperature is the test of 400 ℃ and 450 ℃.At this moment, the residual compressive stresses 40MPa that is not less than without exception in the sample compositing range of heat cracks does not take place.

Thereby it reoxidizes treatment temperature is 900 ℃ to 1000 ℃ sample 2-4, and 2-84 and 2-85 are better preferred among the present invention.This is corresponding to claim 28.In addition, if residual compressive stresses is not less than 40MPa, owing in the soldering iron temperature is 450 ℃ test heat cracks does not take place, this scope also is a better preferable range among the present invention.This is corresponding to the residual compressive stresses in claim 14 and 26.

Like this, reoxidize the temperature in the processing and do not change the magnitude of voltage that composition is controlled varistor, can guarantee the broad range of varistor magnitude of voltage and enough non linear coefficient α, keep big surperficial residual compressive stresses simultaneously by change.Thereby, when keeping high strength and high-fire resistance, can obtain the broad range and the practical α of varistor magnitude of voltage by identical composition by big surface compression stress.So, needn't prepare multiple material, and be easy to control material.

Example 2-8

What will carry out among the example 2-8 is, relatively reoxidizes the sample that time obtained in the treatment conditions by change.

Fix other parameter, such as the mole ratios of A part, the molar percent of semiconductor transformation agent and type, total A/B, and SiO ₂Molar percent, and carry out with example 2-1 in similarly be provided with, different is to change to become to reoxidize treatment conditions as shown in table 2-8, produces sample, its measurement is similar to example 2-1.Yet, do not measure varistor voltage E ₁₀Temperature characterisitic.The results are shown in table 2-8.

About the mark of forming, the content of SrO is expressed as a gram molecule, and the content of BaO is expressed as the b gram molecule, and the content of CaO is expressed as c gram molecule, TiO ₂Content be expressed as d gram molecule, NbO _5/2Content be expressed as the f gram molecule, and SiO ₂Content be expressed as the g gram molecule.Composition is fixed as a/ (a+b+c)=0.35, b/ (a+b+c)=0.35, and c/ (a+b+c)=0.30, f/d * 100=3.00, (a+b+c)/(d+f)=0.98, and g/d * 100=0.20.

The condition that produces sample is: the temperature that reoxidizes processing is 950 ℃, and processing procedure is carried out (partial pressure of oxygen is 0.2 atmospheric pressure) in air.

With reoxidizing time course in the processing procedure, the voltage E of varistor ₁₀The dull rising.When reoxidizing the processing time when surpassing 32 hours, practical compression stress reduces rapidly.At other sample 2-4 except sample 2-97, heat cracks does not take place in 2-89 in the soldering iron temperature is 360 ℃ test in 2-96.At this moment, the residual compressive stresses 24MPa that is not less than without exception in the sample compositing range of heat cracks does not take place.

Thereby it reoxidizes the processing time, and to be not more than 32 hours sample 2-4 and 2-89 be preferred among the present invention to 2-96.This is corresponding to claim 29.In addition, if residual compressive stresses is not less than 15MPa, because heat cracks does not take place in the soldering iron temperature is 360 ℃ test, so this scope also is a preferred range among the present invention.This is corresponding to the residual compressive stresses in claim 12 and 24.

Heat cracks does not take place in sample 2-4,2-90 in the soldering iron temperature is 400 ℃ test in 2-95.At this moment, the residual compressive stresses 38MPa that is not less than without exception in the sample compositing range of heat cracks does not take place.

Thereby it reoxidizes the processing time at 0.25 to 16 hour sample 2-4, and 2-90 is better preferred among the present invention to 2-95.This is corresponding to claim 30.In addition, if residual compressive stresses is not less than 25MPa, owing in the soldering iron temperature is 400 ℃ test heat cracks does not take place, this scope also is a better preferable range among the present invention.This is corresponding to the residual compressive stresses in claim 13 and 25.

In addition, heat cracks does not take place in sample 2-4,2-91 in the soldering iron temperature is 450 ℃ test in 2-94.At this moment, the residual compressive stresses 41MPa that is not less than without exception in the sample compositing range of heat cracks does not take place.

Thereby it reoxidizes the processing time at 0.5 to 8 hour sample 2-4, and 2-91 is better preferred among the present invention to 2-94.In addition, if residual compressive stresses is not less than 40MPa, owing in the soldering iron temperature is 450 ℃ test heat cracks does not take place, this scope also is a better preferable range among the present invention.This is corresponding to the residual compressive stresses in claim 14 and 26.

Example 2-9

What will carry out among the example 2-9 is relatively to reoxidize the sample that partial pressure obtained of the oxygen in the treatment conditions by change.

Fix other parameter, such as the mole ratios of A part, the molar percent of semiconductor transformation agent and type, total A/B, and SiO ₂Molar percent, and carry out with example 2-1 in similarly be provided with, different is to change to become to reoxidize treatment conditions as shown in table 2-9, produces sample, its measurement is similar to example 2-1.Yet, do not measure varistor voltage E ₁₀Temperature characterisitic.The results are shown in table 2-9.

Reoxidize processing and be 950 ℃ with temperature and carried out 2 hours, produce each sample by the partial pressure that changes oxygen.

In sample 2-98 and 2-99, factor alpha is little, and residual compressive stresses is also little.In 2-102, is 360 ℃ in the soldering iron temperature at other sample 2-4 except these samples and 2-100, in the test of 400 ℃ and 450 ℃, heat cracks does not take place.At this moment, the residual compressive stresses 40MPa that is not less than without exception in the sample compositing range of heat cracks does not take place.

Thereby it reoxidizes, and oxygen partial pressure is not less than 0.10 atmospheric sample 2-4 by force in the processing, and 2-100 is preferred among the present invention to 2-102.In addition, when residual compressive stresses is not less than 40MPa, owing to be 360 ℃ in the soldering iron temperature, in the test of 400 ℃ and 450 ℃ heat cracks does not take place, so this scope also is a better preferable range among the present invention.This is corresponding to the residual compressive stresses in claim 14 and 26.

According to the table 2-1 to 2-9, if the composition of each composition, content with reoxidize treatment conditions in scope of the present invention, then can obtain the residual compressive stresses in the invention described above preferable range.Thereby can provide, the outstanding based varistor of high-flexural strength and resistance to sudden heating is arranged, and manufacture method.

The 3rd embodiment

Below will the composition of the based varistor 10 of this 3rd embodiment be described.

This based varistor 10 comprises first composition of the composite perofskite of being made up of the oxide of Sr, Ba, Ca and Ti; Second composition and ternary at least one composition, second composition by at least one class from R (Y and lanthanide series (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu)) oxide that oxide is selected is formed, and the oxide that the 3rd composition is selected from the oxide of M (Nb and Ta) by at least one class is formed; And the four-component of forming by the oxide of Si, and do not contain Mg substantially.If a is the mole number that the Sr of first composition is calculated as SrO, b is the mole number that the Ba of first composition is calculated as BaO, c is the mole number that the Ca of first composition is calculated as CaO, d is the mole number that the Ti of first composition is calculated as TiO, and e is that R to second composition is respectively as YO _3/2, CeO ₂, PrO _11/6, TbO _7/4And RO _3/2The mole number that (other lanthanide series) calculates, f is as NbO to ternary M _5/2And TaO _5/2The mole number of Ji Suaning, and g respectively is that Si to four-component is as SiO ₂The mole number that calculates.So, this based varistor consists of 0.30≤a/ (a+b+c)≤0.40,0.30≤b/ (a+b+c)≤0.40,0.25≤c/ (a+b+c)≤0.35,0.84≤(a+b+c+e)/(d+f)≤1.16,0.75≤(e+f)/d * 100≤10.0, and g/d * 100≤0.6.The best scope of this composition is and 0.96≤(a+b+c+e)/(d+f)≤1.01 again, 0.75≤(e+f)/d * 100≤4.0, and g/d * 100≤0.3.

As for content Sr, the Ba of A part composition, the mole ratios of Ca, preferably Sr comprises two ends between 0.30 and 0.40, and Ba comprises two ends between 0.30 and 0.40, and Ca is 0.25 and 0.35.At this moment, just can improve its electrology characteristic, such as varistor voltage E ₁₀Controllability, varistor voltage E ₁₀Temperature characterisitic, and non linear coefficient α, and improve the resistance to sudden heating of varistor.In other words, if Sr is too many, E then ₁₀Temperature characterisitic will become negatively, if very little, then intensity will descend.In addition, if Ba is too many, E then ₁₀The positive trend of temperature characterisitic will be too strong, and if very little, E then ₁₀Temperature characterisitic become negative.In addition, if Ca too much or very little, for varistor voltage E ₁₀Non linear coefficient α will diminish.If Ca is too many, varistor voltage E ₁₀To become very big so that be difficult to control, and base is by reoxidizing the formation insulator.

By semiconductor transformation agent (the second and/or the 3rd composition) being set to principal component (TiO ₂) molar percent (mole number by metal ion calculates) between 0.75 and 10.0, comprise two ends, or be more preferably between 0.75 and 4.0, comprise two ends, can improve the resistance to sudden heating of varistor.In other words, if the semiconductor transformation agent too much or very little, then intensity reduces and is easy to take place heat cracks.

If be arranged so that total A/B between 0.84 and 1.16, comprises two ends, maybe may be more preferably A/B between 0.96 and 1.01, comprise two ends, make four-component (SiO ₂) amount reduce, then as described below, can improve the sintering degree.In other words, this is because if A/B is too big or too little, then sintering is hindered, thereby base forms insulator owing to reoxidizing.In addition, if A/B is too big or too little, then intensity reduces and is easy to the occurrence temperature be full of cracks.As mentioned above, at SiO- ₂Amount less and add in the scope of a large amount of semiconductor transformation agent, in order to keep resistance to sudden heating, must limit to be limited on total A/B being not more than 1.16, or more preferably be not more than 1.01.

By four-component (SiO is set ₂) to principal component (TiO ₂) molar percent for being not more than 0.6, perhaps be more preferably and be not more than 0.3, can obviously improve the resistance to sudden heating of varistor.In other words, SiO ₂Add as sinter additives, even and under the situation of forming fluctuation, also can stably carry out sintering, if but SiO ₂Amount increase, then becoming is easy to take place heat cracks.Should be noted that and be not more than 0.6 or be not more than 0.3 SiO ₂Content (molar percent) comprise that also its dosage is zero situation.

Because electrode 11 is formed by Cu or the main material of being made by Cu, even at high temperature they also are difficult to be corroded, thereby this can tolerate thermal weld work.

The powder that each of pottery constitutes the compound of element is used as material powder usually.Oxide or become the compound of oxide by sintering can be used as material powder such as carbonate and hydroxide.For example, for regard to the example, then at least one class barium compound is such as BaCO with regard to Ba ₃, BaSiO ₃, BaO, BaCl ₂, Ba (OH) ₂, and Ba (NO ₃) ₂And alkoxide (for example, (CH ₃O) ₂Ba), can be used as raw material.The average particulate diameter of material powder is typically about 0.2 to 5 μ m.

Each material powder, such as Nb, Ta, Y, lanthanide series, Mo, W, Mn can add when Si, Co etc. mix after roasting.

To the semiconductive ceramic of such acquisition, in the oxidizing atmosphere such, heat-treat (reoxidizing processing) such as air, enable to obtain and the suitable varistor voltage of this object.To the temperature T EM in this oxidation processes _RoxWith time T IM _RoxControl as follows:

(1) 850 ℃≤TEM _Rox≤ 900 ℃, 0.25 hour≤TIM _Rox≤ 32 hours

(2) 900 ℃≤TEM _Rox≤ 1050 ℃, 0.1 hour≤TIM _Rox≤ 32 hours

(3) 900 ℃≤TEM _Rox≤ 950 ℃, 0.5 hour≤TIM _Rox≤ 16 hours, perhaps

(4) 950 ℃≤TEM _Rox≤ 1000 ℃, 0.25 hour≤TIM _Rox≤ 16 hours

Reoxidize processing by this this and form insulating barrier 10b at surface portion.Owing to the existence of this insulating barrier shows the varistor characteristic.In general, if this insulating barrier thickening, then non linear coefficient α and varistor voltage become big, and if attenuation, then non linear coefficient α and varistor voltage decreases.

Reoxidize temperature T EM in the processing by such control _RoxWith time T IM _Rox, can in very broad piezo-resistance voltage range, guarantee enough non linear coefficient α, enough bending strengths, and the property of enough heat shock resistances, and can also reduce the dependence that quick resistance voltage changes heat treatment temperature.Owing to can obtain non linear coefficient α practical in the scope of piezo-resistance voltage broadness and enough intensity with single composition, just needn't prepare multiple material, and be easy to control material.If consider to reoxidize the influence of the variation of treatment conditions, then reoxidize the time T IM of processing to varistor voltage _RoxTemperature T EM than oxidation processes _RoxInfluence little.Thereby, reoxidize the time T IM of processing by last adjusting _RoxAnd control varistor magnitude of voltage becomes very little because of the influence that reoxidizes treatment conditions causes the drift to the varistor magnitude of voltage, thereby product is improved, and the control that reoxidizes treatment conditions becomes easy.

After reoxidizing processing,, form electrode on a surface of based varistor, thereby obtain varistor with Cu or the main material of making by Cu.Mainly identical among the material of making by Cu and first embodiment.

In above-mentioned the 3rd embodiment, though electrode is to form on a surface of based varistor, electrode also can be in top and the back side or the side formation of based varistor.

In addition, can make based varistor by adding minor constituent subsequently.That is, can weigh and the mixed material powder, add part content carrying out roasting after, so that regulate these content, make powder have predetermined composition, abrasive flour also is shaped, and the object of shaping is reduced sintering, and reoxidizes.

Below, according to the example of third embodiment of the invention, the present invention is described in more detail.

Example 3-1

What will carry out in example 3-1 is, to the mole ratios by changing the A part and fix other parameter such as reoxidizing treatment conditions, and the molar percent of semiconductor transformation agent and type, and total A/B, the sample that is obtained compares.

At first, by to SrCO as raw material ₃, BaCO ₃, CaCO ₃, TiO ₂, NbO _5/2, and SiO ₂After conversion is weighed respectively and prepared burden, make raw material can have the composition shown in the table 3-1, use the humid medium mill to mix these raw materials and reach 10 to 20 hours, dewater and drying.

After the mixture that obtains with 1150 ℃ of roastings, mixture is carried out rough lapping, reuse the humid medium mill mix reached 10 to 20 hours after, dewater and dry.Afterwards, mix 1.0 to 1.5wt% polyvinyl alcohol as organic bond, make it granulation, and the mixture that makes granulation is at 2t/cm to mixture ²Forming pressure under be shaped, become the shaped-article of external diameter 12mm, internal diameter 9mm, thickness 1.0mm.

Under 600 ℃ in air, to such shaping object carry out after binder remove to handle, at N ₂(95 percent by volume)+H ₂Carry out sintering with about 1350 ℃ in the reducing atmosphere of (5 percent by volume) and reach 2 hours, to obtain semiconductive ceramic.Afterwards, in air, this semiconductive ceramic is carried out two hours the processing that reoxidizes, obtain based varistor with 950 ℃.Next,, semiconductive ceramic is carried out two hours the processing that reoxidizes, to obtain based varistor with 950 ℃ of rising and decline temperature speed in air with 100 to 600 ℃/h.

Afterwards, in neutral atmosphere to a surface applied Cu thickener of the based varistor 10 shown in Fig. 1 a and the 1b, by at 750 ℃ of roasting Cu thickeners, form three Cu electrodes 11 (though five electrodes are arranged shown in these figure), obtain specimen for the varistor of measuring.

Then, at 20 ℃ of voltage E that measure each sample ₁₀And E ₁Afterwards, use the voltage E that records ₁₀And E ₁By α=1/log (E ₁₀/ E ₁) acquisition non linear coefficient α.And then, obtained varistor voltage E ₁₀Temperature characterisitic (temperature coefficient).And, when each sample being carried out the heat cracks test, measure the cross-breaking strength of each sample.

By Δ E _10T={ E ₁₀(85)-E ₁₀(20) }/{ E ₁₀(20) * (85-20) } * 100[%/℃] obtain varistor voltage E to each sample ₁₀Temperature characterisitic (temperature coefficient) Δ E _10TVoltage E ₁₀(85) and E ₁₀(20) be respectively at 20 ℃ of temperature varistor E with 85 ℃ ₁₀Voltage.These temperature are to use constant temperature oven to record.

Use the cross-breaking strength tester, as AIKOH ENGIEERING Co., the MODEL-1311D of Ltd. measures cross-breaking strength.

Use solder, the electrode side that makes the soldering iron that has preestablished temperature touch the sample that is in room temperature reached for 3 seconds, carried out the heat cracks test.The temperature of soldering iron is two class temperature, has promptly used 360 ℃ and 400 ℃.Use ethanol that visual observation has been carried out in the be full of cracks that becomes hundred samples.It the results are shown among the table 3-1.

The gram molecule rate of A part composition is for the electrology characteristic of varistor, and particularly for varistor voltage E ₁₀Temperature characterisitic, have a significant impact.As varistor voltage E ₁₀Temperature characterisitic when negative, the voltage of varistor rises with working temperature and descends, thereby excessive electric current will flow through varistor, maybe might cause thermal runaway.Thereby this is unacceptable.So sample 3-15 is to 3-17,3-26 is in the scope that can not be used as varistor respectively to 3-29 and 3-31.

If voltage E ₁₀Temperature characterisitic be zero or positive, do not wish that so it surpasses 0.06, thereby sample 3-18 should not be as varistor to 3-23 and 3-30.

Sample 3-25 owing to reoxidize handles and by integral insulation, and can not be as varistor work.In addition, because 3-24 and 3-26 comprise too much Ca, their varistor voltage E ₁₀High especially, thereby be difficult to control.

Though the E of sample 3-13,3-14 and 3-32 ₁₀Characteristic be not higher than 0.06, but since contained Ca very little, they are to varistor voltage E ₁₀Non linear coefficient α low, thereby also bad.

So, because varistor voltage E ₁₀Temperature characterisitic be not higher than 0.06, and to varistor voltage E ₁₀Factor alpha not low, so sample 3-1 is preferred to 3-12.In addition, its voltage E ₁₀Temperature characterisitic not to be higher than 0.02 sample 3-1 be better to 3-7 in the present invention.This is corresponding to the mole ratios of determined A part in the claim 47.In this scope, in being 360 ℃ thermal shock test, the soldering iron temperature do not have heat cracks to take place, and and then, in being 400 ℃ thermal shock test, the soldering iron temperature do not have heat cracks to take place yet.Particularly, sample 3-4 has voltage E ₁₀Temperature characterisitic and the balance of non linear coefficient α the best, so near the mole ratios of A part composition this sample is best in the present invention.

Example 3-2

What will carry out among the example 3-2 is, relatively by changing the sample that amount obtained of semiconductor transformation agent.

Fix other parameter, such as reoxidizing treatment conditions, the mole ratios of A part, a based semiconductor agent, total A/B, and SiO ₂Molar percent, carry out with example 3-1 in similarly be provided with, different is the molar percent of setting the semiconductor transformation agent as shown in table 3-2, produces sample, its measurement is similar to the measurement among the example 3-1.The results are shown in table 3-2.

The amount of semiconductor transformation agent influences the heat-resisting cracking of varistor pottery.Because the semiconductor transformation agent of sample 3-33 and 3-39 is respectively very little and too many, in the soldering iron temperature is 360 ℃ test, heat cracks has taken place, thereby these not preferred.Thereby, in the soldering iron temperature is 360 ℃ test, heat cracks does not take place, and cross-breaking strength is not less than 18kgf/mm ²Sample 3-4 and 3-34 be preferred among the present invention to 3-38.This is corresponding to the molar percent of determined semiconductor transformation agent in the claim 47.

Because sample 3-38 in the soldering iron temperature is 400 ℃ test heat cracks has taken place, and sample 3-4 and 3-34 that be full of cracks takes place in this heat cracks of 400 ℃ test are more preferred among the present invention to 3-37.This is corresponding to the molar percent of determined semiconductor transformation agent in the claim 49.In addition, near the molar percent the molar percent of the semiconductor transformation agent of sample 3-4 is best in the present invention.

Example 3-3

What will carry out among the example 3-3 is relatively to change the sample of the type of semiconductor transformation agent.

Fix other parameter, such as reoxidizing treatment conditions, the mole ratios of A part, the molar percent of semiconductor transformation agent, total A/B, and SiO ₂Molar percent, and carry out with example 3-1 in similarly be provided with, different is the type that changes the semiconductor transformation agent as shown in table 3-3, produces sample, its measurement is similar to the measurement among the example 3-1.The results are shown in table 3-3.

All samples 3-4 and 3-40 be to 3-56, do not have heat cracks to take place in the soldering iron temperature is the test of 360 ℃ and 400 ℃, and cross-breaking strength is not less than 18kgf/mm ²Thereby, use NbO among the present invention _5/2, TaO _5/2, YO _3/2, LaO _3/2, CeO ₂, PrO _11/6, NdO _3/2, SmO _3/2, EuO _3/2, GdO _3/2, TbO _7/4, DyO _3/2, HoO _3/2, ErO _3/2, TmO _3/2, YbO _3/2, LuO _3/2Or NbO _5/2+ YO _3/2(waiting mole number) agent is preferred as semiconductor transformation.This is corresponding to the type of the semiconductor transformation agent of determining in the claim 47.

Example 3-4

What will carry out among the example 3-4 is relatively to change total sample that A/B obtained.

Fix other parameter, such as reoxidizing treatment conditions, the mole ratios of A part, the molar percent of semiconductor transformation agent and type, and SiO ₂Molar percent, and carry out with example 3-1 in similarly be provided with, different is to change total A/B as shown in table 3-4, produces sample, its measurement is similar to example 3-1.The results are shown in table 3-4.

The sintering degree of total A/B value influence pottery.Total A/B of sample 3-57 and 3-63 is respectively too little and too big because they can not sintering pottery accurately, and reoxidize to handle and make it integral insulation, so they can not be as varistor work.And, heat cracks when being 360 ℃, the soldering iron temperature takes place.

As show shown in the 3-4, at SiO ₂Amount less and add in the scope of a large amount of semiconductor transformation agent, in order to keep heat-resisting cracking, the upper limit of must special control total A/B.If total A/B surpasses 1.16, begin to take place heat cracks at 360 ℃, and if total A/B surpass 1.01, then begin to take place heat cracks at 400 ℃.

In other words, sample 3-4 and 3-58 be to 3-62, because the soldering iron temperature is in 360 ℃ the test heat cracks not to take place, and cross-breaking strength is not less than 18kgf/mm ², be preferred among the present invention.This is corresponding to determined total A/B in the claim 47.

In addition, sample 3-4 and 3-59 be to 3-61, because the soldering iron temperature is in 400 ℃ the test heat cracks not to take place, is better preferred among the present invention.This is corresponding to determined total A/B in the claim 48.In addition, as among the sample 3-4, near total A/B that the composition of its B part is many slightly the optimum range among the present invention.

Example 3-5

What will carry out among the example 3-5 is relatively to change SiO ₂The sample that molar percent obtained.

Fix other parameter, such as reoxidizing treatment conditions, the mole ratios of A part, the molar percent of semiconductor transformation agent and type, and total A/B, and carry out with example 3-1 in similarly be provided with, different is to change SiO as shown in table 3-5 ₂Molar percent, produce sample, its measurement is similar to example 3-1.Soldering iron temperature in the heat cracks test is three types a temperature, promptly 360 ℃, 400 ℃ and 450 ℃.The results are shown in table 3-5.

Because sample 3-68 and 3-69 have too many SiO ₂, in the soldering iron temperature is 360 ℃ test heat cracks takes place promptly, so be not preferred.So sample 3-4 and 3-64 be to 3-67, in the soldering iron temperature is the test of 360 ℃ and 400 ℃, heat cracks does not take place, and cross-breaking strength is not less than 18kgf/mm ²So, be preferred among the present invention.This is corresponding to the determined SiO in the claim 47 ₂Molar percent.

In the soldering iron temperature is among the sample 3-67 heat cracks to take place in 450 ℃ the test, and sample 3-4 and 3-64 are to 3-66, and heat cracks does not take place in the test of this soldering iron temperature for it, is better preferred among the present invention.This is corresponding to the determined SiO in the claim 50 ₂Molar percent.In addition, near the SiO sample 3-4 ₂Molar percent be the best among the present invention.Though SiO among the sample 3-64 ₂Nominally batching be zero, in fact, SiO ₂Be included in each raw material as impurity, thereby SiO among the sample 3-63 ₂Actual content do not have vanishing.

Example 3-6

What will carry out among the example 3-6 is relatively to have changed the sample of the kind and the amount of additive.

Fix other parameter, such as reoxidizing treatment conditions, the mole ratios of A part, the molar percent of semiconductor transformation agent and type, total A/B, and SiO ₂Molar percent, and carry out with example 3-1 in similarly be provided with, different is kind and the amount that changes additive as shown in table 3-6, produces sample, its measurement is similar to example 3-1.The results are shown in table 3-6.

Additive has the voltage E of adjusting such as varistor ₁₀And the effect of these electrology characteristics of non linear coefficient α.Mn has amplified the voltage E of varistor ₁₀And non linear coefficient α, and Co has amplified the voltage E of varistor ₁₀Find that in addition Mo and W have the effect of amplifying non linear coefficient α.Though do not illustrate among the table 3-6, find other element, such as Li, Na, Ni, Cu, Zn, Sc, Fe, Ga, In also has similar effect.

Because the dosage of sample 3-74 and 3-78 is too big, the sintering degree is hindered, and reoxidize to handle pottery is insulated.Thereby, each additive to the molar percent of principal component be not more than 1.00 and cross-breaking strength be not less than 18kgf/mm ²Sample 3-70 to 3-73,3-75 to 3-80, is the preferred person among the present invention to 3-77 and 3-79.This is included in the kind and molar percent of the additive of defined in the claim 51.

Example 3-7

What will carry out among the example 3-7 is relatively to change the temperature T EM that reoxidizes in the processing _RoxWith time T IM _RoxThe sample that is obtained.

Fix other parameter, such as the mole ratios of A part, the molar percent of semiconductor transformation agent and type, total A/B, and SiO ₂Molar percent, and carry out with example 3-1 in similarly be provided with, different is to change the condition that reoxidizes processing as shown in table 3-7, produces sample, its measurement is similar to example 3-1.The results are shown in table 3-7 and 3-8.

Table 3-7

Good: good

No Good: bad

None: do not have

Table 3-8

Good: good

No Good: bad

None: do not have

About the mark of forming, the content of SrO is expressed as a gram molecule, and the content of BaO is expressed as the b gram molecule, and the content of CaO is expressed as c gram molecule, TiO ₂Content be expressed as d gram molecule, NbO _5/2Content be expressed as the f gram molecule, and SiO ₂Content be expressed as the g gram molecule.Composition is fixed as a/ (a+b+c)=0.35, b/ (a+b+c)=0.35, and c/ (a+b+c)=0.30, f/d * 100=3.00, (a+b+c)/(d+f)=0.98, and g/d * 100=0.20.In addition, sample is to be generation air (partial pressure of oxygen is 0.2 atmospheric pressure) under handling atmosphere.

Reoxidize the voltage E of control varistor under the treatment conditions at this ₁₀As sample 3-85,3-95,3-105,3-115,3-125, such among 3-135 and the 3-145, the temperature T EM in reoxidizing processing _RoxAs a parameter, and the voltage E of control varistor ₁₀The time, for example, as the time T IM that reoxidizes processing _RoxBe fixed on two hours, and temperature is when changing from 800C ° to 1000C °, the voltage E of the varistor that is obtained ₁₀Between 2.5 to 122V, comprise two ends greatly.Here, if condition restriction is not for heat cracks to take place in the test of 400C ° of soldering iron temperature, and cross-breaking strength is not less than 18kgf/mm ², the voltage E of the varistor that is obtained then ₁₀Between 9.3 to 14.5V, comprise two ends greatly.

Yet, as sample 3-111 to 3-120, as time TIM _RoxAs a parameter, and the voltage E of control varistor ₁₀The time, for example, as the TEM that reoxidizes processing _RoxBe fixed on 950C °, and from 0.1 to 64 hour time when changing, the voltage E of the varistor that is obtained ₁₀Between 3.1 to 81.9V, comprise two ends greatly.Here, if condition restriction is not for heat cracks to take place in the test of 400C ° of soldering iron temperature, and cross-breaking strength is not less than 18kgf/mm ², the voltage E of the varistor that is obtained then ₁₀Between 4.9 to 40.6V, comprise two ends greatly.

That is, by control the time T IM that reoxidizes processing as parameter _Rox, can obtain to have the voltage E of the varistor of broad usable range ₁₀, enough stress intensity when keeping welding simultaneously.This is corresponding to claim 42.

Because sample 3-81 is to 3-91,3-100,3-101,3-110,3-120,3-130 and 3-140 to 3-150 to the cross-breaking strength of bending stress less than 18kgf/mm ², these samples do not meet the requirements with regard to intensity.

Except these samples, other sample 3-92 is to 3-99, and 3-102 is to 3-109, and 3-111 is to 3-119, and to 3-139, cross-breaking strength is 18kgf/mm to 3-121 to 3-129 and 3-131 ², and heat cracks does not take place in the soldering iron temperature is 360 ℃ test.Thereby the preferable range among the present invention is the scope corresponding to these samples, that is, and and 850 ℃≤TEM _Rox≤ 900 ℃, 0.25 hour≤TIM _Rox≤ 32 hours, 900 ℃≤TEM _Rox≤ 1050 ℃, 0.1 hour≤TIM _Rox≤ 32 hours.This is corresponding to claim 40.

Sample 3-103 is to 3-108, and 3-112 is to 3-118, and 3-122 is to 3-128, in the soldering iron temperature is 400 ℃ test heat cracks do not take place.Thereby the more preferable range among the present invention is the scope corresponding to these samples, that is, and and 900 ℃≤TEM _Rox≤ 950 ℃, 0.5 hour≤TIM _Rox≤ 16 hours, 950 ℃≤TEM _Rox≤ 1000 ℃, 0.25 hour≤TIM _Rox≤ 16 hours.This is corresponding to claim 41.

Like this, reoxidize the condition in the processing and do not change the magnitude of voltage that composition is controlled varistor by adjusting, can keep the intensity of pottery own in very high level, and can obtain, and overcome enough tolerances of local thermal shock when welding the enough bending strengths of bending stress.Certainly, can guarantee enough non linear coefficient α in very broad piezo-resistance voltage range, and reduce the dependence of quick resistance voltage heat treatment temperature.Like this, owing to can in the scope of piezo-resistance voltage broadness, obtain practical non linear coefficient α and enough intensity, just needn't prepare multiple material, and be easy to control material with single composition.

Example 3-8

What will carry out among the example 3-8 is relatively to change the sample that number of repetition obtained that reoxidizes heat treatment step in the processing.

Fix other parameter, such as the mole ratios of A part, the molar percent of semiconductor transformation agent and type, total A/B, and SiO ₂Molar percent, and carry out with example 3-1 in similarly be provided with, different is to change the condition that reoxidizes processing as shown in table 3-9, its measurement is similar to example 3-1.Identical among the composition of each sample and the sample 3-7.The results are shown in table 3-9.

Table 3-9

Good: good

No Good: bad

None: do not have

Fixedly reoxidize treatment temperature TEM _RoxAt 950C °, and cumulative time TIM is set _RoxBe 12 hours, the sample 3-164 that is produced by single continuous heat step, with three each processing times of independent heat treatment be 4 hours the sample 3-169 that step produced relatively.The result is the varistor voltage E of gained ₁₀, cross-breaking strength and heat cracks test result are much at one.In addition, fixed temperature TEM _RoxAt 900C °, and cumulative time TIM is set _RoxBe 12 hours, the comparative result of gained sample 3-153 and sample 3-158 similarly.

Thereby, when the flexural stress cross-breaking strength is not less than 18Kgf/mm ², to reoxidize processing time TIM _RoxFor parameter is controlled varistor voltage E ₁₀The time, under the situation that the time is set like this, as long as the cumulative time is identical, no matter the number of times that heat treatment step repeats how, can both obtain varistor voltage E ₁₀The pottery of usable range broadness has enough stress intensities when keeping welding simultaneously.This is corresponding to claim 46.

According to above table 3-1 to 3-9, as long as the composition of each composition, content and reoxidize treatment conditions in scope of the present invention then can provide a kind of manufacture method that obtains based varistor, this pottery has above-mentioned cross-breaking strength preferred range, and outstanding resistance to sudden heating is being arranged.

The 4th embodiment

Below will the composition of the based varistor 10 of this 4th embodiment be described.

Based varistor 10 comprises first composition of the composite perofskite of being made up of the oxide of Sr, Ba, Ca and Ti; Second composition and ternary at least one composition, second composition by at least one class from R (Y and lanthanide series (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu)) oxide that oxide is selected is formed, and the oxide that the 3rd composition is selected from the oxide of M (Nb and Ta) by at least one class is formed; And the four-component of forming by the oxide of Si.If a is the mole number that the Sr of first composition is calculated as SrO, b is the mole number that the Ba of first composition is calculated as BaO, c is the mole number that the Ca of first composition is calculated as CaO, d is the mole number that the Ti of first composition is calculated as TiO, and e is that R to second composition is respectively as YO _3/2, CeO ₂, PrO _11/6, TbO _7/4And RO _3/2The mole number that (other lanthanide series) calculates, f is as NbO to ternary M _5/2And TaO _5/2The mole number of Ji Suaning, and g respectively is that Si to four-component is as SiO ₂The mole number that calculates.So, this based varistor consists of 0.10≤a/ (a+b+c)≤0.40,0.30≤b/ (a+b+c)≤0.50,0.20≤c/ (a+b+c)≤0.50,0.84≤(a+b+c+e)/(d+f)≤1.16,0.75≤(e+f)/d * 100≤10.0, and g/d * 100≤0.6.

This composition more preferred range is 0.30≤a/ (a+b+c)≤0.40,0.30≤b/ (a+b+c)≤0.40,0.25≤c/ (a+b+c)≤0.35 and 0.96≤(a+b+c+e)/(d+f)≤1.01,0.75≤(e+f)/d * 100≤4.0, and g/d * 100≤0.3.

As for content Sr, the Ba of A part composition, the mole ratios of Ca, preferably Sr is no less than 0.10 but no more than 0.40, and Ba is no less than 0.30 but no more than 0.50, and Ca is no less than 0.20 but no more than 0.50.Be more preferably Sr and be no less than 0.30 but no more than 0.40, Ba is no less than 0.30 but no more than 0.40, and Ca is no less than 0.25 but no more than 0.35.At this moment, just can improve its electrology characteristic, such as varistor voltage E ₁₀Controllability, such as varistor voltage E ₁₀Temperature characterisitic, and non linear coefficient α, and improve the resistance to sudden heating of varistor.In other words, if Sr is too many, E then ₁₀Temperature characterisitic will become negatively, if very little, then intensity will descend.In addition, if Ba is too many, E then ₁₀The positive trend of temperature characterisitic will be too strong, and if very little, E then ₁₀Temperature characterisitic become negative.In addition, if Ca too much or very little, for varistor voltage E ₁₀Non linear coefficient α will diminish.If Ca is too many, varistor voltage E ₁₀To become very big so that be difficult to control, and base is by reoxidizing the formation insulator.

By semiconductor transformation agent (the second and/or the 3rd composition) being set to principal component (TiO ₂) molar percent (this is that mole number by metal ion calculates) between 0.75 and 10.0, comprise two ends, or better between 0.75 and 4.0, comprise two ends, can improve the resistance to sudden heating of sensitive resistor.In other words, if the semiconductor transformation agent too much or very little, then intensity reduces and is easy to take place heat cracks.

If by total A/B being set between 0.84 and 1.16, comprise two ends, or be more preferably between 0.96 and 1.01, comprise two ends, and reduce four-component (SiO ₂) amount, then as described below, can improve the sintering degree.In other words, this is because if total A/B is too big or too little, then sintering is hindered, thereby base forms insulator owing to reoxidizing.In addition, if total A/B is too big or too little, then intensity reduces and is easy to the occurrence temperature be full of cracks.As mentioned above, at SiO ₂Amount less and add in the scope of a large amount of semiconductor transformation agent, in order to keep resistance to sudden heating, must limit to be limited on total A/B being not more than 1.16, or more preferably be not more than 1.01.

By four-component (SiO is set ₂) to principal component (TiO ₂) molar percent for being not more than 0.6, perhaps be more preferably and be not more than 0.3, can obviously improve the resistance to sudden heating of varistor.In other words, SiO ₂Add as sinter additives, even and under the situation of forming fluctuation, also can stably carry out sintering, however if SiO ₂Amount increase, then becoming is easy to take place heat cracks.Should be noted that and be not more than 0.6 or be not more than 0.3 SiO ₂Content (molar percent) comprise that also its dosage is zero situation.

The manufacture method of this varistor pottery 10 below will be described.

At first, material powder is weighed, make final composition can become above-mentioned composition, and carry out wet mixing usually and close.Then, after carrying out processed, material powder is carried out drying, and with about 1080 to 1250 ℃ of roastings of carrying out 2 to 4 hours.Then, grind the object of roasting.

The milling time of this grinding is to set like this: make grind after the specific area of each particle be 0.5 and 5.0m ²Between/the g, comprise two ends, specifically, this time is greatly about 1 to 25 hour.Because as long as the specific area of each particle is not less than 0.5m after grinding ²/ g, the inhomogeneities of just can generating material not forming or the concentrated gradient of composition, thereby can obtain enough bending strengths of sintered ceramic and resistance to sudden heating.When specific area surpasses 5.0m ²During/g, then milling time becomes oversize, thereby makes the inefficiency that becomes.In addition, because it becomes and be easy to occur the liquid phase of rich Ti, becoming is easy to the local inhomogeneities that occurs forming.Thereby, make specific area be no more than 5.0m ²/ g.

Then, after this grinding, add organic bond to particle, and and then add water, the pH conditioning agent, wetting agents etc. also mix.Afterwards, mixture is shaped.

This shaping is to carry out under such condition, and wherein the density of the feasible object that is shaped can be at 2.80g/cm ³And 3.40g/cm ³Between, comprise two ends.If the density of shaped-article is not less than 2.80g/cm ³,, in manufacture process, never appear problem because the intensity of the object that is shaped is enough.If the density of shaped-article surpasses 3.40g/cm ³, then the life time of former and shaping dies will shorten, and reduces thereby maintenance cost increases the feasible efficient of making.So the density of shaped-article is set to be not more than 3.40g/cm ³

Then, carrying out after adhesive removes, in reducing atmosphere with about 2 to 4 hours of about 1250-1400 ℃ of thermal sintering object, to obtain semiconductive ceramic.

To the semiconductive ceramic of such acquisition, in oxidizing atmosphere, in air, for example under 800 to 1000 ℃ temperature, heat-treating (reoxidizing processing), enable to obtain and the suitable varistor voltage of this object.Reoxidize processing by this and form insulating barrier 10b at surface portion.Owing to the existence of this insulating barrier shows the varistor characteristic.In general, if this insulating barrier thickening, then non linear coefficient α and varistor voltage become big, and if attenuation, then non linear coefficient α and varistor voltage decreases.

After reoxidizing processing,, form electrode on a surface of based varistor with Cu or the main material of making by Cu.In the above-described embodiments, though electrode is to form on a surface of based varistor, electrode also can be in top and the back side or the side formation of based varistor.

Like this, make that by grinding the specific area of each particle after grinding is 0.5 to 5.0m ²/ g, and make the density of shaped-article become 2.80 to 3.40g/cm to shaping particles ³, this intensity that can keep pottery itself is at high level, and acquisition reaches anti-localized heat impact enough when welding to the enough bending strengths of bending stress.

Below, with reference to the example according to the 4th embodiment, the present invention is described in more detail.

Example 4-1

What will carry out in example 4-1 is, by fixing the milling time after other parameter such as the roasting, the density of shaped-article, the molar percent of semiconductor transformation agent and type, total A/B ratio, and SiO ₂Molar percent, and change the mole ratios of A part composition, the sample of such acquisition is compared.

At first, by to SrCO as raw material ₃, BaCO ₃, CaCO ₃, TiO ₂, NbO _5/2, and SiO ₂After conversion is weighed respectively and prepared burden, make raw material can have the composition shown in the table 4-1, use the humid medium mill to mix these raw materials and reach 10 to 20 hours, dewater and drying.

After the mixture that obtains with 1150 ℃ of roastings, mixture is carried out rough lapping, reuse the humid medium mill mix reached 10 to 20 hours after, dewater and dry.The milling time that is provided with after the roasting is 16 hours, and the specific area that grinds each particle of back is fixed as 4.00m ²/ g.

Afterwards, mix 1.0 to 1.5wt% polyvinyl alcohol as organic bond, make it granulation, and the mixture that makes granulation is at 2t/cm to mixture ²Forming pressure under be shaped, become the shaped-article of external diameter 12mm, internal diameter 9mm, thickness 1.0mm.The density p g of shaped-article is fixed as 3.10g/cm ³

Afterwards, in neutral atmosphere to a surface applied Cu thickener of the based varistor 10 shown in Fig. 1 a and the 1b, by at 750 ℃ of roasting Cu thickeners, form (though five electrodes are arranged shown in these figure) three Cu electrodes 11, obtain specimen for the varistor of measuring.

By Δ E _10T={ E ₁₀(85)-E ₁₀(20) }/{ E ₁₀(20) * (85-20) } * 100[%/℃] obtain varistor voltage E to each sample ₁₀Temperature characterisitic (temperature coefficient) Δ E _10TVoltage E ₁₀(85) and E ₁₀(20) be respectively at 20 ℃ of temperature voltage E with 85 ℃ varistor ₁₀These temperature are to use constant temperature oven to record.

Use solder, the electrode side that makes the soldering iron that has preestablished temperature touch the sample that is in room temperature reached for 3 seconds, carried out the heat cracks test.The temperature of soldering iron is two class temperature, promptly 360 ℃ and 400 ℃.Use ethanol that visual observation has been carried out in the be full of cracks of 30 samples.It the results are shown among the table 4-1.

The gram molecule rate of A part composition is for the electrology characteristic of varistor, and particularly for varistor voltage E ₁₀Temperature characterisitic, have a significant impact.As varistor voltage E ₁₀Temperature characterisitic when negative, the voltage of varistor rises with working temperature and descends, thereby excessive electric current will flow through varistor, maybe might cause thermal runaway.Thereby this is unacceptable.So sample 4-15 is to 4-17,4-26 is in the scope that can not be used as varistor respectively to 4-29 and 4-31.

If voltage E ₁₀Temperature characterisitic be zero or positive, do not wish that so it surpasses 0.06, thereby sample 4-18 should not be as varistor to 4-23 and 4-30.

Sample 4-25 owing to reoxidize handles and by integral insulation, and can not be as varistor work.In addition, because 4-24 and 4-26 comprise too much Ca, their varistor voltage E ₁₀High especially, thereby be difficult to control.

Though the E of sample 4-13,4-14 and 4-32 ₁₀Characteristic be not higher than 0.06, but since contained Ca too much or very little, they are to varistor voltage E ₁₀Non linear coefficient α low, thereby also bad.

So, because varistor voltage E ₁₀Temperature characterisitic be not higher than 0.06, and to varistor voltage E ₁₀Factor alpha not low, so sample 4-1 is preferred to 4-12.This is corresponding to the mole ratios of determined A part in the claim 54.In this scope, in being 360 ℃ thermal shock test, the soldering iron temperature do not have heat cracks to take place, and and then, in being 400 ℃ thermal shock test, the soldering iron temperature do not have heat cracks to take place yet.

In addition, its voltage E ₁₀Temperature characterisitic not to be higher than 0.02 sample 4-1 be better to 4-7 in the present invention.This is corresponding to the mole ratios of determined A part in the claim 55.Particularly, sample 4-4 has voltage E ₁₀Temperature characterisitic and the balance of non linear coefficient α the best, so near the mole ratios of A part composition this sample is best in the present invention.

Example 4-2

What will carry out among the example 4-2 is, relatively by changing the sample that amount obtained of semiconductor transformation agent.

Fix other parameter, such as the milling time after the roasting, the density of shaped-article, the mole ratios of A part, a based semiconductor agent, total A/B, and SiO ₂Molar percent, carry out with example 4-1 in similarly be provided with, different is the molar percent of setting the semiconductor transformation agent as shown in table 4-2, produces sample, its measurement is similar to the measurement among the example 4-1.The results are shown in table 4-2.

The amount of semiconductor transformation agent influences the heat-resisting cracking of varistor pottery.Because the semiconductor transformation agent of sample 4-33 and 4-39 is respectively very little and too many, in the soldering iron temperature is 360 ℃ test, heat cracks has taken place, thereby these not preferred.Thereby, in the soldering iron temperature is 360 ℃ test, heat cracks does not take place, and cross-breaking strength is not less than 18kgf/mm ²Sample 4-4 and 4-34 be preferred among the present invention to 4-38.This is corresponding to the molar percent of determined semiconductor transformation agent in the claim 54.

Because sample 4-38 in the soldering iron temperature is 400 ℃ test heat cracks has taken place, and sample 4-4 and 4-34 that be full of cracks takes place in this heat cracks of 400 ℃ test are more preferred among the present invention to 4-37.This is corresponding to the molar percent of determined semiconductor transformation agent in the claim 57.In addition, near the molar percent the molar percent of the semiconductor transformation agent of sample 4-4 is best in the present invention.

Example 4-3

What will carry out among the example 4-3 is relatively to change the sample of the type of semiconductor transformation agent.

Fix other parameter, such as the milling time after the roasting, the density of shaped-article, the mole ratios of A part, the molar percent of semiconductor transformation agent, total A/B, and SiO ₂Molar percent, and carry out with example 4-1 in similarly be provided with, different is the type that changes the semiconductor transformation agent as shown in table 4-3, produces sample, its measurement is similar to the measurement among the example 4-1.The results are shown in table 4-3.

All samples 4-4 and 4-40 be to 4-56, do not have heat cracks to take place in the soldering iron temperature is the test of 360 ℃ and 400 ℃, and cross-breaking strength is not less than 18kgf/mm ²Thereby, use NbO among the present invention _5/2, TaO _5/2, YO _3/2, LaO _3/2, CeO ₂, PrO _11/6, NdO _3/2, SmO _3/2, EuO _3/2, GdO _3/2, TbO _7/4, DyO _3/2, HoO _3/2, ErO _3/2, TmO _3/2, YbO _3/2, LuO _3/2Or NbO _5/2+ YO _3/2(waiting mole number) agent is preferred as semiconductor transformation.This is corresponding to the type of the semiconductor transformation agent of determining in the claim 54.

Example 4-4

What will carry out among the example 4-4 is relatively to change total sample that A/B obtained.

Fix other parameter, such as the milling time after the roasting, the density of shaped-article, the mole ratios of A part, the molar percent of semiconductor transformation agent and type, and SiO ₂Molar percent, and carry out with example 4-1 in similarly be provided with, different is to change total A/B as shown in table 4-4, produces sample, its measurement is similar to example 4-1.The results are shown in table 4-4.

The sintering degree of total A/B value influence pottery.Total A/B of sample 4-57 and 4-63 is respectively too little and too big because they can not sintering pottery accurately, and reoxidize to handle and make it integral insulation, so they can not be as varistor work.And, heat cracks when being 360 ℃, the soldering iron temperature takes place.

As show shown in the 4-4, at SiO ₂Amount less and add in the scope of a large amount of semiconductor transformation agent, in order to keep heat-resisting cracking, the upper limit of must special control total A/B.If total A/B surpasses 1.16, begin to take place heat cracks at 360 ℃, and if total A/B surpass 1.01, then begin to take place heat cracks at 400 ℃.

In other words, sample 4-4 and 4-58 be to 4-62, because the soldering iron temperature is in 360 ℃ the test heat cracks not to take place, and cross-breaking strength is not less than 18kgf/mm ², be preferred among the present invention.This is corresponding to determined total A/B in the claim 54.

In addition, sample 4-4 and 4-59 be to 4-61, because the soldering iron temperature is in 400 ℃ the test heat cracks not to take place, is better preferred among the present invention.This is corresponding to determined total A/B in the claim 56.In addition, as among the sample 4-4, near total A/B that the composition of its B part is many slightly the optimum range among the present invention.

Example 4-5

What will carry out among the example 4-5 is relatively to change SiO ₂The sample that molar percent obtained.

Fix other parameter, such as the milling time after the roasting, the density of shaped-article, the mole ratios of A part, the molar percent of semiconductor transformation agent and type, and total A/B, and carry out with example 4-1 in similarly be provided with, different is to change SiO as shown in table 4-5 ₂Molar percent, produce sample, its measurement is similar to example 4-1.Soldering iron temperature in the heat cracks test is three types a temperature, promptly 360 ℃, 400 ℃ and 450 ℃.The results are shown in table 4-5.

Because sample 4-68 and 4-69 have too many SiO ₂, in the soldering iron temperature is 360 ℃ test heat cracks takes place promptly, so be not preferred.So sample 4-4 and 4-64 be to 4-67, in the soldering iron temperature is the test of 360 ℃ and 400 ℃, heat cracks does not take place, and cross-breaking strength is not less than 18kgf/mm ²So, be preferred among the present invention.This is corresponding to the determined SiO in the claim 54 ₂Molar percent.

Because in the soldering iron temperature is among the sample 4-67 heat cracks to take place in 450 ℃ the test, and sample 4-4 and 4-64 be to 4-66, even in the soldering iron temperature is 450 ℃ test heat cracks does not take place yet, be among the present invention better not preferably.This is corresponding to the determined SiO-in the claim 50 ₂Molar percent.In addition, near the SiO sample 4-4 ₂Molar percent be the best among the present invention.Though SiO among the sample 4-64 ₂Nominally batching be zero, in fact, SiO- ₂Be included in each raw material as impurity, thereby SiO among the sample 4-63 ₂Actual content do not have vanishing.

Example 4-6

What will carry out among the example 4-6 is relatively to have changed the sample of the kind and the amount of additive.Fix other parameter, such as the milling time after the roasting, the density of shaped-article, the mole ratios of A part, the molar percent of semiconductor transformation agent and type, total A/B, and SiO ₂Molar percent, and carry out with example 4-1 in similarly be provided with, different is kind and the amount that changes additive as shown in table 4-6, produces sample, its measurement is similar to example 4-1.The results are shown in table 4-6.

Additive has the voltage E of adjusting such as varistor ₁₀And the effect of these electrology characteristics of non linear coefficient α.Mn has amplified the voltage E of varistor ₁₀And non linear coefficient α, and Co has amplified the voltage E of varistor ₁₀Find that in addition Mo and W have the effect of amplifying non linear coefficient α.Though do not illustrate among the table 4-6, find other element, such as Li, Na, Ni, Cu, Zn, Sc, Fe, Ga, In also has similar effect.

Because the dosage of sample 4-74 and 4-78 is too big, the sintering degree is hindered, and makes ceramic insulation and reoxidize to handle.Thereby each additive is not more than 1.00 to the molar percent of principal component, and cross-breaking strength is not less than 18kgf/mm ²Sample 4-70 to 4-73,4-75 to 4-80, is the preferred person among the present invention to 4-77 and 4-79.This is included in the kind and molar percent of the additive of defined in the claim 59.

Example 4-7

What will carry out among the example 4-7 is relatively to change roasting milling time afterwards, the specific area of each particle after promptly grinding, and the sample that changes over the density of shaped object.

Fix other parameter, such as the mole ratios of A part, the molar percent of semiconductor transformation agent and type, total A/B, and SiO ₂Molar percent, and carry out with example 4-1 in similarly be provided with, different is to change the condition of grinding and being shaped as shown in table 4-7, produces sample, its measurement is similar to example 4-1.The results are shown in table 4-7.

Table 4-7

Good: good

No Good: bad,

None: do not have

About the mark of forming, the content of SrO is expressed as a gram molecule, and the content of BaO is expressed as the b gram molecule, and the content of CaO is expressed as c gram molecule, TiO ₂Content be expressed as d gram molecule, NbO _5/2Content be expressed as the f gram molecule, and SiO ₂Content be expressed as the g gram molecule.Composition is fixed as a/ (a+b+c)=0.35, b/ (a+b+c)=0.35, and c/ (a+b+c)=0.30, f/d * 100=3.00, (a+b+c)/(d+f)=1.16, and g/d * 100=0.30 is to produce sample.

In each sample of this example, total A/B has bigger composition, is 1.16.

To 4-85,, make that the density p g of shaped-article is 2.60g/cm at sample 4-81 by changing after the roasting milling time 1 to 100 hour ³Be lower than common density.The specific area of the particle after the grinding is changed to 0.53 to 10.43m ²/ g.In these samples, cross-breaking strength is less than 18kgf/mm ², and heat cracks has taken place in the test of 360 ℃ of soldering iron temperature and 400 ℃ °.This may be the low-density ρ g owing to shaped-article, and the density of the agglomerate bodies behind the sintering significantly is reduced to and is lower than 4.66g/cm ³, and can not obtain enough bending strengths.

To 4-89, make the density p g of each shaped-article become common 2.80g/cm at sample 4-86 ³, and the specific area of each particle is changed to 0.53 to 7.29m after grinding ²/ g.Though guaranteed bending strength in these samples, made cross-breaking strength substantially exceed 18kgf/mm ², but heat cracks has taken place in the test of 360 ℃ of soldering iron temperature and 400 ℃ °.Owing to need 50 hours milling time, from making the viewpoint of efficient, sample 4-89 is not preferred.

To 4-96, make the density p g of each shaped-article become 3.00g/cm at sample 4-90 ³, and the specific area of each particle is changed to 0.23 to 10.43m after grinding ²/ g.In these samples, because cross-breaking strength substantially exceeds 18kgf/mm ², guaranteed bending strength.And except sample 4-90 and 4-96, in the test of 360 ℃ of soldering iron temperature and 400 ℃ ° heat cracks does not take place.Sample 4-95 and 4-96 are not preferred owing to need 50 hours milling time from the viewpoint of making efficient.

To 4-101, make the density p g of each shaped-article become common 3.20g/cm at sample 4-97 ³, and the specific area of each particle is changed to 0.23 to 7.29m after grinding ²/ g.In these samples, because cross-breaking strength substantially exceeds 18kgf/mm ², guaranteed bending strength.And except sample 4-97, in the test of 360 ℃ of soldering iron temperature and 400 ℃ ° heat cracks does not take place.Sample 4-101 is not preferred owing to need 50 hours milling time from the viewpoint of making efficient.

To 4-106, make the density p g of each shaped-article become common 3.40g/cm at sample 4-102 ³, and the specific area of each particle is changed to 0.23 to 7.29m after grinding ²/ g.In these samples, because cross-breaking strength substantially exceeds 18kgf/mm ², guaranteed bending strength.And except sample 4-102, in the test of 360 ℃ of soldering iron temperature and 400 ℃ ° heat cracks does not take place.Sample 4-106 is not preferred owing to need 50 hours milling time from the viewpoint of making efficient.

To 4-111, make the density p g of each shaped-article become 3.60g/cm at sample 4-107 ³, and the specific area of each particle is changed to 0.53 to 10.43m after grinding ²/ g.In these samples, because cross-breaking strength substantially exceeds 18kgf/mm ², guaranteed bending strength.And except sample 4-111, in the test of 360 ℃ of soldering iron temperature and 400 ℃ ° heat cracks does not take place.Yet, these samples 4-107 to 4-111 since for the density that makes shaped-article be 3.60g/cm ³, significantly reduce the life-span of mould, so be not preferred.

So, make the specific area that grinds each particle of back can become 0.53 to 4.52m by grinding ²Between/the g, comprise two ends, and the density that makes shaped-article is 2.80 and 3.40g/cm ³Between, comprise two ends, can obtain enough bending strengths of sintered ceramic and resistance to sudden heating.In addition, can avoid making inefficient inconvenience such as making because of milling time is oversize, and owing to the shortening of former and die life increases maintenance cost.

In addition, in this example, though the scope of specific area is 0.53 to 4.52m ²/ g, but the error range in order to consider that specific area is measured, preferred range is 0.5 to 5.0m among the present invention ²/ g.This is corresponding to claim 52 and 53.

Example 4-8

What will carry out among the example 4-8 is relatively to change roasting milling time afterwards, the specific area of each particle after promptly grinding, and the sample that changes over the density of shaped object.

Fix other parameter, such as the mole ratios of A part, the molar percent of semiconductor transformation agent and type, total A/B, and SiO ₂Molar percent, and carry out with example 4-1 in similarly be provided with, different is to change the condition of grinding and being shaped as shown in table 4-8, produces sample, its measurement is similar to example 4-1.The results are shown in table 4-8.

Table 4-8

Good: good

No Good: bad

None: do not have

About the mark of forming, the content of SrO is expressed as a gram molecule, and the content of BaO is expressed as the b gram molecule, and the content of CaO is expressed as c gram molecule, TiO ₂Content be expressed as d gram molecule, NbO _5/2Content be expressed as the f gram molecule, and SiO ₂Content be expressed as the g gram molecule.Composition is fixed as a/ (a+b+c)=0.35, b/ (a+b+c)=0.35, and c/ (a+b+c)=0.30, f/d * 100=3.00, (a+b+c)/(d+f)=0.98, and g/d * 100=0.20 is to produce sample.

Each sample has improved composition among this routine 4-8, and total A/B is 0.98, and this composition than the sample among the example 4-7 is quite low.And SiO ₂Molar percent be 0.2, be lower than the molar percent of sample among the example 4-7.

To 4-116,, make that the density p g of shaped-article is 2.60g/cm at sample 4-112 by changing after the roasting milling time 1 to 100 hour ³Be lower than common density.The specific area of each particle after the grinding is changed to 0.52 to 11.06m ²/ g.In these samples, cross-breaking strength is at 18kgf/mm ²Near, and heat cracks has taken place in the test of 360 ℃ of soldering iron temperature and 400 ℃ °.This may be the low-density ρ g owing to shaped-article, and the density of the agglomerate bodies behind the sintering significantly is reduced to and is lower than 4.70g/cm ³, and can not obtain enough bending strengths.

In 4-120, make the density p g of each shaped-article become common 2.80g/cm at sample 4-117 ³, and the specific area of each particle is changed to 0.52 to 7.26m after grinding ²/ g.Guaranteed bending strength in these samples, made cross-breaking strength substantially exceed 18kgf/mm ², and even heat cracks does not take place yet in the test of 360 ℃ of soldering iron temperature and 400 ℃ °.Yet owing to need 50 hours milling time, from making the viewpoint of efficient, sample 4-120 is not preferred.

In 4-127, make the density p g of each shaped-article become 3.00g/cm at sample 4-121 ³, and the specific area of each particle is changed to 0.30 to 11.06m after grinding ²/ g.In these samples, because cross-breaking strength substantially exceeds 18kgf/mm ², guaranteed bending strength.And, heat cracks does not take place in the test of 360 ℃ of soldering iron temperature and 400 ℃ °.Yet sample 4-126 and 4-127 are not preferred owing to need 50 hours milling time from the viewpoint of making efficient.

To 4-132, make the density p g of each shaped-article become common 3.20g/cm at sample 4-128 ³, and the specific area of each particle is changed to 0.30 to 7.26m after grinding ²/ g.In these samples, because cross-breaking strength substantially exceeds 18kgf/mm ², guaranteed bending strength.And, heat cracks does not take place in the test of 360 ℃ of soldering iron temperature and 400 ℃ °.Sample 4-132 is not preferred owing to need 50 hours milling time from the viewpoint of making efficient.

In 4-137, make the density p g of each shaped-article become common 3.40g/cm at sample 4-133 ³, and the specific area of each particle is changed to 0.30 to 7.26m after grinding ²/ g.In these samples, because cross-breaking strength substantially exceeds 18kgf/mm ², guaranteed bending strength.And in the test of 360 ℃ of soldering iron temperature and 400 ℃ ° heat cracks does not take place.Sample 4-137 is not preferred owing to need 50 hours milling time from the viewpoint of making efficient.

In 4-142, make the density p g of each shaped-article become 3.60g/cm at sample 4-138 ³, and the specific area of each particle is changed to 0.52 to 11.06m after grinding ²/ g.In these samples, because cross-breaking strength substantially exceeds 18kgf/mm ², guaranteed bending strength.And, heat cracks does not take place in the test of 360 ℃ of soldering iron temperature and 400 ℃ °.Yet, these samples 4-138 to 4-142 since for the density that makes shaped-article be 3.60g/cm ³, significantly reduce the life-span of mould, so be not preferred.

So, make the specific area that grinds each particle of back can become 0.52 to 4.83 m by grinding ²Between/the g, comprise two ends, and the density that makes shaped-article is 2.80 and 3.40g/cm ³Between, comprise two ends, can obtain enough bending strengths of sintered ceramic and resistance to sudden heating.In addition, can avoid making inefficient inconvenience such as making because of milling time is oversize, and owing to the shortening of former and die life increases maintenance cost.

In addition, in this example, though the scope of specific area is 0.52 to 4.83m ²/ g, but the error range in order to consider that specific area is measured, preferred range is 0.5 to 5.0m among the present invention ²/ g.This is corresponding to claim 52 and 53.

According to above table 4-1 to 4-8, as long as the composition of each composition, milling time after content and the roasting, specific area after promptly grinding, and the density of each shaped-article of each composition is in scope of the present invention, a kind of manufacture method that obtains based varistor just can be provided, and this pottery has above-mentioned cross-breaking strength preferred range, and outstanding resistance to sudden heating is being arranged.

Do not deviating under the spirit and scope of the present invention situation, can construct many embodiment that has nothing in common with each other of the present invention and example.Be to be understood that, except claims definition, the invention is not restricted to specific embodiment and example described in the specification.

Claims

1. thyrite device that comprises the composite perofskite based semiconductor ceramics, this composite perofskite based semiconductor ceramics comprises first composition of being made up of the oxide of Sr, Ba, Ca and Ti; Second composition and ternary at least one composition, the oxide that described second composition is selected by the oxide of at least a R from expression Y and lanthanide series is formed, and described the 3rd composition is made up of the oxide of the oxide selection of at least a M from expression Nb and Ta; And the four-component of forming by the oxide of Si, described pottery does not contain Mg, and has such composition 0.10≤a/ (a+b+c)≤0.40,0.30≤b/ (a+b+c)≤0.50,0.20＜c/ (a+b+c)≤0.50,0.84≤(a+b+c+e)/(d+f)≤1.16,1.0≤(e+f)/d * 100≤10.0, and g/d * 100≤0.6, wherein a is the mole number that the Sr of described first composition is calculated as SrO, b is the mole number that the Ba of described first composition is calculated as BaO, and c is the mole number that the Ca to described first composition calculates as CaO, and d is that Ti to described first composition is as TiO ₂The mole number that calculates, e are that R to described second composition is respectively as YO _3/2, CeO ₂, PrO _11/6, TbO _7/4And the RO of other lanthanide series of expression _3/2The mole number that calculates, f is as NbO to described ternary M _5/2And TaO _5/2The mole number of Ji Suaning respectively, g are that Si to described four-component is as SiO ₂The mole number that calculates.

2. thyrite device as claimed in claim 1, wherein said first composition consist of 0.30≤a/ (a+b+c)≤0.40,0.30≤b/ (a+b+c)≤0.40 and 0.25≤c/ (a+b+c)≤0.35.

3. thyrite device as claimed in claim 1, wherein said first composition and described second and ternary described at least one composition consist of 0.96≤(a+b+c+e)/(d+f)≤1.01.

4. thyrite device as claimed in claim 1, wherein said second and ternary described at least one composition consist of 1.0≤(e+f)/d * 100≤4.0.

5. thyrite device as claimed in claim 1, wherein said four-component consist of g/d * 100≤0.3.

6. thyrite device as claimed in claim 1, wherein said pottery also comprise one the fifty percentth minute, by Li, Na, Mn, Co, Ni, Cu, Zn, Sc, Fe, Ga, In, at least a oxide of selecting in the oxide of Mo and W is formed, and wherein said the fifty percentth minute composition is 0＜h/d * 100≤1.000, wherein h is for described the fifty percentth minute content Li, Na, Mn, Co, Ni, Cu, Zn, Sc, Fe, Ga, In, Mo and W are as LiO _1/2, NaO _1/2, MnO, CoO _4/3, NiO, CuO, ZnO, ScO _3/2, FeO _3/2, GaO _3/2, InO _3/2, MoO ₃And WO ₃And the mole number that calculates.

7. thyrite device as claimed in claim 1, wherein said resistor comprise the electrode that forms at least one surface of described pottery, and wherein said electrode is made up of Cu or the main material of being made by Cu.

8. thyrite device as claimed in claim 7, wherein said electrode is by the Cu alloy composition.

9. thyrite device as claimed in claim 7, wherein said electrode is made up of the Cu that comprises frit.