TWI406304B - Semiconductor porcelain composition and method of manufacturing the same - Google Patents

Abstract

The semiconductor ceramic composition provided by this invention contains no Pb, and is capable of shifting the Curie temperature to positive direction as well as obtaining an excellent jump characteristic while suppressing the increase of room-temperature resistivity to a minimum value. The semiconductor ceramic composition is obtained by sintering a mixed calcined powder consisting of BT calcined powder and BNT calcined powder, where the BT calcined powder is formed from (BaR)TiO3 or Ba(TiM)O3 (wherein each of R and M are semiconductive elements) that are composed of residual BaCO3 and TiO2 in the calcined power; and the BNT calcined powder is formed from (BiNa)TiO3 calcined powder, in which a portion of Ba in BaTiO3 is substituted by Bi-Na.

Description

Semiconductor porcelain composition and method of manufacturing same

The present invention relates to a semiconductor porcelain composition having a positive resistance temperature, such as a PTC thermistor, a PTC heater, a PTC switch, a temperature detector, and the like.

Conventionally, as a material exhibiting PTCR characteristics (Positive Temperature Coefficient of Resistivity), a composition in which various semiconductor elements are added to BaTiO ₃ has been proposed. The Curie temperature of the compositions is around 120 °C. In addition, the compositions must be shifted in accordance with the use of the Curie temperature.

For example, it is proposed to shift the Curie temperature by adding SrTiO _{3 to} BaTiO ₃ , but in this case, the Curie temperature is only shifted in the negative direction and there is no offset in the positive direction. At present, an additive element which shifts the Curie temperature in the positive direction is known as PbTiO ₃ . However, since PbTiO ₃ contains an element which causes environmental pollution, a material which does not use PbTiO ₃ is desired in recent years.

Based on BaTiO ₃ semiconductor porcelain, preventing caused by Pb substitution decreased temperature coefficient of resistance, and a reduced voltage dependence of the circumstances to enhance the productivity and reliability of the object and the like, it has been proposed without the use of PbTiO _3, and the portion ₃ BaTiO Ba is a Ba _1-2x (BiNa) _x TiO ₃ structure substituted with Bi-Na, and any one or a combination of Nb, Ta or rare earth elements is added to the composition in which x is set to 0<x≦0.15. In the above, a method of producing a BaTiO ₃ -based semiconductor ceramic which is subjected to heat treatment in an oxidizing atmosphere after sintering in nitrogen (Patent Document 1).

Patent Document 1: Japanese Patent Laid-Open No. 56-169301

The larger characteristic of the PTC material is that the specific resistance of the PTC material will increase sharply at the Curie point (jump characteristic = resistance temperature coefficient α), which is considered to be due to the resistance formed by the grain boundary (due to the Schottky barrier) The resulting resistance) is caused by an increase. As a characteristic of the PTC material, the jump characteristic of the specific resistance value is required to be high.

In Patent Document 1, the examples disclose a composition in which Nd ₂ O ₃ (0.1 mol%) is added as a semiconductor element, but when the valence control of the composition is performed, trivalent cations are used as a semiconductor. When an element is added, the effect of semiconductorization is lowered by the presence of monovalent Na ions. Therefore, there is a problem that the specific resistance at room temperature is increased.

As described above, in the PTC material which does not contain Pb disclosed in Patent Document 1, the jump characteristics are excellent, and the room temperature specific resistance is high, and the portion having poor jump characteristics tends to excessively decrease the room temperature specific resistance, and there is a possibility that both of them cannot be balanced. Stable room temperature specific resistance and excellent jumping characteristics. Further, in the portion where the jump characteristics are poor, when a current flows through the material, there is a problem that the temperature fluctuation in the vicinity of the Curie point becomes large, and there is a tendency that the stable temperature is higher than the Curie point.

In order to suppress the fluctuation of the stable temperature, it is necessary to improve the material design, and it is necessary to increase the jump characteristics. In this case, it is conceivable to slightly increase the room temperature specific resistance, but in consideration of the maintenance of the high jump characteristic and the suppression of the increase in the specific resistance at room temperature, It is very difficult, and it is usually trapped at room temperature than when the resistance is excessively increased and exceeds the range of use.

Further, in Patent Document 1, the examples disclose that all elements constituting a composition such as BaCO ₃ , TiO ₂ , Bi ₂ O ₃ , Na ₂ O ₃ , and PbO of a starting material are mixed before calcination, and are carried out. Calcination, forming, sintering, heat treatment, and a composition in which a portion Ba of BaTiO ₃ is substituted with Bi-Na, if all the elements constituting the composition are mixed before calcination, in the calcination step, Bi will be volatilized. The Bi-Na composition is deviated, which promotes the generation of heterogeneous phases, increases the resistivity at room temperature, and causes problems such as changes in the Curie temperature.

In order to suppress the volatilization of Bi, it is considered that calcination is performed at a relatively low temperature, but the volatilization of Bi is suppressed, but there is a problem that a complete solid solution cannot be formed and the desired characteristics cannot be obtained.

An object of the present invention is to provide a semiconductor ceramic composition which does not contain Pb, can shift the Curie temperature in the positive direction, and can obtain a high jump characteristic when the room temperature ratio is increased to the minimum limit.

Further, an object of the present invention is to provide a semiconductor porcelain composition and a method for producing the same, which is a semiconductor ceramic composition in which a portion Ba of BaTiO ₃ is substituted with Bi-Na, which suppresses Bi-dispersion in a calcination step and prevents Bi- The compositional variation of Na suppresses the generation of a heterogeneous phase, and the resistivity at room temperature can be further lowered, and the Curie temperature fluctuation can be suppressed.

In order to achieve the above object, the inventors have found through intensive studies that when a semiconductor ceramic composition in which a portion Ba of BaTiO ₃ is substituted with Bi-Na is produced, (BaR)TiO ₃ calcined powder or Ba is separately prepared. (TiM)O ₃ calcined powder (hereinafter referred to as "BT calcined powder"), and (BiNa)TiO ₃ calcined powder (hereinafter referred to as "BNT calcined powder"), and the BT calcined powder and BNT calcined powder By performing calcination at respective appropriate temperatures, it is possible to suppress Bi volatilization of the BNT calcined powder, prevent compositional variation of Bi-Na and suppress generation of heterogeneous phase, and mix and form and calcine the calcined powder. A semiconductor ceramic composition having a low electrical resistivity at room temperature and suppressing changes in the Curie temperature can be obtained.

Furthermore, the inventors have found that, in preparation of the BT calcined powder, BaCO ₃ and TiO ₂ remaining in the calcined powder are prepared, and the BT calcined powder is mixed with the BNT calcined powder and then sintered. The amount of formation of the Schottky barrier can be increased. With the increase in the amount of Schottky barrier formation, the jump characteristics can be improved by suppressing the rise in the room temperature ratio resistance to the minimum limit, and the present invention has been completed.

The semiconductor porcelain composition of the present invention is obtained by calcining BT formed of (BaR)TiO ₃ or Ba(TiM)O ₃ (R and M-based semiconductor elements) obtained by leaving a part of BaCO ₃ and TiO ₂ in the calcined powder. The powder and the mixed calcined powder of the BNT calcined powder formed of the (BiNa)TiO ₃ calcined powder are sintered, and the part Ba of BaTiO ₃ is substituted with Bi-Na.

The present invention is directed to the semiconductor ceramic composition of the above composition, and the BaCO ₃ and TiO ₂ content in the BT calcined powder is proposed to be (BaR)TiO ₃ or Ba(TiM)O ₃ with BaCO ₃ and TiO _{2 .} When the total amount is 100 mol%, BaCO ₃ is 30 mol% or less, TiO ₂ is 30 mol% or less, and at least one of the semiconductor element R-based rare earth elements is used as (BaR)TiO ₃ calcined powder. In the case of BT calcined powder, the composition formula of the semiconductor porcelain composition is expressed by [(BiNa) _x (Ba _1-y R _y ) _1-x ]TiO ₃ , and x, y is 0 < x ≦ 0.3, 0 < y ≦ 0.02; at least one of the semiconductor element M is Nb or Sb, and when Ba(TiM)O ₃ calcined powder is used as the BT calcined powder, the composition formula of the semiconductor porcelain composition depends on [(BiNa) _x Ba _1-x ] [ Ti _1-z M _z ]O ₃ represents, and x and z are 0<x≦0.3, 0<z≦0.005.

Further, the method for producing a semiconductor ceramic composition of the present invention is a method for producing a semiconductor ceramic composition in which a portion Ba of BaTiO ₃ is substituted with Bi-Na, and includes: preparing a portion of BaCO ₃ remaining in the calcined powder and TiO ₂ is (BaR) TiO ₃ or Ba (TiM) O ₃ (R and M based semiconductor elements) the step of BT calcined powder composed of; preparing step BNT calcined powder of the (BiNa) TiO ₃ calcined powder consisting of a step of mixing the BT calcined powder with the BNT calcined powder to prepare a mixed calcined powder, and a step of forming and sintering the mixed calcined powder.

In the method for producing a semiconductor ceramic composition having the above-described configuration, it is proposed that in the step of preparing the BT calcined powder, the calcination temperature is 900 ° C or lower; in the step of preparing the BNT calcined powder, the calcination temperature is 700 ° C. 950 ° C; BaCO ₃ and TiO ₂ content in the BT calcined powder is when the total of (BaR)TiO ₃ or Ba(TiM)O ₃ , BaCO ₃ and TiO ₂ is set to 100 mol %, BaCO ₃ is 30 mol% or less, TiO ₂ is 30 mol% or less; in the step of preparing BT calcined powder or the step of preparing BNT calcined powder, or in two steps, before the calcination, Si oxide is 3.0 mol% or less, And a Ca carbonate or Ca oxide of 4.0 mol% or less; in the step of mixing the BT calcined powder with the BNT calcined powder to prepare a mixed calcined powder, adding Si oxide of 3.0 mol% or less, and Ca carbonate or Ca oxidation 4.0 mol% or less; at least one of the semiconductor element R-based rare earth element, when (BaR)TiO ₃ calcined powder is used as the BT calcined powder, the composition formula of the semiconductor porcelain composition depends on [(BiNa) _x (Ba _{1 -y} R _y ) _1-x ]TiO ₃ represents that x and y are 0<x≦0.3, 0<y≦0.02; the semiconductor element M is Nb, Sb In at least one of the following, when Ba(TiM)O ₃ calcined powder is used as the BT calcined powder, the composition formula of the semiconductor porcelain composition is expressed by [(BiNa) _x Ba _1-x ][Ti _1-z M _z ]O ₃ , x, z are 0 < x ≦ 0.3, 0 < z ≦ 0.005.

According to the present invention, it is possible to provide a semiconductor-ceramic composition which does not contain Pb, can shift the Curie temperature in the positive direction, and can attain a higher jumping characteristic under the limit of suppressing the rise of the room temperature specific resistance.

Further, according to the present invention, it is possible to provide a situation in which Bi volatilization in the calcination step is suppressed, a compositional deviation of Bi-Na is prevented to suppress generation of a hetero phase containing Na, and a resistivity at room temperature can be further lowered, and the residence can be suppressed. A semiconductor porcelain composition with a temperature change.

The semiconductor ceramic composition of the present invention is characterized in that BT is calcined by (BaR)TiO ₃ or Ba(TiM)O ₃ (R and M-based semiconductor elements) composed of a part of BaCO ₃ and TiO ₂ remaining in the calcined powder. The powder and the mixed calcined powder of the BNT calcined powder formed of the (BiNa)TiO ₃ calcined powder are sintered.

When the semiconductor ceramic composition of the present invention contains a portion Ba of BaTiO ₃ substituted with Bi-Na, any composition may be employed, and the composition formula is determined to be [(BiNa) _x (Ba _1-y R _y ) _{1 -x} ]TiO ₃ represents (wherein at least one of R-based rare earth elements), x, y is a composition satisfying 0<x≦0.3, 0<y≦0.02, or the composition formula is [(BiNa) _x Ba _1-x ][Ti _1-z M _z ]O ₃ represents (wherein M is at least one of Nb and Sb), and x and z satisfy the composition of 0<x≦0.3 and 0<z≦0.005. In the case where Pb is not used, the Curie temperature is raised, and when the rise in the room temperature specific resistance is suppressed to the minimum limit, high jump characteristics are obtained.

In the above [(BiNa) _x (Ba _1-y R _y ) _1-x ]TiO ₃ composition, x represents a component range of (BiNa), and 0 < x ≦ 0.3 is a preferred range. If x is 0, the Curie temperature cannot be shifted toward the high temperature side. On the other hand, if it exceeds 0.3, the room temperature resistivity will be close to 10 ⁴ Ω cm, which is difficult to apply to a PTC heater or the like, and thus it is preferable to avoid it.

Further, at least one of the R-based rare earth elements is preferably La. In the composition formula, y means a component range of R, and 0 < y 0.02 is a preferred range. If y is 0, the composition cannot be semiconductorized. On the other hand, if it exceeds 0.02, the room temperature resistivity will become large, and thus it is preferable to avoid it. When the y value is changed and the valence is controlled, in the system in which the partial Ba is substituted with Bi-Na, when the valence control of the composition is performed, when the trivalent cation is used as the semiconductor element, it is added. As a result of the semiconductorization, the effect of the monovalent Na ions and the occurrence of Bi volatilization are reduced, and the effect is lowered, and the resistivity at room temperature is increased. Therefore, the better range is 0.002 ≦ y ≦ 0.02. In addition, 0.002 ≦ y 0.02 is 0.2% by mole to 2.0% by mole, expressed as % by mole. In other words, in the above-mentioned Patent Document 1, Nd ₂ O ₃ (0.1 mol%) as a semiconductor element is added, but it is judged that this is not sufficient semiconductorization in terms of PTC use.

In the composition of [(BiNa) _x Ba _1-x ][Ti _1-z M _z ]O ₃ , x represents a component range of (BiNa), and 0<x≦0.3 is a preferred range. If x is 0, the Curie temperature cannot be shifted toward the high temperature side. On the other hand, if it exceeds 0.3, the room temperature resistivity will be close to 10 ⁴ Ω cm, which is difficult to apply to a PTC heater or the like, and thus it is preferable to avoid it.

Further, M is at least one of Nb and Sb, and among them, Nb is preferable. In the composition formula, z means a component range of M, and 0 < z ≦ 0.005 is a preferred range. If z is 0, the valence control cannot be performed, and the composition cannot be semiconductorized. On the other hand, if it exceeds 0.005, the room temperature resistivity will exceed 10 ³ Ω cm, and thus it is preferable to avoid it. Further, the above 0 < z ≦ 0.005 is 0 to 0.5 mol% (not including 0) if expressed in terms of % by mole.

In the case of the above [(BiNa) _x Ba _1-x ][Ti _1-z M _z ]O ₃ composition, in order to perform valence control, Ti is substituted with M element, and at this time, addition of M element (addition amount) 0<z≦0.005) is for the purpose of controlling the valence of the Ti site of the tetravalent element, and thus has [(BiNa) _x (Ba _1-y R _y ) _1-x which can be used as a semiconductor element in comparison with R. In the TiO ₃ composition, the amount of R element (0.002 ≦ y 0.02) is preferably added in an amount to control the valence, and the internal strain of the semiconductor ceramic composition of the present invention can be alleviated.

In the above two compositions of [(BiNa) _x (Ba _1-y R _y ) _1-x ]TiO ₃ and [(BiNa) _x Ba _1-x ][Ti _1-z M _z ]O ₃ , basically The ratio of Bi to Na was set to 1:1. The composition formula can be [[Bi _0.5 Na _0.5 ) _x (Ba _1-y R _y ) _1-x ]TiO ₃ , [(Bi _0.5 Na _0.5 ) _x Ba _1-x ][Ti _1-z M _z ]O ₃ Said. For the reason that the ratio of Bi to Na is substantially 1:1, for example, in the calcination step or the like, Bi is volatilized and the ratio of Bi to Na varies. In other words, the ratio is 1:1 in the case of blending, but it is not 1:1 in the sintered body, and is also included in the present invention.

Hereinafter, an example of a method for producing a semiconductor ceramic composition of the present invention will be described.

In the present invention, in the case of fabricating a semiconductor-porcelain composition in which a portion Ba of BaTiO ₃ is substituted with Bi-Na, BT composed of (BaR)TiO ₃ calcined powder or Ba(TiM)O ₃ calcined powder is prepared separately. a calcined powder, a BNT calcined powder composed of (BiNa)TiO ₃ calcined powder, and a calcination method of the BT calcined powder and the BNT calcined powder at respective appropriate temperatures (hereinafter referred to as "segmented calcination method") .

By using the above-described segmental calcination method, the Bi volatilization of the BNT calcined powder can be suppressed, and the Bi-Na composition deviation can be prevented, and the generation of the heterophase can be suppressed, and the calcined powder can be mixed and formed and sintered. A semiconductor ceramic composition having a low resistivity at room temperature and suppressing Curie temperature fluctuation.

In the above-described segmental calcination method, when preparing the BT calcined powder, BaCO ₃ , TiO ₂ , and a semiconductor element raw material powder (for example, La ₂ O ₃ , Nb ₂ O ₅ ) are mixed to prepare a mixed raw material powder, and then Calcination is carried out, but so far, in order to form a complete single phase, the calcination temperature is carried out in the range of 900 ° C to 1300 ° C. In the present invention, by setting the calcination temperature to be lower than the temperature below 900 ° C, the (BaR)TiO ₃ or Ba(TiM)O ₃ may not be completely formed, and the residual portion in the calcined powder may be partially formed. BaCO ₃ and TiO ₂ .

In the above method, if the calcination temperature exceeds 900 ° C, (BaR)TiO ₃ or Ba(TiM)O _{3 is} excessively formed, and BaCO ₃ and TiO ₂ cannot be left, so that it is preferably avoided. The calcination time is preferably set to 0.5 hours to 10 hours, preferably 2 to 6 hours.

In the present invention, as described above, when the above-mentioned BT calcined powder is prepared by the segmental calcination method, it is important that a part of BaCO ₃ and TiO ₂ remain in the calcined powder. The reason for this is that the semiconductor ceramic composition obtained by substituting the partial Ba of BaTiO ₃ with Bi-Na finally increases the amount of Schottky barrier formation and increases with the amount of Schottky barrier formation. The jump characteristic can be improved by suppressing the rise of the room temperature specific resistance to the minimum limit.

The BT calcined powder composed of (BaR)TiO ₃ or Ba(TiM)O ₃ which retains a part of BaCO ₃ and TiO ₂ in the calcined powder obtained as described above, and the additionally prepared (BiNa)TiO ₃ calcined powder The BNT calcined powder thus formed is mixed, and the mixed calcined powder is subjected to molding and sintering, whereby a semiconductor porcelain composition in which a part Ba of BaTiO ₃ is substituted with Bi-Na is obtained.

The content of BaCO ₃ and TiO ₂ in the BT calcined powder is preferably BaCO ₃ when the total of (BaR)TiO ₃ or Ba(TiM)O ₃ , BaCO ₃ and TiO ₂ is 100 mol%. 30 mol% or less, TiO ₂ contains 30 mol% or less. The room temperature specific resistance and the jump characteristic can be adjusted by changing the content.

When the content of BaCO ₃ and TiO ₂ in the BT calcined powder is changed, in the step of preparing the BT calcined powder, the calcination temperature is changed below 900 ° C, or the calcination time is changed, or the BT calcination is changed. The composition of the powder can be made. Further, in the above BT calcined powder or BNT calcined powder or the mixed calcined powder, for example, calcination is carried out at a temperature exceeding 900 ° C to form a completely single-phase BT calcined powder, or BaCO ₃ powder and TiO ₂ powder are added, The BaCO ₃ and TiO ₂ content in the BT calcined powder can be changed.

The reason why the BaCO ₃ content is 30 mol% or less is more than 30 mol%, and a heterogeneous phase other than BaCO _{3 is} generated, resulting in an increase in room temperature specific resistance. Moreover, CO ₂ gas will be generated in the sintering step, resulting in cracking of the sintered body, and thus it is preferably avoided. The reason why the content of TiO ₂ is set to 30 mol% or less is more than 30 mol%, and a hetero phase other than BaCO _{3 is} generated, resulting in an increase in room temperature specific resistance.

The upper limit of the content of BaCO ₃ and TiO _{2 is} a total of 60 mol% of BaCO ₃ 30 mol%, TiO ₂ 30 mol%, and the lower limit is an amount exceeding 0. When BaCO ₃ exceeds 20 mol%, TiO ₂ It is preferable to avoid a heterogeneous phase other than BaCO ₃ which is less than 10 mol%, resulting in a rise in room temperature specific resistance. The case where TiO ₂ exceeds 20 mol% and BaCO _{3 does not} exceed 10 mol% is also preferably avoided. Therefore, in the case where one of BaCO ₃ or TiO ₂ exceeds 20 mol%, it is preferred to adjust the calcination temperature, the calcination time, the blending composition, and the like in a manner in which the other is up to 10 mol% or more.

Preparing a BNT calcined powder comprising (BiNa)TiO ₃ calcined powder mixed with the above-mentioned residual BaCO ₃ and TiO ₂ BT calcined powder, firstly, the raw material powder of Na ₂ CO ₃ , Bi ₂ O ₃ , TiO _{2 The} mixture was mixed to prepare a mixed raw material powder. At this time, if Bi ₂ O _{3 is} excessively added (for example, more than 5 mol%), a hetero phase is formed during calcination, and the room temperature specific resistance is improved, so that it is preferably avoided.

Next, the above mixed raw material powder is subjected to calcination. The calcination temperature is preferably set in the range of from 700 ° C to 950 ° C. The calcination time is preferably set to 0.5 hours to 10 hours, preferably 2 hours to 6 hours. If the calcination temperature is less than 700 ° C or the calcination time is less than 0.5 hours, the unreacted Na ₂ CO ₃ or NaO formed by decomposition thereof will react with moisture in the environment or when wet mixing is performed. The solvent reacts, causing compositional variations and characteristic changes, and is therefore preferably avoided. Further, if the calcination temperature exceeds 950 ° C or the calcination time exceeds 10 hours, Bi is volatilized, resulting in compositional variation and promoting heterogeneous formation, and thus it is preferably avoided.

By preparing the BT calcined powder and the BNT calcined powder according to the segmental calcination method, it is possible to provide the BNT calcined powder to be calcined at a lower temperature, suppress the volatilization of Bi, prevent the Bi-Na composition deviation from occurring, and suppress the heterogeneous formation containing Na. The resistivity at room temperature can be further reduced, and the semiconductor porcelain composition having a Curie temperature variation can be suppressed.

In the step of preparing the above-mentioned various calcined powders, when the raw material powders are mixed, the pulverization may be carried out in accordance with the particle size of the raw material powder. In addition, the mixing and pulverizing system can adopt wet mixing using pure water, ethanol, and the like. Crush, or dry mix. Any method of crushing, etc., it is best to perform dry mixing. Shredding will prevent compositional deviations. In the above, examples of the raw material powder include BaCO ₃ , Na ₂ CO ₃ , TiO ₂ and the like, but other Ba compounds, Na compounds, and the like may be used.

As described above, the BT calcined powder of the residual portion of BaCO ₃ and TiO ₂ and the BNT calcined powder were separately prepared, and the calcined powder was blended and quantified. The mixing system may be any method such as wet mixing using pure water, ethanol or the like, or dry mixing, and it is preferable to carry out dry mixing to further prevent composition variation. In addition, the particle size of the calcined powder may be blended, and then mixed and then pulverized, or simultaneously mixed and pulverized. The average particle size of the mixed calcined powder after mixing and pulverization is preferably 0.5 μm to 2.5 μm.

The step of preparing the BT calcined powder and/or the step of preparing the BNT calcined powder, or the step of mixing the calcined powder, if: adding: Mo oxide of 3.0 mol% or less, Ca oxide or Ca carbonate of 4.0 mol Below %, the Si oxide suppresses the abnormal growth of the crystal grains, and the resistivity control can be easily performed, and the Ca oxide or the Ca carbonate can improve the sinterability at a low temperature and can control the reducing property, which is preferable. If either of them exceeds the above-defined amount, the composition will not be able to exhibit semiconductorization, and thus it is preferable to avoid it. The addition is preferably carried out before the mixing in each step.

The mixed calcined powder obtained by the step of mixing the BT calcined powder and the BNT calcined powder is formed by a desired forming means. Before the forming, the pulverized powder may be granulated by a granulator as needed. The molded body after molding has a density of preferably 2.5 to 3.5 g/cm ³ .

The sintering system can be carried out in the atmosphere or in a reducing environment or in an inert gas atmosphere of low oxygen concentration, particularly in a nitrogen or argon atmosphere having an oxygen concentration of less than 1%. The sintering temperature is preferably set to 1250 ° C ~ 1350 ° C. The sintering time is preferably set to 1 hour to 10 hours, preferably 2 hours to 6 hours. If any of the better conditions are deviated, the room temperature specific resistance will rise and the jump characteristics will decrease, so it is best avoided.

The other sintering steps are carried out in an environment with a temperature of 1290 ° C to 1350 ° C and an oxygen concentration of less than 1%, (1) depending on the sintering time of less than 4 hours, or (2) by the satisfaction formula: ΔT ≧ 25t (t = Sintering time (hr), ΔT = cooling rate after sintering (°C/hr)) is performed, and then cooling after sintering is performed at a cooling rate satisfying the above formula, whereby the room temperature specific resistance can be maintained. A semiconductor ceramic composition that raises the temperature coefficient of resistance in a high temperature region (above the Curie temperature) in a low state.

[Examples] [Example 1]

Raw material powders of BaCO ₃ , TiO ₂ , and La ₂ O ₃ were prepared, and blended in a manner of (Ba _0.994 La _0.006 )TiO ₃ , and mixed with pure water. The obtained mixed raw material powder was calcined in the air at 500 ° C to 1300 ° C for 4 hours to prepare (BaLa)TiO ₃ calcined powder. The X-ray diffraction pattern of each calcination temperature in the obtained (BaLa)TiO ₃ calcined powder at 500 ° C to 1200 ° C is shown in FIG. 1 . In addition, the lowermost X-ray diffraction pattern in the figure has no mark temperature, but refers to the case of 500 °C.

A raw material powder of Na ₂ CO ₃ , Bi ₂ O ₃ , and TiO ₂ was prepared, and blended so as to be (Bi _0.5 Na _0.5 )TiO ₃ , and mixed in ethanol. The obtained mixed raw material powder was calcined at 800 ° C for 2 hours in the atmosphere to prepare (BiNa)TiO ₃ calcined powder.

The prepared (BaLa)TiO ₃ calcined powder and the (BiNa)TiO ₃ calcined powder were blended in such a manner that the molar ratio was 73:7, and pure water was used as a medium and mixed and pulverized by a ball mill until the calcined powder was mixed. The center particle diameter is 1.0 μm to 2.0 μm, and then dried. PVA was added to the pulverized powder of the mixed calcined powder and mixed, and then granulated by a granulator. The obtained granulated powder was molded by a uniaxial pressing device, and then the formed body was subjected to a debonding agent at 700 ° C, and then sintered in the atmosphere at a sintering temperature of 1290 ° C, 1320 ° C, and 1350 ° C for 4 hours. Sintered body.

The obtained sintered body was processed into a plate shape of 10 mm × 10 mm × 1 mm to prepare a test piece. After forming an ohmic electrode, each test piece was subjected to a specific resistance value from room temperature to 270 ° C using a resistance measuring device. The temperature change is measured. The measurement results are shown in Table 1. In Table 1, the "*" mark next to the sample number means a comparative example. The calcination time of sample No. 28 was 1 hour, the calcination time of sample No. 29 was 2 hours, and the calcination time of sample No. 30 was 6 hours. In addition, in all of the examples, the temperature coefficient of resistance was obtained according to the following formula. α = (InR _{1 -} InR _c ) × 100 / (T _{1 -} T _c ), where R ₁ is the maximum specific resistance, R _c is the specific resistance at T _c , and T ₁ is the temperature of R ₁ , Tc is Curie temperature.

As is apparent from Fig. 1, the (BaLa)TiO ₃ calcined powder calcined at 500 ° C to 900 ° C did not complete the formation of (BaLa)TiO ₃ , but remained BaCO ₃ and TiO ₂ . On the other hand, it was found that the (BaLa)TiO ₃ calcined powder which was calcined at 1000 ° C to 1200 ° C did not contain BaCO ₃ or TiO ₂ but formed a completely single phase of (BaLa)TiO ₃ .

Further, from the measurement results of Table 1, it was found that the calcined temperature was set to 500 ° C to 900 ° C, and the BaBa TiO ₃ calcined powder in which BaCO ₃ and TiO ₂ remained in the calcined powder was used. The semiconductor porcelain composition of the invention is lower than the semiconductor porcelain composition obtained by using the calcined powder having a calcination temperature of 1000 ° C to 1300 ° C and forming a completely single phase of (BaLa)TiO _{3 .} A higher jump characteristic is obtained, and the rise in room temperature specific resistance is also suppressed.

[Embodiment 2]

In addition to Example 1 to prepare the (BaLa) TiO ₃ calcined powder and (BiNa) TiO ₃ calcined powder, by mole ratio became 73: 7 when formulated embodiment, instead of the addition amount shown in Table 2 SiO ₂ with the addition CaCO _3, the rest were the same method as in sample No. 1 of Example 13 for the embodiment, to obtain a sintered body. The temperature change of the specific resistance was measured in the same manner as in Example 1 with respect to the obtained sintered body. The measurement results are shown in Table 2. As is apparent from Table 2, by adding Si oxide, Ca carbonate or Ca oxide in the step, higher jumping characteristics can be obtained as in Example 1, and the increase in room temperature specific resistance is also suppressed.

[Example 3]

The raw material powder of BaCO ₃ , TiO ₂ , and Nb ₂ O ₅ as a main raw material is prepared so as to be Ba(Ti _0.998 Nb _0.002 )O ₃ and mixed with pure water. The obtained mixed raw material powder was calcined in the air at 700 ° C to 900 ° C for 4 hours to prepare Ba (TiNb) O ₃ calcined powder. The obtained Ba(TiNb)O ₃ calcined powder did not completely form Ba(TiNb)O ₃ , but remained BaCO ₃ and TiO ₂ .

A raw material powder of Na ₂ CO ₃ , Bi ₂ O ₃ , and TiO ₂ was prepared and blended so as to be (Bi _0.5 Na _0.5 )TiO ₃ , and mixed in ethanol. The obtained mixed raw material powder was calcined in the air at 800 ° C for 2 hours to prepare (BiNa)TiO ₃ calcined powder.

The preparation of Ba (TiNb) O ₃ calcined powder and (BiNa) TiO ₃ calcined powder, by mole ratio became 73: 7 for the deployment of the embodiment, and in accordance with the same manner as in Example 1 to obtain a sintered body. The obtained sintered body was subjected to the same method as in Example 1 to measure the temperature change of the specific resistance value. The measurement results are shown in Table 3.

From the measurement results of Table 3, it is known that the present invention [(BiNa) is obtained by using Ba(TiNb)O ₃ calcined powder having a calcination temperature of 700 ° C to 900 ° C and residual BaCO ₃ and TiO ₂ in the calcined powder. _x Ba _1-x ][Ti _1-z M _z ]O ₃ semiconductor porcelain composition, which can be like [(BiNa) _x (Ba _1-y R _y ) _1-x ]TiO ₃ semiconductor porcelain of Example 1 The composition obtains a high jump characteristic and also suppresses an increase in room temperature specific resistance.

While the invention has been described with respect to the specific embodiments of the embodiments of the present invention, it will be understood by those skilled in the art.

This application is based on a Japanese patent application filed on Oct. 27, 2006 (Japanese Patent Application No. 2006-293366), and Japanese Patent Application No. 2006-298305 filed on Nov. 1, 2006. The content is also cited in this case.

(industrial availability)

The semiconductor porcelain composition obtained according to the present invention is suitable as a material such as a PTC thermistor, a PTC heater, a PTC switch, a temperature detector or the like.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a view showing an X-ray diffraction pattern of each of calcination temperatures of a (BaLa)TiO ₃ calcined powder of the present invention.

Claims (10)

A semiconductor porcelain composition comprising BT calcined powder formed of (BaR)TiO ₃ or Ba(TiM)O ₃ (R and M-based semiconductor elements) obtained by leaving a portion of BaCO ₃ and TiO _{2 in the} calcined powder, And the mixed calcined powder of the BNT calcined powder formed by the (BiNa)TiO ₃ calcined powder is sintered, and the Ba of the BaTiO ₃ is substituted with Bi-Na; the content of BaCO ₃ and TiO ₂ in the BT calcined powder, When the total of (BaR)TiO ₃ or Ba(TiM)O ₃ and BaCO ₃ and TiO ₂ is 100 mol%, BaCO ₃ is 30 mol% or less, and TiO ₂ is 30 mol% or less. The semiconductor-ceramic composition according to claim 1, wherein at least one of the semiconductor element R-based rare earth elements and the composition of the semiconductor-ceramic composition are used when (BaR)TiO ₃ calcined powder is used as the BT calcined powder. According to [(BiNa) _x (Ba _1-y R _y ) _1-x ]TiO ₃ , x and y are 0<x≦0.3, 0<y≦0.02. The semiconductor-ceramic composition according to claim 1, wherein at least one of the semiconductor element M is Nb or Sb, and when Ba(TiM)O ₃ calcined powder is used as the BT calcined powder, the composition of the semiconductor porcelain composition is used. The formula is represented by [(BiNa) _x Ba _1-x ][Ti _1-z M _z ]O ₃ , and x and z are 0<x≦0.3, 0<z≦0.005. A method for producing a semiconductor porcelain composition by substituting a portion Ba of BaTiO ₃ with Bi-Na, comprising: preparing (BaR)TiO ₃ or Ba from a portion of BaCO ₃ and TiO ₂ remaining in the calcined powder a step of preparing a BT calcined powder composed of (TiM)O ₃ (R and M-based semiconductor elements); preparing a BNT calcined powder composed of (BiNa)TiO ₃ calcined powder; and the above-mentioned BT calcined powder and BNT calcined powder a step of mixing to prepare a mixed calcined powder; and a step of forming and sintering the above mixed calcined powder; wherein the BaCO ₃ and TiO ₂ content in the BT calcined powder is when (BaR)TiO ₃ or Ba (TiM) When the total of O ₃ , BaCO ₃ and TiO ₂ is 100 mol%, BaCO ₃ is 30 mol% or less, and TiO ₂ is 30 mol% or less. The method for producing a semiconductor ceramic composition according to claim 4, wherein in the step of preparing the BT calcined powder, the calcination temperature is 900 ° C or lower. The method for producing a semiconductor ceramic composition according to claim 4, wherein in the step of preparing the BNT calcined powder, the calcination temperature is 700 ° C to 950 ° C. The method for producing a semiconductor ceramic composition according to claim 4, wherein the step of preparing the BT calcined powder or the step of preparing the BNT calcined powder, or the two steps, adding 1.0% of the Si oxide before calcination Hereinafter, the Ca carbonate or Ca oxide is 4.0 mol% or less. The method for producing a semiconductor-ceramic composition according to the fourth aspect of the invention, wherein the step of mixing the BT calcined powder with the BNT calcined powder to prepare the mixed calcined powder, adding 1.0 mol% or less of the Si oxide, and Ca carbonate Or Ca oxide 4.0 mol% or less. The method for producing a semiconductor ceramic composition according to claim 4, wherein at least one of the semiconductor element R-based rare earth elements and the (BaR)TiO ₃ calcined powder is used as the BT calcined powder, the semiconductor ceramic composition is used. The composition formula is represented by [(BiNa) _x (Ba _1-y R _y ) _1-x ]TiO ₃ , and x and y are 0<x≦0.3, 0<y≦0.02. The method for producing a semiconductor ceramic composition according to claim 4, wherein at least one of the semiconductor element M is Nb or Sb, and when Ba(TiM)O ₃ calcined powder is used as the BT calcined powder, the semiconductor porcelain is composed. The composition of the substance is represented by [(BiNa) _x Ba _1-x ][Ti _1-z M _z ]O ₃ , and x and z are 0<x≦0.3, 0<z≦0.005.