JP2001348269A - Zinc oxide ceramic composition, method of producing the same and zinc oxide varistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a zinc oxide ceramic composition useful for producing a zinc oxide varistor which is excellent in electric characteristics, has high reliability against direct current load and surge load and is stable to heat treatment. SOLUTION: The zinc oxide ceramic composition is obtained by adding and mixing a boron oxide-containing synthetic material obtained by adding either one of or two or three kinds of bismuth oxide, antimony oxide and zinc oxide to boron oxide and heat-treating the resulting mixture, bismuth oxide or a bismuth oxide-containing synthetic material, antimony oxide or an antimony oxide-containing synthetic material, a chromium oxide-containing synthetic material obtained by adding either one or two or three kinds of boron oxide, bismuth oxide and antimony oxide to chromium oxide and then heat-treating the resulting mixture, an iron-group oxide selected from cobalt oxide, manganese oxide and nickel oxide and any one of aluminum hydroxide, an aluminum oxide hydrate and an aluminum compound to zinc oxide, then press- forming the resulting mixture into a disk and sintering the disk. Further, a disk-type varistor is obtained by forming electrodes on both surfaces of the disk and attaching a lead wire to each electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit in an electric circuit.
The present invention relates to a porcelain composition for a zinc oxide varistor used for absorption and the like, a method for producing the same, and a zinc oxide varistor.

[0002]

2. Description of the Related Art Zinc oxide varistors form a zinc oxide raw material powder containing zinc oxide, basic additives such as bismuth oxide, cobalt oxide and manganese oxide, and various oxides added for further improving the performance. It is manufactured using a sintered body of a zinc oxide porcelain composition obtained by firing and firing. It is known that the rising voltage of the zinc oxide varistor increases almost in proportion to the number of grain boundaries in the zinc oxide sintered body existing between the electrodes. That is, the rise voltage rises by 3 to 4 volts per grain boundary in the sintered body. Therefore, in order to manufacture a zinc oxide varistor for a high voltage of about 300 to 400 V per 1 mm thickness,
It is necessary to produce a zinc oxide sintered body having ZnO particles having a small average particle diameter of about 4 to 40 μm. Therefore, conventionally, in order to manufacture a zinc oxide varistor for high voltage, a method of suppressing the growth of ZnO particles by adding a grain growth inhibitor of ZnO particles such as Sb ₂ O ₃ has been used. Sb ₂ O ₃ also plays an important role in stabilizing the nonlinear resistance characteristics of zinc oxide varistors.

The rising voltage refers to a voltage between both terminals when a current of 1 mA flows through the varistor, and is expressed as V _{1 mA} . The voltage between both terminals when a current of 1 mA flows through a sample having a thickness of 1 mm is defined as one of the constants of this material, and V _{1 mA}
/ mm. This means a rising voltage per 1 mm thickness of the sample.

[0004]

However, in order to obtain a high-performance, high-performance zinc oxide varistor for high voltage, 1150 ° C.
High sintering temperatures of 1300 ° C. were required. When firing at these high temperatures, evaporation of Bi ₂ O _{3 and the} like is active even in the air. Further, Bi ₂ O ₃ easily reacts with many kinds of substances and easily corrodes many substances such as ceramic materials of furnace materials and containers. In other words, a high sintering temperature causes not only power consumption but also intense scattering of Bi ₂ O _{3 and the} like, and concomitant consumption of furnace materials and containers. Therefore, a lower sintering temperature has been demanded. Also, when the firing temperature is high, the temperature, the heating rate, Bi ₂ O ₃
And Sb ₂ O ₃ have differences in vapor pressure and the like, making it difficult to keep them uniform, and causing problems such as characteristic variations.

[0005] On the other hand, if the firing temperature is lowered with the conventional composition of zinc oxide varistor, sufficient sintering is not performed, and therefore, the rising voltage rapidly increases, and ZnO
And the non-linear resistance characteristics decrease. Further, deterioration due to a power load, a pulse current load, or the like is likely to progress.

When a powder mixture obtained by adding Sb ₂ O ₃ or the like to zinc oxide powder is subjected to pressure molding and sintering, Sb ₂
O ₃ easily sublimates to cover the surface of ZnO particles, and furthermore Sb ₂ O ₃
Reacts with ZnO to suppress the contact between ZnO and ZnO, thereby suppressing the growth of ZnO grains. As a result, high temperatures are required for sufficient sintering. Also, in the sintered body, if the concentration of Sb ₂ O ₃ varies, a part where the grain growth is not promoted and a part where the grain growth is promoted are mixed. It was difficult to manufacture the body. Therefore, it is easy to cause non-uniform quality and lot-to-lot quality variation.

With the basic composition of the porcelain of the zinc oxide varistor
A certain ZnO-Bi_TwoO_ThreeEutectic group with eutectic temperature of 740 ℃
ZnO and Bi_TwoO_Three800 ° C
It reacts and sinters easily even at near temperatures. Properly
Sb in additives_TwoO_ThreeExists and Sb_TwoO_ThreeSublimates at low temperatures
Covering around ZnO, ZnO and Bi _TwoO_ThreeContact between the two
Hinders this reaction, making sintering difficult. And this
Bi_TwoO_ThreeAnd ZnO react to form ZnO-Bi between ZnO-ZnO_TwoO_Three-Sb_TwoO_Threeof
A strong pyrochlore phase film is formed, and further sintering is performed.
Make it go. ZnO-Bi_TwoO_Three-Sb_TwoO_ThreeIn systems, solid phase
Pyrochlore phase is formed and liquid phase Bi_TwoO_ThreePhase formation is impeded
And the progress of liquid phase sintering is delayed. Sb_TwoO_ThreeIs an additive
Things or Sb_TwoO_ThreeCompounds prevent contact between ZnO particles
And a place to form a chemically stable pyrochlore
There is a match. However, Sb_TwoO_ThreeSublimation is suppressed
If the pyrochlore phase film was not formed,
Oxides such as cobalt, manganese, nickel and chromium
When present, these are zinc, antimony oxides and
A spinel phase is formed and Bi is in a liquid phase at a relatively low temperature._TwoO_Three
A phase is generated and the liquid phase sintering of ZnO begins.

In order to generate a Bi ₂ O ₃ phase in a liquid phase at a relatively low temperature and perform a liquid phase sintering of ZnO, a method of adding antimony oxide which suppresses sublimation of Sb ₂ O ₃ is employed. As a result, a sintered body having excellent non-linear resistance characteristics can be obtained at a low temperature, but these zinc oxide varistors have inherent instability.

The excellent electrical characteristics of the zinc oxide varistor include, for example, a small leakage current and a high non-linear resistance index of _{0.1 mA} α _{1 mA} described later. Also, excellent reliability means that when a long-term voltage is applied, when a long-term power load is applied at a high temperature, or when a pulse current is applied,
Matters such as the original electrical characteristics being maintained without a decrease in the electrical characteristics are given.

In the case of a zinc oxide varistor produced by a conventional manufacturing method, 2 to 5 particles are contained in zinc oxide particles as an n-type semiconductor.
There are × 1017 conduction electrons / cm ³ . When aluminum is not added, these conduction electrons are mainly interstitial zinc atoms existing between lattice points located between lattice points of zinc and oxygen atoms of the zinc oxide crystal, so-called interstitial. The electrons of Char Zn are excited. When aluminum is added for the purpose of improving the VI characteristics in a high current region, conduction electrons become excited by interstitial Zn and excited by aluminum. The biggest problem with these zinc oxide varistors is electrical instability. One is that if a DC or AC voltage is continuously applied for a long time, the VI characteristics deteriorate and the current gradually increases. The other one is
When the sintered body of the zinc oxide varistor is subjected to a heat treatment at about 700 ° C., the VI characteristics are rapidly deteriorated, and the leakage current is increased, and in some cases, it may not be practical. The deterioration of these two VI characteristics is caused by the movement of interstitial Zn in the depletion layer generated along the grain boundary of the zinc oxide particles of the sintered body of the zinc oxide varistor.

More specifically, in ZnO particles generated at a high temperature in the atmosphere, interstitial Zn atoms are formed between ZnO crystal lattices, and the interstitial Zn atoms act as donors to supply electrons to the conduction band. Thus, zinc oxide is an n-type semiconductor. It is said that the concentration of interstitial Zn atoms in ZnO decreases as the oxygen partial pressure in the atmosphere increases, and increases as the atmosphere temperature increases. Such ZnO powder Bi ₂ O _3, CoO, etc. was added MnO, when sintered at a high temperature atmosphere and pressure molding, ZnO varistors are obtained having a very high nonlinear resistance characteristics. At the grain boundaries of these sintered bodies, conduction electrons in ZnO on both sides of the grain boundaries are captured by the grain boundaries, so that a depletion layer is formed on both sides of the grain boundaries, preventing electron transfer on both sides of the grain boundaries A barrier is formed. A so-called double Schottky barrier is formed. n−
Since the main electric conduction of the type ZnO semiconductor is conduction electrons generated from interstitial Zn atoms, interstitial Zn atoms having positive charge remain in the depletion layer. Even when no voltage is applied to the sintered body from the outside, a strong electric field is acting in the depletion layer, and the positively charged interstitial Zn atoms in the depletion layer exert an attractive force toward the grain boundary. is recieving. When a voltage is externally applied to such a sintered body,
Since the voltage is applied only to the thin depletion layer, a larger electric field acts in one depletion layer, and the interstitial Zn atoms are relatively easy to move. Move and reach grain boundaries. Then, the positively charged interstitial Zn atoms combine with the negatively charged oxygen atoms to form neutral ZnO. At the same time, the negative charge trapped at the grain boundaries is reduced, so that the barrier that has provided the varistor characteristics is lowered, and the nonlinear resistance characteristics are reduced. As described above, even when a voltage is not externally applied to the sintered body, a strong electric field works in the depletion layer, and the interstitial Zn having a positive charge in the depletion layer.
The atoms are attracted to the grain boundaries. In such a situation, when the element is heated, the interstitial Zn atoms are likely to move due to the heat, and a part of the element moves toward the grain boundary due to the electric field, and has a negative charge at the grain boundary. Combines with oxygen atoms to form neutral ZnO, which reduces the nonlinear resistance characteristics of the varistor. As described above, the semiconductorization of ZnO crystal is mainly brought about by interstitial Zn atoms naturally occurring in the manufacturing process,
Therefore, it was accompanied by electrical instability.

On the other hand, the conversion of ZnO crystal into an n-type semiconductor is as follows.
It was also performed by the addition of Al ₂ O ₃ . In particular, Al ₂ O ₃ was added to improve the current-voltage nonlinear resistance in the high current region. Improvement of the current-voltage nonlinear resistance in the high current region can be achieved by lowering the electric resistance in the ZnO particles. The reduction of the electrical resistance in the ZnO particles was performed by doping Al ₂ O ₃ as a donor of the n − type semiconductor ZnO. When Al ₂ O ₃ is added, the nonlinear resistance characteristics in a high current region are improved, but at the same time, the nonlinear resistance characteristics in a low current region are reduced. Even when Al ₂ O ₃ is added, if there is a positively charged interstitial Zn atom in the depletion layer,
As in the case where Al ₂ O ₃ is not added, there is a problem that the barrier is lowered at the time of voltage application or heat treatment, and the wetting current is increased. As described above, an increase in the current value causes a rise in temperature due to heat generation, and the rise in temperature lowers the non-linear resistance characteristics, further increasing the current, and eventually causing a runaway of the varistor. In particular, when heat treatment is performed for electrode baking or side coating, there is a problem that the non-linear resistance characteristic in a low current region is greatly reduced. 500 ° C to 600 ° C beforehand on the sintered body of ZnO varistor
However, this method has been adopted as a measure against deterioration, but it cannot be said that the instability has been sufficiently eliminated. 50
By performing heat treatment at 0 to 600 ° C, interstitial Zn ions in the depletion layer, which caused the deterioration, are reduced, and as a result, the instability of the IV characteristics is reduced. Has not been reached.

The instability of the electrical characteristics is caused by the movement of the interstitial Zn.
Al is added to the lattice point where Zn atoms come as a donor to reduce Zn.
It was necessary to replace the atoms so that the electrical conduction in the zinc oxide particles was covered by electrons from the Al donor. It seems necessary to maintain zinc oxide at high temperature and high oxygen partial pressure as a method of reducing interstitial Zn. As one of the methods, sintering a zinc oxide varistor under a high oxygen pressure can be considered, but it is difficult to effectively reduce interstitial Zn when the element becomes large.

In order to sinter the zinc oxide varistor in the presence of closed pores having a high oxygen partial pressure, oxygen is generated in the closed sintered body, and boron is formed at a low temperature to form a wettable liquid phase. An attempt was made to add a substance containing. As a result, not only the initial characteristics are excellent, but also AC, DC
A device stable with respect to application and heat treatment was obtained. These devices required a small amount of aluminum to be uniformly doped into the zinc oxide particles to reduce interstitial Zn and instead maintain conduction electrons. Heretofore, attempts have been made to uniformly add aluminum to zinc oxide particles by adding a solution of an aluminum salt at the stage of granulation before forming the zinc oxide mixed powder. According to this method, excellent characteristics can be obtained in a laboratory. However, there is a problem that these methods are not mass-produced. There was a problem that it was difficult to stably mass-produce.

The present invention solves the above problems and provides a zinc oxide porcelain composition for producing a zinc oxide varistor excellent in electrical characteristics such as non-linear resistance characteristics and reliability at low temperature sintering with high yield. And a method of manufacturing the same, and a zinc oxide varistor excellent in electrical characteristics and reliability.

[0016]

In order to achieve the above object,
In other words, efficient and homogeneous aluminum oxide zinc oxide
To obtain a high-performance and highly stable device.
Therefore, the zinc oxide porcelain composition of the present invention contains boron oxide (B
_TwoO_Three) To bismuth oxide (Bi_TwoO_Three) Or antimony oxide
(Sb_TwoO_Three, Or Sb_TwoO_Four, Or Sb_TwoO_Five) Or zinc oxide (Zn
O) or any mixture of these two or three
A boron oxide-containing composition obtained by the treatment and a bismuth oxide
Or bismuth oxide-containing compound and antimony oxide (Sb
_TwoO_Three, Or Sb_TwoO_Four, Or Sb_TwoO_Five) Or containing antimony oxide
Chromium oxide (Cr_TwoO_Three) To boron oxide or acid
Either bismuth oxide or antimony oxide or these
Chromium oxide obtained by subjecting a mixture containing two or three
And at least cobalt oxide (CoO, or C
o_TwoO_ThreeOr Co_ThreeO_Four) And manganese oxide (MnO or MnO)_Two,
Or Mn_TwoO_ThreeOr Mn_ThreeO_Four) And nickel oxide (NiO)
Two or three iron-group oxides and at least hydroxyl
Aluminum (Al (OH) _Three) And aluminum oxide hydrate
(Al_TwoO_Three・ NH_TwoO) and boehmite (AlOOH) and ultrafine aluminum
Na (Al_TwoO_Three) And aluminum salts and aluminum-containing organic
Aluminum oxide selected from zinc oxide (Zn oxide)
O), mixed, molded and fired
It is provided with.

In order to achieve the above object, the present invention
The zinc oxide porcelain composition is different from the zinc oxide porcelain composition described above.
And at least cobalt oxide (CoO or Co_TwoO_ThreeOr
Co_ThreeO_Four) And manganese oxide (MnO or MnO_Two, Or Mn
_TwoO_ThreeOr Mn_ThreeO _Four) And nickel oxide (NiO)
Two or three iron group oxides are
Iron group with at least one valence greater than divalent
It has a structure of being an oxide.

Further, in order to achieve the above-mentioned object,
The zinc oxide porcelain composition of the present invention has a configuration in which the zinc oxide porcelain composition is a zinc oxide porcelain composition in which a donor to zinc oxide that provides electrical conductivity of the n-type semiconductor zinc oxide particles is mainly made of aluminum. Things.

Furthermore, in order to achieve the above object, the zinc oxide porcelain composition according to the present invention is characterized in that closed pores in the zinc oxide porcelain composition are occupied by oxygen having a partial pressure higher than the atmospheric oxygen partial pressure. Provided that the composition is a zinc oxide porcelain composition.

Next, in order to achieve the above object, a method for producing a zinc oxide porcelain composition according to the present invention provides a method for producing a mixture of boron oxide, bismuth oxide, antimony oxide, or zinc oxide, or a mixture of two or three of them. Heat-treating to produce a boron oxide-containing compound, and heat-treating a mixture of bismuth oxide, antimony oxide, or boron oxide, or a mixture of these two or three members to chromium oxide, to produce a chromium oxide-containing compound. And at least cobalt oxide, two or three iron group oxides selected from manganese oxide and nickel oxide, the boron oxide-containing composition, the chromium oxide-containing composition, and bismuth oxide or bismuth oxide-containing Compound and antimony oxide or compound containing antimony oxide and at least aluminum hydroxide and aluminum oxide A step of adding and mixing an aluminum compound selected from hydrate, boehmite, ultrafine alumina, aluminum salt, and an aluminum-containing organic compound to zinc oxide to form a zinc oxide mixture, and performing a granulation treatment from the zinc oxide mixture. And forming a zinc oxide mixed powder, forming the zinc oxide mixed powder to form a molded body, and firing the molded body.

Further, in order to achieve the above object, the method for producing a zinc oxide porcelain composition of the present invention has a configuration in which the step of firing the molded body is a step of firing the molded body at 800 ° C. to 1100 ° C. It is a thing.

In order to achieve the above object, the zinc oxide varistor of the present invention is obtained by subjecting a mixture of boron oxide, bismuth oxide, antimony oxide, or zinc oxide or a mixture of two or three of these to heat treatment. A boron oxide-containing composition, and either chromium oxide containing bismuth oxide, antimony oxide, or boron oxide, or a mixture thereof.
A chromium oxide-containing composition obtained by performing a heat treatment on the mixture obtained by adding the three components, bismuth oxide or a bismuth oxide-containing composition, and antimony oxide or an antimony oxide-containing composition,
At least cobalt oxide, two or three iron group oxides selected from manganese oxide and nickel oxide, and at least aluminum hydroxide, aluminum oxide hydrate, boehmite, ultrafine alumina, aluminum salt, and an aluminum-containing organic compound. It is provided with a configuration in which an electrode is formed on a zinc oxide porcelain composition obtained by adding and mixing a selected aluminum compound to zinc oxide, molding, and firing.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION The zinc oxide porcelain composition of the present invention comprises:
Various additives are added to the main component ZnO powder for adjusting sintering and improving the electrical properties of the sintered body after sintering, mixing, molding the mixture, and firing the molded body. obtain. The present invention comprises a zinc oxide porcelain composition thus obtained, a method for producing the same, and a zinc oxide varistor obtained by applying an electrode to the zinc oxide porcelain composition. FIG. 1 is a perspective view schematically showing a disk-type zinc oxide varistor 10 made using the zinc oxide porcelain composition of the present invention. Aluminum is sprayed on both surfaces of the sintered body 11 obtained as described above to form an aluminum layer (not shown), and then copper is sprayed on the aluminum layer formed on both surfaces. Thus, the electrode 12 is formed. After a lead wire 13 is attached to the electrode 12 with solder, a zinc oxide varistor is obtained by applying a resin coating to a molded body other than the lead wire.
FIG. 2 is a schematic perspective view of an arrester-type zinc oxide varistor 20 prepared using the zinc oxide porcelain composition of the present invention. Electrodes 22 are formed on both upper and lower surfaces of zinc oxide porcelain 21 by thermal spraying of aluminum. A mica-resin film 23 made of a mixture of mica and resin is formed on the side surface of the sintered body. In the zinc oxide porcelain composition of the present invention, in order to secure the priority of the reaction in the firing process, a part of the additives are mixed and heat-treated in advance, added to the zinc oxide together with the other additives, molded and fired. I do. Further, in the zinc oxide porcelain composition of the present invention, the formation of interstitial Zn, which causes the deterioration of electrical characteristics, is prevented, and the zinc oxide is reduced to n.
Aluminum is the sole donor for a type semiconductor. The chromium oxide added to prevent the formation of the pyrochlore phase at low temperatures and to promote the formation of a liquid phase containing bismuth oxide as the main component at low temperatures requires that chromium oxide reacts with zinc oxide first to form ZnCr ₂ O _4. In order to prevent this, it is desirable to add heat treatment in advance together with other additives. In the present invention, in order to prevent the formation of interstitial Zn, it is necessary to form an oxygen-excess atmosphere inside the sintered body during sintering, but this generates oxygen by decomposition and solid solution in zinc oxide. This is made possible by the addition of an iron group oxide. Then, oxygen is confined inside the sintered body by forming a liquid phase. Ultimately, a ZnO-Sb ₂ O ₅ spinel is formed. For this purpose, it is preferable that antimony have 4 to 5 valence in advance. It is desirable that the donor aluminum is added so as to be directly in contact with zinc oxide while avoiding dissolution into the liquid phase.

The zinc oxide porcelain composition contains 950
Since these materials include those having excellent electrical properties by sintering at a temperature of ≦ ° C. or less, these zinc oxide porcelain compositions are formed into sheets, alternately laminated with electrode materials, and sintered. When the electrodes are connected by a predetermined connection method, a laminated varistor is obtained. At that time, in the case of a conventional laminated varistor, a firing temperature of 1200 ° C. or more was required to obtain a good varistor. For this purpose, a noble metal such as platinum was used as an electrode material. However, when a zinc oxide porcelain composition that can be sintered at a temperature of 950 ° C. or less is used, it is possible to use relatively inexpensive silver as an electrode material. Thus, one of the advantages of the present invention is that silver can be integrally fired as the internal electrode of the varistor.

[0025]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to Examples. In the following examples, "weight" is
May be displayed as "wt".

Example 1 B ₂ O ₃ powder and Sb ₂ O ₃ powder (each powder has an average particle diameter of 2-3 μm) were mixed at a molar ratio of 2: 1. 370 ° C under air atmosphere
In after heat treatment for 5 hours, ball mono malonic pots stabilized zirconia and cobble - Synthesis powder B ₂ O ₃ and Sb ₂ O ₃ by milling in mill (average particle size of about 0.5 to 1.5
μm). Hereinafter, the synthetic powder adjusted by B ₂ O ₃ and Sb ₂ O ₃ is referred to as B ₂ O ₃ / Sb ₂ O ₃ synthetic powder. B thus obtained
Most of the ₂ O ₃ / Sb ₂ O ₃ synthetic powder was amorphous as a result of X-ray analysis. Further, Bi ₂ O ₃ powder and Cr ₂ O ₃ powder (each powder has an average particle diameter of 2 to 3 μm) were mixed at a molar ratio of 1: 1. 500 ℃
And then pulverized with a ball mill of a monomalon pot made of stabilized zirconia to obtain a synthetic powder of Bi ₂ O ₃ and Cr ₂ O ₃ (average particle size of about 0.5 to 1.5).
μm). Hereinafter, the synthetic powder adjusted by Bi ₂ O ₃ and Cr ₂ O ₃ is referred to as Bi ₂ O ₃ / Cr ₂ O ₃ synthetic powder. Next, Zn
O, wherein _{B 2 O 3 / Sb 2 O} 3 synthetic powder, Bi ₂ O _3, the Bi ₂ O ₃ / Cr ₂ O
₃ Synthetic powder, Co ₃ O ₄ , MnO ₂ , NiO, Sb ₂ O ₄ , AlOOH, in a weight ratio of 81.38: 0.6: 2.33: 1.2: 0.954: 0.414: 0.383: 1.
1: 0.0024 and mixed and pulverized by a wet method. The obtained compounded powder was dried and pressed into a disk. Next, the obtained molded body was heated in the air at a temperature rising rate of 50 ° C.
/ Hour, and kept at a high temperature for 10 hours. Then, the temperature was lowered at a rate of 50 ° C./hour to obtain a sintered body. As the high holding temperature, 800, 850, 900, 950, 100
0, 1100, 1200 ° C were selected. The sample size of the sintered body was 1.2 mm in thickness and 14 mm in diameter. Further, the obtained sintered body was subjected to a heat treatment at 700 ° C. for a holding time of 1 hour.

Next, a method for manufacturing a zinc oxide varistor will be described with reference to FIG. FIG. 1 is a schematic perspective view of a disk-type zinc oxide varistor 10 made using the zinc oxide porcelain composition of the present invention. An aluminum layer (not shown) is formed by spraying aluminum on both surfaces of the sintered body 11 obtained as described above, and then copper is sprayed on the aluminum layer formed on both surfaces. Thus, the electrode 12 was formed. After a lead wire 13 was attached to the electrode 12 with solder, a molded body other than the lead wire was coated with a resin to obtain a zinc oxide varistor.

The electrical characteristics of the zinc oxide varistor thus obtained were evaluated. The initial electrical characteristics include the rising voltage V _1mA / mm (voltage for 1mm thickness between both terminals when a current of 1mA flows) and non-linear resistance index _0.1mA
α _{1 mA} (value obtained using V _{1 mA} and V _{0.1 mA} ) was measured (in the following description, the nonlinear resistance index is _{0.1 mA}
α _{1 mA} is sometimes simply referred to as α value). The larger the nonlinear resistance index, the greater the surge absorption capacity. or,
The reliability to DC load was evaluated. A DC load of 0.5 watts was applied for 500 hours in a high-temperature atmosphere of 80 ° C., and the change rate of the varistor rise voltage V _{1 mA} ΔV _{1 mA} / V _{1 mA} (DC load change rate) was measured. The smaller the rate of change of the varistor rise voltage V _1mA △ V _1mA / V _1mA , the more stable the electrical characteristics of the zinc oxide varistor, indicating higher reliability.

Further, the reliability of the surge was evaluated. Variation rate of varistor rise voltage V _1mA by applying 10 pulses of 8 × 20μsec, 1.5kA △ V _1mA / V _1mA
(Surge change rate) was measured. Table 1 shows the composition of the sample, and Table 2 shows the evaluation results of the electrical characteristics. The smaller the value of the surge rate, the more stable the electrical characteristics of the zinc oxide varistor and the higher the reliability. In each case, the reliability is high when the absolute value of the change rate is 5% or less. The numerical values indicating the evaluation results of the electrical characteristics indicate the minimum value and the maximum value in the lot.

[0030]

[Table 1]

[0031]

[Table 2]

According to Tables 1 and 2, the zinc oxide varistor using the zinc oxide porcelain composition of the present embodiment can be sintered even at an extremely low temperature of 800 ° C., and 750 ° C.
Except for the fired sample (Sample No. # 001), it has good non-linear resistance characteristics, and the rate of change of the rising voltage _V1mA (△ _V1mA / V) for both long-time DC load and _surge. The absolute value of _{1 mA} ) was 5% or less, and the reliability was excellent. Table 2
As shown in Table 2, the variation in the electrical characteristics within the lot was small. Although not shown in Table 2, when a zinc oxide varistor is prepared using the zinc oxide porcelain of the present embodiment,
The variation in the electrical characteristics between lots was also small, as was the variation in the electrical characteristics within the lot. The firing temperature is 12
When the temperature exceeds 00 ° C., a plurality of compacts are stacked and fired during firing, so that the sintered bodies are fused together (the samples stick together), and the electrical characteristics cannot be measured. (Sample # 00
8).

Example 2 B ₂ O ₃ powder and Bi ₂ O _{3 in} molar ratio
2: 1 powder, Bi ₂ O ₃ powder and Sb ₂ O ₃ powder 7: 3, and then Cr ₂ O ₃ powder and Sb ₂ O ₃ powder 1: 1 did. These mixed powders were mixed in air at 410 ° C for 5 hours, 550 ° C for 5 hours, and 500 ° C for 5 hours, respectively.
After heat treatment time, volume of mono-malonic pots stabilized zirconia and cobble - consisting of B ₂ O ₃ and Bi ₂ O ₃ by milling in mill _{B 2 O 3 / Bi 2 O} 3 synthetic powder , Bi ₂ O ₃
And consisting of _{Sb 2 O 3 Bi 2 O 3} / Sb 2 O 3 synthetic powder, Cr ₂ O ₃ and Sb ₂ O ₃
Cr ₂ O ₃ / Sb ₂ O ₃ synthetic powder consisting of

ZnO powder, the B ₂ O ₃ / Bi ₂ O ₃ synthetic powder, the Bi ₂ O ₃ / Sb ₂ O ₃ powder, the Cr ₂ O ₃ / Sb ₂ O ₃ powder, and the Co ₃ O ₄ powder, MnO ₂ powder, NiO powder, and Al (NO ₃ ) ₃
· 9H ₂ O powder and in a weight ratio of 81.38: 1.2: 3.4: 0.8: 0.95
4: 0.414: 0.383: 0.015, and mixed and pulverized for 18 hours by a wet method, and a zinc oxide mixed powder was obtained by a spray dryer. An arrester was prepared using the zinc oxide mixed powder thus obtained. Table 3 shows the composition of the sample.

[0035]

[Table 3]

The zinc oxide mixed powder obtained by the spray dryer is formed into a column by a RIP (Rubber Isostatic Press, rubber isostatic press) method, and calcined at 900 ° C. for 10 hours to form a columnar zinc oxide porcelain. Obtained. The size of the obtained zinc oxide porcelain was 32 mm in diameter and 27 mm in height. Electrodes were formed by spraying aluminum metal on the upper and lower surfaces of the zinc oxide porcelain, and the mica-resin coating was applied to the side surfaces to obtain an arrester-type zinc oxide varistor. V _1mA = 6
kV. FIG. 2 is a schematic perspective view of an arrester-type zinc oxide varistor 20 prepared using the zinc oxide porcelain composition of the present invention. Electrodes 22 are formed on both upper and lower surfaces of zinc oxide porcelain 21 by thermal spraying of aluminum. Also,
Mica made of a mixture of mica and resin is on the side of the sintered body
-The resin film 23 is formed. Table 4 shows the current-voltage characteristics of the arrester type zinc oxide varistor.

[0037]

[Table 4]

As can be seen from Table 4, the arrester type zinc oxide varistor using the zinc oxide porcelain of the composition of the present embodiment has excellent non-linear resistance characteristics even in a high current region. Next, an acceleration test of AC power application was performed to predict the service life. The service life is one of the most important evaluation items of the arrester. Here, the test was performed under the conditions of an ambient temperature of 130 ° C. and a charge rate of 95%. As a result, the initial I of 1 mA
r hardly changes for tests over 100 hours,
When used as a gapless arrester, a life of 100 years or more was obtained under the conditions of an ambient temperature of 70 ° C. and a charge rate of 80%.

Example 3 B ₂ O ₃ powder and Cr ₂ O ₃ powder were mixed at a molar ratio of 1: 1, and these mixed powders were mixed at 380 ° C. for 5 hours in an air atmosphere. after heat treatment, ball mono malonic pots stabilized zirconia and cobble - consisting of B ₂ O ₃ and Cr ₂ O ₃ by milling in mill B ₂ O ₃ / C
r ₂ O ₃ synthetic powder was obtained. Next, a powder of Sb ₂ O _{3 and} a powder of ZnO were mixed at a molar ratio of 1: 1. The mixed powder was subjected to a heat treatment at 500 ° C. for 5 hours in an air atmosphere, and then stabilized zirconia. Sb ₂ O ₃ consisting of Sb ₂ O ₃ and ZnO by finely pulverizing with a ball mill
/ ZnO synthetic powder was obtained. Next, a sample was prepared in the same manner as in Example 1.

The ZnO powder, the B ₂ O ₃ / Cr ₂ O ₃ powder, and the Bi ₂ O
₃ powder, Co ₃ O ₄ powder, MnO ₂ powder, NiO powder,
Sb ₂ O ₃ / ZnO synthetic powder and aluminum hydroxide acetate in a weight ratio of 81.38: 1.1: 2.33: 0.954: 0.414: 0.383:
It was blended so that the ratio became 1.5: 0.0065 and mixed and pulverized for 18 hours by a wet method. Subsequently, the mixture was dried, granulated, molded and fired, and a zinc oxide varistor was obtained in the same manner as in Example 1. Table 5
Shows the composition of the sample, and Table 6 shows the evaluation results of the electrical characteristics.

[0041]

[Table 5]

[0042]

[Table 6]

As can be seen from Tables 5 and 6, the zinc oxide varistor using the zinc oxide-based porcelain of the present embodiment is a reference sample fired at 800 ° C. (sample No. # 201) and a reference sample fired at 1200 ° C. Except for sample number ♯207), the nonlinear resistance characteristics are good, and the rate of change of the rising voltage V _1mA (△ V _1mA / V _1mA ) both for long-term DC load and for surge
Was 5% or less, and the reliability was excellent. In many of the reference samples of sample No. # 207, the porcelain and the porcelain adhered to each other and were not separated.

[0044]

As described above with reference to the embodiments,
The zinc oxide porcelain composition of the present invention suppresses the generation of interstitial Zn, which is a cause of instability, and has an excellent stability in which aluminum is added as a donor instead.
Since it is made of zinc oxide as a constituent material, when it is made into a varistor, it has excellent electrical characteristics such as non-linear resistance characteristics from low current range to high current range, and interstitial
The movement of Zn is suppressed, and it is extremely stable against DC and AC voltage application and heat. Also, the present invention
An object of the present invention is to provide a method for producing the zinc oxide porcelain composition for a zinc oxide varistor at a high yield, and is excellent in industrially distributing a trace amount of aluminum uniformly in zinc oxide particles in a sintered body. When manufacturing the sintered body,
After expelling the reducing gas generated in the early stage of the sintering process, which is harmful to the device, a boron compound with excellent wettability forms a liquid phase to reduce open pores and contain oxygen at a high oxygen partial pressure. Sintered with shrinkage in a state where closed pores are formed. It is believed that high oxygen partial pressure oxygen reduces interstitial Zn in zinc oxide particles.
Even if the firing temperature is lowered to 800 ° C., it is possible to uniformly sinter and grow the grain size important for the varistor uniformly. Further, even if the sintering temperature is lowered, it can withstand a high current pulse sufficiently and keep high performance.

Further, since the zinc oxide porcelain composition of the present invention can be sintered at a low temperature, it is possible to reduce the power consumption during sintering, and at the same time, the furnace material and container of an electric furnace used for sintering. Consumption can be reduced, which can greatly contribute to energy saving and resource saving. Furthermore, some of the zinc oxide porcelain compositions of the present invention sinter even at a temperature lower than the melting temperature of silver, and it becomes possible to form a silver electrode inside these porcelains simultaneously with firing. Was.
As a result, a high-performance laminated zinc oxide varistor having a silver internal electrode can be manufactured. In the examples, although the data of firing at 800 to 1200 ° C. is shown, by adjusting the type and amount of the additive, 750 is obtained.
It became clear that a varistor with good characteristics could be obtained even when the firing temperature was lowered to ℃. In the conventional arrester, a heat treatment at 500 ° C. to 600 ° C. was required after baking to reduce the adverse effect of interstitial Zn in order to withstand the AC voltage application. It is shown that it is.

Further, germanium oxide (Ge) is mainly used as an additive mainly for controlling grain growth and improving reliability.
O ₂ ), magnesium oxide (MgO), niobium oxide (Nb
₂ O ₅ ), lead oxide (PbO), silicon oxide (SiO ₂ ), tin oxide (SnO ₂ ), tantalum oxide (Ta ₂ O ₅ ), titanium oxide (Ti
O ₂ ), tungsten oxide (WO ₃ ), and rare earth oxides or composites containing these may be added.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of a disk-type zinc oxide varistor prepared using the zinc oxide porcelain composition of Example 1 of the present invention.

FIG. 2 is a schematic perspective view of an arrester-type zinc oxide varistor made using the zinc oxide porcelain composition of Example 2 of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Disc type zinc oxide varistor 11 Zinc oxide sintered body 12 Electrode 13 Lead wire 20 Arrester type zinc oxide varistor 21 Zinc oxide sintered body 22 Electrode 23 Side coat film

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Takashi Miyamoto 2-7-1, Ayumino, Izumi-shi, Osaka F-term in Osaka Prefectural Industrial Technology Research Institute (reference) 4G030 AA22 AA25 AA28 AA29 AA32 AA35 AA36 AA42 AA43 BA02 BA04 GA09 5E034 CA09 CB01 CC02 DA03 DA05 DC03 DE01 DE05 DE07 DE08

Claims (7)

[Claims] (1) Bismuth oxide (Bi ₂ O ₃ ) is added to boron oxide (B ₂ O ₃ ).
₃ ) or antimony oxide (Sb ₂ O ₃ ) or zinc oxide (Zn
O) or a mixture obtained by heat-treating a mixture of these two or three, a boron oxide-containing composition, bismuth oxide or a bismuth oxide-containing composition, and antimony oxide (Sb
₂ O ₃ , or Sb ₂ O ₄ , or Sb ₂ O ₅ ) or a compound containing antimony oxide, and either chromium oxide (Cr ₂ O ₃ ), boron oxide, bismuth oxide, or antimony oxide, or a few of them Chromium oxide-containing composite obtained by subjecting the mixture to which heat is added to heat treatment, and at least cobalt oxide (CoO, or C
o ₂ O ₃ or Co ₃ O ₄ ) and manganese oxide (MnO or MnO ₂ ,
Or Mn ₂ O ₃ or Mn ₃ O ₄ ) and two or three iron group oxides selected from nickel oxide (NiO), and at least aluminum hydroxide (Al (OH) ₃ ) and aluminum oxide hydrate (Al ₂ O ₃ .nH ₂ O), boehmite (AlOOH), ultrafine alumina (Al ₂ O ₃ ), aluminum salt and aluminum-containing organic compound are converted to zinc oxide (Zn oxide)
A zinc oxide porcelain composition which is added to O), mixed, molded and fired. 2. At least cobalt oxide (CoO or Co
₂ O ₃ or Co ₃ O ₄ ) and manganese oxide (MnO, or MnO ₂ ,
Or Mn ₂ O ₃ , or Mn ₃ O ₄ ) and nickel oxide (NiO), wherein at least one of the iron group oxides has a valence greater than divalent. 2. The zinc oxide porcelain composition according to claim 1, wherein the zinc oxide porcelain composition is an iron group oxide. 3. The zinc oxide porcelain composition according to claim 1, wherein the zinc oxide porcelain composition is a zinc oxide porcelain composition in which the donor to zinc oxide for providing electrical conductivity of the n-type semiconductor zinc oxide particles is mainly aluminum. Zinc oxide porcelain composition. 4. The zinc oxide porcelain composition wherein the closed pores therein are occupied by oxygen at a partial pressure higher than the atmospheric oxygen partial pressure. 2. The zinc oxide porcelain composition according to 1. 5. A process for preparing a boron oxide-containing compound obtained by subjecting a mixture of boron oxide, bismuth oxide, antimony oxide, or zinc oxide or a mixture of two or three of them to a heat treatment, and oxidizing the chromium oxide. A step of preparing a chromium oxide-containing compound obtained by subjecting any one of bismuth, antimony oxide, and boron oxide or a mixture of these two or three to a heat treatment, and at least cobalt oxide, manganese oxide, and nickel oxide. Two or three iron group oxides, the boron oxide-containing composition, the chromium oxide-containing composition, bismuth oxide or bismuth oxide-containing composition, antimony oxide or antimony oxide-containing composition, and at least aluminum hydroxide and aluminum oxide Hydrate and boehmite and ultrafine alumina, aluminum salt and aluminum A step of preparing a zinc oxide mixture by adding and mixing an aluminum compound selected from an ammonium-containing organic compound to zinc oxide, and a step of forming a zinc oxide mixed powder by subjecting the zinc oxide mixture to a granulation treatment,
A method for producing a zinc oxide porcelain composition, comprising a step of forming a molded body by molding the zinc oxide mixed powder, and a step of firing the molded body. 6. The step of firing the molded body is performed at a temperature of 800 ° C. to 1 ° C.
The step of firing at 100 ° C.
The method for producing a zinc oxide porcelain composition described in 1 above. 7. A boron oxide-containing composition obtained by subjecting a mixture of boron oxide, bismuth oxide, antimony oxide, or zinc oxide or a mixture of two or three of them to heat treatment, and chromium oxide to bismuth oxide or oxidized oxide. A chromium oxide-containing composition obtained by subjecting any one of antimony or boron oxide or a mixture of the two or three to a heat treatment, bismuth oxide or a bismuth oxide-containing composition, and antimony oxide or an antimony oxide-containing composition; , At least cobalt oxide, two or three iron group oxides selected from manganese oxide and nickel oxide, at least aluminum hydroxide, aluminum oxide hydrate, boehmite, ultrafine alumina, aluminum salt, and an aluminum-containing organic compound. Add aluminum compound selected from zinc oxide to zinc oxide, mix and mold Zinc oxide varistor obtained by forming electrodes on made by sintering zinc oxide ceramic composition.