JP2002373801A - Zinc oxide-based sintered body, manufacturing method thereof and zinc oxide varistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a zinc oxide-based sintered body which has excellent electric characteristics, high reliability in DC/AC load and surge load and is industrially baked at a temperature from 800 deg.C to 1,100 deg.C, particularly, 1,000 deg.C or less, thereby being manufacturing into a zinc oxide varistor stable for heat treatment. SOLUTION: A first preliminary heat-treated synthetic powder containing, 3 to 60 wt.% boron oxide, a second preliminary heat-treated synthetic powder containing 10 to 75 wt.% chromium oxide, and a fifthpreliminary heat-treated synthetic powder containing 20 to 50 wt.% antimony oxide, are previously prepared. Resultant powder is added to and mixed with zinc oxide powder together with cobalt oxide powder, manganese oxide powder, nickel oxide powder, bismuth oxide powder, and aluminum compound powder to prepare zinc oxide-based mixed powder. Then, the resultant zinc oxide-based mixed powder is sintered at a temperature from 800 deg.C to 1,100 deg.C to be made zinc oxide-based sintered body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zinc oxide based sintered body as a varistor manufacturing material used for absorbing surges in an electric circuit, a method for manufacturing the same, and a zinc oxide varistor.

[0002]

2. Description of the Related Art Zinc oxide varistors are basically composed of zinc oxide, essential additives such as bismuth oxide, cobalt oxide and manganese oxide, and various oxides which may be added for improving the performance. Is manufactured using a zinc oxide-based sintered body after molding and firing a zinc oxide-based raw material mixed powder containing The rising voltage of the zinc oxide varistor rises almost in proportion to the number of zinc oxide grain boundaries in the zinc oxide sintered body existing between the electrodes. That is, the rising voltage rises by about 3 V to 4 V per one grain boundary in the sintered body. Therefore, 200 V to 400 V per 1 mm thickness
In order to manufacture a zinc oxide varistor for a high voltage of about V, it is necessary to manufacture a zinc oxide based sintered body containing ZnO particles having a small average particle diameter of about 7 to 15 μm. Conventionally, in order to manufacture a zinc oxide varistor for high voltage, a method of suppressing the growth of ZnO particles by blending a grain growth inhibitor of ZnO particles such as Sb ₂ O ₃ and SiO ₂ into a raw material has been used. It has been. This Sb ₂ O
₃ is an indispensable additive component because it also exerts an important function of stabilizing the nonlinear resistance characteristics of the zinc oxide varistor. Note that the above “rise voltage”
It means the voltage between both terminals when a current of 1 mA flows through the varistor, and is represented by 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 is expressed as V _{1 mA} / mm. Therefore, the value represented by " _V1mA / mm"
It means a rising voltage per 1 mm thickness of the sample.

However, in the prior art, in order to obtain a high-performance zinc oxide varistor for high voltage, it is necessary to fire a molded product of the raw material mixture powder at a high temperature of 1150 to 1300 ° C. When baking is performed at such a high temperature, Bi ₂ O ₃ , Co ₃ O _{4 and the} like evaporate in a large amount even in the air. Since the evaporated Bi ₂ O ₃ has high reactivity, for example, it easily reacts with many kinds of substances and easily corrodes ceramics such as furnace materials and container materials.
That is, when the raw material mixture molded body is fired at a high temperature, not only the power consumption is increased, but also the scattering due to the evaporation of the components such as Bi ₂ O ₃ and the accompanying consumption of the furnace material and the container material are caused. Therefore, there is a demand for the establishment of a new technology that enables firing of a raw material mixture compact at lower temperatures. Furthermore, when the firing temperature of the raw material mixture molded body is high, the temperature in the firing furnace tends to be non-uniform, so that the firing temperature, the heating rate, the Bi ₂ O ₃ and Sb ₂ O ₃ cause a difference in vapor pressure and the like, which causes a problem that the characteristics of the zinc oxide-based sintered body and the characteristics of the zinc oxide varistor manufactured using the same tend to vary.

If the sintering temperature of a raw material mixture for a zinc oxide varistor having a conventional composition is lowered in order to address the above-mentioned problem, sufficient sintering will not be performed, and the particle size of ZnO will vary, resulting in a final variation. As a result, the rising voltage of the zinc oxide varistor suddenly increases, and the nonlinear resistance characteristics decrease. Further, there arises a problem that the zinc oxide varistor is likely to be deteriorated by an electric power load, a pulse current load, and the like.

[0005] The basic raw material powder for a zinc oxide varistor produced _{Sb 2 O 3, Cr 2 O} 3, SiO ₂ or the like mixed powder was press added, and baked, _Sb 2 _{O 3} in the Atsushi Nobori process
Sublimates to cover the surface of the ZnO particles and further reacts with ZnO to prevent contact between the ZnO particles and to suppress the growth of the ZnO particles. Originally, the ZnO—Bi ₂ O ₃ system, which is a basic composition of a raw material for producing a zinc oxide varistor, includes:
Since there is a eutectic composition having a eutectic temperature of 740 ° C.,
The binary mixture of nO and Bi ₂ O ₃ easily reacts and sinters even at around 800 ° C. However, when Sb ₂ O ₃ is present in the additive to the binary mixture, as described above, Sb ₂ O ₃ sublimates at a low temperature and ZnO
By covering around the particles, ZnO particles and Bi ₂ O ₃
Since it hinders contact between the particles and suppresses the reaction between these two components, it becomes difficult to sinter the raw material mixture molded body. Further, the ZnO—Sb ₂ O ₃ film easily reacts with Bi ₂ O ₃ at a low temperature, and ZnO—Bi ₂ O ₃ —S is formed between ZnO and ZnO.
A strong and stable pyrochlore phase film of b ₂ O ₃ is formed, which further hinders sintering. More specifically, the pyrochlore phase in the solid phase prevents the formation of the Bi ₂ O ₃ phase in the liquid phase and delays the progress of the liquid phase sintering.

[0006] In the raw material for the zinc oxide varistor, CoO, MnO and NiO are further blended.
_{Bi 2 O 3 -Sb 2 O 3} - (CoO, MnO, NiO)
System. Also in this case, when firing the raw material molded body,
In order for the pyrochlore phase to react with ZnO to form a liquid phase containing Bi ₂ O ₃ as a main component, high-temperature firing at 1200 ° C. or higher is required. Moreover, in this system, Bi ₂
Even if a liquid phase containing O ₃ as a main component is formed, the opposite reaction occurs during the cooling process.
A pyrochlore phase is formed at the nO grain boundary. As described above, when the Bi ₂ O ₃ phase is not formed at the grain boundary of the sintered body and the pyrochlore phase is present instead, a varistor exhibiting excellent characteristics cannot be obtained. Cr ₂ O is added to the above composition.
₃ added ZnO—Bi ₂ O ₃ —Sb ₂ O ₃ — (C
oO, MnO, NiO) in _-Cr 2 _{O 3} system, in order to form a liquid phase pyrochlore phase is mainly composed of _Bi 2 _{O 3} reacts with ZnO, again requires a high temperature sintering of 1200 ° C. or higher and There is a problem of doing. However, once formed, the Bi ₂ O ₃ -based liquid phase is stably present at the grain boundaries even after cooling, and does not return to the pyrochlore phase. And the zinc oxide varistor obtained using the obtained sintered body shows excellent initial characteristics. In order to suppress sublimation of Sb ₂ O _3, was subjected in advance heat treatment (usually about 500 to 600 ° C.) a powder mixture consisting of _Bi 2 _{O 3} and _Sb 2 _{O 3} Prefecture, be added to ZnO, It is known that it is effective for promoting sintering of a raw material mixture molded body.
That is, according to this method, the raw material mixture molded body is
Even when firing at 0 ° C., sublimation of Sb ₂ O ₃ is suppressed, and formation of a film such as a pyrochlore phase on the surface of ZnO particles is suppressed, so that sintering proceeds fairly well. However, it is difficult to obtain a ZnO varistor having stable electric characteristics even with the sintered body adjusted in this way.

In the zinc oxide varistor, “excellent in electrical characteristics” means, for example, that the varistor has a small leakage current and a high non-linear resistance index value ( _{0.1 mA} α _{1 mA} ) described later. Means that a high current generated instantaneously in an electric circuit in which the electric current is incorporated is absorbed and a high voltage is prevented from being generated in the circuit. In addition, “excellent reliability” refers to various cases, such as when a voltage is applied to a varistor for a long time, when a power load is applied at a high temperature for a long time, or when a pulse current is applied. This means that even under the conditions, the initial electrical characteristics are substantially maintained. However, conventional zinc oxide varistors
It has the following intrinsic instability.

That is, in ordinary zinc oxide, an interstitial zinc atom (so-called interstitial Zn) is formed between a lattice point at which a zinc atom constituting a zinc oxide crystal is located and a lattice point at which an oxygen atom is located. Exists. The conductivity of zinc oxide is provided by electrons excited from these interstitial Zn atoms. One of the biggest problems with conventional zinc oxide varistors is various electrical instabilities. As one of the electrical instabilities, there is a phenomenon that when a DC or AC voltage is continuously applied to the varistor for a long time, the VI characteristic deteriorates and the current gradually increases. In addition, a zinc oxide varistor having a sintered body
When subjected to a heat treatment at about 00 ° C., a phenomenon in which the VI characteristics rapidly deteriorate is also observed. In particular, in the latter case, the leakage current becomes large, and it may become impossible to put it to practical use. These two types of V- in a zinc oxide varistor with a sintered body structure
The deterioration phenomenon of the I characteristic occurs due to the movement of interstitial Zn in the depletion layer generated along the grain boundary of the zinc oxide particles. When a raw material to which aluminum is not added is used, in a zinc oxide varistor formed by a conventional manufacturing method, 2 to 7 × 10 ¹⁷ supplied from interstitial Zn atoms in zinc oxide particles as an n-type semiconductor. It is estimated that there are about conduction electrons / cm ³ . Experimentally, the number of conduction electrons in the ZnO particles present in the zinc oxide varistor was determined by Mukae, Tsuda and N
agasawa method ("Cap
activity-vs-Voltage Chara
ceramics of ZnO Varisto
rs ", J. Appl. Phys., 50 [6] 447.
5-76 (1977)).

It is known that in pure zinc oxide crystals, the concentration of interstitial Zn atoms in ZnO increases as the ambient temperature during firing increases. Further, it is known that when a zinc oxide film is formed in oxygen by sputtering, almost no interstitial Zn atoms are generated. That is, it has an extremely high electric resistance. _Bi 2 _O 3 to ZnO powder, Co
_{3 O 4, Cr 2 O 3} , MnO 2, NiO, formulated by appropriately selecting the powder, such as _Sb 2 _{O 3,} the resulting mixture was press-molded and sintered at a high temperature atmosphere, very high A zinc oxide varistor having non-linear resistance characteristics is obtained. In these sintered bodies, n-type semiconductor Zn existing on both sides of the crystal grain boundary is used.
Since the conduction electrons in O are captured at the grain boundaries, a depletion layer is formed on both sides of the grain boundaries, and a barrier layer that blocks the movement of electrons on both sides of the grain boundaries, a so-called “double Schottky barrier”.
Is formed. Since the main electric conduction of the n-type ZnO semiconductor is conduction electrons derived from the interstitial Zn atoms, the positively charged interstitial Zn atoms remain in the depletion layer.

[0010] Even when no voltage is externally applied to such a sintered body, an interstitial Zn having a positive charge in the depletion layer works because a strong electric field works in the depletion layer. The atom is attracted to grain boundaries. In such a sintered body, when a voltage is applied from the outside, the voltage acts only on the thin depletion layer, so that a larger electric field acts in one depletion layer. Since interstitial Zn atoms are relatively easy to move, some of them move toward grain boundaries and reach grain boundaries. As a result, the positively charged interstitial Zn atoms combine with the negatively charged grain boundary oxygen atoms to form neutral ZnO. At the same time, the negative charge trapped in the grain boundaries is reduced, so that the barrier function that has contributed to the varistor characteristics is reduced, and the nonlinear resistance characteristics are reduced. As described above, even when a voltage is not externally applied to the sintered body, since a strong electric field works in the depletion layer, the interstitial Zn atom having a positive charge in the depletion layer becomes It is attracted to grain boundaries. In such a situation, when the varistor element is heated, the thermally excited interstitial Zn atoms easily move, and a part of them moves toward the grain boundary by the electric field, and the negative charge at the grain boundary is generated. To form neutral ZnO by combining with an oxygen atom having a negative electrode, thereby reducing the nonlinear resistance characteristics of the varistor. As described above, the conversion of ZnO crystal into a semiconductor is brought about mainly by interstitial Zn atoms naturally occurring in the manufacturing process, and thus involves electrical instability.

The conversion of a ZnO crystal into an n-type semiconductor is based on Al ₂
It also occurs with the addition of O ₃ . In order to improve the current-voltage non-linear resistance characteristics particularly in a high current region, it is important to increase the electrical conductivity in the zinc oxide particles. The improvement alone is not enough. Therefore, in order to improve the current-voltage non-linear resistance characteristics particularly in a high current region, Al ₂ O ₃ is added as a donor to increase the electric conductivity in the ZnO particles. However, in the case of adding _Al 2 _{O 3} also, as long as the interstitial Zn atoms with a positive charge present in the depletion layer, _Al 2 O
_As with the case where ₃ is not added, the problem of electrical instability cannot be solved. That is, the problem that the barrier function is reduced during voltage application and heat treatment, the nonlinear resistance characteristics are reduced, and the leakage current is increased is not solved. In particular, when heat treatment is performed for electrode baking, side coating, and the like, the non-linear resistance characteristics in a low current region are greatly reduced.

A method of improving the stability to AC application by preliminarily heat-treating a sintered body for manufacturing a zinc oxide varistor in a temperature range of about 500 to 600 ° C. has also been adopted. In this method, the preliminary heat treatment of the sintered body reduces interstitial Zn ions in the depletion layer, which has caused the deterioration of the varistor performance,
As a result, the instability of the IV characteristics is somewhat alleviated, but the basic problem has not been solved.

[0013]

The unstable electrical characteristics of zinc oxide varistors are mainly caused by the movement of interstitial Zn. It is necessary that electrons from the Al donor contribute to the electrical conductivity in the zinc oxide particles by substituting and introducing an Al atom as a donor. In order to reduce the amount of interstitial Zn, it is considered necessary to maintain zinc oxide at a high temperature in a high oxygen partial pressure atmosphere. As a specific method, sintering of a zinc oxide compact under a high oxygen pressure in the production of a varistor element can be considered, but this method is practically disadvantageous. As described above, the zinc oxide-based sintered body for a varistor element or a varistor device has two major problems: lowering the sintering temperature during production and stabilizing the electrical characteristics of the sintered body.

Japanese Patent Publication No. 09-312203 describes B ₂ O ₃ powder, Cr ₂ O ₃ powder, GeO ₂ powder, L
a ₂ O ₃ powder, MgO powder, Nb ₂ O ₅ powder, Nd ₂ O
₃ powder, PbO powder, Sb ₂ O ₃ powder, SiO ₂ powder,
SnO ₂ powder, Ta ₂ O ₅ powder, Nb ₂ O ₅ powder, WO
₃ powder and a powder mixture of at least one selected from Y ₂ O ₃ powder and Bi ₂ O ₃ powder are preheated at 400 to 700 ° C. and pulverized to form a synthetic powder. Powder, cobalt oxide powder and at least one of manganese oxide powder are added to zinc oxide powder, and the obtained raw material mixture is sintered at 750 to 1100 ° C .; a method for producing the same; and a zinc oxide varistor. Has been disclosed.

According to the technique described in Japanese Patent Publication No. 09-067161, S is particularly liable to sublimate at low temperatures.
By preliminarily heat-treating a powder mixture of b ₂ O ₃ powder and Bi ₂ O ₃ powder at a low temperature, sublimation of the Sb ₂ O ₃ powder is suppressed, and low-temperature sintering of the raw material mixture is achieved. However, although the amount is small compared to the amount of zinc oxide as a main component, in industrial production of varistors,
Since the amount of the additive component composed of the Sb ₂ O ₃ powder, the Bi ₂ O ₃ powder and other components is considerably large, the properties of the synthetic powder obtained by the preliminary heat treatment tend to vary. As a result, the electrical characteristics of the finally obtained individual varistors may not be stable and may lack reliability.

Accordingly, an object of the present invention is to provide a new technique capable of producing a homogeneous zinc oxide-based sintered body by sintering at a low temperature. Another object of the present invention is to provide a technique for manufacturing a zinc oxide varistor excellent in electrical characteristics such as non-linear resistance characteristics and reliability using a sintered body obtained by the above method. I do.

[0017]

Means for Solving the Problems The inventors of the present invention have conducted various studies in order to solve the above-mentioned problems of the prior art, and as a result, have found that when producing a zinc oxide based sintered body as a basic material of a zinc oxide varistor. , Mixed oxide preheat-treated synthetic powder containing a specific amount of boron oxide (hereinafter referred to as “first preheat-treated synthetic powder”)
), A mixed oxide preliminary heat-treated synthetic powder containing a specific amount of chromium oxide (hereinafter sometimes referred to as a “second preliminary heat-treated synthetic powder”), a specific amount of antimony oxide and at least zinc oxide. , One selected from cobalt oxide, manganese oxide, nickel oxide and chromium oxide
An oxide mixed powder consisting of five specific amounts of oxides is preliminarily heated at a high temperature, preferably at a temperature of 1000 to 1400 ° C., and then pulverized to obtain a substance having a spinel structure containing antimony oxide. After preparing each of the mixed oxide preheat-treated synthetic powders (hereinafter sometimes referred to as “fifth preheat-treated synthetic powder”) as components, these preheat-treated synthetic powders are mixed with zinc oxide and other additional components. When adding to the powder mixture containing, molding and sintering at low temperature,
It has been found that a zinc oxide-based sintered body having a uniform composition and stable properties can be obtained.

According to the study of the present inventor, a mixed oxide preliminary heat-treated synthetic powder containing a specific amount of boron oxide and a specific amount of chromium oxide (hereinafter referred to as “third preliminary heat-treated synthetic powder”)
) And the fifth preheat-treated synthetic powder, and then the preheat-treated synthetic powder is added to a powder mixture containing zinc oxide and other additives, molded, and sintered at a low temperature. Also in this case, it has been found that a zinc oxide-based sintered body having a uniform composition and a stable property can be obtained.

Furthermore, according to the study of the present inventor, a specific amount of boron oxide, a specific amount of chromium oxide, and at least one of bismuth oxide, antimony oxide and rare earth oxide are provided.
After preparing a mixed oxide pre-heat-treated synthetic powder (hereinafter, sometimes referred to as a “fourth pre-heat-treated synthetic powder”) and a fifth pre-heat-treated synthetic powder containing a specific amount of oxide consisting of a seed, Even when the preheat-treated synthetic powder is added to a powder mixture containing zinc oxide and other additives, molded, and sintered at a low temperature, a zinc oxide-based baked powder having a uniform composition and stable properties is also obtained. We found that we could get a solid body. Further, when a zinc oxide varistor is manufactured using the sintered body obtained by the above three methods, a product having excellent electrical characteristics such as non-linear resistance characteristics and reliability can be obtained at low cost. I found that.

That is, the present invention provides the following zinc oxide-based sintered body and a method for producing the same: a boron oxide content of 3 to 60% by weight, and at least one of bismuth oxide, antimony oxide and rare earth oxide. Seed content 40-97
A first preheat-treated synthetic powder containing boron oxide, which has a chromium oxide content of 10 to 75 wt%, and a content of at least one of bismuth oxide, antimony oxide and a rare earth oxide of 25 to 90 wt%. A second preheat-treated synthetic powder containing chromium oxide, and an antimony oxide content of 2
Fifth preliminary heat-treated synthetic powder containing antimony oxide having a content of 0 to 50% by weight and containing 50 to 80% by weight of at least 1 to 5 kinds selected from zinc oxide, cobalt oxide, manganese oxide, nickel oxide and chromium oxide. A body is prepared in advance, and zinc oxide powder 81.38 parts by weight (including the contribution of the fifth preheat-treated synthetic powder containing antimony oxide),
The boron oxide-containing first preliminary heat-treated synthetic powder 0.05 to
5.0 parts by weight, 0.05 to 7.0 parts by weight of the second preheat-treated synthetic powder containing chromium oxide, 0.5 to 10.0 parts by weight of the fifth preheated synthetic powder containing antimony oxide, cobalt oxide Powder or two or three powders selected from the group consisting of manganese oxide powder and nickel oxide powder 0.3
To 8.0 parts by weight (including the contribution of the antimony oxide-containing fifth preheat-treated synthetic powder), 1.0 to 10.0 parts by weight of the bismuth oxide powder (the boron oxide-containing first preheat-treated synthetic powder and The zinc oxide-based mixed powder is prepared by mixing the chromium oxide-containing second preheat-treated synthetic powder (including the contribution of the synthetic powder) and the aluminum compound powder in an amount of 0.0001 to 0.05 parts by weight (in terms of aluminum oxide). A zinc oxide-based sintered body obtained by molding the zinc oxide-based mixed powder and sintering the obtained molded body at 800 to 1100 ° C.

Further, in the method for producing a zinc oxide-based sintered body, 3 to 60% by weight of boron oxide powder and 40 to 97% by weight of at least one of bismuth oxide powder, antimony oxide powder and rare earth oxide powder After preheating the oxide mixed powder consisting of at 300 to 1400 ° C.,
A step of obtaining a first preheat-treated synthetic powder containing boron oxide by pulverization, 10 to 75% by weight of chromium oxide;
An oxide mixed powder comprising at least 25 to 90% by weight of at least one of bismuth oxide powder, antimony oxide powder and rare earth oxide powder is preliminarily heated at a temperature of 400 to 1400 ° C., and then pulverized to obtain an oxide. Step of obtaining a second preheat-treated synthetic powder containing chromium, antimony oxide 2
An oxide mixed powder composed of 0 to 50% by weight and at least 1 to 5 kinds of 50 to 80% by weight selected from zinc oxide, cobalt oxide, manganese oxide, nickel oxide and chromium oxide is preferably used at 1000 to 1400 at a high temperature. A step of obtaining a fifth preliminarily heat-treated synthetic powder containing antimony oxide by preheating at a temperature of 5 ° C. and then pulverizing, 81.38 parts by weight of zinc oxide powder (contribution by the fifth preheated synthetic powder) ), The boron oxide-containing first preliminary heat-treated synthetic powder 0.05 to 5.0 parts by weight, the chromium oxide-containing second preliminary heat-treated synthetic powder 0.05 to 7.0 parts by weight,
The fifth preheat-treated synthetic powder containing antimony oxide 0.5
0.3 to 8.0 parts by weight of a powder selected from the group consisting of cobalt oxide powder, manganese oxide powder, and nickel oxide powder. 1.0 to 10.0 parts by weight of bismuth oxide powder (including the contribution of the first and second preheated synthetic powders) and 0.0001 to 0.05 part by weight of aluminum compound powder (including (Amount in terms of aluminum oxide) to prepare a zinc oxide-based mixed powder, a step of molding the zinc oxide-based mixed powder, and sintering the compact obtained in the step at 800 to 1100 ° C. A manufacturing method comprising the step of:

The present invention further provides the following zinc oxide-based sintered body and a method for producing the same: a boron oxide content of 3 to
A boron oxide / chromium oxide-containing third preheat-treated synthetic powder containing 70% by weight and a chromium oxide content of 30 to 97% by weight, and an antimony oxide content of 20 to 50% by weight and at least oxidized 1 selected from zinc, cobalt oxide, manganese oxide, nickel oxide and chromium oxide
A preliminarily prepared antimony oxide-containing fifth preheat-treated synthetic powder having a content of 50% to 80% by weight of 50% to 50% by weight was prepared in advance, and zinc oxide powder was 81.38 parts by weight (based on the antimony oxide-containing fifth preheat-treated synthetic powder). And the third preliminary heat-treated synthetic powder containing boron oxide / chromium oxide 0.05 to 0.05%.
7.0 parts by weight, the antimony oxide-containing fifth preliminary heat-treated synthetic powder 0.5 to 10.0 parts by weight, cobalt oxide powder,
0.3 to 8.0 parts by weight of two or three kinds of powder selected from the group consisting of manganese oxide powder and nickel oxide powder (including the contribution of the fifth preheat-treated synthetic powder containing antimony oxide), oxidation Bismuth powder 1.0-10.0
Parts by weight and aluminum compound powder 0.0001 to
A zinc oxide-based mixed powder is prepared by mixing 0.05 parts by weight (however, the equivalent amount of aluminum oxide), the zinc oxide-based mixed powder is molded, and the obtained compact is sintered at 800 to 1100 ° C. A zinc oxide-based sintered body obtained by:

A method for producing a zinc oxide-based sintered body, comprising 3 to 70% by weight of boron oxide powder and 30 to 9% of chromium oxide powder
Oxide mixed powder consisting of 7% by weight of 300 to 1400
A preliminary heating heat-treated synthetic powder containing boron oxide / chromium oxide, obtained by preliminarily heating at a temperature of 0 ° C. to obtain a third preliminary heat-treated synthetic powder containing 20 to 50% by weight of antimony oxide, at least zinc oxide, cobalt oxide, 1 to 5 species selected from manganese, nickel oxide and chromium oxide 50 to 80
% Of the oxide mixed powder consisting of
A step of obtaining a fifth preliminarily heat-treated synthetic powder containing antimony oxide by preliminarily heating at a temperature of 000 to 1400 ° C. and then pulverizing, 81.38 parts by weight of zinc oxide powder (fifth preliminarily heat-treated synthetic powder) The boron-containing / chromium oxide-containing third preliminary heat-treated synthetic powder in an amount of 0.08 to 5.0 parts by weight, and the antimony oxide-containing fifth powder.
Two or three kinds of powder selected from the group consisting of 0.5 to 10.0 parts by weight of preheat-treated synthetic powder, cobalt oxide powder, manganese oxide powder and nickel oxide powder
8.0 parts by weight (including the contribution of the fifth preheat-treated synthetic powder), 1.0 to 10.0 parts by weight of bismuth oxide powder and 0.0001 to 0.05 parts by weight of aluminum compound powder (in terms of aluminum oxide) (A) to prepare a zinc oxide-based mixed powder, (b) molding the zinc oxide-based mixed powder, and
A production method comprising a step of sintering at 00 to 1100 ° C.

The present invention further provides the following zinc oxide-based sintered body and a method for producing the same: a boron oxide content of 3 to
60% by weight, the content of chromium oxide is 10 to 75% by weight, and the content of at least one of bismuth oxide, antimony oxide and rare earth oxide is 30 to 80% by weight.
And a fourth preheat-treated synthetic powder containing boron oxide / chromium oxide, which has an antimony oxide content of 20 to 50% by weight and is at least selected from zinc oxide, cobalt oxide, manganese oxide, nickel oxide and chromium oxide. One
A preliminarily heat-treated synthetic powder containing antimony oxide having a content of 50 to 80% by weight is prepared beforehand, and 81.38 parts by weight of zinc oxide powder (contributed by the fifth preheat-treated synthetic powder containing antimony oxide) Min.), The boron oxide /
Chromium oxide-containing fourth preheat-treated synthetic powder 0.1 to 5.0
Parts by weight, 0.5 to 10.0 parts by weight of the fifth preheat-treated synthetic powder containing antimony oxide, two or three kinds of powders selected from the group consisting of cobalt oxide powder, manganese oxide powder and nickel oxide powder 0.3 to 5.0 parts by weight (including the contribution of the fifth preheat-treated synthetic powder containing antimony oxide), 1.0 to 10.0 parts by weight of bismuth oxide powder (the fourth preheat-treated synthesis containing boron oxide / chromium oxide) Powder) and aluminum compound powder 0.0
001 to 0.05 parts by weight (in terms of aluminum oxide) are mixed to prepare a zinc oxide-based mixed powder, and the zinc oxide-based mixed powder is molded to obtain a molded body.
A zinc oxide-based sintered body sintered at 00 to 1100 ° C.

A method for producing a zinc oxide-based sintered body, comprising 3 to 60% by weight of boron oxide powder and 10 to 7% of chromium oxide powder
Preheating 30 to 80% by weight of an oxide mixed powder composed of 5% by weight and at least one of bismuth oxide powder, antimony oxide powder and rare earth oxide powder at 300 to 1400 ° C. and then pulverizing The boron oxide content of 3 to 60% by weight and the chromium oxide content of 10 to
Obtaining a fourth preheat-treated synthetic powder of 75% by weight, antimony oxide 20-50% by weight, at least zinc oxide
An oxide mixed powder composed of 50 to 80% by weight of 1 to 5 kinds selected from cobalt oxide, manganese oxide, nickel oxide and chromium oxide is preferably used at a high temperature of 1000 to 14%.
A step of obtaining a fifth preliminarily heat-treated synthetic powder containing antimony oxide by preliminarily heating at a temperature of 00 ° C. and then pulverizing; 0.1 to 6.0 parts by weight of the fourth preliminary heat-treated synthetic powder containing boron oxide / chromium oxide, 0.5 to 10.0 parts by weight of the fifth pre-heat-treated synthetic powder containing antimony oxide, 0.3 to 5.0 parts by weight of a powder selected from the group consisting of a cobalt oxide powder, a manganese oxide powder and a nickel oxide powder (including the contribution of the fifth preheat-treated synthetic powder), oxidation A mixture of 1.0 to 10.0 parts by weight of bismuth powder (including the contribution from the fourth preheat-treated synthetic powder) and 0.0001 to 0.05 parts by weight of aluminum compound powder (in terms of aluminum oxide) Preparing a zinc oxide-based mixed powder Te, step molding the zinc oxide-based mixed powder and,
A manufacturing method comprising a step of sintering the molded body obtained in the above step at 800 to 1100 ° C.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the particle diameters of the initial coarse raw material powder and the mixed powder as the molding material are the same as those of the same powder used in the ordinary method.
Generally, the particle size of these powders varies depending on the type of oxide and the like, but is usually in the range of about 0.1 to 15 μm, and more preferably in the range of about 0.5 to 10 μm. In addition, the term “powder” may be used to refer to various raw materials, such as “aluminum compound”. Further, the particle size of ZnO indicates a value obtained by observation with an electron microscope photograph, and the particle size of other powders indicates a value obtained by a laser diffraction analysis method.

In the first aspect of the present invention, a first preheat-treated synthetic powder is prepared in advance as a boron oxide source in a zinc oxide-based molded sintered body. The first preheat-treated synthetic powder is a mixture of boron oxide or boric acid, and at least one of bismuth oxide, antimony oxide (at least one of antimony trioxide, antimony pentoxide, and antimony pentoxide) and a rare earth oxide. After preheating the obtained mixed powder at 300 to 1400 ° C., the mixture is prepared by pulverizing the heated agglomerate. When a small amount of the first preliminary heat-treated synthetic powder is produced, it is preferable that the mixed powder is heated and melted, rapidly cooled, and pulverized by a known wet method or dry method. 300-500 for mass production
It is preferable to pulverize after heating at about ℃, more preferably about 350 to 450 ℃. In order to make the properties of the first preliminary heat-treated synthetic powder more uniform, it is preferable to perform heating and pulverization twice or more. As rare earth elements used in the form of oxides as components contained in the first preheat-treated synthetic powder, atomic numbers 21 (Sc), 39 (Y),
And elements of 57 (La) to 71 (Lu), among which Y, La, Nd, Pr and the like are more preferable. The content of boron oxide in the first preheat-treated synthetic powder is usually about 3 to 60% by weight, and more preferably about 5 to 45% by weight. Boron oxide is used in such a first
By preliminarily blending it with the preheat-treated synthetic powder, effects such as control of ZnO grain growth and improvement of varistor reliability are achieved.

A second preheat-treated synthetic powder is prepared in advance as a chromium oxide source in the sintered body. The second preheat-treated synthetic powder uniformly mixes chromium oxide with at least one of bismuth oxide, antimony oxide (at least one of antimony trioxide, antimony tetroxide, and antimony pentoxide) and a rare earth oxide. After preheating the obtained mixed powder at 400 to 1400 ° C., the mixture is prepared by pulverizing the heated agglomerate. The employment of the pulverizing method according to the heating temperature is the same as in the case of the first preliminary heat-treated synthetic powder. The rare earth element used in the form of oxide as a component contained in the second preheat-treated synthetic powder is the same as that in the case of the first preheat-treated synthetic powder. The content of chromium oxide in the second preheat-treated synthetic powder is usually about 10 to 75% by weight, and more preferably about 15 to 50% by weight. The content of at least one of bismuth oxide, antimony oxide (at least one of antimony trioxide, antimony tetroxide, and antimony pentoxide) and rare earth oxide in the second preheat-treated synthetic powder is usually 25 to 90% by weight. And more preferably about 75 to 50% by weight. By blending chromium oxide in such a second preheat-treated synthetic powder in advance, an effect of stabilizing sintering mainly at the time of low-temperature sintering is achieved.

A fifth preheat-treated synthetic powder is prepared in advance as a source of antimony oxide in the sintered body. The fifth preheat-treated synthetic powder is selected from antimony oxide (at least one of antimony trioxide, antimony tetroxide and antimony pentoxide) and at least zinc oxide, cobalt oxide, manganese oxide, nickel oxide and chromium oxide. After preheating the oxide mixed powder consisting of 1 to 5 kinds of 50 to 80% by weight at a high temperature, preferably at a temperature of 1000 to 1400 ° C., pulverization is performed to obtain a fifth preheat-treated synthetic powder. Prepare. The content of antimony oxide in the fifth preheat-treated synthetic powder is usually about 20 to 50% by weight. By mixing antimony oxide in such a fifth preheat-treated synthetic powder in advance, an effect of stabilizing sintering mainly at the time of low-temperature sintering is achieved.

The zinc oxide-based sintered body according to the first aspect of the present invention contains zinc oxide powder as a main component and contains the first and second zinc oxide powders.
It is manufactured by the following method using a mixed powder raw material containing the preheat-treated synthetic powder and the fifth preheat-treated synthetic powder. That is, zinc oxide 81.38 parts by weight (Zn
The value corresponding to 1 mole of O = 81.38 g is expressed in parts by weight and includes the contribution from the fifth preheat-treated synthetic powder.)
On the other hand, the first preliminary heat-treated synthetic powder containing boron oxide 0.0
5 to 5.0 parts by weight, chromium oxide-containing second preliminary heat-treated synthetic powder 0.05 to 7.0 parts by weight, antimony oxide-containing fifth
0.5 to 10.0 parts by weight of preheat-treated synthetic powder, 0.3 to 8.0 parts by weight of at least two kinds selected from the group consisting of cobalt oxide, manganese oxide and nickel oxide (the above fifth preheated synthetic powder) 1.2 to 7.0 parts by weight of bismuth oxide (including the contributions from the first and second preheat-treated synthetic powders), and 0.0001 to 0.1. In a conventional manner, wet-pulverized or dry-pulverized, and if necessary, sieved to obtain a zinc oxide-based mixed powder as a molding material having a predetermined particle size. Prepare.

With respect to at least two members selected from the group consisting of cobalt oxide, manganese oxide and nickel oxide contained in the zinc oxide-based mixed powder, at least one of them has a valence larger than two. Is preferred.
In this case, these oxides are thermally decomposed at the time of sintering of the molded body, which will be described later, and solid-dissolve in zinc oxide as a divalent oxide, and the generated high-pressure oxygen forms closed pores in the molded body. As a result, the effect of improving the electrical characteristics of the varistor is achieved.

As the aluminum compound, Al (O
H) ₃ , Al ₂ O ₃ .nH ₂ O, AlOOH, ultrafine alumina having an average particle size of 0.1 μm or less, Al (NO ₃ ) _3.
Aluminum salts such as 9H ₂ O, Al ₂ (SO ₄ ) ₃ ,
Aluminum-containing organic compounds such as Al (OH) (CH ₃ COO) ₂ and aluminum oxalate can be used. As these aluminum compounds, AlOOH,
Al (OH) (CH ₃ COO) ₂ , Al (NO ₃ ) _3.
9H ₂ O and the like are more preferable.

The zinc oxide-based mixed powder may include at least one selected from germanium oxide, niobium oxide, lead oxide, silicon oxide, tin oxide, tantalum oxide, titanium oxide, and tungsten oxide, if necessary. Powder can be added. The individual loadings of these optional additives are:
It is usually 2.0 parts by weight or less, more preferably about 1.5 parts by weight, based on 81.38 parts by weight of zinc oxide. Also, when two or more optional additives are blended, the total blending amount is usually 2.0 parts by weight or less, more preferably about 1.5 parts by weight. When these optional additives are used, effects such as control of ZnO particle size and improvement of varistor reliability are achieved.

Next, the zinc oxide-based mixed powder obtained above is molded into a predetermined shape according to a conventional method.
Sintering is performed at about 200 ° C, more preferably at about 850 to 1100 ° C. The sintering of the molded body may be performed according to a conventional method. Next, the sintered body is cooled to room temperature at a rate of about 25 to 100 ° C./hr. Thus, a sintered body that is a base material for manufacturing a zinc oxide varistor is obtained. The obtained sintered body is preferably heat-treated at about 500 to 800 ° C (more preferably, about 550 to 750 ° C). By this heat treatment, a γ-bismuth phase is formed as a bismuth oxide main component phase.

In the second embodiment of the present invention, a third preheat-treated synthetic powder is prepared as a boron oxide source and a chromium oxide source for producing a zinc oxide-based molded sintered body.
The third preheat-treated synthetic powder is composed of boron oxide or boric acid powder 3 to 70% by weight and chromium oxide powder 30 to 97% by weight.
Is prepared by preliminarily heating an oxide mixed powder consisting of
The zinc oxide-based sintered body according to the second aspect of the present invention comprises, as a main component, a zinc oxide powder and a mixed powder material containing the third preheat-treated synthetic powder, by the following method. Manufactured. That is, with respect to zinc oxide 81.38 parts by weight (including the contribution from the fifth preheat-treated synthetic powder),
0.05 to 5.0 parts by weight of the third preheat-treated synthetic powder containing boron oxide and chromium oxide, 0.5 to 10.0 parts by weight of the fifth preheat-treated synthetic powder containing antimony oxide,
0.3 to 7.0 parts by weight (including the contribution from the fifth preheat-treated synthetic powder) of at least two selected from the group consisting of cobalt oxide, manganese oxide, and nickel oxide;
1.0 to 10.0 parts by weight of bismuth oxide and 0.0001 to 0.05 parts by weight of aluminum compound powder (in terms of aluminum oxide) are mixed, wet-pulverized or dry-pulverized according to a conventional method, and sieved. Then, a zinc oxide-based mixed powder as a molding material having a predetermined particle size is prepared. The second aspect of the present invention is the same as the first aspect of the present invention except that a third preheat-treated synthetic powder is used as a boron oxide source and a chromium oxide source.

In the third embodiment of the present invention, a fourth preheat-treated synthetic powder is prepared as a boron oxide source and a chromium oxide source for producing a zinc oxide-based molded sintered body.
The fourth preheat-treated synthetic powder is an oxide powder selected from the group consisting of 3 to 60% by weight of boron oxide powder, 10 to 75% by weight of chromium oxide powder, bismuth oxide powder, antimony oxide powder and rare earth oxide powder. At least one of the three
0 to 80% by weight of an oxide mixed powder in an amount of 300 to 1
It is prepared by preheating at 400 ° C. and then pulverizing.

The zinc oxide-based sintered body according to the third aspect of the present invention uses a mixed powder raw material containing zinc oxide powder as a main component and the fourth preheat-treated synthetic powder as follows. It is manufactured by the method. That is, zinc oxide 81.38
Parts by weight (including the contribution from the fifth preheat-treated synthetic powder), 0.1 to 7.0 parts by weight of the fourth preheat-treated synthetic powder containing boron oxide / chromium oxide, and the fifth powder containing antimony oxide. 0.5 to 10.0 parts by weight of preheat-treated synthetic powder,
0.3 to 7.0 parts by weight (including the contribution from the fifth preheat-treated synthetic powder) of at least two selected from the group consisting of cobalt oxide, manganese oxide, and nickel oxide;
A mixture of 1.0 to 10.0 parts by weight of bismuth oxide (including the contribution from the fourth preheat-treated synthetic powder) and 0.0001 to 0.05 parts by weight of aluminum compound powder (in terms of aluminum oxide) is mixed. According to a conventional method, wet or dry pulverization and sieving are performed to prepare a zinc oxide-based mixed powder as a molding material having a predetermined particle size. The third aspect of the present invention is the same as the first aspect of the present invention except that a fourth preheat-treated synthetic powder is used as a boron oxide source and a chromium oxide source.

The zinc oxide varistor according to the present invention is manufactured using the zinc oxide-based sintered body obtained as described above, for example, as follows. The shape and manufacturing method of the zinc oxide varistor are the same as those of the varistor according to the known technique, and are not particularly limited. FIG. 1 is a schematic perspective view of a disk-type zinc oxide varistor made using the zinc oxide-based sintered body of the present invention. Zinc oxide sintered body 1
An aluminum layer (not shown) was formed by spraying aluminum on both the front and back surfaces of No. 1, and then the electrode 12 was formed by further spraying copper on the formed aluminum layer. After the lead wire 13 is soldered to the electrode 12, the sintered body other than the lead wire portion and the electrode portion are covered with a non-conductive layer (for example, a resin layer such as an epoxy resin). The varistor type varistor shown in FIG. 2 is formed by applying a known coating material to the circumferential surface of a columnar zinc oxide based sintered body 21 and sintering it to form an insulating layer 23, and then forming metal aluminum electrodes on the upper and lower surfaces. The electrode 22 is formed by spraying a material. This type of varistor is housed in a container (not shown) surrounded by insulators, connected to electrodes, and used as an arrester device according to a conventional method. Further, although not shown, the zinc oxide-based mixed powder according to the present invention is formed into a thin plate according to a conventional method, and the obtained thin plate-shaped formed body and the metal electrode material are alternately laminated, and the obtained laminated body is formed. When baking is performed, a laminated zinc oxide varistor can be obtained.

Hereinafter, the present invention will be described more specifically with reference to examples. In the following examples, “parts” means “parts by weight”. In each example, in order to facilitate comparison, the amount of aluminum added and
The addition amounts of the oxides of cobalt, manganese and nickel were made constant. Also, the initial raw material powder and heat treatment,
The particle size of the powder after pulverization is as follows. ^* Zn
O: 0.5 to 1.0 μm, ^* Co ₃ O ₄ , MnO ₂ , N
iO: 1 to 5 μm, ^* Bi ₂ O ₃ , Y ₂ O ₃ : 1 to 10
μm, ^* Sb ₂ O ₃ , Sb ₂ O ₄ , Sb ₂ O ₅ : 0.5
５5 μm, ^* Cr ₂ O ₃ : 1-5 μm, ^* B ₂ O ₃ : 1
^* 1st, 2nd, 3rd, 4th and 5th preheat-treated synthetic powders (after pulverized by a ball mill for 60 hours):
0.8-2.5 μm, ^* Mixed powder for molding (after pulverized by a ball mill for 60 hours): 2.7 μm on average.

[0040] (Example ₁₎ B 2 _{O 3} powder and _Cr 2 _{O 3} and powder of 1: 1 (molar ratio), i.e. the weight ratio 0.31
4: After mixing at 0.686 and heat-treating at 500 ° C. for 5 hours in an air atmosphere, B was finely ground using a monomalon pot using stabilized zirconia as a grinding medium.
_A third preliminary heat-treated synthetic powder containing ₂ O ₃ / Cr ₂ O ₃ was obtained. Next, Sb ₂ O ₃ powder: ZnO powder: Co ₃ O
₄ powder: NiO powder = 0.340: 0.382: 0.1
After mixing at a ratio of 88: 0.088 (weight ratio) and heat-treating at 1200 ° C. for 5 hours in an air atmosphere, the mixture was finely pulverized using a monomalon pot using stabilized zirconia as a pulverizing medium to obtain Sb _2. A fifth preheat-treated synthetic powder containing O ₃ was obtained.

Next, various raw materials for producing a zinc oxide-based sintered body were prepared using ZnO powder: the above-mentioned third preliminary heat-treated synthetic powder containing B ₂ O ₃ / Cr ₂ O ₃ : Bi ₂ O ₃ powder: Co ₃ O ₄ powder :
MnO ₂ powder: NiO powder: the _Sb 2 _{O 3} containing 5 preliminary heat treatment synthetic _{powder: Al (NO 3) 3 ·} 9H 2 O = 8
0.81: x: 3.4: 0.672: 0.414: 0.
251: 1.5: 0.0075 (weight ratio), and wet-mixed and pulverized with a ball mill of a monomalon pot. Here, x = 0.03, 0.05, 0.1, 0.
5,1,3,5,7 were selected. After drying the obtained compounded powder and pressing it into a disk shape, the obtained molded body was heated in the air at a rate of 50 ° C./hour, kept at 900 ° C. for 10 hours, and then heated at a rate of 50 ° C./hour. Then, the temperature was lowered to room temperature to obtain a zinc oxide-based sintered body (hereinafter, also a heat-treated zinc oxide-based sintered body may be simply referred to as a "zinc oxide-based sintered body"). The obtained sintered body has a thickness of 1.2 m.
m and a diameter of 14 mm. Next, a part of the obtained sintered body was heat-treated at 700 ° C. for 1 hour.

FIG. 1 is a schematic perspective view of a disk-type zinc oxide varistor made using the zinc oxide-based sintered body of the present invention. Zinc oxide-based sintered body 1 obtained as described above
An aluminum layer (not shown) is formed by spraying aluminum on both surfaces of the first electrode 1, and then copper is further sprayed on the formed aluminum layer to form an electrode 12.
Was formed. After soldering the lead wire 13 to the electrode 12, the sintered body other than the lead wire portion and the electrode portion were resin-coated to obtain a zinc oxide varistor according to the present invention (hereinafter, containing Sb ₂ O ₃ Zinc oxide-based varistors obtained by using three types of sintered bodies obtained from different mixed materials of the fifth preheat-treated synthetic powder are # 1
01, # 102 and # 103. Also in Example 2 and thereafter, zinc oxide varistors obtained by using sintered bodies obtained from mixed materials having different compositions are similarly shown).

The electrical characteristics of the zinc oxide varistor thus obtained were evaluated. 1 mA as initial electrical characteristics
, A voltage for a thickness of 1 mm between both terminals when the current flows, that is, a rising voltage V _{1 mA} / mm,
Non-linear resistance index obtained using _{1 mA} and V _{0.1 mA
0.1 mA} α _{1 mA} was measured. In the following,
The non-linear resistance index _{0.1 mA} α _{1 mA} may be simply referred to as α value. The larger the non-linear resistance index, the greater the surge absorbing ability. Further, the non-linear resistance characteristics in the low current region were evaluated at V _{1 mA} / V _{0.0 lmA} . V
_{When 1 mA} / V0 and _{01 mA} take a value of 1.15 or less, the leakage current is small, and it is not necessary to _pay attention to heat generation, and the varistor element has excellent stability.

Further, the reliability of the varistor against a DC load was evaluated. That is, after applying a DC load of 0.5 Watt to the varistor in a high temperature atmosphere of 80 ° C. for 500 hours, the varistor is cooled, and the change rate of the varistor rise voltage V1 _mA , that is, the DC load change rate ΔV _1mA / V _1mA.
Was measured. The smaller the rate of change ΔV _1mA / V _{1mA of the} varistor rise voltage V _1mA, the more stable the electrical characteristics of the zinc oxide varistor, indicating higher reliability.
Further, the reliability of the varistor against current surge was evaluated as follows. 8 × 20 μsec, 2.5 kA
Of the varistor rise voltage V _{1 mA} when 10 pulses are applied, that is, the surge change rate ΔV _{1 mA}
/ V _{1 mA} was measured. The smaller the value of the surge change 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.
In addition, the minimum value and the maximum value within the same lot are shown as numerical values indicating the evaluation results of the electrical characteristics. Table 1 shows the composition used in Example 1 and the evaluation results of the electrical characteristics of the varistor obtained in Table 2.

[0045]

[0045]

[Table 1]

[0046]

[Table 2]

From the results shown in Table 2, it is clear that the raw material mixture powder compact according to the present example can be sintered even at a temperature as low as 900 ° C. The varistor obtained using this sintered body, the non-linear resistance characteristic is good, even for long-time DC loading, and also against a surge current, the change in threshold voltage V _1mA Rate (△
The absolute value of (V _1mA / V _1mA ) is 5% or less, and the reliability is excellent. Further, as is clear from the results shown in Table 1, the variation in the electric characteristics within the same lot was small. Further, although not shown in Table 1, when a zinc oxide varistor is prepared using the zinc oxide-based sintered body of the present embodiment, variations in electrical characteristics between different lots are also reduced. As small as the variation in characteristics.

[0048] (Example 2) Example 1 and using the third preliminary heat treatment synthetic powder and _Sb 2 _{O 3} containing 5 preliminary heat treatment combining the powder with _B 2 _O 3 / _Cr 2 _{O 3,} prepared contained the same , Zn
_{O: B 2 O 3 / Cr} 2 O 3 containing third preliminary heat treatment synthetic _{powder: Bi 2 O 3: Co 3} O 4: MnO 2: NiO: Sb
Fifth preliminary heat-treated synthetic powder containing ₂ O ₃ : Al (NO ₃ ) ₃
9H ₂ O = 80.81: 0.4: 3.4: 0.67
2: 0.414: 0.251: 1.5: 0.0075
(Weight ratio), and wet-mixed and pulverized with a ball mill of a monomalon pot, and then granulated using a spray dryer to obtain a zinc oxide-based mixed powder. An arrester was prepared using the zinc oxide-based mixed powder thus obtained.

For the preparation of the arrester, the zinc oxide-based mixed powder obtained by spray drying was mixed with RIP (Rubber).
Isostatic Press (rubber isostatic pressing) method, and molded into a column. A mixture of bismuth borosilicate glass powder and MnO ₂ was applied to the side surface of the obtained molded body, and the mixture was heated at 900 ° C. or 950 ° C. for 10 hours. By firing, two types of columnar zinc oxide based sintered bodies # 2
01 and # 202 were obtained. The size of the obtained two types of zinc oxide-based sintered bodies was 32 mm in diameter × 25 mm in height. Aluminum electrodes were sprayed on the upper and lower surfaces of these zinc oxide-based sintered bodies to form electrodes, and then a circumferential example surface was coated with a mica resin mixture to obtain two arrester-type zinc oxide varistors. V _1mA is V
_{1 mA} = 5.99 kV and V _1mA = 5.89 kV.

FIG. 2 is an oblique view of an arrester-type zinc oxide varistor prepared using a zinc oxide-based sintered body according to the present embodiment. Element electrodes 22 are formed on both upper and lower surfaces of the zinc oxide based sintered body 21 by aluminum spraying.
Further, a side surface insulating film 23 made of a mixture of mica and resin is formed on the side surface of the zinc oxide based sintered body, and the zinc oxide based varistor element Is formed. Table 3 shows the current-voltage characteristics of the arrester type zinc oxide varistor device obtained in this example.

[0051]

[0051]

[Table 3]

As is clear from Table 3, the two types of arrestor-type zinc oxide varistors manufactured using the zinc oxide-based sintered body having the composition according to the present embodiment can be used even in a high current region.
It can be seen that the non-linear resistance characteristics are excellent. Next, the service life was estimated by performing an AC power acceleration test. 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 power application rate of 95%. As a result, the initial Ir hardly changed in both devices after the test for 100 hours or more. Therefore, when used as a gapless arrester, under the conditions of an ambient temperature of 70 ° C. and a power application rate of 80%,
The result is that the service life of more than 100 years is guaranteed.

Example 3 B ₂ O ₃ powder, Cr ₂ O ₃ powder and Y ₂ O ₃ powder were mixed at various weight ratios, heat-treated at 410 ° C. for 5 hours in an air atmosphere, pulverized, and then re-pulverized. Heat-treated under the same conditions, and finely pulverized with a ball mill of a monomalon pot using stabilized zirconia as a pulverizing medium,
A fourth preheat-treated synthetic powder containing B ₂ O ₃ / Cr ₂ O ₃ was obtained. In addition, Sb ₂ O ₃ powder and ZnO powder were mixed at a weight ratio of Sb ₂ O ₃ powder: ZnO powder = 0.34: 0.66, heat-treated at 1250 ° C. for 5 hours in an air atmosphere, and pulverized. Heat treatment was again performed under the same conditions, and the mixture was finely pulverized with a ball mill of a monomalon pot using stabilized zirconia as a pulverizing medium to obtain a fifth preheat-treated synthetic powder containing Sb ₂ O ₃ . Next, a sample was prepared in the same manner as in Example 1. That is, ZnO powder: B ₂ O ₃ / Cr ₂
O ₃ -containing fourth preliminary heat-treated synthetic powder: Bi ₂ O ₃ powder: C
o ₃ O ₄ powder: MnO ₂ powder: NiO powder: Sb ₂ O ₃
Containing fifth preheat-treated synthetic powder: aluminum hydroxide acetate (Al (OH) (CH ₃ COO) ₂ ) powder = 81.38
-0.66x: 0.5: 4: 0.954: 0.414:
0.383: x: 0.0065 (weight ratio). Where x = 0.3,0.5,1,2,5,
8, 10, and 15 were selected. These were mixed and pulverized by a wet method for 60 hours, dried, granulated, and molded. The obtained molded body was fired at 900 ° C. or 950 ° C. to obtain a zinc oxide-based sintered body. A part of each lot was subjected to a heat treatment at 700 ° C., and a zinc oxide varistor was produced in the same manner as in Example 1, and its electrical characteristics were evaluated. The composition is shown in Table 4 and the measurement results are shown in Table 5.

[0054]

[0054]

[Table 4]

[0055]

[Table 5]

The zinc oxide varistor manufactured using the zinc oxide-based sintered body according to the present embodiment has good non-linear resistance characteristics, and can be used for a long-time DC load and a surge. Change rate of rising voltage V _{1 mA} (△ V _{1 mA}
/ V _1mA ) was 5% or less, indicating excellent reliability. In Comparative Example # 301, the varistor voltage (V
_{1 mA} / mm) and the variation of the α value were large, and the rate of change of V _{1 mA} with respect to the load was large. Further, in Comparative Example # 308, V _{1 mA}
Was large and measurement was impossible.

Example 4 B ₂ O ₃ powder: Sb ₂ O ₃ powder was used in a molar ratio of 2: 1, that is, in a weight ratio of 0.1.
333: 0.667, and heat-treated at 370 ° C. for 5 hours in an air atmosphere, and then finely pulverized with a ball mill of a monomalon pot using stabilized zirconia as a pulverizing medium to obtain a B ₂ O ₃ -containing 1 Preheat-treated synthetic powder (average particle size: about 0.5 to 1.5 μm) was obtained. Also, B
i ₂ O ₃ powder: Cr ₂ O ₃ powder: Y ₂ O ₃ powder are mixed in a weight ratio of 0.5: 0.246: 0.254, and heat-treated at 500 ° C. for 5 hours in an air atmosphere. Then, a second preliminary heat-treated synthetic powder containing Cr ₂ O ₃ was obtained by finely pulverizing with a ball mill of a monomalon pot using stabilized zirconia as a pulverizing medium. Also, Sb ₂ O ₃ powder:
The Co ₃ O ₄ powder was mixed at a weight ratio of 0.3: 0.7, and heat-treated at 1050 ° C. for 5 hours in an air atmosphere, and then finely ground by a ball mill of a monomalon pot using stabilized zirconia as a grinding media. By pulverizing, a fifth preheat-treated synthetic powder containing Sb was obtained.

Next, ZnO: wherein _B 2 O3 containing first preliminary heat treatment synthetic powder: _Bi 2 _{O 3:} The _Cr 2 _{O 3} containing second
Preheat-treated synthetic powder: Co ₃ O ₄ : MnO ₂ : NiO:
The Sb-containing fifth preheat-treated synthetic powder: AlOOH = 8
1.38: 1.2: 4.25-0.5x: x: 0.11
4: 0.414: 0.383: 1.2: 0.0012
(Weight ratio) and mixed and pulverized by a wet method. Here, x = 0.03, 0.05, 0.1, 0.
2,0.5,1,2,5,7,10 were selected. After drying the obtained raw material blended powder and pressing it into a disk shape, the temperature of the green body was raised at a rate of 50 ° C./hour in the air, and
After maintaining at 50 ° C. for 10 hours, the temperature was decreased at a temperature decreasing rate of 50 ° C./hour to obtain a sintered body. Part of each lot,
A heat treatment at 700 ° C. was performed, and a zinc oxide varistor was manufactured in the same manner as in Example 1, and the electrical characteristics were evaluated. Table 6 shows the sample composition, and Table 7 shows the results.

[0059]

[Table 6]

[0060]

[Table 7]

The zinc oxide-based sintered body obtained according to this embodiment can be sintered even at a low temperature of 950 ° C.
A zinc oxide varistor made using this sintered body,
Except for # 401 and # 410, the non-linear resistance characteristics are good, and the change rate of the rising voltage V1mA ΔV _1mA /
The absolute value of V _{1 mA} was 5% or less, _indicating excellent reliability. Also, the variation in the electrical characteristics within the same lot was small. When a zinc oxide varistor was prepared using the zinc oxide-based sintered body according to the present embodiment, the variation in the electrical characteristics between different lots was as small as the variation in the electrical characteristics in the same lot. In # 401 and # 410, an electrically stable element was not obtained, and deterioration due to load was large.

Example 5 B ₂ O ₃ powder and Sb ₂ O ₃ powder were mixed at a molar ratio of 1: 1, that is, 0.19 by weight.
After subjecting the mixed powder to 0.807 to a heat treatment at 380 ° C. for 5 hours in an air atmosphere, the powder was finely pulverized by a ball mill of a monomalon pot using stabilized zirconia as a pulverizing medium. _A first preliminary heat-treated synthetic powder containing ₂ O ₃ was obtained. Next, the Cr ₂ O ₃ powder and the Sb ₂ O ₃ powder were mixed at a molar ratio of 2: 1, that is, at a weight ratio of 0.51:
The powder mixed to be 0.49 is placed in an air atmosphere for 60
After subjecting to a heat treatment at 0 ° C. for 5 hours, the second preliminary heat treatment containing Cr composed of Cr ₂ O ₃ and Sb ₂ O ₃ is performed by finely pulverizing with a ball mill of a monomalon pot using stabilized zirconia as a grinding media. A synthetic powder was obtained. Also, Sb
₂ O ₃ powder: ZnO powder: Co ₃ O ₄ powder: NiO powder (the average particle diameter of each powder is 2 to 3 μm) in a weight ratio of 0.34: 0.382: 0.188: 0. 088
And heat-treated at 1100 ° C. for 5 hours in an air atmosphere, and then finely pulverized by a ball mill of a monomalon pot using stabilized zirconia as a pulverizing medium, thereby obtaining a fifth preheat-treated synthetic powder containing Sb (average). Particle size approx.
5-1.5 [mu] m).

ZnO powder: B ₂ O ₃ -containing first preliminary heat-treated synthetic powder: Bi ₂ O ₃ : Cr ₂ O ₃ -containing second preliminary heat-treated synthetic powder: Co ₃ O ₄ powder: MnO ₂ powder: N
iO powder: Sb-containing fifth preheat-treated synthetic powder: Al
(OH) (CH ₃ COO) ₂ = 81: 0.5: 4.2:
0.5: 0.766: 0.414: 0.295: 1.
0: 0.0065 (weight ratio), mixed and pulverized by a wet method for 60 hours, and then 750 ° C., 800 ° C., 850 ° C., 900 ° C., 95
Various firing temperatures of 0 ° C., 1000 ° C., 1100 ° C., and 1200 ° C. were selected to obtain a zinc oxide-based sintered body. The sample numbers at respective temperatures are # 501, # 502, # 503, # 5
04, # 505, # 506, # 507, and # 508. After applying a silver electrode material to both surfaces of the zinc oxide based sintered body obtained above and baking at 700 ° C. to form an electrode,
The lead wire was soldered to produce a zinc oxide varistor. Table 8 shows the measurement results of the electrical characteristics of the obtained varistors.

[0064]

[0064]

[Table 8]

From the results shown in Table 8, it is clear that the zinc oxide-based sintered body of this example can be sintered even at a low temperature of 800 to 1100 ° C. Zinc oxide varistor produced using the obtained sintered body can also be non-linear resistance characteristic is good, even for long-time DC loading, against surge, the rate of change in threshold voltage V _{1 mA} ( △
The absolute value of ( _V1mA / _V1mA ) is 5% or less, and the reliability is excellent. Further, the variation in the electrical characteristics within the same lot was small. Furthermore, when a zinc oxide varistor is prepared using the zinc oxide-based sintered body according to the present embodiment, the variation in electric characteristics between different lots is also small, similarly to the variation in electric characteristics in the same lot. Was. #
In the case of 501, the varistor temperature was so high that the initial characteristics could not be measured.

[0066]

According to the present invention, by using a zinc oxide-based raw material mixed powder having a specific composition, even when the mixed powder compact is sintered at a low temperature, the composition is uniform and the properties are improved. A stable zinc oxide-based sintered body can be obtained. Prior to the preparation of the raw material mixture powder, a small amount of boron oxide and chromium oxide are separately mixed with other oxide components and heat-treated in advance, or boron oxide and chromium oxide are combined. By mixing with other oxide components such as antimony oxide and heat-treating in advance, the heat treatment energy is greatly reduced compared to the prior art in which most of the additional components are preliminarily heat-treated, and the manufacturing process is reduced. Since it is shortened, the manufacturing cost of the zinc oxide varistor can be reduced.

Further, when a zinc oxide varistor is manufactured using the obtained sintered body, a product having excellent electrical characteristics such as non-linear resistance characteristics and reliability can be obtained. More specifically, not only the initial characteristics are excellent, but also the stability to AC, DC and pulse application, 500 to 80
It is also excellent in stability against heat treatment at 0 ° C. Further, the yield rate is improved because the incidence of defective products is reduced.

By using the method for manufacturing a zinc oxide varistor according to the present invention, it is possible to easily provide a material having a high start-up voltage, which has been difficult to realize by the conventional manufacturing method. In the zinc oxide varistor of the present invention, the existence density of interstitial Zn (interstitial zinc atom) in the zinc oxide particles is 1.5 ×
It is 10 ¹⁶ pieces / cm ³ or less.

According to the present invention, although depending on the raw material composition, 9
By sintering at a low temperature of 50 ° C. or less, a zinc oxide-based sintered body having excellent electric characteristics can be obtained. Therefore, a laminated varistor can be obtained by forming a zinc oxide-based sintered body into a sheet shape, alternately laminating it with an electrode material, sintering, and connecting the electrodes by a predetermined connection method. In the prior art, a firing temperature of 1200 ° C. or more is required to impart good characteristics to the laminated varistor, so that a noble metal such as platinum had to be used as an electrode material. On the other hand, according to the method of the present invention in which a zinc oxide-based sintered body can be manufactured at 950 ° C. or lower, there is obtained a great advantage that relatively low-cost silver can be used as an electrode material.

[Brief description of the drawings]

FIG. 1 is a side view schematically showing a disk-type zinc oxide varistor manufactured using a zinc oxide-based sintered body according to the present invention.

FIG. 2 is a side view showing an outline of an arrester-type zinc oxide varistor manufactured using a zinc oxide-based sintered body according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Zinc oxide-based sintered body 12 Electrode 13 Lead wire 21 Zinc oxide-based sintered body 22 Electrode 23 Side insulating film

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4G030 AA11 AA16 AA20 AA21 AA22 AA24 AA25 AA28 AA29 AA32 AA35 AA36 AA37 AA38 AA39 AA40 AA42 AA43 BA04 GA03 GA04 GA08 GA27 GA33 5E034 BB01 DA03 DC02

Claims (18)

[Claims] (1) a boron oxide content of 3 to 60% by weight;
A first preheat-treated synthetic powder containing boron oxide containing at least one of bismuth oxide, antimony oxide and rare earth oxide in a content of 40 to 97% by weight, a bismuth oxide containing 10 to 75% by weight of chromium oxide , The content of at least one of antimony oxide and rare earth oxide is 25 to
A second preheat-treated synthetic powder containing 90% by weight of chromium oxide; Antimony oxide-containing fifth material having a content of five kinds of 50 to 80% by weight.
Preliminarily heat-treated synthetic powder was prepared, and zinc oxide powder 81.
38 parts by weight (including the contribution of the antimony oxide-containing fifth preheat-treated synthetic powder) and the boron oxide-containing first powder
0.05 to 5.0 parts by weight of the preheat-treated synthetic powder, 0.05 to 7.0 parts by weight of the second preheat-treated synthetic powder containing chromium oxide, and 0.5 of the fifth preheat-treated synthetic powder containing antimony oxide 0.3 to 8.0 parts by weight of two or three kinds of powders selected from the group consisting of cobalt oxide powder, manganese oxide powder, and nickel oxide powder (the fifth preliminary heat treatment containing antimony oxide). 1.0 to 10.0 parts by weight of the bismuth oxide powder (including the contribution of the synthetic powder) and the contribution of the boron oxide-containing first preliminary heat-treated synthetic powder and the chromium oxide-containing second preliminary heat-treated synthetic powder And aluminum compound powder 0.0001 to
A zinc oxide-based mixed powder is prepared by mixing 0.05 parts by weight (however, the equivalent amount of aluminum oxide), the zinc oxide-based mixed powder is molded, and the obtained compact is sintered at 800 to 1100 ° C. A zinc oxide-based sintered body obtained by: 2. The zinc oxide-based sintered body according to claim 1, further subjected to a heat treatment at 500 to 800 ° C. 3. A method according to claim 1, further comprising adding germanium oxide, niobium oxide, lead oxide, silicon oxide, tin oxide, and oxide to 81.38 parts by weight of the zinc oxide powder (including the contribution of the fifth preheat-treated synthetic powder containing antimony oxide). The zinc oxide-based sintered body according to claim 1, wherein the zinc oxide-based sintered body is obtained by mixing 0.1 to 2.0 parts by weight of at least one selected from the group consisting of tantalum, titanium oxide, tungsten oxide, and rare earth oxide. 4. A method for producing a zinc oxide-based sintered body, comprising 3 to 60% by weight of a powder of either boron oxide or boric acid.
An oxide mixed powder consisting of at least one of bismuth oxide powder, antimony oxide powder, and rare earth oxide powder in an amount of 40 to 97% by weight is preliminarily heated at 300 to 1400 ° C., and then pulverized to obtain an oxide. Step of obtaining a first boron-containing preheat-treated synthetic powder, chromium oxide 10 to 7
An oxide mixed powder composed of 5% by weight and at least one of bismuth oxide powder, antimony oxide powder and rare earth oxide powder in 25 to 90% by weight is preliminarily heated at a temperature of 400 to 1400 ° C., and then pulverized. To obtain a second preheat-treated synthetic powder containing chromium oxide, by adding 20 to 50% by weight of antimony oxide and at least zinc oxide;
An oxide mixed powder composed of 50 to 80% by weight of 1 to 5 kinds selected from cobalt oxide, manganese oxide, nickel oxide and chromium oxide is preferably used at a high temperature of 1000 to 14%.
A step of obtaining a fifth preliminarily heat-treated synthetic powder containing antimony oxide by preliminarily heating at a temperature of 00 ° C. and then pulverizing, a step of obtaining 81.38 parts by weight of zinc oxide powder (based on the fifth preheated synthetic powder) The boron oxide-containing first preheat-treated synthetic powder in an amount of 0.05 to 5.0 parts by weight, and the chromium oxide-containing second preheat-treated synthetic powder in an amount of 0.05 to 5.0 parts by weight.
7.0 parts by weight, the antimony oxide-containing fifth preliminary heat-treated synthetic powder 0.5 to 10.0 parts by weight, cobalt oxide powder,
0.3 to 8.0 parts by weight of a powder selected from the group consisting of manganese oxide powder and nickel oxide powder (including the contribution of the fifth preheat-treated synthetic powder), bismuth oxide powder 0 to 10.0 parts by weight (first and second parts)
Preparing a zinc oxide-based mixed powder by mixing 0.0001 to 0.05 parts by weight (in terms of aluminum oxide) of an aluminum compound powder (including the contribution of the preheat-treated synthetic powder); A step of molding the mixed powder, and forming the molded body obtained in the step from 800 to 1
A manufacturing method comprising a step of sintering at 100 ° C. 5. A zinc oxide varistor obtained by forming a side insulating film and an electrode on a zinc oxide based sintered body obtained by the method according to claim 1. 6. A laminated zinc oxide varistor, wherein the content of boron oxide is 3 to 60% by weight and the content of at least one of bismuth oxide, antimony oxide and rare earth oxide is 40 to 97% by weight. A first boron oxide-containing first preheat-treated synthetic powder and a chromium oxide content of 10 to 75% by weight
A chromium oxide-containing second preheat-treated synthetic powder containing at least one of bismuth oxide, antimony oxide and a rare earth oxide in a content of 25 to 90% by weight, and an antimony oxide content of 20 to 50% by weight, At least zinc oxide,
A preliminarily heat-treated synthetic powder containing antimony oxide having a content of 1 to 5 selected from cobalt oxide, manganese oxide, nickel oxide and chromium oxide of 50 to 80% by weight; .38 parts by weight (including the contribution of the fifth preheat-treated synthetic powder containing antimony oxide), 0.05 to 5.0 parts by weight of the first preheat-treated synthetic powder containing boron oxide, and the second containing chromium oxide. 0.05 to 7.0 parts by weight of preheat-treated synthetic powder, 0.5 to 10.0 of the fifth preheat-treated synthetic powder containing antimony oxide
Parts by weight, 0.3 to 8.0 parts by weight of two or three kinds of powders selected from the group consisting of cobalt oxide powder, manganese oxide powder and nickel oxide powder (based on the fifth preheat-treated synthetic powder containing antimony oxide) 1.0 to 10.0 parts by weight of the bismuth oxide powder (including the contribution of the first preliminary heat-treated synthetic powder containing boron oxide and the second preliminary heat-treated synthetic powder containing chromium oxide) and aluminum A zinc oxide-based mixed powder is prepared by mixing 0.0001 to 0.05 parts by weight (in terms of aluminum oxide) of a compound powder, and the zinc oxide-based mixed powder is formed into a thin plate. A laminated zinc oxide varistor obtained by alternately laminating shaped bodies and metal electrode materials and firing the obtained laminated body. 7. A boron oxide / chromium oxide-containing third preheat-treated synthetic powder having a boron oxide content of 3 to 70% by weight and a chromium oxide content of 30 to 97% by weight, and an antimony oxide content. The antimony oxide-containing fifth material has an amount of 20 to 50% by weight, and contains at least 1 to 5 kinds selected from zinc oxide, cobalt oxide, manganese oxide, nickel oxide and chromium oxide in an amount of 50 to 80% by weight. Preliminarily heat-treated synthetic powder was prepared, and zinc oxide powder 81.38 was prepared.
Parts by weight (including the contribution of the fifth preheat-treated synthetic powder containing antimony oxide), 0.08 to 5.0 parts by weight of the third preheat-treated synthetic powder containing boron oxide / chromium oxide, and the fifth powder containing antimony oxide. Preheat-treated synthetic powder 0.5-1
0.02 parts by weight of a powder selected from the group consisting of cobalt oxide powder, manganese oxide powder, and nickel oxide powder
0.3 or 8.0 parts by weight (including the contribution of the antimony oxide-containing fifth preheat-treated synthetic powder),
By mixing 1.0 to 10.0 parts by weight of bismuth oxide powder and 0.0001 to 0.05 parts by weight of aluminum compound powder (in terms of aluminum oxide), a zinc oxide-based mixed powder is prepared. A zinc oxide-based sintered body obtained by molding a mixed powder and sintering the obtained molded body at 800 to 1100 ° C. 8. A zinc oxide based sintered body according to claim 7, which is further subjected to a heat treatment at 500 to 800 ° C. 9. The method further comprises: germanium oxide, niobium oxide, lead oxide, silicon oxide, tin oxide, tin oxide, The zinc oxide-based sintered body according to claim 7, which is obtained by blending at least 0.1 to 2.0 parts by weight of at least one selected from the group consisting of tantalum, titanium oxide, tungsten oxide, and rare earth oxide. 10. A method for producing a zinc oxide-based sintered body, comprising:
Boron oxide powder 3 to 70% by weight and chromium oxide powder 30 to
Oxide mixed powder consisting of 97% by weight
A step of obtaining a third preliminary heat-treated synthetic powder containing boron oxide / chromium oxide by preliminarily heating at 0 ° C. and then pulverizing the mixture; 20 to 50% by weight of antimony oxide and at least zinc oxide, cobalt oxide, oxide 1 to 5 species selected from manganese, nickel oxide and chromium oxide 50 to 80
% Of the oxide mixed powder consisting of
A step of obtaining a fifth preliminarily heat-treated synthetic powder containing antimony oxide by preliminarily heating at a temperature of 000 to 1400 ° C. and then pulverizing the mixture; The boron oxide / chromium oxide-containing third preheat-treated synthetic powder in an amount of 0.08 to 5.0 parts by weight, and the antimony oxide-containing fifth powder.
Two or three kinds of powder selected from the group consisting of 0.5 to 10.0 parts by weight of preheat-treated synthetic powder, cobalt oxide powder, manganese oxide powder and nickel oxide powder
8.0 parts by weight (including the contribution of the fifth preheat-treated synthetic powder), 1.0 to 10.0 parts by weight of bismuth oxide powder and 0.0001 to 0.05 parts by weight of aluminum compound powder (in terms of aluminum oxide) (A) to prepare a zinc oxide-based mixed powder, (b) molding the zinc oxide-based mixed powder, and
A production method comprising a step of sintering at 00 to 1100 ° C. 11. A zinc oxide varistor obtained by forming a side insulating film and an electrode on a zinc oxide based sintered body obtained by the method according to claim 7. 12. A laminated zinc oxide varistor, wherein a boron oxide / chromium oxide-containing third preliminary heat treatment having a boron oxide content of 3 to 70% by weight and a chromium oxide content of 30 to 97% by weight. The content of the synthetic powder and antimony oxide is 20 to 50% by weight, and the content of at least 1 to 5 kinds selected from zinc oxide, cobalt oxide, manganese oxide, nickel oxide and chromium oxide is 50 to 8
A fifth preliminarily heat-treated synthetic powder containing antimony oxide, which is 0% by weight, was previously prepared, and 81.38 parts by weight of zinc oxide powder (including the contribution of the fifth preliminarily heat-treated synthetic powder containing antimony oxide), boron oxide / 0.08 to 5.0 parts by weight of the third preheat-treated synthetic powder containing chromium oxide, 0.5 to 10.0 parts by weight of the fifth preheat-treated synthetic powder containing antimony oxide, cobalt oxide powder, manganese oxide powder and oxidized Two or three powders selected from the group consisting of nickel powders
0.3 to 8.0 parts by weight of the seed (the antimony oxide-containing fifth
Zinc oxide by mixing 1.0 to 10.0 parts by weight of bismuth oxide powder and 0.0001 to 0.05 parts by weight of aluminum compound powder (in terms of aluminum oxide). A mixed powder is prepared, the zinc oxide-based mixed powder is formed into a thin plate, the obtained thin plate-shaped formed body and the metal electrode material are alternately laminated, and the obtained laminated body is fired. Stacked zinc oxide varistor. 13. The content of boron oxide is 3 to 60% by weight and the content of chromium oxide is 10 to 75% by weight,
A fourth preheat-treated synthetic powder containing boron oxide / chromium oxide, wherein the content of at least one of bismuth oxide, antimony oxide and rare earth oxide is 30 to 80% by weight, and the content of antimony oxide is 20 to 50% by weight A preliminarily heat-treated synthetic powder containing antimony oxide having a content of at least 1 to 5 selected from zinc oxide, cobalt oxide, manganese oxide, nickel oxide and chromium oxide of 50 to 80% by weight is prepared in advance. Prepared, zinc oxide powder 81.3
8 parts by weight (including the contribution of the fifth preheat-treated synthetic powder containing antimony oxide), 0.1 to 5.0 parts by weight of the fourth preheat-treated synthetic powder containing boron oxide / chromium oxide, 5 Preheat-treated synthetic powder 0.5-1
0.02 parts by weight of a powder selected from the group consisting of cobalt oxide powder, manganese oxide powder, and nickel oxide powder
0.3 to 5.0 parts by weight (including the contribution of the fifth preheat-treated synthetic powder containing antimony oxide) and 1.0 to 10.0 parts by weight of bismuth oxide powder (containing boron oxide / chromium oxide) (Including the contribution from the fourth preheat-treated synthetic powder) and the aluminum compound powder (0.0001 to 0.1).
A zinc oxide-based mixed powder was prepared by mixing the powdered mixture with the above-mentioned zinc oxide-based mixed powder, and a compact was obtained.
A zinc oxide sintered body that sinters at ℃. 14. A zinc oxide based sintered body according to claim 13, further subjected to a heat treatment at 500 to 800 ° C. 15. With respect to 81.38 parts by weight of the zinc oxide powder (including the contribution of the fifth preheat-treated synthetic powder containing antimony oxide), germanium oxide, niobium oxide, lead oxide, silicon oxide, tin oxide, oxide The zinc oxide-based sintered body according to claim 13, which is obtained by blending at least one member selected from the group consisting of tantalum, titanium oxide, tungsten oxide, and rare earth oxide in an amount of 0.1 to 2.0 parts by weight. 16. A method for producing a zinc oxide-based sintered body, comprising:
Boron oxide powder 3-60% by weight and chromium oxide powder 10
75% by weight and at least one of bismuth oxide powder 30-80% by weight, antimony oxide powder 30-80% by weight and rare earth oxide powder 30-80% by weight. 300-1400
A preliminary heating treatment powder containing boron oxide / chromium oxide by preliminarily heating the mixture to obtain a fourth preheat-treated synthetic powder containing boron oxide / chromium oxide, containing 20 to 50% by weight of antimony oxide and at least zinc oxide, cobalt oxide, 1 to 5 species selected from manganese, nickel oxide and chromium oxide 50 to 80
% Of the oxide mixed powder consisting of
A step of obtaining a fifth preheat-treated synthetic powder containing antimony oxide by preliminarily heating at a temperature of 000 to 1400 ° C. and then pulverizing the mixture; Of the fourth preheat-treated synthetic powder containing boron oxide / chromium oxide, 0.1 to 6.0 parts by weight, and the fifth preheat-treated synthetic powder containing antimony oxide, 0.5 to 10.0. Parts by weight, two or three powders selected from the group consisting of cobalt oxide powder, manganese oxide powder, and nickel oxide powder.
0 parts by weight (including the contribution from the fifth pre-heat-treated synthetic powder), 1.0 to 10.0 parts by weight (including the contribution from the fourth pre-heat-treated synthetic powder), and the aluminum compound powder A step of preparing a zinc oxide-based mixed powder by mixing 0.0001 to 0.05 parts by weight (however, the equivalent amount of aluminum oxide), a step of molding the zinc oxide-based mixed powder, and a step obtained by the step. 80 compacts
A production method comprising a step of sintering at 0 to 1100 ° C. 17. A zinc oxide varistor obtained by forming a side surface insulating film and an electrode on a zinc oxide based sintered body obtained by the method according to claim 13. 18. A laminated zinc oxide varistor, wherein the content of boron oxide is 3 to 60% by weight, the content of chromium oxide is 10 to 75% by weight, bismuth oxide, antimony oxide and rare earth oxide. A fourth preheat-treated synthetic powder containing boron oxide / chromium oxide, wherein the content of at least one of the substances is 30 to 80% by weight, and the content of antimony oxide is 20 to 50% by weight, and at least zinc oxide; A preliminarily heat-treated synthetic powder containing antimony oxide having a content of 1 to 5 selected from cobalt oxide, manganese oxide, nickel oxide and chromium oxide of 50 to 80% by weight is prepared in advance, and zinc oxide powder 81. 38 parts by weight (including the contribution of the fifth preheat-treated synthetic powder containing antimony oxide), and 0.1 to 6 of the fourth preheat-treated synthetic powder containing boron oxide / chromium oxide 0 parts by weight, 0.5 to 10.0 parts by weight of the fifth preheat-treated synthetic powder containing antimony oxide, two or three kinds of powders selected from the group consisting of cobalt oxide powder, manganese oxide powder and nickel oxide powder 0.
3 to 5.0 parts by weight (including the contribution of the fifth preheat-treated synthetic powder containing antimony oxide), bismuth oxide powder
0 to 10.0 parts by weight (boron oxide / chromium oxide containing
The zinc oxide-based mixed powder was prepared by mixing 0.0001 to 0.05 parts by weight of aluminum compound powder (including aluminum oxide) in addition to the zinc oxide-based powder. A laminated zinc oxide varistor formed by molding a mixed powder into a thin plate shape and alternately laminating the obtained molded body and the metal electrode material, and firing the obtained laminated body.