JP2002097071A - Zinc oxide ceramic composition and its production method and zinc oxide varistor and device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a zinc oxide ceramic composition and a manufacturing method of a zinc oxide varistor having excellent electrical properties, reliability against DC and surge loads and stability in heat treatment, which can be sintered at 750-1,100 deg.C, especially at a low temperatures of <=1,000 deg.C. SOLUTION: To zinc oxide, at least bismuth oxide, antimony oxide, iron oxide, and an aluminum compound, and then 0.1-5.0 pts.wt. of a synthetic compound containing boron oxide and chromium oxide (vs. 81.38 pts.wt. (1 mole) of zinc oxide) are added, mixed, shaped and fired to give a zinc oxide ceramic composition. Electrodes are formed on both surfaces of the ceramic composition and leads are connected to them to give a disk-type varistor.

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 or a zinc oxide varistor apparatus.

[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.

The ZnO—Bi ₂ O ₃ system, which is the basic composition of the porcelain of the zinc oxide varistor, has a eutectic composition having a eutectic temperature of 740 ° C., so that the mixture of ZnO and Bi ₂ O ₃ is It reacts and sinters easily even at temperatures around 800 ° C. Zn However if the Sb ₂ O ₃ in the additives present Sb ₂ O ₃ is sublimed at a low temperature
It covers around O and hinders the contact between ZnO and Bi ₂ O ₃ , hindering this reaction and making sintering difficult. In addition to this
Bi ₂ O ₃ and ZnO react to form a strong pyrochlore phase film of ZnO—Bi ₂ O ₃ —Sb ₂ O ₃ between ZnO and ZnO, which further causes sintering. In the ZnO-Bi ₂ O ₃ -Sb ₂ O ₃ system, a solid pyrochlore phase is easily formed at a low temperature, and the formation of a liquid Bi ₂ O ₃ phase is hindered, and the progress of liquid phase sintering is delayed. In the case of Sb ₂ O ₃ , the additive itself or the compound of Sb ₂ O ₃ may prevent contact between ZnO particles, or may form a chemically stable pyrochlore. However, when the sublimation of Sb ₂ O ₃ is suppressed and a pyrochlore phase film is not formed, if oxides such as cobalt, manganese, nickel, and chromium are present, these are oxides of zinc and antimony. At the same time, a spinel phase is formed, and a liquid phase Bi ₂ O ₃ phase is generated at a relatively low temperature, and the liquid phase sintering of ZnO starts.

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 prepared by a conventional manufacturing method, two particles are contained in zinc oxide particles as an n-type semiconductor.
There are ~ 5 × 10 ¹⁷ 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 is that if a sintered body of zinc oxide varistor is subjected to heat treatment around 700 ° C for electrode baking, etc., the VI characteristics will rapidly deteriorate and the leakage current will increase, making it impossible to commercialize it in some cases. Get up. 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, an even larger electric field acts in one of the depletion layers on both sides of the grain boundary, and the interstitial Zn atoms are relatively mobile. Therefore, a part thereof moves toward the grain boundary, and eventually reaches the grain boundary. 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 is acting in the depletion layer, and the positively charged interstitial Zn atoms in the depletion layer 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 conversion of ZnO crystal into a semiconductor was mainly caused by interstitial Zn atoms naturally occurring in the manufacturing process, and was accompanied by electrical instability.

On the other hand, conversion of ZnO crystal into an n-type semiconductor was also performed by adding Al ₂ O ₃ . In particular, to improve the current-voltage nonlinear resistance in the high current region, Al ₂ O ₃
Was added. Improvement of the current-voltage nonlinear resistance in the high current region can be achieved by lowering the electric resistance in the ZnO particles. Then, the decrease in electric resistance in the ZnO particles is n-
This was done by doping Al ₂ O ₃ as a donor of the 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. 500-6
By performing the heat treatment at 00 ° C., the interstitial Zn ions in the depletion layer, which caused the deterioration, were reduced, and as a result, I
Although the instability of the -V characteristic is alleviated, it has not yet been solved.

Since the cause of the instability of the electrical characteristics is the movement of the interstitial Zn, the interstitial Zn is reduced, and the lattice point where the Zn atom comes as a donor is reduced.
It was necessary to replace the Al atoms so that the electrical conduction in the zinc oxide particles was taken over 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.

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 at a high yield. An object of the present invention is to provide a zinc oxide varistor excellent in electrical characteristics and reliability, and a zinc oxide varistor device using the same.

[0015]

In order to achieve the above object, a zinc oxide porcelain composition according to the present invention is characterized by adding at least bismuth oxide, antimony oxide, iron group oxide and aluminum compound to zinc oxide and further oxidizing the zinc oxide. 81.38 parts by weight of zinc oxide (ZnO) (1 mol)
0.1 to 5.0 parts by weight with respect to
It is provided with a configuration of firing.

Further, in order to achieve the above object, the zinc oxide porcelain composition of the present invention comprises a zinc oxide (ZnO) 81.38 parts by weight, a boron oxide / chromium oxide containing compound 0.1 to 5.0 parts by weight, a bismuth oxide (BiO 2 ₂ O ₃ ) 1.0 to 10.0 parts by weight, antimony oxide (Sb ₂ O ₃ , Sb ₂ O ₄ , or Sb ₂ O ₅ ) 0.2 to 5.0 parts by weight, and at least cobalt oxide (CoO, or Co ₂ O ₃ , or Co
₃ O ₄ ), manganese oxide (MnO, or MnO ₂ , or Mn ₂ O ₃ , or Mn ₃ O ₄ ), and 0.2 to 5.0 parts by weight of two or three iron group oxides selected from nickel oxide (NiO) If, by adding an aluminum compound containing 0.0001 parts by weight in terms of aluminum oxide (Al ₂ O ₃₎ were mixed, shaped, those having a structure that fired composed.

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.

In order to achieve the above object, the zinc oxide porcelain composition of the present invention is characterized in that, in the above zinc oxide porcelain composition, the composition containing boron oxide and chromium oxide is oxidized to boron oxide (B ₂ O ₃ ). It is provided with a composition that is a boron oxide / chromium oxide-containing composite obtained by subjecting a mixture containing chromium (Cr ₂ O ₃ ) to a heat treatment.

In order to achieve the above object, a zinc oxide porcelain composition according to the present invention is characterized in that, in the above zinc oxide porcelain composition, the compound containing boron oxide and chromium oxide is mainly chromium borate (BCrO ₃ ). It is provided with such a configuration.

In order to achieve the above object, the zinc oxide porcelain composition of the present invention is characterized in that, in the above zinc oxide porcelain composition, the compound containing boron oxide and chromium oxide is oxidized to boron oxide (B ₂ O ₃ ). A compound containing boron oxide, chromium oxide, and rare earth oxide obtained by subjecting a mixture of chromium (Cr ₂ O ₃ ) and a rare earth oxide (R ₂ O ₃ , where R = rare earth element) to a heat treatment Is provided.

In order to achieve the above object, the zinc oxide porcelain composition of the present invention is characterized in that, in the above zinc oxide porcelain composition, the composition containing boron oxide, chromium oxide and rare earth oxide is mainly composed of rare earth boron chromate [ RCr (BO ₃ ) ₂ ].

In order to achieve the above object, the zinc oxide porcelain composition of the present invention is characterized in that, in the above zinc oxide porcelain composition, the compound containing boron oxide and chromium oxide is oxidized to boron oxide (B ₂ O ₃ ). It is provided with a composition comprising a boron oxide / chromium oxide / antimony oxide-containing composite obtained by subjecting a mixture obtained by adding heat treatment to antimony oxide in addition to chromium (Cr ₂ O ₃ ).

In order to achieve the above object, the zinc oxide porcelain composition of the present invention comprises a zinc oxide, a composite containing boron oxide and chromium oxide, and at least two kinds selected from cobalt oxide, manganese oxide and nickel oxide. Alternatively, three kinds of iron group oxides, bismuth oxide, antimony oxide, and an aluminum compound are added, mixed, molded, fired, cooled, and then subjected to heat treatment at 500 to 800 ° C. again. It is provided with a configuration of being a zinc porcelain composition.

Further, in order to achieve the above 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 of the present invention comprises a zinc oxide, a boron oxide / chromium oxide-containing composite, bismuth oxide, antimony oxide, and at least two or three types selected from cobalt oxide, manganese oxide, and nickel oxide. It is a zinc oxide porcelain composition obtained by adding an iron group oxide, magnesium oxide, and a trace amount of an aluminum compound, mixing, molding, and firing.

Next, in order to achieve the above object, a method for producing a zinc oxide porcelain composition according to the present invention comprises producing a boron oxide / chromium oxide-containing composite obtained by subjecting a mixture of boron oxide and chromium oxide to heat treatment. And zinc oxide (81.3
8 parts by weight) and at least two or three iron group oxides (0.2 to 5.0 parts by weight) selected from cobalt oxide, manganese oxide and nickel oxide, and the boron oxide / chromium oxide-containing composite (0.1 to 5.0 parts by weight) ) And bismuth oxide (1.0 to 10.0)
Parts by weight), an antimony oxide (0.2 to 5.0 parts by weight) and an aluminum compound are added and mixed to form a zinc oxide mixed powder, and a step of forming the zinc oxide mixed powder to form a compact. And a step of firing the compact at 800 to 1100 ° C.

In order to achieve the above object, a method for producing a zinc oxide porcelain composition of the present invention is characterized in that, in the method for producing a zinc oxide porcelain composition, the step of producing a boron oxide / chromium oxide-containing composite comprises: This is a process for producing a boron oxide / chromium oxide / rare earth oxide-containing composite obtained by subjecting a mixture of boron oxide to a rare earth oxide in addition to chromium oxide.

In order to achieve the above object, a method for producing a zinc oxide porcelain composition according to the present invention is directed to the method for producing a zinc oxide porcelain composition according to the above method, wherein the mixture obtained by subjecting a mixture of boron oxide and chromium oxide to a heat treatment. The composition in which the step of producing the boron-chromium oxide-containing composition is a step of producing a boron oxide-chromium oxide-containing composition obtained by subjecting a mixture of boron oxide and chromium oxide to a heat treatment at 300 ° C to 450 ° C. It is provided with.

Further, in order to achieve the above object, the method for producing a zinc oxide porcelain composition of the present invention provides a method for producing a mixture of boron oxide and chromium oxide by subjecting a mixture of boron oxide and chromium oxide to heat treatment.
A step of preparing a chromium oxide-containing composite;
1.38 parts by weight) at least two or three iron group oxides (0.2 to 5.0 parts by weight) selected from cobalt oxide, manganese oxide and nickel oxide, and the boron oxide / chromium oxide-containing composite (0.1 to 5.0 parts by weight) ) And bismuth oxide (1.0-10.
0 parts by weight), antimony oxide (0.2 to 5.0 parts by weight) and an aluminum compound are added and mixed to form a zinc oxide mixed powder, and the zinc oxide mixed powder is formed to form a molded body. And a step of firing the molded body to 800 to 1100 ° C. to obtain a sintered body, and a step of cooling and, after cooling, performing a heat treatment at 500 ° C. to 800 ° C. again. It is provided.

Further, in order to achieve the above object, the zinc oxide varistor of the present invention provides a zinc oxide varistor comprising a compound containing boron oxide and chromium oxide, and at least two kinds selected from cobalt oxide, manganese oxide and nickel oxide. Three types of iron group oxides, bismuth oxide, antimony oxide, and aluminum compounds are added, mixed, molded, and fired to form electrodes on a zinc oxide porcelain composition. It is a thing.

Further, in order to achieve the above object,
The zinc oxide varistor of the present invention is the above zinc oxide varistor, wherein the boron oxide / chromium oxide-containing composite is obtained by subjecting a mixture of boron oxide and chromium oxide to a rare earth oxide to a heat treatment. Chromium oxide
It is provided with a constitution that it is a rare earth oxide-containing composite.

Further, in order to achieve the above object,
The zinc oxide varistor of the present invention is a zinc oxide, a boron oxide / chromium oxide-containing composite, at least two or three iron group oxides selected from cobalt oxide, manganese oxide, and nickel oxide, and bismuth oxide. Add and mix antimony oxide and aluminum compound, mold,
After baking and cooling, the electrode is formed on a zinc oxide porcelain composition obtained by heat treatment at 500 to 800 ° C. again.

Further, in order to achieve the above object,
The zinc oxide varistor of the present invention is a zinc oxide, a boron oxide / chromium oxide-containing composite, at least two or three iron group oxides selected from cobalt oxide, manganese oxide, and nickel oxide, and bismuth oxide. An antimony oxide and an aluminum compound are added and mixed, the resulting zinc oxide mixture is molded, the obtained molded body and the metal electrode material are alternately laminated, and the laminated zinc oxide varistor is obtained by firing. There is a configuration that there is.

Further, in order to achieve the above object,
The zinc oxide varistor device of the present invention is characterized in that a zinc oxide, a boron oxide / chromium oxide-containing composite, at least two or three iron group oxides selected from cobalt oxide, manganese oxide and nickel oxide, and bismuth oxide , Antimony oxide, and an aluminum compound are added, mixed, molded, and fired to obtain a zinc oxide porcelain composition, and the side surfaces of the zinc oxide porcelain composition are covered with an insulating film. Electrodes are formed on the two surfaces to obtain a single zinc oxide varistor, and the single zinc oxide varistor or a plurality of zinc oxide varistors are sealed in an insulating container.

[0035]

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, a zinc oxide varistor obtained by applying an electrode to the zinc oxide porcelain composition, and a zinc oxide varistor device using the same.

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, and added to the zinc oxide together with other additives. Mold and fire. In addition, in the zinc oxide porcelain composition of the present invention, aluminum is the sole donor for preventing the formation of interstitial Zn, which causes deterioration of electrical characteristics, and for converting zinc oxide into an n-type semiconductor. In the firing of zinc oxide porcelain, the chromium oxide added to prevent the formation of a pyrochlore phase at low temperatures and to promote the formation of a liquid phase containing bismuth oxide as a main component at low temperatures reacts with zinc oxide first and reacts with ZnCr. _In order to prevent the formation of ₂ O ₄ , heat treatment is performed in advance with boron oxide to form a boron oxide / chromium oxide-containing composite, and then added. 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, the generated oxygen is confined inside the sintered body by forming a liquid phase. Finally, a ZnO-Sb ₂ O ₅ spinel is formed. 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. In these devices, it is necessary to uniformly dope a small amount of aluminum into zinc oxide particles in order to reduce interstitial Zn and to maintain conduction electrons instead. A closed pore having a high oxygen partial pressure is efficiently generated and sintered as if sintered under high-pressure oxygen to obtain a device having high performance and excellent stability.

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.

[0038]

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 Powder of B ₂ O ₃ and Cr ₂ O _{3 in} molar ratio
Was mixed so as to be 1: 1. These powders are mixed at 410 ° C for 5 hours and 500 ° C for 5 hours in the atmosphere.
After heat treatment for a long time, a synthetic powder composed of B ₂ O ₃ and Cr ₂ O ₃ was obtained by finely pulverizing with a ball mill of a monomalon pot using stabilized zirconia as a cobblestone. Hereinafter, B ₂ O ₃
If will be referred synthetic powder is adjusted by Cr2O ₃ and _{B 2 O 3 / Cr 2 O} 3 synthetic powder. As a result of X-ray analysis, most of the B ₂ O ₃ / Cr ₂ O ₃ synthesized powder thus obtained was BCrO ₃ .

The ZnO powder, the B ₂ O ₃ / Cr ₂ O ₃ synthetic powder, the Bi ₂ O ₃ powder, the Co ₃ O ₄ powder, the MnO ₂ powder, the NiO powder, and the Sb ₂ O ₄ powder , 8 _{Al (NO 3) 3 · 9H} 2 O powder in a ratio of
1.38: 0.3: 3.4: 0.954: 0.414: 0.383: 0.8: 0.015 were blended and mixed and pulverized by a wet method. The obtained compounded powder was dried and pressed into a disk. Next, the temperature of the obtained molded body was raised in the air at a temperature rising rate of 50 ° C./hour, and maintained at a high temperature for 10 hours. Then, the temperature was lowered at a temperature lowering rate of 50 ° C./hour to obtain a sintered body. High holding temperature of 750,
800, 850, 900, 950, 1000, 1100, 1200 ° C were selected. The sample size of the sintered body was 1.2 mm in thickness and 14 mm in diameter. A part of the obtained sintered body was subjected to a heat treatment at 700 ° C. for a holding time of 1 hour.

Next, a method for forming 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, a nonlinear resistance index of _{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 0.7 watts was applied for 500 hours in a high-temperature atmosphere of 80 ° C., and the change rate of the varistor rising 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 8 × 20μsec, 2.0kA pulse 10 times △ V _1mA / V _1mA
(Surge change rate) was measured. The smaller the value of the surge rate, the more stable the electrical characteristics of the zinc oxide varistor,
This indicates that reliability is high. Rate of change △ V _1mA
When the absolute value of / V _{1 mA} is 5% or less, the reliability is high. Table 1 shows the composition of the sample, and Table 2 shows the evaluation results of the electrical characteristics. The numerical values indicating the evaluation results of the electrical characteristics indicate the minimum value and the maximum value in the lot.

[0044]

[Table 1]

[0045]

[Table 2]

According to Tables 1 and 2, the zinc oxide varistor using the zinc oxide porcelain composition of the present example 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 at the time of firing, so that the sintered bodies are fused together (the sample sticks), and the electrical characteristics cannot be measured (sample number #). 00
8).

(Example 2) A powder of B ₂ O _{3 and} a powder of Cr ₂ O ₃ (the average particle diameter of each powder is 2-3 μm, respectively) are 0.5: 9.5, 1: 9 in molar ratio. , 2: 8, 4: 6, 5: 5, 6: 4, 8:
After mixing at 2,9: 1,9.5: 0.5 and heat-treating at 370 ° C for 5 hours under air atmosphere, pulverize in a mortar and heat-treat at 450 ° C for 5 hours. , synthetic powder B ₂ O ₃ of B ₂ O ₃ and Cr ₂ O ₃ by milling in a mortar
/ Cr ₂ O ₃ (average particle size of about 0.5 to 1.5 μm) was obtained. Also, Bi ₂ O
₃ and Sb ₂ O ₃ powder (each powder has an average particle diameter of 2 to 3 μm) were mixed at a molar ratio of 6: 4, and mixed at 500 ° C. in an air atmosphere. after heat treatment time, volume of mono-malonic pots stabilized zirconia and cobbles - synthesis of Bi ₂ O ₃ and Sb ₂ O ₃ by milling in mill powder _{Bi 2 O 3 / Sb 2 O} 3 ( An average particle size of about 0.5 to 1.5 μm) was obtained. Then, while changing the type and amount of _{B 2 O 3 / Cr 2 O} 3 synthetic powder as shown in Table 3, ZnO, wherein the _{B 2 O 3 / Cr 2 O} 3 synthetic powder,
Bi ₂ O ₃ / Sb ₂ O ₃ synthetic powder, Co ₃ O ₄ , MnO ₂ , NiO, AlOOH
In weight ratio of 81.38: (0.05-8): 2.33: 0.954: 0.414:
0.383: 0.0024, and mixed and pulverized for 18 hours by a wet method, and a zinc oxide mixed powder was obtained by a spray dryer. The obtained compounded powder was dried and pressed into a disk. Next, the temperature of the obtained molded body was raised in the air at a temperature rising rate of 50 ° C./hour, maintained at 900 ° C. for 10 hours, and then lowered at a temperature lowering rate of 50 ° C./hour to obtain a sintered body. The sample size of the sintered body was 1.2 mm in thickness and 14 mm in diameter.
Further, a part of the obtained sintered body was held at 700 ° C. for a holding time of 1 hour.
Time heat treatment was applied. A zinc oxide varistor was prepared using the sintered body thus obtained, and the electrical characteristics were evaluated. Table 3 shows the composition of the sample, and Table 4 shows the electrical characteristics. # 103, # 104, # 1
The samples of Nos. 05, # 106, # 107 and # 108 show good electrical characteristics.

[0048]

[Table 3]

[0049]

[Table 4]

Example 3 B ₂ O ₃ powder, Cr ₂ O ₃ powder and S
b ₂ O ₃ powder is mixed in a molar ratio of 1: 2: 10,
These mixed powders were subjected to a heat treatment at 380 ° C. for 5 hours in an air atmosphere, and then pulverized with a ball mill of a monomalon pot using stabilized zirconia to form B ₂ O ₃ .
A B ₂ O ₃ / Cr ₂ O ₃ / Sb ₂ O ₃ synthetic powder composed of Cr ₂ O ₃ and Sb ₂ O ₃ was obtained.

ZnO powder, the above-mentioned B ₂ O ₃ / Cr ₂ O ₃ / Sb ₂ O ₃ powder, Bi ₂ O ₃ powder, Co ₃ O ₄ powder, MnO ₂ powder, NiO powder, and hydroxide 81.38: 1 by weight ratio with aluminum acetate.
5: 4: 0.954: 0.414: 0.383: 0.0065 were blended and mixed and pulverized by a wet method for 18 hours. 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.

[0052]

[Table 5]

[0053]

[Table 6]

From Tables 5 and 6, it is found that the oxidized
Zinc oxide varistors using lead porcelain are fired at 850 ° C.
Reference sample (sample No. 201, voltage too high
It could not be measured. ) Except for non-linear resistance characteristics
Long-term DC load and surge
Also the rising voltage V_1mA Change rate (△ V _1mA / V_1mA )
Was not more than 5%, and the reliability was excellent.

Example 4 The same composition ratio as in Example 1 was blended, mixed and pulverized by a wet method for 18 hours, and a zinc oxide mixed powder was obtained by a spray dryer. An arrester was prepared using the zinc oxide mixed powder thus obtained. The zinc oxide mixed powder obtained by the spray dryer is RIP (Rub
A columnar zinc oxide porcelain was obtained by molding into a columnar shape by a ber isostatic press (rubber isostatic press) method and firing at 950 ° C. for 10 hours. The size of the zinc oxide porcelain obtained is the diameter
It was 32 mm and 27 mm high. Electrodes are formed by spraying aluminum metal on the upper and lower surfaces of zinc oxide porcelain, and mica
-An arrester-type zinc oxide varistor was obtained by coating with a resin. V _1mA was approximately 5.8 kV. FIG. 2 is a cross-sectional view of an arrester-type zinc oxide varistor device 20 prepared using the zinc oxide porcelain composition of the present invention. Element electrodes 22 are formed on both upper and lower surfaces of the zinc oxide porcelain 21 by thermal spraying of aluminum. Further, a side surface insulating film 23 of a mica-resin film made of a mixture of mica and resin is formed on a side surface of the zinc oxide porcelain, and a zinc oxide varistor element is formed by the zinc oxide porcelain, the device electrode, and the side surface insulating film. ing. At the lower part of the zinc oxide varistor element, there is a ground terminal 25 having a mounting screw hole 24, and at the upper part there is a line side terminal 27 via a spring 26. Molded at 28. Table 7 shows the current-voltage characteristics of the arrester type zinc oxide varistor.

[0056]

[Table 7]

As can be seen from Table 7, the arrester-type zinc oxide varistor device using the zinc oxide porcelain of the composition of the present example has excellent nonlinear resistance characteristics even in a high current region. Next, the accelerated life test of AC power application was performed to predict the power application life. The service life is one of the most important evaluation items of the arrester. Here the ambient temperature is 130
The test was performed under the condition of 95 ° C. and a charge rate of 95%. As a result, 1
The initial Ir of the mA hardly changed for the test of 100 hours or more, and when used as a gapless arrester, under the condition of an ambient temperature of 70 ° C. and a charge rate of 80%,
The result is that a lifetime of more than 100 years is guaranteed.

(Example 5) B ₂ O ₃ powder, Cr ₂ O ₃ powder and Y
₂ O ₃ powders were mixed in a molar ratio of 2: 1: 1, and these mixed powders were subjected to a heat treatment at 380 ° C. for 5 hours in an air atmosphere to be finely pulverized, and then heat treated again under the same conditions. alms, ball mono malonic pots stabilized zirconia and cobble - consisting of B ₂ O ₃ and Cr ₂ O ₃ and Y ₂ O ₃ by milling in mill _{B 2 O 3 / Cr 2 O} 3 / Y ₂ O ₃ synthetic powder was obtained. Next, a sample was prepared in the same manner as in Example 1.

ZnO powder, the above-mentioned B ₂ O ₃ / Cr ₂ O ₃ / Y ₂ O ₃ synthetic powder, Bi ₂ O ₃ powder, Co ₃ O ₄ powder, MnO ₂ powder, NiO
The powder, Sb ₂ O ₄ powder, and aluminum nitrate were blended in a weight ratio of 81.38: 0.5: 4: 0.954: 0.414: 0.383: 1.0: 0.015, and mixed and pulverized by a wet method for 18 hours. 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 8 shows the composition of the sample, and Table 9 shows the evaluation results of the electrical characteristics.

[0060]

[Table 8]

[0061]

[Table 9]

As shown in Tables 8 and 9, the zinc oxide varistor using the zinc oxide-based porcelain of this example is a comparative sample fired at 800 ° C. (Sample No. # 401 has a too high rising voltage and cannot be measured. ), And the rate of change of the rising voltage V _1mA (△ V _1mA /
The absolute value of V _1mA ) was 5% or less, and the reliability was excellent.

[0063]

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.
It is formed using zinc oxide as a constituent material. As a result, varistors made using the present zinc oxide porcelain composition have excellent electrical characteristics such as non-linear resistance characteristics from a low current region to a high current region, and the movement of interstitial Zn is suppressed so that DC and AC Is extremely stable against voltage application and heat. The present invention also provides a method for producing the zinc oxide porcelain composition for a zinc oxide varistor at a high yield, and industrially distributes a small amount of a boron oxide / chromium oxide-containing composite uniformly in a sintered body. Materials and devices with good characteristics are obtained. When manufacturing the sintered body, after expelling reducing gas generated at 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. Then, sintering is performed with shrinkage in a state where closed pores having high oxygen partial pressure oxygen 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, it is possible to uniformly sinter and grow the particle size important for the varistor uniformly. or,
Even if the sintering temperature is lowered, it can withstand a high current pulse sufficiently and keep high performance.

Further, the zinc oxide porcelain composition of the present invention
Since sintering can be performed at a low temperature, power consumption during sintering can be reduced, and at the same time, the consumption of furnace materials and containers of an electric furnace used for sintering can be reduced.
And greatly contribute to 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 has become possible to form silver electrodes inside these porcelains simultaneously with firing. As a result, a high-performance laminated zinc oxide varistor having a silver internal electrode can be manufactured. In addition,
In the embodiment, the data of sintering at 800 to 1200 ° C. is shown.
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. Not that it is.

As additives mainly for adjusting grain growth and improving reliability, germanium oxide (GeO ₂ ), magnesium oxide (MgO), and niobium oxide (Nb ₂
O ₅ ), lead oxide (PbO), silicon oxide (SiO ₂ ), tin oxide (S
nO ₂ ), tantalum oxide (Ta ₂ O ₅ ), titanium oxide (TiO 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 made using the zinc oxide porcelain composition of Example 1 of the present invention.

FIG. 2 is a schematic cross-sectional view of an arrester-type zinc oxide varistor device prepared using the zinc oxide porcelain composition of Example 4 of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 disk type zinc oxide varistor 11 zinc oxide sintered body 12 electrode 13 lead wire 20 zinc oxide varistor device 21 zinc oxide porcelain 22 element electrode 23 side insulating film 24 mounting screw hole 25 ground terminal 26 spring 27 line side Terminal 28 Resin tube

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C04B 35/00 Q (72) Inventor Daiki Miyamoto 2-7-1, Ayumino, Izumi City, Osaka Prefecture Osaka Prefecture Sangyo 4G030 AA11 AA22 AA25 AA27 AA28 AA29 AA32 AA35 AA36 AA42 AA43 BA04 GA09 GA27 5E032 AB10 BA21 BA23 BB11 CA12 CC05 CC06 5E034 CA10 CB01 CC02 CC05 CC06 DA03 DA07 DB05 DE02 DE09 DE08 EB04 5G013 AA01 AA02 BA02 DA12

Claims (20)

[Claims] (1) To a zinc oxide, at least bismuth oxide, antimony oxide, an iron group oxide and an aluminum compound are added, and further a boron oxide / chromium oxide-containing compound is added to zinc oxide (ZnO) 81.38 parts by weight (1 mol). A zinc oxide porcelain composition obtained by adding 0.1 to 5.0 parts by weight, mixing, molding and firing. 2. A method according to claim 1, wherein 81.38 parts by weight (1 mol) of zinc oxide (ZnO)
0.1 to 5.0 parts by weight of a compound containing boron oxide and chromium oxide,
Bismuth oxide (Bi ₂ O ₃ ) 1.0 to 10.0 parts by weight, and antimony oxide (Sb ₂ O ₃ , Sb ₂ O ₄ , or Sb ₂ O ₅ ) 0.2 to 5.0 parts by weight,
At least cobalt oxide (CoO, or Co ₂ O ₃ , or Co
₃ O ₄ ), manganese oxide (MnO, or MnO ₂ , or Mn ₂ O ₃ , or Mn ₃ O ₄ ), and 0.2 to 5.0 parts by weight of two or three iron group oxides selected from nickel oxide (NiO) And an aluminum compound containing 0.0001 to 0.05 parts by weight in terms of aluminum oxide (Al ₂ O ₃ ), mixed, molded and fired. 3. 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 two or three iron group oxides selected from nickel oxide (NiO), at least one of which has a trivalent or tetravalent valence The zinc oxide porcelain composition according to claim 2, which is an iron group oxide. 4. The composition containing boron oxide and chromium oxide,
Zinc oxide according to claim 2, characterized in that the chromium oxide (Cr ₂ O ₃₎ mixed boron oxide-chromium oxide-containing compounds obtained by applying a heat treatment product was added to boron oxide (B ₂ O ₃₎ Porcelain composition. 5. The composition containing boron oxide and chromium oxide,
_{3. The} zinc oxide porcelain composition according to claim 2, wherein the composition is mainly chromium borate (BCrO ₃ ). 6. The composition containing boron oxide and chromium oxide,
Boron oxide obtained by subjecting a mixture of boron oxide (B ₂ O ₃ ) to chromium oxide (Cr ₂ O ₃ ) to which a rare earth oxide (R ₂ O ₃ , where R = rare earth element) is subjected to a heat treatment 3. The zinc oxide porcelain composition according to claim 2, which is a composite containing chromium oxide and rare earth oxide. 7. The composition containing boron oxide, chromium oxide, and rare earth oxide is mainly composed of boron chromate rare earth [RCr (BO ₃ )].
₂ ]. The zinc oxide porcelain composition according to claim 6, wherein 8. The composition containing boron oxide and chromium oxide,
Synthesis containing boron oxide, chromium oxide, and antimony oxide obtained by subjecting a mixture of boron oxide (B ₂ O ₃ ) to chromium oxide (Cr ₂ O ₃ ) plus antimony oxide (Sb ₂ O ₃ ) to heat treatment The zinc oxide porcelain composition according to claim 2, which is a material. 9. A zinc oxide, a composition containing boron oxide and chromium oxide, at least two or three iron group oxides selected from cobalt oxide, manganese oxide and nickel oxide, bismuth oxide, and antimony oxide. , Aluminum compound added and mixed, molded, fired, cooled and then
A zinc oxide porcelain composition obtained by performing a heat treatment again at 500 ° C to 800 ° C. 10. A zinc oxide porcelain composition wherein the zinc oxide porcelain composition provides the electrical conductivity of the n-type semiconductor zinc oxide particles and the donor to the zinc oxide is mainly aluminum. 11. A zinc oxide comprising a boron oxide / chromium oxide-containing composite, bismuth oxide, antimony oxide, and at least two or three iron group oxides selected from cobalt oxide, manganese oxide and nickel oxide. A zinc oxide porcelain composition obtained by adding, mixing, shaping, and firing magnesium oxide and a trace amount of an aluminum compound. 12. A process for preparing a boron oxide / chromium oxide-containing composite obtained by subjecting a mixture of boron oxide and chromium oxide to a heat treatment, and adding at least cobalt oxide, manganese oxide and nickel oxide to zinc oxide (81.38 parts by weight). Two or three iron group oxides selected from the group consisting of 0.2 to 5.0 parts by weight, the above-mentioned compound containing boron oxide and chromium oxide (0.1 to 5.0 parts by weight), bismuth oxide (1.0 to 10.0 parts by weight), and antimony oxide (0.2 to 5.0 parts by weight) and an aluminum compound (0.0001 to 0.05 parts by weight in terms of aluminum oxide Al ₂ O ₃ ) are added and mixed to form a zinc oxide mixed powder,
A method for producing a zinc oxide porcelain composition, comprising: a step of forming a compact by molding the zinc oxide mixed powder; and a step of firing the compact at 800 to 1100 ° C. 13. A process for producing a boron oxide / chromium oxide-containing composite, comprising the step of subjecting a mixture obtained by adding a rare earth oxide to boron oxide to chromium oxide to a heat treatment. The method for producing a zinc oxide porcelain composition according to claim 10, wherein the step is a step of preparing a containing composition. 14. A process for preparing a boron oxide / chromium oxide-containing composition obtained by subjecting a mixture of boron oxide and chromium oxide to a heat treatment, wherein the mixture of boron oxide and chromium oxide is subjected to a heat treatment at 300 ° C. to 450 ° C. The method for producing a zinc oxide porcelain composition according to claim 10, wherein the step is a step of producing a boron oxide / chromium oxide-containing composite that can be applied. 15. A process for preparing a boron oxide / chromium oxide-containing composite obtained by subjecting a mixture of boron oxide and chromium oxide to heat treatment, and adding at least cobalt oxide, manganese oxide and nickel oxide to zinc oxide (81.38 parts by weight). Two or three iron group oxides selected from the group consisting of 0.2 to 5.0 parts by weight, the above-mentioned compound containing boron oxide and chromium oxide (0.1 to 5.0 parts by weight), bismuth oxide (1.0 to 10.0 parts by weight), and antimony oxide (0.2 to 5.0 parts by weight) and an aluminum compound (0.0001 to 0.05 parts by weight in terms of aluminum oxide Al ₂ O ₃ ) are added and mixed to form a zinc oxide mixed powder,
A step of molding the zinc oxide mixed powder to form a molded body, a step of firing the molded body to 800 to 1100 ° C. to obtain a sintered body, and after cooling, the sintered body is again cooled to 500 ° C. 800 ℃
And subjecting the composition to a heat treatment. 16. A zinc oxide, a composition containing boron oxide and chromium oxide, at least two or three iron group oxides selected from cobalt oxide, manganese oxide and nickel oxide, bismuth oxide, and antimony oxide. A zinc oxide varistor obtained by adding an aluminum compound, mixing, molding and firing to form an electrode on the zinc oxide porcelain composition. 17. The composition containing boron oxide and chromium oxide,
The zinc oxide varistor according to claim 14, wherein the zinc oxide varistor is a composite containing boron oxide, chromium oxide, and rare earth oxide obtained by subjecting a mixture obtained by adding a rare earth oxide to boron oxide to chromium oxide. . 18. A method according to claim 18, wherein the zinc oxide comprises a compound containing boron oxide and chromium oxide, at least two or three iron group oxides selected from cobalt oxide, manganese oxide and nickel oxide, bismuth oxide, and antimony oxide. , Aluminum compound added and mixed, molded, fired, cooled and then
A zinc oxide varistor in which an electrode is formed on a zinc oxide porcelain composition obtained by performing a heat treatment again at 500 ° C to 800 ° C. 19. A zinc oxide comprising a compound containing boron oxide and chromium oxide, at least two or three iron group oxides selected from cobalt oxide, manganese oxide and nickel oxide, bismuth oxide and antimony oxide. , An aluminum compound is added and mixed, the obtained zinc oxide mixture is molded, the obtained molded body and the metal electrode material are alternately laminated and fired to obtain a laminated zinc oxide varistor. 20. Zinc oxide, a compound containing boron oxide and chromium oxide, at least two or three iron group oxides selected from cobalt oxide, manganese oxide and nickel oxide, bismuth oxide, and antimony oxide. , An aluminum compound, and the mixture was mixed, molded, and fired to obtain a zinc oxide porcelain composition, and the side surfaces of the zinc oxide porcelain composition were covered with an insulating film, and further coated on two sides of the zinc oxide porcelain composition. A zinc oxide varistor device obtained by forming electrodes and obtaining a single zinc oxide varistor and enclosing the single zinc oxide varistor or a plurality thereof in an insulating container.