JP2005145809A - Zinc oxide-based sintered compact, zinc oxide varistor, and lamination type zinc oxide varistor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problems in firing of the conventional zinc oxide varistor that the firing generates a pyrochlore phase and the like being solid at low temperature and results in high-temperature sintering and therefore electric power consumption is heretofore high and the materials liable to evaporate at elevated temperature are heretofore wasted. <P>SOLUTION: Cr<SB>2</SB>O<SB>3</SB>-containing Bi<SB>2</SB>O<SB>3</SB>compound synthetic powder is prepared by previously mixing Cr<SB>2</SB>O<SB>3</SB>and Bi<SB>2</SB>O<SB>3</SB>so as to attain a molar ratio of 1:02 to 0.15 and heat treating the mixture. A ZnO-based sintered compact is obtained by adding at least 0.05 to 5.0 parts by weight the Bi<SB>2</SB>O<SB>3</SB>compound synthetic powder, 0.1 to 10.0 parts by weight at least one oxide selected from the group consisting of respective oxides of Sb, Ti, Sn, Zr, Nb, Ta, V, Mo, W, Si, and rare earths, and 0.5 to 7.0 parts at least one compound selected from the group consisting of respective oxides of Bi, Co, Mn, Ni, and B, and boric acid and Al salt, to 100 parts by weight ZnO and mixing the mixture, then molding the mixture and firing the molding at 700 to 980°C. An electrode and side face insulation coating are formed therefrom and the zinc oxide varistor having excellent electric characteristics is thus obtained. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

Detailed Description of the Invention

The present invention relates to a zinc oxide sintered body, a zinc oxide varistor, and a laminated zinc oxide varistor used for surge absorption in an electric circuit.

Conventional low temperature sintered zinc oxide varistors are composed of zinc oxide powder and additive composite composite powder of bismuth oxide and antimony oxide, composite composite powder of bismuth oxide and chromium oxide, composite composite powder of bismuth oxide and boron oxide, It is known that cobalt oxide powder, manganese oxide powder and aluminum nitrate (corresponding to aluminum oxide) are mixed, molded, fired, cooled and sintered (for example, see Patent Document 1).
In addition, conventional low temperature sintered zinc oxide varistors are composed of composite powder of zinc oxide powder and additives boron oxide and chromium oxide, bismuth oxide powder, antimony oxide powder, cobalt oxide powder, manganese oxide powder, nickel oxide It is also known that powder and aluminum nitrate (corresponding to aluminum oxide) are mixed, molded, fired, cooled and sintered (for example, see Patent Document 2).
In addition, conventional zinc oxide varistors for high-temperature sintering are prepared by mixing zinc oxide and additives bismuth oxide, antimony oxide, cobalt oxide, manganese oxide, chromium oxide, forming, firing, and granulating in the cooling process. It is known that sintering is performed in the course of forming a composite component of chromium oxide and bismuth oxide in the liquid phase at the boundary portion (see, for example, Non-Patent Document 1).

        JP-A-9-67161 (pages 22-23)         JP 2002-97071 A (Pages 7-8)         Masanori Inada. "Effects of Heat-Treatment on Crystal Properties and Electrical Professionals" Effects of Heat Treatment on Crystal Phase, Microstructure and Electrical Properties on Non-Ohmic Zinc Oxide Ceramics (Effects of Heat-Treatment on Crystal Properties and Electrical Professionals) of Nonohmic Zinc Oxide Ceramics). (European) Journal of Applied Physics (Japan Journal of Applied Physics). Published by Japan Society for Applied Physics. August 1979 (1979). Volume 18. No.8. P. 1439-1446

Problems to be solved by the invention

In order to obtain a high-performance zinc oxide varistor by the conventional method, a high sintering temperature of 1150 ° C. to 1300 ° C. was required. Evaporation of bismuth oxide etc. is active even in the atmosphere when firing at these high temperatures. In addition, bismuth oxide easily reacts with many kinds of substances and easily corrodes many substances such as furnace materials and ceramic materials such as containers. In other words, the high sintering temperature not only consumes a large amount of power, but also causes severe scattering of bismuth oxide and concomitant consumption of furnace materials and containers, so attempts have been made to lower the firing temperature. Also, when the firing temperature is high, depending on the place where the fired product is placed in the furnace, the temperature, the rate of temperature rise, the vapor pressure of bismuth oxide and antimony oxide, etc., it is difficult to keep them uniform, Since there were problems such as the tendency of variations in characteristics, attempts have been made to lower the firing temperature.

In recent years, research on the amount and method of additives has progressed, and zinc oxide varistors that have been sintered at 900 to 950 ° C. and have higher performance than before have been developed. That is, by adding bismuth oxide, boron oxide, etc. to chromium oxide, applying heat treatment and adding it together with other additives to zinc oxide, the firing temperature has been greatly lowered. In other words, bismuth oxide, boron oxide, etc. are added to chromium oxide to a mixed powder obtained by adding iron oxides of cobalt oxide, manganese oxide, nickel oxide together with bismuth oxide, antimony oxide, etc. to zinc oxide powder. It was revealed that a sintered body having a high level of electrical characteristics could be obtained by firing at 900 ° C. to 950 ° C. by adding the chromium oxide composite composite powder obtained by heat treatment. In the conventional composition, a pyrochlore solid phase was generated at a low temperature. Instead, the liquid phase was prevented and the liquid phase sintering was difficult to occur.

In the composition of conventional zinc oxide varistors, bismuth oxide comes into contact with various oxides and generates a solid pyrochlore phase, etc. at a low temperature. Solid phases such as these pyrochlore phases exist until they reach a high temperature. Only after the reaction with zinc oxide, a liquid phase mainly composed of bismuth oxide was generated, and finally liquid phase sintering occurred. Thus, when trying to sinter with the conventional composition, high temperature sintering was required. Sintering at high temperatures not only consumes high power, but also wastes materials that tend to evaporate at high temperatures. From these things, there was an expectation that the sintering temperature would be lowered if possible.

The present invention solves the above problems, promotes grain growth by low-temperature sintering, and produces a low-voltage zinc oxide varistor excellent in electrical characteristics such as non-linear resistance characteristics and reliability at a high yield. The purpose is to provide a zinc oxide-based sintered body.

Means for solving the problem

In order to achieve the above object, the zinc oxide-based sintered body of the present invention is preliminarily subjected to a chemical conversion treatment by adding 0.02 to 0.15 mole ratio of chromium oxide to 1 mole ratio of bismuth oxide to form a bismuth oxide-based chemical composition. A composition containing at least 0.05 to 7.0 parts by weight of the above bismuth oxide-based chemical is formed with respect to 100 parts by weight of zinc oxide, and calcined at 700 to 980 ° C. It has the following structure.

In order to achieve the above object, the zinc oxide-based sintered body of the present invention has a chromium oxide 0.02 to 0.15 molar ratio and a boron oxide 0.02 to 0.15 molar in advance with respect to 1 molar ratio of bismuth oxide. A bismuth oxide-based chemical compound is prepared by adding a chemical conversion treatment in a ratio, and the composition contains the bismuth oxide-based chemical compound in an amount of at least 0.05 to 7.0 parts by weight with respect to 100 parts by weight of zinc oxide. Is formed, and is fired at 700 ° C. to 980 ° C.

In order to achieve the above object, the zinc oxide-based sintered body of the present invention is preliminarily subjected to a chemical conversion treatment by adding 0.02 to 0.15 mole ratio of chromium oxide to 1 mole ratio of bismuth oxide to form a bismuth oxide-based chemical conversion. The product is prepared or oxidized beforehand by adding a chemical conversion treatment with 0.02 to 0.15 mole ratio of chromium oxide and 0.02 to 0.15 mole ratio of boron oxide with respect to 1 mole ratio of bismuth oxide. A bismuth-based chemical is prepared, and the bismuth oxide-based chemical is at least 0.05 to 7.0 parts by weight with respect to 100 parts by weight of zinc oxide, at least ankymon oxide, titanium oxide, tin oxide, and zircon oxide. And at least one selected from the group consisting of: niobium oxide, tantalum oxide, vanadium oxide, molybdenum oxide, tungsten oxide, silicon oxide, macnesium oxide, and rare earth oxide Containing the compound from 0.05 to 8.0 parts by weight to form a composition, in which a structure formed by baking at 700 ℃ ~980 ℃.

In order to achieve the above object, the zinc oxide varistor of the present invention is prepared by adding 0.02 to 0.15 mole ratio of chromium oxide to 1 mole ratio of bismuth oxide and subjecting it to a chemical conversion treatment. In addition, a composition containing at least 0.05 to 7.0 parts by weight of the above bismuth oxide-based chemical is formed with respect to 100 parts by weight of zinc oxide, and obtained by firing at 700 ° C. to 980 ° C. Zinc oxide-based sintered body, or chromium oxide and boron oxide are added in advance at a molar ratio of 0.02 to 0.15 and 0.02 to 0.15 molar ratio with respect to 1 molar ratio of bismuth oxide, and a chemical conversion treatment is added. A bismuth oxide-based chemical is prepared, and a composition containing at least 0.05 to 7.0 parts by weight of the bismuth oxide-based chemical is formed with respect to 100 parts by weight of zinc oxide. Baked at ℃ A zinc oxide-based sintered body, or a bismuth oxide-based chemical compound prepared by adding 0.02 to 0.15 mole ratio of chromium oxide to a mole ratio of bismuth oxide in advance, First, chromium oxide and boron oxide were added in a molar ratio of 0.02 to 0.15 and a molar ratio of 0.02 to 0.15 with respect to 1 molar ratio of bismuth oxide to form a bismuth oxide-based chemical composition. And 100 parts by weight of zinc oxide, the bismuth oxide-based chemical compound is contained in an amount of at least 0.05 to 7.0 parts by weight, and at least ankymon oxide, titanium oxide, tin oxide, zircon oxide, and niobium oxide. 0.05 to 8.0 weights of at least one oxide selected from the group consisting of tantalum oxide, vanadium oxide, molybdenum oxide, tungsten oxide, silicon oxide, and rare earth oxides Part forming a composition containing, at the electrodes and sides 700 ℃ ~980 zinc oxide-based sintered body obtained by firing at ° C. those with a structure that insulating coating is formed.

In order to achieve the above object, the laminated zinc oxide varistor of the present invention is prepared by adding 0.02 to 0.15 mole ratio of chromium oxide to 1 mole ratio of bismuth oxide and subjecting it to a chemical conversion treatment. To obtain a composition containing at least 0.05 to 7.0 parts by weight of the above bismuth oxide-based chemical with respect to 100 parts by weight of zinc oxide, or in advance at a molar ratio of bismuth oxide of 1 On the other hand, chromium oxide and boron oxide are added at 0.02 to 0.15 molar ratio and 0.02 to 0.15 molar ratio, and a chemical conversion treatment is performed to prepare a bismuth oxide-based chemical, and 100 parts by weight of zinc oxide On the other hand, a composition containing at least 0.05 to 7.0 parts by weight of the bismuth oxide-based chemical is obtained, or at least an ankymon oxide and an acid are further added to each of the two types of compositions. Containing at least one oxide selected from the group consisting of titanium, tin oxide, zircon oxide, niobium oxide, tantalum oxide, vanadium oxide, molybdenum oxide, tungsten oxide, silicon oxide, magnesium oxide and rare earth oxide, and zinc oxide 100 A composition is obtained by adding 0.05 to 8.0 parts by weight of the above oxide with respect to parts by weight, and then the resulting composition is formed into a thin plate shape. Are laminated and fired, and the resulting laminated zinc oxide varistor is provided.

In order to adjust the sintering and to improve the electrical characteristics of the sintered body after sintering, the zinc oxide-based sintered body of the present invention is preliminarily added as an additive to the main component zinc oxide powder. Various additives including bismuth oxide-based chemical powders that have been subjected to chemical conversion treatment and pulverization are added and mixed, the mixture is molded, and the compact is fired. In the present invention, a zinc oxide-based sintered body thus obtained, a zinc oxide varistor obtained by applying an electrode and a side coat to the zinc oxide-based sintered body, and a mixture are formed into a thin plate shape, laminated alternately with electrode materials, and sintered. Thus, a laminated zinc oxide varistor is obtained.

For some time, zinc oxide varistors with bismuth oxide as the main additive have had important problems. In other words, bismuth oxide used as an additive has a property of facilitating a solid-phase reaction when it comes into contact with various oxides at a solid stage. Some of these compounds containing bismuth oxide remain solid and stable even when the melting point of bismuth oxide is reached. As a result, even when these temperatures are reached, liquid phase sintering becomes difficult. That is, the temperature of liquid phase sintering becomes high and the sintering temperature becomes high. However, when bismuth oxide and a small amount of chromium oxide coexist instead of bismuth oxide, these bismuth oxide phases do not form solid compounds at low temperatures even when they come into contact with various oxides. It was revealed that the bismuth oxide phase of bismuth oxide reacts with zinc oxide to generate a liquid phase mainly composed of bismuth oxide at a low temperature, and liquid phase sintering occurs at a low temperature. Thus, high-performance zinc oxide varistors can be obtained at low temperatures.

Hereinafter, the present invention will be described more specifically with reference to examples. In the following examples, “weight” may be displayed as “wt”.

In the following examples, the aluminum addition amount and the addition amounts of cobalt, manganese and nickel oxides were made constant in each example for easy comparison. The particle sizes of the original raw material powder and the powder after heat treatment and pulverization are as follows.

* ZnO: 0.5 to 1.0 μm
* Co ₃ O ₄ , MnO ₂ , NiO: 1 to 5 μm
* Bi ₂ O ₃ : 1 to 10 μm
* Sb ₂ O ₃ : 1 to 5 μm
* SnO ₂ : 0.5 to 5 μm
* Cr ₂ O ₃ : 1 to 5 μm
* B ₂ O ₃ : 1 to 10 μm
* SiO ₂ : 1 to 5 μm
* TiO ₂ : 1 to 5 μm
* ZrO ₂ : 1 to 5 μm
* Nb ₂ O ₅ : 1 to ₅ μm
* Ta ₂ O ₅ : 1 to ₅ μm
* V ₂ O ₅ : 1 to ₅ μm
* MoO ₃ : 1 to 5 μm
* WO ₃ : 1 to 5 μm
* Rare earth oxide (Y ₂ O ₃ , Pr ₆ O ₁₁ ): 1 to 10 μm
* In any case, powder formed by adding bismuth oxide to at least one of chromium oxide and boron oxide (after grinding for 60 hours with a ball mill): 0.8 to 2.5 μm
* Molded powder for molding (after grinding for 60 hours with a ball mill): 2.7 μm on average
In the following examples, the “/” part indicates a mixture obtained by adding the left and right oxides.
(Example 1)

Bi ₂ O ₃ powder and Cr ₂ O ₃ powder were mixed at a molar ratio of 1: 0.05, heat treated at 550 ° C. for 5 hours in an air atmosphere, and then a monomalon pot using stabilized zirconia as a grinding medium was used. By pulverizing, a bismuth oxide / chromium oxide heat-treated bismuth oxide-based chemical compound powder containing Bi ₂ O ₃ / Cr ₂ O ₃ was obtained. Subsequently, various compounding materials for producing the zinc oxide-based sintered body are obtained by using ZnO powder: Bi ₂ O ₃ / Cr ₂ O ₃ bismuth oxide-based chemical powder: Sb ₂ O ₃ powder: Co ₃ O ₄ powder: MnO ₂ powder: NiO _{powder; Al (NO 3) 3 ·} 9H 2 O = 100: x: 1.0: 0.672: 0.414: 0.251: 0.0075 formulated to be (weight ratio), Monomaron Wet mixed and pulverized with a pot ball mill. However, x = 0.04, 0.1, 0.3, 0.5, 1, 3, 5, and 10 were selected as the amount of Bi ₂ O ₃ / Cr ₂ O ₃ bismuth oxide-based chemical compound powder. After drying the obtained blended powder and press-molding it into a disk shape, the obtained molded body was held in the atmosphere at 900 ° C. for 10 hours, and then cooled to room temperature to obtain a zinc oxide-based sintered body. It was. The obtained sintered body had a thickness of 1.2 mm and a diameter of 14 mm. Next, a part of the obtained sintered body was heat-treated at 700 ° C. for 1 hour (in the following, a heat-treated zinc oxide-based sintered body may be simply referred to as “zinc oxide-based sintered body”). ).

FIG. 1 is a schematic slope view of a disk-type zinc oxide varistor made using the zinc oxide-based sintered body of the present invention. By spraying aluminum on both surfaces of the zinc oxide-based sintered body 11 obtained as described above, an aluminum layer (not shown) is formed, and then copper is sprayed on the formed aluminum layer. The electrode 12 was formed. After soldering the lead wire 13 to the electrode 12, the zinc oxide varistor according to the present invention was obtained by resin coating the sintered body and the electrode portion other than the lead wire portion. The electrical characteristics of the zinc oxide varistor thus obtained were evaluated. As the initial electrical characteristics, a voltage with respect to 1 mm thickness between both terminals when a current of 1 mA was passed, that is, a rising voltage V1 mA / mm, was measured, and a non-linear resistance index of 0. 1 was obtained using V1 mA and V0.1 mA. 1 mAα1 mA was measured. In the following, the non-linear resistance index 0.1 mAα1 mA may be simply abbreviated as α value. The greater the non-linear resistance index, the greater the surge absorption capacity. Furthermore, the non-linear resistance characteristics in the low current region were evaluated at V1 mA / V0.01 mA. When V1mA / V0.01mA takes a value of 1.15 or less, the leakage current is small, and attention to heat generation is unnecessary, and the varistor element is excellent in stability.

Furthermore, the reliability of the varistor for DC load was evaluated. That is, a 0.7 watt DC load was applied to the varistor in a high-temperature atmosphere at 80 ° C. for 500 hours and then cooled, and the change rate of the varistor rising voltage V1 mA, that is, the DC load change rate ΔV1 mA / V1 mA was measured. did. The smaller the change rate ΔV1mA / V1mA of the varistor rising voltage V1mA, the more stable the electrical characteristics of the zinc oxide varistor and the higher the reliability. Furthermore, the reliability of the varistor against current surge was evaluated as follows. The rate of change of the varistor rising voltage V1 mA when a pulse of 8 × 20 μsec and 1.5 kA was applied 10 times, that is, the rate of change of surge ΔV1 mA / V1 mA was measured. Table 1 shows the formulation of Example 1, and Table 2 shows the evaluation results of the electrical characteristics of the varistor obtained in Example 1.

The smaller the value of the rate of change in surge, the more stable the electrical characteristics of the zinc oxide varistor and the higher its reliability. Both show high reliability when the absolute value of the rate of change is 5% or less. From the results shown in Table 2, in the case of # 101 (comparative example), the amount of additive bismuth oxide-based chemical compound powder is small, and characteristic data cannot be obtained due to poor sintering. The properties were not able to be measured due to the sticking together, and in the case of # 101 and # 108, no properties were obtained. On the other hand, in # 102 to # 107, it is clear that the compounding material mixture powder compact according to the present example can be sintered even at a low temperature of 900 ° C. The varistor obtained by using this sintered body has good non-linear resistance characteristics, and the rate of change of the rising voltage V1 mA with respect to a long-time DC load and a surge of current. The absolute value of (ΔV1mA / V1mA) is 5% or less, and the reliability is excellent. As is clear from the results shown in Table 2, there was little variation in electrical characteristics within the same lot. Furthermore, although not shown in Table 2, when a zinc oxide varistor is made using the zinc oxide-based sintered body of this example, the variation in electrical characteristics between different lots is also different from that in the same lot. It was as small as the characteristic variation.
(Example 2)

Bi ₂ O ₃ powder and Cr ₂ O ₃ powder were mixed at a molar ratio of 1: x, heat-treated at 550 ° C. for 5 hours in an air atmosphere, and then finely mixed using a monomalon pot using stabilized zirconia as a grinding medium. By pulverizing, a bismuth oxide / chromium oxide heat-treated bismuth oxide-based chemical powder containing Bi ₂ O ₃ / Cr ₂ O ₃ was obtained. _{However, Bi 2 O 3 / Cr 2} O 3 with _Bi 2 _{O 3} powder and _Cr 2 _{O 3} powder and the molar ratio of bismuth oxide-based chemical powder 1: x = 0.01,0.03,0 as x. 05, 0.1, 0.13, and 0.20 were selected. Subsequently, various compounding materials for producing the zinc oxide-based sintered body are made of ZnO powder: Bi ₂ O ₃ / Cr ₂ O ₃ bismuth oxide-based chemical powder: SnO ₂ powder: Co ₃ O ₄ powder: MnO ₂ powder: NiO powder. _{: Al (NO 3) 3 ·} 9H 2 O = 100: 0.3: 0.8: 0.672: 0.414: 0.251: 0.0075 formulated to be (weight ratio), Monomaron Wet mixed and pulverized with a pot ball mill. After drying the obtained blended powder and press-molding it into a disk shape, the obtained molded body was held in the atmosphere at 950 ° C. for 10 hours and then cooled to room temperature to obtain a zinc oxide-based sintered body. It was. Next, a zinc oxide varistor was obtained by a method similar to Example 1. Table 3 shows the composition of the sample, and Table 4 shows the evaluation results of the electrical characteristics.

From the results shown in Table 4, in the case of # 301 (comparative example), the additive Bi ₂ O ₃ / Cr ₂ O ₃ bismuth oxide composite synthetic powder Bi ₂ O ₃ powder and Cr ₂ O ₃ powder were used in a molar ratio of 1: x. As a result, the amount of x is small, the characteristic data varies widely, and in the case of # 306 (comparative example), the characteristic voltage becomes high and measurement is impossible. In the case of # 301 and # 306, the characteristic value is It can be said that it is not good. On the other hand, in # 302 to # 305, it is clear that the compounding material mixture powder compact according to the present example can be sintered even at a low temperature of 950 ° C. The varistor obtained by using this sintered body has good non-linear resistance characteristics, and the rate of change of the rising voltage V1 mA with respect to a long-time DC load and a surge of current. The absolute value of (ΔV1mA / V1mA) is 5% or less, and the reliability is excellent. As is clear from the results shown in Table 4, the variation in electrical characteristics within the same lot was also small. Furthermore, although not shown in Table 4, when a zinc oxide varistor is produced using the zinc oxide-based sintered body of the present example, the variation in electrical characteristics between different lots is also different from that in the same lot. It was as small as the characteristic variation.
(Example 3)

Bi ₂ O ₃ powder: Cr ₂ O ₃ powder: B ₂ O ₃ powder = 1: 3 types of powders were mixed so as to be x: x (molar ratio) and heat-treated at 600 ° C. for 5 hours in an air atmosphere. After pulverization, heat treatment is performed again under the same conditions, and pulverization is performed with a monomalon pot ball mill using stabilized zirconia as the pulverization medium to obtain a bismuth oxide-based chemical powder containing bismuth oxide, chromium oxide, and boron oxide. It was. However, x = 0.01, 0.03, 0.07, 0.1, 0.12, and 0.20 were selected as the amount of the bismuth oxide-based chemical powder. Next, various compounding materials for producing the zinc oxide-based sintered body were used as ZnO powder: Bi ₂ O ₃ / Cr ₂ O ₃ / B ₂ O ₃ bismuth oxide-based chemical powder: Y ₂ O ₃ powder: Co ₃ O _4. powder: MnO ₂ powder: NiO _{powder: Al (NO 3) 3 ·} 9H 2 O = 100: 3.5: 0.5: 0.672: 0.414: 0.251: 0.0075 (weight ratio) The mixture was mixed and pulverized with a monomalon pot ball mill. After drying the obtained blended powder and press-molding it into a disk shape, the obtained molded body was held in the atmosphere at 900 ° C. for 10 hours, and then cooled to room temperature to obtain a zinc oxide-based sintered body. Obtained. Subsequently, a heat treatment at 700 ° C. was performed on a part of the obtained zinc oxide-based sintered body. Next, a zinc oxide varistor was obtained and evaluated 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.

From the results shown in Table 6, in # 501 (comparative example), the amount of bismuth oxide composite synthetic powder additive Bi ₂ O ₃ / Cr ₂ O ₃ / B ₂ O ₃ is small, and the characteristic data is In the case of # 508 (comparative example), there are large variations in electrical characteristics such as the characteristic voltage. In the case of # 501 and # 508, the characteristic values are not good. On the other hand, in # 502 to # 507, it is clear that the compounded mixture powder molded body according to the present example can be sintered even at a low temperature of 900 ° C. The varistor obtained by using this sintered body has good non-linear resistance characteristics, and the rate of change of the rising voltage V1 mA with respect to a long-time DC load and a surge of current. The absolute value of (ΔV1mA / V1mA) is 5% or less, and the reliability is excellent. As is clear from the results shown in Table 6, the variation in electrical characteristics within the same lot was also small. Furthermore, although not shown in Table 6, when a zinc oxide varistor is made using the zinc oxide-based sintered body of this example, the variation in electrical characteristics between different lots is also different from that in the same lot. It was as small as the characteristic variation.
Example 4

Bi ₂ O ₃ powder: Cr ₂ O ₃ powder: B ₂ O ₃ powder = 1: 0.05: 0.07 (molar ratio) 3 kinds of powders were mixed and 5 at 400 ° C. in an air atmosphere. After heat-treating for a time and finely pulverizing, heat-treating again under the same conditions, and finely pulverizing with a ball mill of a monomalon pot using stabilized zirconia as a pulverizing medium, Bi ₂ O ₃ / Cr ₂ O ₃ / B ₂ O ₃ A bismuth oxide based chemical powder was obtained. Next, a sample was prepared in the same manner as in Example 1. That is, ZnO powder: Bi ₂ O ₃ / Cr ₂ O ₃ / B ₂ O ₃ bismuth oxide-based chemical powder: Ta ₂ O ₅ powder: Co ₃ O ₄ powder: MnO ₂ powder: NiO powder: Al (NO ₃ ) ₃ · 9H ₂ O powder = 100: 4: x: 0.672 : 0.414: 0.251: 0.0075 ( formulated as a weight ratio), after 60 hours were mixed by a wet method , Dried, granulated and molded. However, x = 0.03, 0.07, 0.1, 0.5, 1, 3, 6, and 10 were selected as the amount of Ta ₂ O ₅ powder. The obtained molded body was fired at 900 ° C. A part of the sintered body was heat-treated at 700 ° C. Next, a zinc oxide varistor was obtained and evaluated in the same manner as in Example 1. Table 7 shows the composition of the sample, and Table 8 shows the evaluation results of the electrical characteristics.

From the results shown in Table 8, in the case of # 701 (comparative example), the amount of Ta ₂ O ₅ powder is small and the characteristic data has a large variation. In the case of # 708 (comparative example), the variation in electrical characteristics such as the characteristic voltage. In the case of # 701 and # 708, it can be said that the characteristic value is not good. On the other hand, in # 702 to # 707, it is clear that the compounding material mixture powder compact according to this example can be sintered even at a low temperature of 950 ° C. The varistor obtained by using this sintered body has good non-linear resistance characteristics, and the rate of change of the rising voltage V1 mA with respect to a long-time DC load and a surge of current. The absolute value of (ΔV1mA / V1mA) is 5% or less, and the reliability is excellent. As is clear from the results shown in Table 8, the variation in electrical characteristics within the same lot was also small. Furthermore, although not shown in Table 8, when a zinc oxide varistor is made using the zinc oxide-based sintered body of this example, the variation in electrical characteristics between different lots is also different from that in the same lot. It was as small as the characteristic variation. The zinc oxide varistors manufactured using the zinc oxide-based sintered bodies according to these examples have good non-linear resistance characteristics, and have a rising voltage against a long-term DC load and surge. The absolute value of the change rate of V1mA (ΔV1mA / V1mA) was 5% or less, and the reliability was excellent.

The invention's effect

As described above with reference to the examples, the zinc oxide-based sintered body of the present invention contains a bismuth oxide-based chemical compound containing at least a small amount of chromium oxide as an additive to zinc oxide, Sintering enables high-performance electrical properties at low temperatures. Further, the zinc oxide-based sintered body of the present invention contains a bismuth oxide-based chemical composition containing at least a small amount of chromium oxide and a small amount of boron oxide as an additive to zinc oxide, and is sintered. This enables high-performance electrical characteristics at low temperatures. By adding these bismuth oxide-based chemicals, a stable solid phase was not formed during the temperature rise, and low-temperature sintering proceeded. The zinc oxide sintered body of the present invention comprises zinc oxide, antimony oxide, titanium oxide, tin oxide, zircon oxide, niobium oxide, tantalum oxide, vanadium oxide, molybdenum oxide, tungsten oxide, silicon oxide, magnesium oxide, and rare earth oxidation. When at least one oxide selected from the group consisting of substances is added and the bismuth oxide based chemical compound is contained and added, it is effective and leads to an excellent zinc oxide varistor.

In addition, since the zinc oxide-based sintered body of the present invention can be sintered at a low temperature, it is possible to reduce power consumption during sintering, and at the same time, consumption of furnace materials and containers of an electric furnace used for sintering. Can be reduced, and can greatly contribute to energy and resource saving. Furthermore, some of the zinc oxide-based sintered bodies of the present invention are sintered even at a temperature lower than the melting temperature of silver or the like, and a silver electrode is simultaneously formed inside these sintered bodies at the time of firing. Became possible. As a result, high-performance multilayer zinc oxide varistors with silver internal electrodes can be manufactured. In the examples, the firing data mainly at 900 ° C. and 950 ° C. were shown. However, even if sintered at a lower temperature, a product having good characteristics can be obtained, and the kind and amount of the additive can be adjusted. Thus, it has become clear that a good varistor can be obtained even when the firing temperature is lowered to 700 ° C.

  FIG. 3 is a schematic perspective view of a disk-type zinc oxide varistor produced using the zinc oxide-based sintered body of Example 1 of the present invention.

Explanation of symbols

Fig. 1 Disc type zinc oxide varistor 11 Zinc oxide sintered body 12 Electrode 13 Lead wire

Claims (5)

In advance, 0.02 to 0.15 mole ratio of chromium oxide is added to 1 mole ratio of bismuth oxide to perform chemical conversion treatment to prepare a bismuth oxide based chemical composition. A zinc oxide-based sintered body obtained by forming a composition containing at least 0.05 to 7.0 parts by weight of a chemical and firing at 700 to 980 ° C. First, chromium oxide and boron oxide were added in a molar ratio of 0.02 to 0.15 and a molar ratio of 0.02 to 0.15 with respect to 1 molar ratio of bismuth oxide to form a bismuth oxide-based chemical composition. A zinc oxide obtained by forming a composition containing the bismuth oxide-based chemical compound in an amount of at least 0.05 to 7.0 parts by weight with respect to 100 parts by weight of zinc oxide and firing at 700 ° C. to 980 ° C. System sintered body. The composition is at least one oxide selected from the group consisting of at least ankymon oxide, titanium oxide, tin oxide, zircon oxide, niobium oxide, tantalum oxide, vanadium oxide, molybdenum oxide, tungsten oxide, silicon oxide, magnesium oxide, and rare earth oxide. 3. The zinc oxide-based sintered body according to claim 1, wherein the oxide is 0.05 to 8.0 parts by weight with respect to 100 parts by weight of zinc oxide. A zinc oxide varistor formed by forming an electrode on the zinc oxide-based sintered body according to claim 1, claim 2 or claim 3, and further forming an insulating film on a side surface. In a laminated zinc oxide varistor, the composition according to claim 1, claim 2 or claim 3 is formed into a thin plate shape, and the obtained compact and metal electrode material are alternately laminated and fired. A laminated zinc oxide varistor characterized by that.

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