JPH06204006A - Manufacture of zinc oxide varistor - Google Patents

Abstract

PURPOSE:To uniformize the growth of ZnO grains by adjusting the mixed material of titanium oxide and bismuth oxide by previously heat treating it so as to form synthetic powder. CONSTITUTION:After mixing titanium oxide fine powder and bismuth oxide powder by a prescribed weight ratio, heat treatment is performed and the mixed material is finely powdered to form synthetic powder. Then, zinc oxide powder, the titanium oxide/bismuth synthetic powder, cobalt oxide powder and manganese dioxide powder are mixed by the prescribed weight ratio by wet method and are powdered. The powder is dried and pressure molded. After calcinating and powdering it, the material is molded in disc-shape and is sintered in the atmosphere. Aluminum layers are formed on the both planes of the sintered body 11 by flame spraying, copper is flame sprayed and electrodes 12 are formed. The electrode 12 is fitted with a lead wire 13 by solder and the compact is coated. Thus, a zinc oxide varistor which has excellent electric characteristics and reliability is manufactured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a zinc oxide varistor used for absorbing surges in an electric circuit, and more particularly,
The present invention relates to a method for manufacturing a zinc oxide varistor for low voltage, which is widely used for the purpose of protecting semiconductor elements from various surges in electronic circuits.

[0002]

2. Description of the Related Art A zinc oxide varistor burns a zinc oxide raw material powder containing zinc oxide, basic additives bismuth oxide, manganese dioxide and cobalt oxide, and various oxides added for improving performance. It is manufactured using the sintered body obtained by It is known that the rising voltage of a zinc oxide varistor rises almost in proportion to the number of grain boundaries existing between electrodes. That is, the rise voltage of 3 to 4 volts per grain boundary rises.
Therefore, in order to manufacture a zinc oxide varistor for low voltage, it is necessary to manufacture a sintered body containing ZnO particles having a large particle size. Therefore, conventionally, titanium oxide (TiO ₂ )
A method of promoting the growth of ZnO particles has been used by adding a growth promoting material such as.

[0003]

However, it was not possible to uniformly promote grain growth by simply adding titanium oxide. It often caused extreme abnormal grain growth, resulting in a wide distribution of zinc oxide particle size.

The current flowing through zinc oxide flows through the path having the smallest number of grain boundaries existing between the electrodes. Therefore, if the particle size distribution of ZnO particles in the sintered body is wide, the current will flow concentratedly in a part of the sintered body, and as a result, the electrical characteristics of the zinc oxide varistor for low voltage will deteriorate in a short period of time. , There was a problem of low reliability. Further, since it was difficult to sufficiently control abnormal grain growth, there was a problem that variations in electrical characteristics and reliability among zinc oxide varistors obtained from one manufacturing lot (variations within lots) were large. . Further, there is a problem that variations in electrical characteristics and reliability among zinc oxide varistors obtained from different manufacturing lots (variations between lots) are also large.

As described above, according to the conventional manufacturing method, it was not possible to stably manufacture a zinc oxide varistor for low voltage which is excellent in electrical characteristics and reliability.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for producing a zinc oxide varistor for low voltage, which is excellent in electrical characteristics and reliability at low voltage, with high yield. To provide.

[0007]

A method for producing a zinc oxide varistor according to the present invention comprises a step of preparing a synthetic powder by heat-treating a mixture of titanium oxide and bismuth oxide, and adding the synthetic powder to a zinc oxide raw material powder. The above-mentioned object is achieved thereby.

A step of adding an aluminum component to the zinc oxide raw material powder may be further included. In one embodiment, the amount of the aluminum component added is ZnO 10 by weight.
It is in the range of 0.00062 to 0.372 in terms of AL ₂ O ₃ with respect to 0.
In one embodiment, the aluminum component is a solution of aluminum salt. In another embodiment, the aluminum salt is aluminum nitrate. In one embodiment, the aluminum salt is aluminum acetate.

A step of adding an antimony component to the zinc oxide raw material powder may be further included. In one embodiment,
The amount of the antimony component added is in the range of 0.018 to 0.72 in terms of Sb ₂ O _{3 with} respect to ZnO 100 by weight.

A step of adding a tin component to the zinc oxide raw material powder may be further included. In one embodiment, the addition amount of the tin component is in the range of 0.005 to 0.37 in terms of SnO _{2 with} respect to ZnO 100 by weight.

A step of adding a chromium component to the zinc oxide raw material powder may be further included. In one embodiment, the amount of the chromium component added is in the range of 0.005 to 0.18 in terms of Cr ₂ O _{3 based on} ZnO 100.

[0012]

[Function] The present invention has been accomplished as a result of intensive research on the mechanism of grain growth promotion by titanium oxide. The present inventors have found that when titanium oxide reacts with zinc oxide, it cannot promote the grain growth of zinc oxide, and the reaction product of titanium oxide and bismuth oxide promotes the grain growth of zinc oxide. It was Therefore, when titanium oxide is simply added to the zinc oxide raw material powder as in the conventional manufacturing method, there are portions where titanium oxide reacts with zinc oxide and portions where titanium oxide reacts with bismuth oxide. As a result, in the sintered body, a portion where grain growth is not promoted and a portion where grain growth is promoted coexist. Therefore, the conventional manufacturing method cannot manufacture a sintered body having a narrow particle size distribution. The synthetic powder prepared by pre-heating the mixture of titanium oxide and bismuth oxide according to the present invention can uniformly promote the growth of ZnO particles.

The present inventors have also found that the antimony component, the tin component and the chromium component added together with the antimony component act to suppress abnormal growth of zinc oxide particles. When the above-mentioned components are added to the zinc oxide raw material powder, the zinc oxide particles become twin crystals and act to suppress abnormal growth.

As a result of the above two effects, ZnO particles having a large average particle size and a narrow particle size distribution can be obtained. These phenomena were first discovered by the present inventor as a result of earnest research on a method of adding a bismuth component and a titanium component to a zinc oxide raw material powder.

Further, the aluminum component forms a solid solution in the ZnO particles and acts as a donor, which has the effect of lowering the electrical resistance of ZnO.

[0016]

Embodiments of the present invention will be described below with reference to the tables and the drawings.

(Example 1) Fine powder of titanium oxide (TiO ₂ )
And bismuth oxide powder (Bi ₂ O ₃ ) in a weight ratio of 11.4: 88.6
Mixed so that After heat treatment at 600 ° C. for 5 hours, the mixture was pulverized to obtain a synthetic powder. Hereinafter, the synthetic powder thus prepared from titanium oxide and bismuth oxide is referred to as titanium oxide / bismuth oxide synthetic powder.

Zinc oxide powder (ZnO), titanium oxide /
Bismuth oxide synthetic powder, cobalt oxide powder (CoO) and manganese dioxide powder (MnO ₂ ) in a weight ratio of 100: 2.93: 0.8
04: 0.555 to mix the powder blended by a wet method,
Crushed. The obtained powder is dried, and the product molded under pressure is
It was calcined at 600 ° C, crushed, and then shaped into a disc. The obtained molded body was heated in the atmosphere at a temperature rising rate of 100 ° C./hour, held at 1250 ° C. for 2 hours, and then cooled at a temperature lowering rate of 100 ° C./hour to obtain a sintered body. The sample size of the sintered body is 1.2 m thick
m, diameter 14 mm.

Next, a method for manufacturing a zinc oxide varistor will be described with reference to FIG. By spraying aluminum on both surfaces of the sintered body 11 obtained as described above,
An aluminum layer (not shown) was formed. Next, the electrode 12 was formed by spraying copper on the aluminum layers formed on both surfaces. After the lead wire 13 was attached to the electrode 12 with solder, a molded body other than the lead wire was coated to obtain a zinc oxide varistor.

The electrical characteristics of the zinc oxide varistor obtained as described above were evaluated. As the initial electrical characteristics, V ₁ m
A / mm (voltage for 1 mm thickness between both terminals when a current of 1 mA is applied) and non-linear resistance index _0.1 α _{1 mA} (V ₁ mA and V _0.1
The value obtained using mA and) was measured.

Moreover, the reliability with respect to the DC load is evaluated.
It was 5 dc load of 0.2 watt in high temperature atmosphere of 80 ℃
Applied for 00 hours, varistor rising voltage V₁mA change
Rate ΔV ₁mA / V₁mA (DC load change rate) was measured. Furthermore
In addition, the reliability with respect to the surge was evaluated. 8x20 μsec, 0.5
Varistor rising voltage V by applying a kA pulse twice
₁mA change rate (surge change rate) ΔV₁mA / V₁Calculate mA
It was The composition of the sample is shown in (Table 1), and the electrical characteristics are shown in (Table 2).
Value results are shown. A numerical value showing the evaluation result of the electrical characteristics
Indicates the minimum and maximum values within the lot.

[0022]

[Table 1]

[0023]

[Table 2]

As can be seen from (Table 1) and (Table 2), the zinc oxide varistor manufactured by the method for manufacturing a zinc oxide varistor according to the present invention has a low rising voltage, and is resistant to a DC load for a long time. Also for the surge, the absolute value of the change rate ΔV ₁ mA / V ₁ mA of the rising voltage V ₁ mA was 5% or less, and the reliability was excellent. In addition, as shown in (Table 2), there was little variation in the electrical characteristics within the lot.

Although not shown in Table 2, when the zinc oxide varistor was produced by this manufacturing method, the variation in the electrical characteristics between lots was as small as the variation within the lot.
As a result, the yield is remarkably improved.

(Comparative Example) A zinc oxide varistor using a sintered body having the same composition as in Example 1 was produced by a conventional production method.

Zinc oxide powder (ZnO), bismuth oxide powder (Bi ₂ O ₃ ), titanium oxide fine powder (TiO ₂ ), cobalt oxide powder (CoO) and manganese dioxide powder (MnO ₂ ) were used in a weight ratio of 100: The powder compounded so as to be 2.60: 0.33: 0.804: 0.555 was mixed by a wet method and ground. The obtained powder was dried, pressure-molded, calcined at 600 ° C., crushed, and then molded into a disk shape. The obtained molded body in the atmosphere,
The temperature was raised at a temperature rising rate of 100 ° C./hour, the temperature was held at 1250 ° C. for 2 hours, and then the temperature was lowered at a temperature lowering rate of 100 ° 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.

A zinc oxide varistor was manufactured in the same manner as in Example 1 below. Further, in the same manner as in Example 1, the electrical characteristics of the obtained zinc oxide varistor were evaluated. Table 3 shows the sample composition, and Table 4 shows the evaluation results of the electrical characteristics.

[0029]

[Table 3]

[0030]

[Table 4]

As can be seen from (Table 3) and (Table 4),
The zinc oxide varistor manufactured by the conventional manufacturing method is 0.2
V ₁ mA after the DC load of watts was remarkably reduced, and the absolute value of the DC load change rate ΔV ₁ mA / V ₁ mA was 25% or more.
The absolute value of the surge change rate also exceeded 40%, and the reliability was extremely low. Further, as shown in (Table 4), there was a large variation within the lot.

Although not shown in (Table 4), the conventional method
Between lots of electrical properties of zinc oxide varistors manufactured by the method
The variation is even larger than the variation within the lot.
It was V ₁mA / mm and α value are lower than those shown in (Table 4)
There were many baristas.

As described above, as is clear from the comparison between Example 1 and the comparative example, the zinc oxide varistor according to the manufacturing method of the present invention shows initial electrical characteristics, reliability, and intra-lot and inter-lot electrical characteristics. Any variation is superior to the zinc oxide varistor manufactured by the conventional manufacturing method.

Example 2 Titanium oxide fine powder and bismuth oxide powder were mixed at a weight ratio of 20.5: 79.5. After heat treatment at 800 ° C. for 5 hours, the mixture was pulverized to obtain a titanium oxide / bismuth oxide synthetic powder. The synthetic powder was a powder containing bismuth titanate (Bi ₄ Ti ₃ O ₁₂ ) as a main component.

Zinc oxide powder, titanium oxide / bismuth oxide synthetic powder, cobalt oxide powder and manganese dioxide powder were blended in a weight ratio of 100: 3.15: 0.922: 0.534, and mixed and pulverized by a wet method. . The obtained powder was dried and pressure-molded, and the powder was calcined at 600 ° C., crushed, and then molded into a disk shape. The obtained molded body was heated in the atmosphere at a temperature rising rate of 100 ° C./hour, held at 1250 ° C. for 2 hours, and then cooled at a temperature lowering rate of 100 ° 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.

A zinc oxide varistor was manufactured in the same manner as in Example 1 below. Further, in the same manner as in Example 1, the electrical characteristics of the obtained zinc oxide varistor were evaluated. Table 5 shows the sample composition, and Table 6 shows the evaluation results of the electrical characteristics.

[0037]

[Table 5]

[0038]

[Table 6]

As can be seen from (Table 5) and (Table 6), the zinc oxide varistor manufactured by the method for manufacturing a zinc oxide varistor according to the present invention has a low rising voltage, and is resistant to a DC load for a long time. Also for the surge, the absolute value of the change rate ΔV ₁ mA / V ₁ mA of the rising voltage V ₁ mA was 5% or less, and the reliability was excellent. In addition, as shown in (Table 6), there was little variation in the electrical characteristics within the lot.

Although not shown in Table 6, when the zinc oxide varistor was produced by this manufacturing method, the variation in the electrical characteristics between lots was as small as the variation within the lot. As a result, the yield is remarkably improved.

Example 3 Titanium oxide fine powder and bismuth oxide powder were mixed at a weight ratio of 11.4: 88.6. After heat treatment at 600 ° C. for 5 hours, the mixture was pulverized to obtain a titanium oxide / bismuth oxide synthetic powder. Zinc oxide powder, cobalt oxide powder, manganese dioxide powder, tin oxide powder and titanium oxide /
Bismuth oxide synthetic powder, the weight ratio, 100: 0.804: 0.555:
0.518: X (X = 0.1, 0.2, 0.5, 1.0, 2.0, 5.0, 10.0, 15.0, 20.
The powder compounded so as to be 0) was mixed and pulverized by a wet method. The obtained powder was dried and then pressure-molded to obtain 600
It was calcined at ℃. An aqueous solution of aluminum nitrate containing aluminum in an amount of 0.007 by weight relative to 100 parts of zinc oxide in terms of aluminum oxide (Al ₂ O ₃ ) was added to the obtained molded body, which was ground and then molded into a disk shape. The obtained molded body is heated in the atmosphere at a temperature rising rate of 100 ° C./hour,
After holding at 1200 ° C. for 2 hours, the temperature was lowered at a temperature lowering rate of 100 ° 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.

A zinc oxide varistor was manufactured in the same manner as in Example 1 below. Further, in the same manner as in Example 1, the electrical characteristics of the obtained zinc oxide varistor were evaluated. Table 7 shows the sample composition, and Table 8 shows the evaluation results of the electrical characteristics.

[0043]

[Table 7]

[0044]

[Table 8]

From (Table 7) and (Table 8), the zinc oxide varistor manufactured by the method for manufacturing a zinc oxide varistor according to the present invention has an additive amount of titanium oxide / bismuth oxide synthetic powder of 0.
When the weight ratio is 2 or more (Sample Nos. 12 to 18), the α value is large, and the change rate of the rising voltage V ₁ mA of ΔV ₁ mA / V ₁ mA can be increased even with a long-term DC load and surge. The absolute value was 5% or less, which was excellent in reliability. The amount of synthetic powder of bismuth oxide and titanium oxide added was 20% or more (Sample No. 19).
In this case, if the molded bodies are stacked and fired at the time of firing, the sintered bodies are fused to each other, and thus the mass productivity of the varistor is lacking.

(Example 4) A fine powder of titanium oxide and a powder of bismuth oxide were mixed so that the weight ratio of bismuth oxide to titanium oxide was 1.5 to 59,
By heat-treating at 500 ° C. for 5 hours and finely pulverizing, a titanium oxide / bismuth oxide synthetic powder was obtained.

The zinc oxide powder, the cobalt oxide powder, the manganese dioxide powder, the antimony oxide powder and the titanium oxide / bismuth oxide synthetic powder have a weight ratio of 100: 0.555: 0.291:
The powder compounded so as to be 3.0 was mixed by a wet method and pulverized. The powder obtained is dried and pressure molded to 600 ° C.
It was calcined in. Aluminum oxide (Al
_In terms of ₂ O ₃ ), an aqueous solution of aluminum acetate containing aluminum in an amount of 0.001 with respect to 100 parts of zinc oxide was added, crushed, and then molded into a disk shape. The obtained molded body is heated in the atmosphere at a temperature rising rate of 100 ° C./hour to 1200
After holding at ℃ for 2 hours, the temperature was decreased at a temperature decreasing rate of 100 ℃ / hour to obtain a sintered body. The sample size of the sintered body is 1.2 mm thick and the diameter is
It was 14 mm.

The obtained sintered body was subjected to a scanning electron microscope (SE
As a result of observation in M), it was found to have a characteristic microstructure having twinned ZnO particles.

A zinc oxide varistor was manufactured in the same manner as in Example 1 below. Further, in the same manner as in Example 1, the electrical characteristics of the obtained zinc oxide varistor were evaluated. In particular, in order to examine the reliability against surges in detail, V _0.01 mA at which the change with respect to surge appears more significantly was measured. In the pulse
A pulse of 8 × 20 μsec, 1.0 kA was used. Table 9 shows the sample composition, and Table 10 shows the evaluation results of the electrical characteristics.

[0050]

[Table 9]

[0051]

[Table 10]

As can be seen from (Table 9) and (Table 10),
From the weight ratio of bismuth oxide to titanium oxide of 2.0
A zinc oxide varistor having good electrical characteristics and reliability was obtained in the range of 29.0 (sample numbers 22 to 28). If the composition is out of this range (Sample Nos. 21 and 29), the change rate of V _0.01 mA due to the pulse ΔV _0.01 mA / V _0.01 mA absolute value is 10%.
As described above, the reliability is lowered.

(Example 5) Fine powder of titanium oxide and powder of bismuth oxide were mixed at a weight ratio of 25:75 and 650
Heat treatment was performed at 5 ° C. for 5 hours and finely pulverized to obtain a titanium oxide / bismuth oxide synthetic powder.

Zinc oxide powder, titanium oxide / bismuth oxide synthetic powder, cobalt oxide powder, manganese dioxide powder, antimony oxide powder and chromium oxide powder, by weight,
100: 2.5: 0.804: 0.555: X: X / 4 (X = 0.010, 0.018, 0.030,
0.060, 0.10, 0.20, 0.36, 0.720, 0.80) were mixed and pulverized by a wet method. The obtained powder is dried and converted into aluminum oxide (Al ₂ O ₃ ),
An aqueous solution of aluminum acetate containing 0.001 of aluminum was added to 100 parts of zinc oxide, and calcined at 600 ° C. The obtained molded body was crushed, mixed, and then molded into a disk shape. The temperature rise rate of the obtained compact in the atmosphere
The temperature was raised at 100 ° C./hour, the temperature was held at 1200 ° C. for 2 hours, and then the temperature was lowered at a temperature lowering rate of 100 ° 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.

The obtained sintered body was subjected to a scanning electron microscope (SE
As a result of observation in M), it was found to have a characteristic microstructure having twinned ZnO particles.

A zinc oxide varistor was manufactured in the same manner as in Example 1 below. Further, in the same manner as in Example 1, the electrical characteristics of the obtained zinc oxide varistor were evaluated. In particular, in order to examine the reliability against surges in detail, V _0.01 mA at which the change with respect to surge appears more significantly was measured. In the pulse
A pulse of 8 × 20 μsec, 1.0 kA was used. Table 11 shows the sample composition, and Table 12 shows the evaluation results of the electrical characteristics.

[0057]

[Table 11]

[0058]

[Table 12]

As can be seen from (Table 11) and (Table 12), by only adding a trace amount of Sb ₂ O ₃ to the zinc oxide raw material powder,
Improved reliability against surges. That is, the added amount of antimony oxide X = 0.018 or more, the added amount of chromium oxide X / 4 =
When 0.0045 or more (Sample Nos. 32 to 39), surge change rate ΔV
The absolute value of _0.01 mA / V _0.01 mA was 10% or less. But,
When the added amount of antimony oxide is X = 0.8 or more and the added amount of chromium oxide is X / 4 = 0.2 or more (Sample No. 39), V ₁ mA / mm exceeds 50 V and cannot be used as a low voltage varistor.

(Example 6) Zinc oxide powder, bismuth oxide powder, the same titanium oxide / bismuth oxide synthetic powder as in Example 5, cobalt oxide powder, manganese dioxide powder and tin oxide powder were mixed in a weight ratio of 100: 1.0: 2.00. : 0.804: 0.555: X (X = 0.0
03, 0.005, 0.010, 0.030, 0.050, 0.10, 0.20, 0.370,
The powder blended so as to be 0.50) was mixed by a wet method and pulverized. The obtained powder is dried and aluminum oxide (Al ₂ O
Converted to ₃ ), an aqueous solution of aluminum acetate containing aluminum in an amount of 0.001 with respect to 100 parts of zinc oxide was added, mixed, and calcined at 600 ° C. The obtained molded body was crushed, mixed, and then molded into a disk shape. The resulting molded body is heated in the air at a temperature rising rate of 100 ° C / hour to 1200 ° C.
After holding for 2 hours, the temperature was decreased at a temperature decreasing rate of 100 ° C./hour to obtain a sintered body. The sample size of the sintered body is 1.2 mm in thickness and 14 in diameter.
It was mm.

The obtained sintered body was scanned with a scanning electron microscope (SE
As a result of observation in M), it was found to have a characteristic microstructure having twinned ZnO particles.

A zinc oxide varistor was manufactured in the same manner as in Example 1 below. Further, in the same manner as in Example 1, the electrical characteristics of the obtained zinc oxide varistor were evaluated. In particular, in order to examine the reliability against surges in detail, V _0.01 mA at which the change with respect to surge appears more significantly was measured. In the pulse
A pulse of 8 × 20 μsec, 1.0 kA was used. Table 13 shows the sample composition, and Table 14 shows the evaluation results of the electrical characteristics.

[0063]

[Table 13]

[0064]

[Table 14]

As can be seen from (Table 13) and (Table 14), the amount of tin oxide added X = 0.005 or more (Sample Nos. 42 to 4)
In 9), the absolute value of surge change rate ΔV _0.01 mA / V _0.01 mA is 1
It will be 0% or less. However, when the amount of tin oxide added is X = 0.5 or more (Sample No. 49), V ₁ mA / mm exceeds 50 V and cannot be used as a low voltage varistor.

[0066]

As described above, according to the present invention, the synthetic powder prepared by preliminarily heat treating the mixture of titanium oxide and bismuth oxide promotes uniform growth of ZnO particles. Further, the antimony component, the tin component, and the chromium component added together with the antimony component act to suppress abnormal growth of zinc oxide particles. Therefore, according to the production method of the present invention, ZnO particles having a large average particle size and a narrow particle size distribution can be obtained. That is, it becomes possible to manufacture a zinc oxide varistor having excellent electrical characteristics and reliability with a high yield.

[Brief description of drawings]

FIG. 1 is a schematic view showing a zinc oxide varistor manufactured according to an embodiment of the present invention.

[Explanation of symbols]

 11 Zinc oxide sintered body 12 Electrode 13 Lead wire

Claims (12)

[Claims] 1. A method for producing a zinc oxide varistor, comprising: a step of heat-treating a mixture of titanium oxide and bismuth oxide to prepare a synthetic powder; and a step of adding the synthetic powder to a zinc oxide raw material powder. 2. The method for producing a zinc oxide varistor according to claim 1, further comprising the step of adding an aluminum component to the zinc oxide raw material powder. 3. The amount of aluminum component added is Zn by weight.
The method for producing a zinc oxide varistor according to claim 2, which is in the range of 0.00062 to 0.372 in terms of AL ₂ O _{3 with} respect to O 100. 4. The method for producing a zinc oxide varistor according to claim 3, wherein the aluminum component is a solution of an aluminum salt. 5. The method for producing a zinc oxide varistor according to claim 4, wherein the aluminum salt is aluminum nitrate. 6. The method for producing a zinc oxide varistor according to claim 4, wherein the aluminum salt is aluminum acetate. 7. The method for producing a zinc oxide varistor according to claim 3, further comprising the step of adding an antimony component to the zinc oxide raw material powder. 8. The added amount of antimony component is ZnO by weight.
The method for producing a zinc oxide varistor according to claim 7, which is in the range of 0.018 to 0.72 in terms of Sb ₂ O _{3 with} respect to 100. 9. The method for producing a zinc oxide varistor according to claim 3, further comprising the step of adding a tin component to the zinc oxide raw material powder. 10. The amount of tin component added is ZnO 100 by weight.
On the other hand, the method for producing a zinc oxide varistor according to claim 9, which is in the range of 0.005 to 0.37 in terms of SnO ₂ . 11. The method for producing a zinc oxide varistor according to claim 8, further comprising the step of adding a chromium component to the zinc oxide raw material powder. 12. The amount of chromium component added is ZnO 10 by weight.
The method for producing a zinc oxide varistor according to claim 11, wherein the value is in the range of 0.005 to 0.18 in terms of Cr ₂ O _{3 with} respect to 0.