JPH025001B2 - - Google Patents

Description

[Detailed description of the invention]

In the present invention, when sintering a mixture containing zinc oxide as a main component and additives such as bismuth oxide, cobalt oxide, manganese oxide, antimony oxide, chromium oxide, and silicon dioxide, the voltage Regarding linear resistors. In recent years, molding has been made using zinc oxide as the main component, and additives such as bismuth oxide, cobalt oxide, antimony oxide, manganese oxide, chromium oxide, and silicon dioxide, as well as boron oxide, lead oxide, and aluminum oxide, as needed. 2. Description of the Related Art Voltage nonlinear resistors made of fired sintered bodies are widely used in voltage stabilizing elements, surge absorbers, arresters, and the like. In the above-mentioned voltage nonlinear resistor, zinc oxide particles are surrounded by another boundary layer (grain boundary layer) mainly composed of bismuth oxide having high resistance, so to speak, the zinc oxide is covered with the grain boundary layer. When a voltage is applied to the voltage nonlinear resistor, an electrical barrier is formed between the grain boundary layer and the zinc oxide particles, resulting in an excellent voltage resistance. It is thought that linear resistance develops. In general, the voltage-current characteristics of a voltage nonlinear resistor are approximated by the formula (1): I=kV〓 (1) (where I is the current, k is a constant, V is the voltage and α
represents the nonlinear coefficient). The voltage nonlinear resistor whose main component is zinc oxide as described above is α
The value of α is 5 to 60, which is considerably larger than the value of α of 3 to 4 for conventional voltage nonlinear resistors made of silicon carbide, and in the region where the current-voltage characteristics are flat, the Since the voltage is almost constant, it has the characteristic that the voltage required to flow 1 mA of current (hereinafter referred to as V _{1 nA} ) can be freely changed simply by changing the thickness of the voltage nonlinear resistor. Its uses are increasingly being expanded. However, even with elements made from voltage non-linear resistors that have the above-mentioned advantages, if a constant DC or AC voltage is continuously applied, the leakage current flowing through the element generally increases over time, resulting in an increase in leakage current. There is a limit to the lifespan of the device, such as thermal runaway due to the heat generated by the device, which may eventually lead to device destruction. In particular, in the case of gear press zinc oxide type lightning arresters, a constant voltage is constantly applied, so element destruction due to increased leakage current is an extremely important problem. It is also desirable to obtain a long-life element in which the increase in leakage current over time is as small as possible. Conventionally, various glass compositions have been further added to a mixture containing zinc oxide as a main component for producing voltage nonlinear resistors with the aim of improving the energized life characteristics of voltage nonlinear resistor elements. , improvements to the firing process have been made, but although the results are effective for the charging life characteristics, for example, the limiting voltage ratio (which shows nonlinearity in a large current range and is Applying current to a linear resistor element
The ratio of the voltage required to flow 10 kA to the voltage required to flow 1 mA (V _{10 kA} / V _{1 nA} is often used) is often associated with disadvantages such as a large value, and it is not required for power surge arresters. However, it does not fully satisfy the characteristics described above. The inventors of the present invention have conducted intensive research to resolve the problems in the electrical characteristics such as the voltage application life characteristics and limiting voltage ratio of voltage nonlinear resistor elements as described above. bismuth,
cobalt oxide, manganese oxide, antimony oxide,
When sintering a mixture containing chromium oxide and silicon dioxide as additives, zinc oxide and boron oxide are each added in an amount of 40 to 65% (wt%, the same applies hereinafter).
and 25 to 40%, and at least one selected from the group consisting of titanium oxide, zirconium oxide, tantalum oxide, lanthanum oxide, and yttrium oxide, with a content of 1 to 10% and 0.7 to 18%, respectively, based on the total amount of glass, Glass containing 1 to 35%, 1 to 35%, and 1 to 25% is 0.004 to 100 parts (parts by weight, same hereinafter) of the above mixture.
By adding 0.6 parts of this to create a voltage non-linear resistor, we have solved the problems in the electrical properties of conventionally used voltage non-linear resistor elements, such as the energized life characteristics and limiting voltage ratio. The invention has been completed. Zinc oxide (ZnO), bismuth oxide (Bi ₂ O ₃ ), cobalt oxide (Co ₂ O ₃ ), manganese oxide (MnO ₂ ), chromium oxide (Cr ₂ O ₃ ), antimony oxide (Sb ₂ O) used in the present invention ₃ ) and silicon dioxide (SiO ₂ ) are powders with a purity of approximately 99% or higher, and these powders are mixed, and if necessary, boron oxide,
A zinc oxide based mixture is prepared with addition of additives such as aluminum oxide. Zinc oxide, boron oxide (B ₂ O ₃ ), titanium oxide (TiO ₂ ), zirconium oxide (ZrO ₂ ), tantalum oxide (Ta ₂ O ₅ ), lanthanum oxide (La ₂ O ₃ ) and yttrium oxide (Y ₂ O ₃ ) each have a purity of 99%.
Among the above powders, it is preferable that the boron oxide is sufficiently dried and does not contain metaboric acid. The ratio of their use is 40 to 65% each of zinc oxide and boron oxide, which are always included in glass, based on the total amount of glass.
and 25-40%, with the remaining amount being one or more compounds selected from the group consisting of titanium oxide, zirconium oxide, tantalum oxide, lanthanum oxide and yttrium oxide. The contents of titanium oxide, zirconium oxide, tantalum oxide, lanthanum oxide, and yttrium oxide contained in the glass are 1 to 10% and 0.7%, respectively, based on the total amount of the glass.
-18%, 1-35%, 1-35%, and 1-25%, and if it is out of this range, the leakage current changes over time during DC energization will increase, and the energized life will be shortened. It may become impossible to obtain a uniform glass, and as a result, the leakage current of the manufactured device when DC current is applied increases over time. In addition, if the proportions of zinc oxide and boron oxide, which are always included in the above-mentioned glass, are outside the ranges of 40-65% and 25-40%, respectively, it will be difficult to vitrify, or even if vitrified, a portion will remain in the crystalline phase. The effect of glass addition is reduced due to
The limited voltage ratio characteristics and the energized life characteristics of the fabricated voltage nonlinear resistor element deteriorate, making it unsuitable as a power element. The components for producing the glass described above may be mixed with a mixture containing zinc oxide as the main component and fired to produce a voltage nonlinear resistor. After uniformly dispersing components that have the effect of extending the energized life of voltage nonlinear resistors in the glass, it is made into a powder of approximately 400 mesh or less by a method such as pulverization, and the main component is zinc oxide. By mixing and sintering with a mixture that has the above effect, the components having the above effect can be uniformly distributed in the sintered body, resulting in a uniformly stabilized grain boundary layer, which further extends the energized life. Effects such as this can be obtained. It should be noted that the effect of lengthening the energized life when glass is not used as the component for manufacturing the glass is halved compared to the effect when glass is used. Mixture containing zinc oxide as a main component used in the present invention
The amount of glass used in the present invention per 100 parts is
The amount of glass used is preferably 0.004 to 0.6 parts.
If the amount is less than 0.004 part, the effect of using the glass will not be obtained, and even if the amount used exceeds 0.6 part, not only will there be almost no effect compared to the amount used, but also electricity Adversely affects properties. After mixing a predetermined amount of the zinc oxide-based mixture used in the present invention with the above-mentioned glass, granulation and pressure molding are carried out in the usual manner, followed by firing under predetermined conditions (e.g., 1200°C, 2 hours, air The voltage nonlinear resistor of the present invention is obtained by performing heat treatment (for example, at 550 to 650° C. for 2 hours in air) and the like. Next, the voltage nonlinear resistor of the present invention will be explained using manufacturing examples, examples, and comparative examples. Production Example 1 Glass was obtained by melting powders having the composition shown in Table 1 at about 1200 to 1300°C for about 2 hours and then rapidly cooling them. The resulting glass was crushed to obtain a fine powder with a uniform particle size that could pass through a 400-mesh sieve.

[Table] Examples 1 to 7 and Comparative Examples 1 to 2 Zinc oxide, bismuth oxide, cobalt oxide, manganese oxide, chromium oxide, antimony oxide, and silicon dioxide each having a purity of 99% or more, 91.0%,
2.7%, 0.96%, 0.67%, 0.88%, 3.38% and
0.41% mixed. To 100 parts of the resulting mixture (hereinafter referred to as mixture A), add the glass shown in Table 2 obtained in Production Example 1 in the amount shown in Table 2, mix thoroughly, and then granulate it by spray drying. 40mm thickness
After pressure forming into a 12 mm disc, it was baked in air at 1200°C for about 2 hours, and then in air at 550 to 650°C (630°C, 630°C in Examples 1 to 7, respectively).
A sintered body was obtained by heat treatment at 600°C, 600°C, 570°C, 650°C, 630°C for 2 hours. An Al electrode was attached to the obtained sintered body to fabricate a voltage nonlinear resistor element. DC voltage was applied to the obtained device under the conditions that the applied voltage, expressed as the voltage when 1 mA flows through the device, was 0.8 and the ambient temperature was 100°C, and the leakage current flowing through the device at that time was measured over time. Changes were measured. The results are shown in FIG. Also, the limiting voltage ratio for the obtained element is
V _2.5kA /V ₁₀₀ 〓 _A was measured. The results are shown in Table 2.

[Table] As shown in Figure 1, the element of Comparative Example 2, which was manufactured without adding glass containing zinc oxide and boron oxide as main components, had a large initial leakage current and a large change in leakage current over time due to direct current application. , a thermal runaway phenomenon occurs in a short period of time, whereas the devices of Examples 1 to 5, which were prepared by adding glass, had a small initial leakage current due to direct current application, and the leakage current did not change over time. It can be seen that the charging life characteristics are significantly improved. On the other hand, the leakage current of the device of Comparative Example 1 prepared by adding glass made of zinc oxide and boron oxide is close to the characteristics of the device of Comparative Example 2, and is large, but the change over time of the leakage current is similar to that of Examples 1 to 5. It can be seen that the addition of glass consisting of zinc oxide and boron oxide is effective in reducing the change over time in leakage current due to direct current application to the element. Furthermore, from a comparison between Comparative Example 1 and Examples 1 to 5, when titanium oxide, zirconium oxide, tantalum oxide, lanthanum oxide, or yttrium oxide is contained in the glass, leakage current due to DC charging of the element is reduced, and the titanium oxide Even if the composition contains two or more of zirconium oxide, tantalum oxide, lanthanum oxide, and yttrium oxide, if the composition can form a uniform glass, the leakage current due to direct current application will be reduced, and the leakage current will change over time. It can be seen from the results of Examples 6 and 7 that the The limiting voltage ratio shown in Table 2 also shows that the elements of Examples 1 to 7 and Comparative Example 1 in which glass was added showed superior characteristics compared to the element of Comparative Example 2 in which glass was not added. It can be seen that by adding this element, an element with desirable characteristics as a power surge arrester can be obtained. Examples 8 to 12 and Comparative Examples 3 to 4 and 8 to 9 To 100 parts of the mixture A obtained in Example 1, glass E obtained in Production Example 1 was added in the amount shown in Table 3, and Example 8 For ~12, the heat treatment temperature after firing was 650℃, 630℃, 600℃, 630℃, and 650℃, respectively.
A device was produced in the same manner as in Example 1 except that Direct current was applied to the obtained device in the same manner as in Example 1, and the change over time in the leakage current flowing through the device was measured. The results are shown in FIG. For 100 parts of mixture A as shown in Figure 2
It can be seen that the element manufactured by adding 0.005 to 0.5 parts of glass has a smaller change in leakage current over time due to direct current charging, and the charging life characteristics are improved. However, when the amount of glass added is 0.003 part (Comparative Example 4), the leakage current change over time approaches that of Comparative Example 2, in which no glass is added, and it can be seen that the energized life characteristics are not improved much. On the other hand, as shown in Table 3, the limiting voltage ratio in the current/voltage characteristics of the device becomes poor when the amount of glass added is 0.7 parts, making it unsuitable as a power device. Therefore, the appropriate amount of glass added is 0.004~
It is 0.6 part, more preferably 0.005 to 0.5 part.

【table】

[Table] Example 13 Glass E used in Examples 8 to 12 was made of titanium oxide,
The charged life characteristics and limiting voltage ratio were measured in the same manner as in Examples 8 to 12, except that glass A, glass B, glass C, or glass D containing zirconium oxide, tantalum oxide, or lanthanum oxide was used. The results were similar to Examples 8-12. Examples 14 to 19 and Comparative Examples 5 to 7 Glass having the glass composition shown in Table 4 was prepared in the same manner as in Production Example 1. mixed glass
0.01 part was added to 100 parts of A, and in Examples 14 to 19, the heat treatment temperature after firing was 650℃,
Elements were produced in the same manner as in Example 1, except that the temperatures were 630°C, 600°C, 570°C, 570°C, and 650°C. Note that when the content of zirconium oxide in the glass was 20%, a glass with a partially crystalline phase was obtained. Direct current was applied to the obtained device in the same manner as in Example 1, and the change over time in the leakage current flowing through the device was measured. The results are shown in FIG. Figure 3 shows that the elements of Examples 14, 16, and 19, which were fabricated by adding glass with a zirconium oxide content of 1 to 15% to Mixture A, showed small changes in leakage current over time, and It can be seen that the life is longer and, as shown in Table 4, the limiting voltage ratio characteristics are also excellent. On the other hand, when the content of zirconium oxide is reduced to 0.5% as in Comparative Example 5, the leakage current changes with time during DC voltage application becomes large, and the life of the current application becomes short. On the other hand, when the content of zirconium oxide is 20%, it becomes impossible to obtain a uniform glass, and the leakage current changes over time when DC current is applied to devices manufactured by adding this glass increases, making it difficult to use as a power device. become inappropriate.

[Table] Example 20 Titanium oxide, tantalum oxide, lanthanum oxide, or yttrium oxide was used instead of zirconium oxide in Examples 14 to 19, and the heat treatment temperature after firing was changed.
Except that the temperature was 600°C, the same procedure as in Examples 14 to 19 was carried out to determine the change in leakage current over time and the limiting voltage ratio during direct current application. As a result, the proportions of titanium oxide, tantalum oxide, lanthanum oxide, and yttrium oxide in the glass were 1 to 10%, 1 to 35%, respectively.
Ranges of 1-35% and 1-25% have been found to be suitable. Example 21 The elements obtained in Examples 1 to 20 and Comparative Examples 1 to 9 were subjected to alternating current charging in the same manner as in the case of direct current charging. As a result, when an element is made by adding glass, the change in leakage current over time becomes smaller even when AC voltage is applied, similar to when DC voltage is applied.
It was found that it exhibited good power characteristics.

[Brief explanation of drawings]

Figures 1 to 3 show the charging times when direct current was applied to an element obtained from the voltage nonlinear resistor of the present invention and an element obtained from the voltage nonlinear resistor fabricated as a comparison, respectively. FIG.

Claims (1)

[Claims] 1. When sintering a mixture containing zinc oxide as a main component and additives such as bismuth oxide, cobalt oxide, manganese oxide, antimony oxide, chromium oxide and silicon dioxide, 40 to 65% by weight of zinc oxide and boron oxide and 25 to 40% by weight, and at least one selected from the group consisting of titanium oxide, zirconium oxide, tantalum oxide, lanthanum oxide, and yttrium oxide, each having a content of 1 to 10% by weight based on the total amount of glass,
It is characterized by adding 0.004 to 0.6 parts by weight of glass containing 0.7 to 18% by weight, 1 to 35% by weight, 1 to 35% by weight and 1 to 25% by weight per 100 parts by weight of the mixture. Voltage nonlinear resistor.