JPS6156844B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a voltage non-linear resistor containing ZnO as a main component, and particularly to a method for insulating its side surfaces.

Conventionally, the side insulation methods for voltage nonlinear resistors (hereinafter abbreviated as resistors) whose main component is ZnO are to coat the sides of the resistor with an epoxy-based organic material after firing, or to insulate the resistor by baking it. Previously, various inorganic compounds were applied to the side surfaces of the resistor and then fired to form a glassy or crystalline insulating film for insulation.

However, the former method has the disadvantage that moisture is adsorbed to the resistor due to poor adhesion between the applied epoxy-based organic substance and the resistor, resulting in significant deterioration of characteristics and weakening of short-wave tail resistance. Furthermore, since there is a difference in thermal expansion between the resistor and the epoxy organic material, there is a drawback that the epoxy organic material cracks due to thermal shock, causing deterioration. In addition, in the latter method, it is necessary to match the shrinkage rates of the resistor and the side insulating material during firing, so after the resistor is first fired to shrink to some extent, the side insulating material is applied and the main It is fired to form an insulating coating on the sides. Therefore, in this case, the firing has to be carried out twice, which increases fuel (including electric power) costs, and the firing apparatus is used twice, which increases manufacturing costs. Furthermore, both methods have the disadvantage that considerable skill and equipment are required to make the side insulating coating uniform to the required thickness.

For this reason, a method has been proposed in which antimony oxide (Sb ₂ O _3, etc.) is placed in the firing container during firing of the resistor, and a side insulating film is formed through a gas-solid phase reaction at the same time as the firing. The method utilizes a gas-solid phase reaction between antimony oxide vapor and the resistor, so it has good adhesion between the resistor and the insulating film.
An insulating film with dense and uniform crystal grains without pinholes can be obtained, and various electrical properties such as current discharge withstand, corona resistance, and arc resistance are significantly improved compared to when epoxy-based organic materials are applied. In addition, compared to the case where an inorganic compound is applied and fired, there is less need to consider the shrinkage rate, the firing can be completed in one time, and manufacturing is easy and inexpensive. However, in this case, the evaporation rate of Sb ₂ O ₃ is 0.07 at 1000℃
mg/min, relatively fast at 0.45mg/min at 1050℃. For this reason, the side surfaces react with gas remaining in the resistor, and when the temperature rises further, the residual gas is released from the resistor, leaving pores at the interface between the resistor and the side insulation coating. Summer. Therefore, the adhesion between the resistor and the side insulating coating deteriorated, and various electrical characteristics also deteriorated.

The present invention eliminates the above-mentioned drawbacks, makes it possible to form a side insulating coating of a voltage nonlinear resistor with good adhesion, improving various electrical characteristics, and making the side insulating coating easy and inexpensive to manufacture. It is an object of the present invention to provide a method for manufacturing a voltage nonlinear resistor that can be formed as follows.

A first embodiment of the present invention will be described below with reference to the drawings. First, the configuration of the firing apparatus will be explained with reference to FIG. In the figure, 1 is an alumina sheath (firing container), 2 is a pedestal made of heat-resistant ceramic material placed on the bottom of the sheath 1, and the material of the pedestal 2 is alumina or zinc oxide sintered plate, etc. In particular, since the zinc oxide-based sintered plate is the same as the main component of the resistor, there is no risk of impairing the characteristics of the resistor. 3 is a voltage nonlinear resistor whose main component is compression molded ZnO.
The resistor 3 is placed on the pedestal 2 with a bedding material 4 interposed therebetween. The bedding powder 4 is for preventing molten deposits between the pedestal 2 and the resistor 3, and is required to be similar or the same as the components of the resistor 3. Powder etc. that are calcined and crushed are used. If the pedestal 2 is made of the same material as the resistor 3, the bedding powder 4 may be omitted. 5 is a coating agent applied to the inner surface of the sheath 1 to form a side insulating coating on the resistor 3; 6 is a lid that covers the upper part of the sheath 1 in a substantially hermetically sealed manner; Formed by members.
The coating agent 5 may be applied to a part or all of the inner surface of the sheath 1 or to the inner surface of the lid 6, and it is sufficient if it is provided inside the firing container. In addition, in reality, resistor 3
A shielding member is provided on the upper surface of the housing to prevent the formation of an insulating film.

Next, we will discuss the manufacturing method using the above firing equipment. First, resistor 3 is made of ZnO (91 mol%).
A total of 9 mol % of Sb ₂ O ₃ , Bi ₂ O ₃ , Cc ₂ O ₃ , Mno ₂ , Cr ₂ O ₃ , SiO ₂ and the like are added, thoroughly mixed, and then compression molded into a suitable shape. For example, it is a cylindrical molded body with a diameter of 40 mmφ and a thickness of 30 mm. Furthermore, coating agent 5 contains Sb ₂ O ₃ and Bi ₂ O ₃ (75 mol% relative to Sb ₂ O ₃ ) as starting materials.
(below) and ZnO (60 mol % or less based on Sb ₂ O ₃ ), water is added to these, and the resulting slurry is thoroughly mixed and applied to the inner wall of the sheath 1 and dried. Then, the resistor 3 is placed inside the sheath 1 as shown in FIG.
The sheath 1 is almost sealed with the lid 6. 1000℃~ in this state
When fired at a temperature range of 1400°C (preferably 1100°C to 1300°C), Sb ₂ O ₃ and
Bi ₂ O ₃ evaporates, and the inside of the sheath 1 is filled with these atmospheres, and it reacts with ZnO, Bi ₂ O ₃ , etc. inside the resistor 3 in a gas-solid phase, and a high-resistance insulating film is formed on the surface of the resistor 3. is formed. When this insulating coating was examined by X-ray diffraction, as shown in FIG. 2, it was found that spinel (Zn ₂ . ₃₃ Sb ₀ . ₆₇ O ₄ ) was the main component. This was also confirmed when examined using an X-ray microanalyzer.

In the above gas-solid phase reaction, the coating agent 5 is
Sb ₂ O ₃ , Bi ₂ O ₃ , and ZnO become 7ZnO + Sb ₂ O ₃ +O ₂ →Zn ₇ Sb ₂ O ₁₂ 4ZnO + 3Bi ₂ O ₃ +3Sb ₂ O ₃ +O ₂ →Zn ₂ Sb ₃ Bi ₃ O during the heating process up to 1000℃. Limit the evaporation of Sb ₂ O ₃ by reactions such as ₁₄ .
Sb ₂ O ₃ evaporates at around 1000°C because the amount of Sb 2 O 3 applied is greater than that required for the above reaction production. However, since this evaporation occurs together with the above reaction, the evaporation rate becomes slower than in the case of a single application of Sb ₂ O ₃ . Figure 3 shows the case where the coating agent 5 is Sb ₂ O ₃ alone and 60Sb ₂ O ₃ −
Temperature and Sb ₂ O ₃ in the case of 20Bi ₂ O ₃ −20ZnO
This shows the relationship with the amount of evaporation, 60Sb ₂ O ₃ −
It can be seen that in the case of 20Bi ₂ O ₃ −20ZnO, the evaporation rate is slower than in the case of Sb ₂ O ₃ alone. On the other hand, resistor 3
ZnO starts shrinking around 800℃, and ZnO starts shrinking around 1000℃.
In addition to Zn ₂ SiO ₄ , Zn ₂ Bi ₃ Sb ₃ O ₁₄ , Zn ₂ . ₃₃ Sb ₀ . ₆₇ O ₄ ,
14Bi ₂ O ₃ −Cr ₂ O ₃ etc. are formed. On the side surface of the resistor 3, the vapor of Sb ₂ O ₃ and the ZnO of the resistor 3 react to form a high-resistance insulating film containing Zn ₂ . ₃₃ Sb ₀ . ₆₇ O ₄ as a main component.

In the above example, Sb ₂ O ₃ in coating 5 was
Since it also reacts with Bi ₂ O ₃ and ZnO, the evaporation start temperature of Sb ₂ O ₃ is high and the evaporation rate is slow. Therefore, a gas-solid phase reaction occurs after the resistor 3 has sufficiently shrunk and released gas, and no residual gas is generated, resulting in good adhesion between the resistor 3 and the side insulating coating. Therefore, electrical properties such as current discharge withstand capacity, corona resistance, and arc resistance are improved. Incidentally, as a result of measuring the short wave tail discharge capacity of resistor 3,
For example, when the coating material 5 was 60Sb ₂ O ₃ -20Bi ₂ O ₃ -20ZnO, a discharge withstand capacity of 75 KA was obtained by applying an impulse of 4×10 μS twice. In addition, since the method does not apply the coating material 5 directly to the side surface of the resistor 3, there is no need to consider the difference in shrinkage rate between the resistor 3 and the coating material 5 during firing, and the method is simple and inexpensive with one firing. A high-resistance side insulating film can be formed on the surface. Furthermore, the Bi ₂ O ₃ vapor suppresses the evaporation of Bi ₂ O ₃ from the resistor 3, which dominates the voltage nonlinearity of the resistor 3, so that the voltage nonlinearity is improved. still,
The Bi ₂ O ₃ vapor also serves to promote the reaction between the resistor 3 and the Sb ₂ O ₃ vapor.

Next, a second embodiment of the present invention will be described.
The firing apparatus is the same as that used in the first example. Further, the resistor 3 is also formed in the same manner as in the first embodiment. Coating agent 5 uses Sb ₂ O ₃ and ZnO as starting materials.
After weighing so that Sb ₂ O ₃ /ZnO > 1/7, water is added and thoroughly mixed to obtain a slurry, which is applied to the inner wall of the sheath 1 and dried. Then, place the resistor 3 inside the sheath 1 as shown in FIG.
almost completely sealed. 1000℃~1400℃ in this state
(preferably from 1100°C to 1300°C), Sb ₂ O ₃ in the coating agent 5 evaporates and the sheath 1
The interior is filled with an atmosphere of Sb ₂ O ₃ , and the inside of the resistor 3
A gas-solid phase reaction occurs with ZnO, _{Bi2O3 ,} etc., and a high-resistance insulating film is formed on the surface of the resistor 3. When this insulating film was examined by X-ray diffraction, as shown in FIG. 2, it was found that spinel (Zn ₂ . ₃₃ Sb ₀ . ₆₇ O ₄ ) was the main component. This is X
It was also confirmed by a line microanalyzer.

In the above gas-solid phase reaction, the coating agent 5 is
During the heating process of Sb ₂ O ₃ and ZnO up to 1000°C, ZnSb ₂ O ₆ begins to be formed at 600°C to 700°C due to the reaction of ZnO + Sb ₂ O ₃ + O ₂ →ZnSb ₂ O ₆ …………(1). The amount produced increases up to 900℃ and then decreases. Further, due to the reaction 7ZnO+Sb ₂ O ₃ +O ₂ →Zn ₇ Sb ₂ O ₁₂ (2), Zn ₇ Sb ₂ O ₁₂ begins to be formed from around 800°C and increases thereafter. The mutual reaction of these compounds in the coating agent 5 slows down the evaporation of Sb ₂ O ₃ . However, as shown in Figure 4, 7ZnO−
As can be seen from the change in the crystal structure of the Sb ₂ O ₃ system during the heating process, ZnSb ₂ O ₆ also changes to Zn ₇ Sb ₂ O ₁₂ at temperatures above 900°C, so the evaporation of Sb ₂ O ₃ results in ( This means that it was suppressed by the reaction of equation 2). Therefore, Sb ₂ O ₃
In order to evaporate ZnO, an amount exceeding that required for the reaction of equation (2) is required, so the ratio of Sb ₂ O ₃ and ZnO in coating agent 5 is Sb ₂ O ₃ /ZnO > 1/7. There is. In this way, since Sb ₂ O ₃ is present in an amount greater than that required for the above reaction, the Sb ₂ O ₃ remaining from the above reaction evaporates at around 1000°C. However, this evaporation is slower than in the case of a single application of Sb ₂ O ₃ as a result of the above reaction. Figure 5 shows the coating agent 5.
This shows the relationship between temperature and Sb ₂ O ₃ evaporation amount in the case of single Sb ₂ O ₃ and in the case of 80Sb ₂ O ₃ −20ZnO, and it can be seen that evaporation is slower in the latter case than in the former case. . On the other hand, resistor 3 starts shrinking at around 800°C, and at around 1000°C, Zn 2 SiO 4 , Zn ₂ SiO ₄ , etc.
Zn ₂ Bi ₂ Sb ₃ O ₁₄ , Zn ₂ . ₃₃ Sb ₀ . ₆₇ O ₄ , 14Bi ₂ O ₃ −Cr ₂ O ₃
is formed. On the side surface of the resistor 3, the vapor of Sb ₂ O ₃ and the ZnO of the resistor 3 react to form a high-resistance insulating film containing Zn ₂ . ₃₃ Sb ₀ . ₆₇ O ₄ as a main component.

Also in the second embodiment described above, in the coating agent 5,
Evaporation of Sb ₂ O ₃ is slowed down because Sb ₂ O ₃ reacts with ZnO. Therefore, after the resistor 3 sufficiently contracts and releases sufficient gas, a gas-solid phase reaction occurs, and no residual gas is generated, resulting in good adhesion between the resistor 3 and the side insulating coating, resulting in electrical Various properties become better.
For example, when the coating material 5 was 80Sb ₂ O ₃ -20ZnO, the short wave tail discharge capacity of the resistor 3 was 78KA when a 4×10 μS impulse was applied twice. Further, as in the first embodiment, a high-resistance side insulating coating can be easily and inexpensively formed by one firing.

In each of the above embodiments, the resistor 3 housed in the sheath 1 may be compressed and then pre-fired to shrink to some extent. Alternatively, instead of forming the coating agent 5, the slurry may be dried into powder and spread within the sheath 1. Furthermore, the coating agent 5 contains Sb ₂ O ₃ and Bi ₂ O ₃
The antimony oxide and a compound that reacts with the antimony oxide to delay the evaporation of the antimony oxide may be placed in the firing container.

As described above, in the present invention, when firing a voltage nonlinear resistor whose main component is zinc oxide, antimony oxide and a compound that reacts with the antimony oxide and delays the evaporation of the antimony oxide are placed in the firing container. is placed, and at the same time as firing, a side insulating coating of the voltage nonlinear resistor is formed by a gas-solid phase reaction between the antimony oxide and the voltage nonlinear resistor. Therefore, due to the reaction between the antimony oxide and the compound, the evaporation of the antimony oxide becomes slower than when only the antimony oxide is placed, and the voltage nonlinear resistor sufficiently contracts and releases sufficient gas before the gas is released. An insulating film is formed by solid phase reaction. Therefore, no residual gas is generated between the resistor and the side insulating coating, resulting in good adhesion between the two, resulting in good electrical properties such as current discharge withstand capacity, corona resistance, and arc resistance. In addition, since this method does not directly apply antimony oxides or compounds to the sides of the resistor, there is no need to consider the difference in shrinkage rate between these oxides and the resistor during firing, and the process can be completed in one firing. It is possible to easily and inexpensively form a high-resistance side insulation coating.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional front view of a firing apparatus according to each embodiment of the present invention, FIG. 2 is an X-ray diffraction diagram of a side insulating coating according to each embodiment of the present invention, and FIG. FIG. 4 is a diagram showing the relationship between temperature and Sb ₂ O ₃ evaporation amount according to the embodiment, and FIG.
FIG. 5 is a diagram showing changes in the crystal structure of the Sb ₂ O ₃ system during the heating process, and FIG. 5 is a diagram showing the relationship between temperature and Sb ₂ O ₃ evaporation amount according to the second embodiment of the present invention. 1... Sheath (container for firing), 3... Voltage nonlinear resistor, 5... Coating agent, 6... Lid.

Claims (1)

[Claims] 1. When a voltage non-linear resistor whose main component is zinc oxide is placed in a firing container and fired, a compound is added to the firing container that reacts with antimony oxide and antimony oxide to delay the evaporation of antimony oxide. A method for manufacturing a voltage nonlinear resistor, characterized in that bismuth dioxide and zinc oxide, or zinc oxide are disposed as a material, and a side insulating coating of the voltage nonlinear resistor is formed by a gas-solid phase reaction at the same time as the firing.