JPH0754763B2 - Method of manufacturing voltage non-linear resistor element - Google Patents

Description

TECHNICAL FIELD The present invention relates to a voltage non-linear resistor element in which a high resistance layer is formed on the side surface of a sintered body containing zinc oxide as a main component and having voltage non-linearity itself. The present invention relates to a manufacturing method.

2. Description of the Related Art Voltage non-linear resistance elements are generally called varistor and are used as elements for voltage stabilization and surge absorption.

Among them, zinc oxide varistors containing zinc oxide as a main component and a small amount of bismuth, cobalt, manganese, antimony, chromium, etc. added to them as gapless arresters in recent years due to their large surge current withstanding capability and excellent voltage nonlinearity. It is widely used in place of the conventional silicon carbide varistor.

When using a zinc oxide varistor as an arrester, there are two very important characteristic factors. The first is discharge withstand capability. This is the limit value of the peak current defined by JEC-187-1973, which is obtained by applying an impact current of 4 × 10 μs twice at 5-minute intervals. Secondly, the life characteristic of voltage application, which is the time until the arrester element causes thermal runaway when a prescribed AC voltage is applied. Normally, the ambient temperature is set to 100 ° C or higher, the charge rate (V applied voltage × 100 / V _1mA ) is set to 90% or higher, and an accelerated test is performed to predict the life. In recent years, there has been a strong demand for the development of a high performance arrester element having these characteristics.

Conventionally, as a method of manufacturing a voltage non-linear resistor element (arrestor element), Japanese Patent Laid-Open No. 56-69804 and Japanese Patent Publication No. 60-15128 have been proposed.
Japanese publications are known. The former is a compact obtained by adding a small amount of bismuth oxide, cobalt oxide, manganese oxide, nickel oxide, etc. to zinc oxide, pulverizing, mixing, and granulating, or calcination at 700 ° C to 1150 ° C. This is to manufacture an arrester element having a high resistance layer on the side surface after applying a substance containing Zn ₂ SiO ₄ , Zn ₇ Sb ₂ O ₁₂ , Bi ₂ O ₃ etc. on the side surface of the fired body and sintering it. In the latter case, when a molded body obtained in the same manner is fired, antimony oxide, bismuth oxide, and silicon oxide are placed in a firing vessel, and by gas-solid reaction,
This is to manufacture an arrester element having a high resistance layer on the side surface.

Problems to be Solved by the Invention The former method has a drawback in that the structure of the side surface high resistance layer is unstable, the adhesion between the element and the side surface agent is poor, and the discharge withstand characteristic is poor. Further, in the latter method, since the vapor of the coating agent made of Sb ₂ O ₃ , Bi ₂ O ₃ , and SiO ₂ appropriately arranged inside the firing container is allowed to react with the molded body, the thickness of the side surface high resistance layer is sufficient. Not only the discharge resistance is low,
The number of elements that can be fired in the same firing container is limited, and there is a drawback that mass productivity is lacking.

The present invention solves such a problem, and an object of the present invention is to improve the performance of a zinc oxide varistor as an arrester, that is, to greatly improve the discharge withstand voltage characteristic and the charging life characteristic.

Means for Solving the Problems In order to achieve this object, the present invention calcinates a molded body containing zinc oxide as a main component at 700 to 1150 ° C., and then Zn ₇ Sb is formed on the side surface of the molded body. After applying a first side agent composed of ₂ O _{12, a second} side surface containing SiO ₂ as a main component and 0 to 30 mol% of Bi ₂ O ₃ as a sub-component on top of the first side agent. A high resistance layer in which the first layer (lower layer) is made of Zn ₇ Sb ₂ O ₁₂ and the second layer (upper layer) is made of Zn ₂ SiO _{4 on the} side surface of the sintered body by applying an agent and then sintering. Is formed.

By this structure, a stable high resistance layer having a two-layer structure is formed on the side surface of the zinc oxide varistor element. The lower layer is Zn ₇ Sb ₂ O
_{With 12} crystal layers, the adhesion between the zinc oxide varistor element and the high resistance layer can be improved, and the discharge withstand voltage characteristic can be improved. The upper layer is made of Zn ₂ SiO ₄ , and it is possible to suppress the scattering of Bi ₂ O ₃ from the inside of the zinc oxide varistor element, and to significantly improve the voltage life characteristic.

Examples Hereinafter, the manufacturing method of the present invention and the voltage non-linear resistance element obtained thereby will be described in detail based on Examples.

First, ZnO powder was added to the total amount of Bi ₂ O ₃ 0.5 mol% and Co ₂
O ₃ 0.5 mol%, MnO ₂ 0.5 mol%, Sb ₂ O ₃ 1.0 mol%, Cr ₂ O
₃ 0.5 mol% and NiO 0.5 mol% were added, thoroughly pulverized and mixed, and then granulated to obtain a raw material powder. This raw powder is 40mm in diameter,
It was compression molded to a size of 30 mm in thickness. The molded body thus obtained was baked at 900 ° C. for 2 hours and cooled to obtain a calcined body.

On the other hand, the paste for the side surface high resistance layer is Zn ₇ Sb ₂ O ₁₂ , Bi ₂ O ₃ ,
A raw material powder in which SiO ₂ was mixed at an appropriate ratio and a binder composed of 25 wt% of ethyl cellulose and 75 wt% of butyl carbitol were mixed at a ratio of 1 to 3 by weight, and kneaded to be uniform. . In the present invention, there are two types of paste for the side surface high resistance layer, one for the lower layer made of Zn ₇ Sb ₂ O ₁₂ and the other for the upper layer containing SiO ₂ as a main component.

The paste for the lower layer was applied to the side surface of the calcined body described above, dried, and then the paste for the upper layer was applied, dried again, and then sintered in air at 1200 ° C. Both end surfaces of the thus obtained sintered body were polished to form a sprayed aluminum electrode.

FIG. 1 is a sectional view of the voltage non-linear resistance element obtained as described above, where 1 is a sintered body containing ZnO as a main component, and 2 is Z
First layer (lower layer) of the lateral high-resistance layer containing n ₇ Sb ₂ O ₁₂ as a main component,
3 is a second layer (upper layer) of the lateral high-resistance layer containing Zn ₂ SiO ₄ as a main component, and 4 is an electrode formed by aluminum spraying. The components of the side surface high resistance layers 2 and 3 were confirmed by X-ray diffraction. In addition, from the analysis by the X-ray microanalyzer, it was confirmed that Mn, Co, Cr, etc. were solid-dissolved in the first layer (lower layer) 2 and Co was mainly dissolved in the second layer (upper layer) 3. Was done.

The following Table 1 is a composition table of the side surface agent for the first and second side surface high resistance layers. The side agent for the first layer is a mixture of Zn ₇ Sb ₂ O ₁₂ and a binder, and the side agent for the second layer is SiO ₂ 100-50.
There are 6 types in which Bi ₂ O ₃ 0 to 50 mol% is added to the mol%.

This paste is applied to the calcined body in the order of the side agent for the first layer and the side agent for the second layer, and after sintering, V _1mA / mm, V _1mA / V
_The appearance was checked at _{10 μA} . The results are shown in Table 2 below. For comparison, when a side agent containing Bi ₂ O ₃ , Sb ₂ O ₃ , and Si ₂ O _{3 in an amount} of 10 mol%, 10 mol%, and 80 mol%, respectively, was applied as Conventional Example 1, Bi ₂ O ₃ was used as Conventional Example 2. , Sb ₂ O ₃ containing 10 mol% and 90 mol%, respectively, was applied to the inside of the baking container,
The data when the side surface high resistance layer is formed by the gas-solid reaction is added.

As can be seen from Table 2, the voltage non-linearity increases as the Bi ₂ O ₃ concentration increases, regardless of whether the side agent is applied in one layer or two layers. However, when the added amount of Bi ₂ O ₃ is 40 mol% or more, the side agent flows down. Further, when only SiO ₂ is used as the side agent (Sample 8), the varistor element and the side agent are partially unreacted. Further, V _1mA / mm slightly decreases with the Bi ₂ O ₃ concentration, but this is not a problem.

Table 3 below shows the discharge withstand voltage characteristics and the applied voltage life characteristics of the samples. Here, the discharge withstand test is based on JEC-187-19
An impact current of 4 × 10 μs defined in 73 was applied twice in the same direction at intervals of 5 minutes, the appearance was visually observed, and the deterioration of voltage nonlinearity was examined at a constant power supply current. In addition, the applied voltage life test was performed under the conditions of an ambient temperature of 130 ° C and an applied voltage of 95% (60Hz, AC), and when the leakage current exceeded 10mA, it was judged as thermal runaway.

Focusing on the discharge withstand characteristics in Table 3, when the Bi ₂ O ₃ concentration in the side surface agent for the second layer is 0 to 30 mol% (Samples 1 to 4), that is, according to the production method of the present invention, the discharge withstand capacity is Is up to 90kA1
It can be seen that the discharge resistance is greatly improved compared to the discharge withstand capacity of the conventional examples 1 and 2 (up to 50 kA 2 times). Further, in this state, the structure of the side surface high resistance layer is as shown in FIG.
_A clear two-layer structure in which the ₇ Sb ₂ O ₁₂ polycrystalline phase is surrounded by the Zn ₂ SiO ₄ polycrystalline phase of the second layer (upper layer) is formed. And Bi ₂ O
_{3 When the} concentration exceeds 30 mol%, a flow occurs on the side surface of the sintered body, a part of Zn ₇ Sb ₂ O ₁₂ applied to the first layer is exposed on the surface, and a stable two-layer structure cannot be obtained and discharge occurs. The withstanding characteristic deteriorates. In addition, excessive Bi ₂ O ₃ is Zn ₇ Sb ₂ O ₁₂ , Zn _{2 in the} lateral high-resistance layer.
It is considered that the fact that SiO ₄ remains in the grain boundary layer and the strength of the side surface high resistance layer is reduced is also one of the causes of the reduction in discharge withstand capability. On the other hand, when the side agents (A1, B1 to 6) for two-layer coating described above are used alone (Samples 7 to 13), the discharge resistance is extremely low.

Next, paying attention to the result of the voltage-applied life, the samples 1 to 6 produced by the production method of the present invention have a life performance of 50 Hr or more, while each side agent is used alone and the conventional example has a performance of -30 Hr. The life performance is also inferior. In FIG. 2, the Bi ₂ O ₃ concentration in the side surface agent for the second layer and the time required for samples 1 to 6 to reach thermal runaway are plotted. Voltage application life characteristics as the Bi ₂ O ₃ of the second layer for side material is increased, the better but, Bi ₂ O ₃ concentration is slightly decreased becomes more than 40 mol%. This is considered to be related to the flow of the side surface high resistance layer.

As described above, the reason why the voltage non-linear resistance element produced by the manufacturing method of the present invention exhibits high performance in both discharge withstand characteristics and electric charge life characteristics has not been completely clarified, but Bi ₂ O ₃ is contained in the side agent. ,
Zn ₇ Sb ₂ O ₁₂ , Zn ₂ S which is the product when Sb ₂ O ₃ , SiO ₂ is used
It is considered that the effect of changing from a system in which iO ₄ is mixed to a system in which two layers are layered as in the example of the present invention is very large. In addition, the lower Zn ₇ Sb ₂ O ₁₂ phase has high resistance and high adhesion to the varistor element and contributes to the discharge withstand capacity, while the upper Zn ₂ SiO ₄ layer reduces Bi ₂ O ₃ scattering from the varistor element. It is considered that this contributes to the improvement of the electric life characteristics. Furthermore, since the Zn ₇ Sb ₂ O ₁₂ phase has many bores, it is considered that the Zn ₂ SiO ₄ phase compensates for the defects and is also useful for improving the discharge withstand characteristic.

In the present embodiment, description has been made only on the case where one kind of side agent for the side surface high resistance layer is applied to the calcined body.
The same effect is obtained when both the side agent for the second layer and the side agent for the second layer are applied to the molded body, or when the side agent for the first layer is applied to the molded body and the side agent for the second layer is applied to the calcined body. It was confirmed.

As described above, the present invention applies the first side agent made of Zn ₇ Sb ₂ O ₁₂ to the side surface of the formed body or the calcined body of the zinc oxide varistor element, and then, from above, A _second side surface agent containing SiO ₂ as a main component and Bi ₂ O ₃ as an accessory component in an amount of 0 to 30 mol% is applied and then sintered to obtain a voltage nonlinear resistor element. With this configuration, a stable high-resistance layer having a two-layer structure is formed on the side surface of the zinc oxide varistor element, and as an arrester, extremely high performance is achieved in both discharge withstand characteristic and electric charge life characteristic, which are extremely important characteristics. Show. Here, the lower layer is a crystalline layer of Zn ₇ Sb ₂ O ₁₂ , and it seems that the adhesion between the zinc oxide varistor element and the high resistance layer is enhanced and the discharge withstand voltage characteristic is improved. Further, the upper layer is composed of a Zn ₂ SiO ₄ crystal layer, and it is considered that the scattering of Bi ₂ O ₃ from the inside of the zinc oxide varistor element is suppressed, and the electric charge life characteristic is significantly improved. Further, although the lower Zn ₇ Sb ₂ O ₁₂ crystal layer has many bores, it is considered that the upper Zn ₂ SiO ₄ compensates for the defective portion to improve the discharge withstand characteristic.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a voltage non-linear resistor element obtained by a manufacturing method according to an embodiment of the present invention, and FIG. 2 shows the concentration of Bi ₂ O ₃ in a side agent for the second layer in the method of the present invention. It is a figure which shows the relationship of a charging life characteristic. 1 ... Zinc oxide varistor element, 2 ... Side surface high resistance layer first layer (lower layer), 3 ... Side surface high resistance layer second layer (upper layer), 4
……electrode.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takayoshi Toyomi 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) Reference JP-A-58-194303 (JP, A) JP-A-56-69804 (JP, A)

Claims (3)

[Claims] 1. A molded body containing zinc oxide as a main component is 700-115.
After calcination at 0 ° C., and then applying a first side agent made of Zn ₇ Sb ₂ O ₁₂ to the side surface of the molded body, SiO ₂ is used as a main component on the upper side of the first side agent. And Bi ₂ O ₃ as an accessory component in an amount of 0 to 3
A second side agent containing 0 mol% was applied and then sintered, and the side surface of the sintered body had a first layer (lower layer) made of Zn ₇ Sb ₂ O ₁₂ and a second layer (upper layer) made of Zn ₂ SiO ₄ A method of manufacturing a voltage non-linear resistor element for forming a high resistance layer made of. 2. A side surface of a molded body containing zinc oxide as a main component,
A first side agent made of Zn ₇ Sb ₂ O ₁₂ is applied, and then SiO ₂ is contained as a main component and Bi ₂ O ₃ is contained as an auxiliary component in an amount of 0 to 30 mol% on the first side agent. A second side agent including is applied and then sintered, and the first layer (lower layer) is Zn ₇ Sb ₂ O on the side surface of the sintered body.
_A method of manufacturing a voltage non-linear resistor element comprising a high resistance layer consisting of ₁₂ and a second layer (upper layer) of Zn ₂ SiO ₄ . 3. A side surface of a molded body containing zinc oxide as a main component,
A first side agent composed of Zn ₇ Sb ₂ O ₁₂ was applied, and then the molded body was calcined at 700 to 1150 ° C., and then SiO ₂ was formed on the first side agent of the molded body. Is applied as a main component, and a second side agent containing Bi ₂ O ₃ as an accessory component in an amount of 0 to 30 mol% is applied and then sintered, and the first layer (lower layer) has Zn ₇ Sb ₂ on the side surface of the sintered body. O
_A method of manufacturing a voltage non-linear resistor element comprising a high resistance layer consisting of ₁₂ and a second layer (upper layer) of Zn ₂ SiO ₄ .