JPH0754762B2 - 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, and calcination obtained by crushing, mixing, and granulating steps or calcination at 700 ℃ ~ 1150 ℃. A substance containing Zn ₂ SiO ₄ , Zn ₇ Sb ₂ O ₁₂ , Bi ₂ O ₃ or the like is applied to the side surface of the body and then sintered to manufacture an arrester element having a high resistance layer on the side surface. In the latter, when firing a molded body obtained in the same manner, antimony oxide, bismuth oxide, and silicon oxide are placed in a firing container, and an arrester element having a high resistance layer on the side surface is produced by a gas-solid reaction. To do.

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 is to calcinate a molded body containing zinc oxide as a main component at 700 to 1150 ° C., and then to form Zn _{7 on} the side surface of the molded body. Sb ₂ O ₁₂ as the main component and Bi ₂ as the accessory component
After applying a first side agent containing 0.1 to 30 mol% of O ₃ or Sb ₂ O ₃ , SiO ₂ is contained as a main component and Bi ₂ O ₃ is added as a sub-component to the upper portion of the first side agent to 0%. A second side agent containing ˜30 mol% is applied and then sintered, and the side surface of the sintered body has a first layer (lower layer) made of Zn ₇ Sb ₂ O ₁₂ and a second layer (upper layer) made of Zn ₂ The high resistance layer made of SiO ₄ is formed.

Action With this configuration, a stable high-resistance layer having a two-layer structure is formed on the side surface of the sintered body, the lower layer being a Zn ₇ Sb ₂ O ₁₂ crystal layer and the upper layer being a Zn ₂ SiO ₄ crystal layer. . Where the lower layer
Bi ₂ O ₃ can further improve the voltage application life characteristics. Sb ₂ O ₃ was added to ZnO in the zinc oxide varistor element during the sintering process.
Reacting with to form a _{Zn 7 Sb 2 O 12, Zn} 7 is a lower layer of the main components
Further improve the adhesion between Sb ₂ O ₁₂ and the sintered body-high resistance layer,
The discharge withstand voltage characteristic can be further improved. Further, by covering the Zn ₂ SiO ₄ layer as the upper layer, the scattering of Bi ₂ O ₃ from the inside of the sintered body can be suppressed, and the life span characteristics can be significantly improved.

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 calcined 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 , Sb ₂ O ₃ ,
A raw material powder in which Bi ₂ O ₃ and SiO ₂ are mixed in an appropriate ratio and a binder composed of 25 wt% of ethyl cellulose and 75 wt% of butyl carbitol are mixed at a weight ratio of 1: 3 so that the mixture becomes uniform. It was made by kneading. In the present invention, there are two kinds of pastes for the side surface high resistance layer, one for a lower layer containing Zn ₇ Sb ₂ O ₁₂ as a main component and the other for an 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 surface agent for the first layer is Zn ₇ Sb ₂ O ₁₂ ,, Bi
₂ O ₃ and Sb ₂ O ₃ , and the side surface agent for the second layer is SiO ₂ and Bi ₂ O ₃ .

After applying the side agent for the first layer and the side agent for the second layer on the calcined body in this order and sintering, V _1mA / mm, V _1mA /
V _{10 μA} , appearance, etc. were examined. The results are shown in Table 2 below. For comparison, when a side agent containing Bi ₂ O ₃ , Sb ₂ O ₃ , and SiO ₂ of 10 mol%, 10 mol%, and 80 mol%, respectively, was applied to the calcined body as Conventional Example 1, Bi ₂ The data for the case where the paste containing O ₃ and Sb ₂ O ₃ at 10 mol% and 90 mol% respectively were applied to the inside of the baking container and the lateral high resistance layer was formed by the gas-solid reaction was added.

As can be seen from Table 2, V _1mA / mm is Bi ₂ O ₃ in the side agent
As the concentration increases, it decreases slightly, conversely V _1mA / V
_{10 μA} tends to improve. In addition, in the second layer side agent
When the Bi ₂ O ₃ concentration exceeds 40 mol%, flow occurs in the lateral high-resistance layer. Further, in the system in which Sb ₂ O ₃ is added to the side surface agent of the first layer, V _1mA / V _{10 μA} shows a bad value as compared with the Bi ₂ O ₃ system.

2 to 7 and Table 3 below show the results of the discharge withstand voltage characteristic and the charging life characteristic of the voltage non-linear resistance element according to the manufacturing method of the present invention. The discharge withstand test here is JEC-187-19.
An impact current of 4 × 10 μs specified in 73 was applied twice in the same direction at intervals of 5 minutes to check for abnormal appearance and the like. The test was performed by a step-up method every 10 KA, and is shown by a solid line with black circles in the figure. For samples that could not withstand two impact currents, 5KA was subtracted from the applied current. In addition, the voltage application life test is performed at an ambient temperature of 130 ° C and an application rate of 95% (60HzA
When the leakage current exceeded 10 mA, it was judged to be thermal runaway, and the time required for that was shown by the dotted line with white circles in the figure.

From Table 3, in the conventional Bi ₂ O ₃ , Sb ₂ O ₃ , SiO ₂ -based side agent coating method, discharge withstand capacity of 50 KA 1 time, charging life 29 hours, Bi ₂ O ₃ , Sb ₂ O ₃ gas-
The solid-state reaction system had a discharge withstand capability of 50 KA2 times and a voltage life of 31 hours. 2 to 4 show that the side surface agent for the first layer is
A1 ~ A8 (Zn ₇ Sb ₂ O ₁₂ , Bi ₂ O ₃ series), side agent for the second layer is B1, B
Data for 2, B5 (Bi ₂ O ₃ , SiO ₂ series). From each of the figures, it can be seen that the electric charge life characteristic is improved when the Bi ₂ O ₃ concentration in the side surface agent for the first layer is around 10 ^-1 mol%. It is considered that this is because Bi ₂ O ₃ in the side surface agent for the first layer can reduce the scattering of Bi ₂ O ₃ from the side surface of the varistor element. However, when the concentration of Bi ₂ O ₃ in the side surface agent for the first layer exceeds 30 mol%, the life property of voltage application is deteriorated again. It is considered that this is because during the sintering reaction of the side surface high resistance layer, a part of the portion forming the Zn ₂ SiO ₄ phase flows down and Bi ₂ O ₃ easily scatters. On the other hand, the discharge endurance characteristics begin to deteriorate when the Bi ₂ O ₃ concentration exceeds 10 mol%, and become equal to the level of the conventional example at 50 mol%. Therefore, it is understood that Bi ₂ O ₃ added to the first layer of the side surface agent is mainly effective in improving the electric charge life. Also,
Bi ₂ O _{3 which} is a side agent for the second layer is also effective in improving the life characteristics of the applied voltage, as is clear from comparing FIGS. 2 and 3. However, as the concentration of Bi ₂ O ₃ increases, the discharge withstand capacity decreases remarkably, and when it is 40 mol%, it further decreases as compared with the conventional method, and it becomes almost impossible to use it as an arrester.

5 to 7 show that the side surface agent for the first layer is A1, A9 to A15 (Zn ₇ Sb ₂
O ₁₂ , Sb ₂ O ₃ system), the side surface agent for the second layer is B1, B2, B5 (Bi ₂ O ₃ , SiO)
₂ system) data. According to each figure, the discharge withstand characteristic is improved when the Sb ₂ O ₃ concentration in the side surface agent for the first layer is around 10 ^-1 mol%, and becomes maximum at 10 to 20 mol%, and when the added amount becomes 50 mol%. It decreases to almost the same level as when Sb ₂ O ₃ was not added to the side surface agent for the first layer. This is considered to be because when the Sb ₂ O ₃ concentration exceeds 30 mol%, a part of the Zn ₂ SiO ₄ phase in the upper layer flows down, and the thickness of the side surface high resistance layer becomes thin.
However, when Sb ₂ O ₃ is added to the side surface agent for the first layer, α is generally low, and the electric charge life characteristic is not good as compared with the addition of Bi ₂ O ₃ . From the above, it can be seen that Sb ₂ O _{3 as the} side surface agent for the first layer mainly contributes to the improvement of the discharge withstand voltage characteristics.

Table 3 above shows the first component of the three-component system (Zn ₇ Sb ₂ O ₁₂ , Sb ₂ O ₃ , SiO ₂ ).
These are discharge withstand characteristics and voltage life characteristics when a layer side agent is used. Here, it can be seen that both discharge withstand characteristics and electric charge life characteristics show stable and high performance. Comparing the samples 35 and 36, the sample 35 containing a large amount of Bi ₂ O ₃ is excellent in the electric charge life characteristic, and the sample 36 containing a large amount of Sb ₂ O ₃ is excellent in the discharge withstanding property.

As described above, the reason why the voltage non-linear resistor element manufactured by the manufacturing method of the present invention exhibits high performance in both discharge withstanding characteristic and electric charge life characteristic is presumed as follows. Conventional Bi ₂ O
₃ , Sb ₂ O ₃ , when using a SiO ₂ ternary single-layer side surface agent, the product is a system in which Zn ₇ Sb ₂ O ₁₂ and Zn ₂ SiO ₄ are mixed,
When using a two-layer coating type side agent, the first layer (lower layer)
A Zn ₇ Sb ₂ O ₁₂ phase is generated, and a Zn ₂ SiO ₄ phase is generated in the second layer (upper layer), which is structurally extremely stable. In addition, the lower layer Zn ₇ Sb ₂
The O ₁₂ phase has high resistance and high adhesion to the varistor element, contributing to the improvement of discharge withstand capacity, and the Zn ₂ SiO ₄ phase in the upper layer reduces Bi ₂ O ₃ scattering from the varistor element and improves the life expectancy characteristics. It is considered to have contributed. Further, Sb ₂ O ₃ was added to the first layer to form a Zn ₇ Sb ₂ O ₁₂ reacts with ZnO in the varistor element, further the adhesion of Zn ₇ Sb ₂ O ₁₂ and the varistor element is the main component On the other hand, Bi ₂ O ₃ suppresses the scattering of Bi ₂ O ₃ in the varistor element body and suppresses the Bi ₂ O ₃ concentration gradient on the side surface of the device, which contributes to the improvement of the voltage-carrying life 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, 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.

Effects of the Invention As described above, the present invention has Zn ₇ Sb ₂ O ₁₂ as the main component on the side surface of the formed body or calcined body of the zinc oxide varistor element, and Bi ₂ O ₃ and Sb ₂ O ₃ as the sub-components. At least one of them is 0.1-3
A first side agent containing 0 mol% was applied, and then a _second side agent containing SiO ₂ as a main component and Bi ₂ O ₃ as a subcomponent of 0 to 30 mol% was applied thereon. Then, it is sintered to obtain a voltage non-linear resistance element having a stable two-layer high resistance layer in which the lower layer is Zn ₇ Sb ₂ O ₁₂ and the upper layer is Zn ₂ SiO _{4 on the} side surface of the sintered body. Is. As a result, it is possible to obtain a voltage non-linear resistance element having extremely high performance in both discharge withstand characteristic and electric charge life characteristic which are extremely important characteristics as an arrester. Here, it is considered that the lower layer enhances the adhesion between the sintered body and the high resistance layer, and improves the discharge withstand voltage characteristic. Further, Bi ₂ O ₃ contained in the first side agent is
By suppressing the scattering of Bi ₂ O ₃ in the device and suppressing the concentration gradient on the side surface of the device, it helps to improve the life characteristics of electric charge, and Sb ₂ O 3
₃ reacts with ZnO in the element to form Zn ₇ Sb ₂ O ₁₂ in the sintering process, further improving the adhesion and discharge withstand characteristics of Zn ₇ Sb ₂ O ₁₂ which is the main component and the sintered body. There is. The upper layer is Zn ₂ SiO.
The cover ring of ₄ suppresses the scattering of Bi ₂ O ₃ from the inside of the element and greatly improves the life span of charging voltage. In addition,
By using the first side agent containing both Sb ₂ O ₃ and Bi ₂ O ₃ , it is possible to obtain a voltage non-linear resistor element with improved discharge withstand characteristics and voltage-applied life characteristics.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a voltage nonlinear resistor element obtained by the manufacturing method of the present invention, and FIGS. 2 to 7 are discharge withstand voltage characteristics and characteristics of the voltage nonlinear resistor element obtained by the manufacturing method of the present invention. It is a figure which shows an electric 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.
It is calcined at 0 ° C., and then Zn ₇ Sb ₂ O ₁₂ as a main component and Bi ₂ O ₃ or Sb ₂ O ₃ as a sub-component is added to the side surface of the molded body in an amount of 0.1 to 30.
After applying the first side agent containing mol%, a second side agent containing SiO ₂ as a main component and 0 to 30 mol% of Bi ₂ O ₃ as a sub-component is formed on the first side agent. After coating, sinter,
A method for manufacturing a voltage non-linear resistor element, comprising forming a high resistance layer in which a first layer (lower layer) is made of Zn ₇ Sb ₂ O ₁₂ and a second layer (upper layer) is made of Zn ₂ SiO _{4 on a} side surface of a sintered body. 2. A side surface of a molded body containing zinc oxide as a main component,
Zn ₇ Sb ₂ O ₁₂ as a main component, and Bi ₂ O ₃ or Sb ₂ O as a secondary component
_After the first side agent containing 0.1 to 30 mol% of ₃ is applied, a first side agent containing SiO ₂ as a main component and 0 to 30 mol% of Bi ₂ O ₃ as a subcomponent is applied to the upper portion of the first side agent. The side surface agent of No. 2 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,
Zn ₇ Sb ₂ O ₁₂ as a main component, and Bi ₂ O ₃ or Sb ₂ O as a secondary component
The first side agent containing 0.1 to 30 mol% of ₃ is applied, and then the molded body is calcined at 700 to 1150 ° C., and then SiO ₂ is applied to the upper portion of the first side agent of the molded body. Is applied as a main component, and a second side agent containing 0 to 30 mol% of Bi ₂ O ₃ as a sub-component is applied,
Then, it is sintered, and the first layer (lower layer) is Zn ₇ Sb ₂ on the side surface of the sintered body.
A method of manufacturing a voltage non-linear resistor element, comprising a high resistance layer made of O ₁₂ and a second layer (upper layer) made of Zn ₂ SiO ₄ .