JPH02238604A - Voltage-dependent nonlinear resistor - Google Patents

Abstract

PURPOSE:To obtain a voltage-dependent nonlinear resistor whose moistureproof property at a side-face high-resistance layer is improved, whose lightning surge- resistant amount is enhanced and whose element secular change (voltage application life) is good by a method wherein a crystallization rate of the side-face high-resistance layer is set to 80% or lower. CONSTITUTION:A crystallization rate of an oxide in a high-resistance layer formed on a side-face part of a voltage-nonlinear resistor which is composed mainly of zinc oxide and which contains at least an oxide of bismuth is set to 80% or lower. It is desirable that at least bismuth oxide is contained in the oxide because the bismuth oxide is a main amorphous component and acts as a flux in the side-face high-resistance layer. It is preferable that zinc silicate is contained as a crystal phase. Thereby, it is possible to obtain a voltage- dependent nonlinear resistor whose moistureproof property of the side-face high-resistance layer is enhanced and whose lightning surge-resistant amount is enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a voltage nonlinear resistor containing zinc oxide as a main component.

(Conventional technology) Conventionally, zinc oxide is the main component, and Biz03, Sbz
03S1021 It is widely known that resistors containing additives such as MnO■ exhibit excellent voltage nonlinearity, and are used in lightning arresters and the like by taking advantage of this property.

In this voltage non-linear resistor, when a surge current such as lightning is applied to the element, a flashover so-called creeping flash mainly occurs along the side of the element, which may destroy the element. Bi-Sb-Si compound or Bi-S
It is common to provide a high resistance layer made of a b-Si-Zn compound.

(Problem to be solved by the invention) In a conventional voltage nonlinear resistor, the side high resistance layer formed on the side surface is made of a crystalline material that is less likely to cause cranking at grain boundaries due to the difference in thermal expansion during firing. It was a structure.

However, the crystalline structure has poor moisture resistance, resulting in variations in characteristics, changes in discharge withstand capacity, and shortened lifespan when charged.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a voltage nonlinear resistor that improves the moisture resistance of the side surface resistance layer and improves lightning surge resistance.

(Means for Solving the Problems) The voltage nonlinear resistor of the present invention contains zinc oxide as a main component,
A high resistance layer formed on a side surface of a voltage nonlinear resistor comprising at least bismuth oxide, characterized in that the crystallization rate of the oxide forming the high resistance layer is 80% or less. It is something.

(Function) In the above-described configuration, the present inventors improved the hygroscopicity of the side high resistance layer by reducing the crystallization rate of the oxide in the side resistance layer to 80% or less, resulting in good lightning surge resistance. I discovered that

Further, in this case, it is preferable that the above-mentioned oxide contains at least bismuth oxide. The reason for this is that bismuth oxide is an amorphous main component and acts as a flux in the side high resistance layer.

Further, it is preferable that zinc silicate be included as a crystal phase.

The reason for this is that zinc silicate improves lightning surge resistance.

(Example) To obtain a voltage nonlinear resistor whose main component is zinc oxide,
First, zinc oxide raw material adjusted to a predetermined particle size and Bi2(L++ CO3041 Mn02Sb
203+ Cr20, l+ s; o2, additives made of NiO, etc.? Mix quantities. At this time, in the present invention, S
Amorphous silica with an average particle size of 10 μm or less is used as the iO₂ source material. A predetermined amount of polyvinyl alcohol aqueous solution or the like is added to these raw material powders, mixed preferably using a disper mill, and then granulated, preferably using a spray dryer, to obtain a granulated product. After granulation, molding pressure 50-1
It is molded into a predetermined shape under 00 MPa.

Then, the molded body was heated and cooled at a heating and cooling rate of 50 to 70°C/hr.
Preliminary firing is carried out under the conditions of 50 to 980°C and a holding time of 1 to 5 hours.

In addition, before calcining, the molded body is heated and cooled at a rate of 10 to 100'.
It is preferable to carry out a heat treatment at 400 to 600° C. for a holding time of 1 to 10 hours to remove the binder by scattering.

Next, a side high resistance layer is formed on the side surface of the calcined body. In the present invention, a mixed paste for side high resistance layer is prepared by adding ethyl cellulose, butyl carbitol, n-butyl acetate, etc. as an organic binder to a predetermined amount of bismuth oxide, antimony oxide, silicon oxide, etc. to a thickness of 60 to 300 μm. Apply to the side of the molded body. At this time, in the present invention, in the above mixed paste, the particle size of bismuth oxide is 1 to 10 μm, preferably 1 to 5 μm, the particle size of silicon oxide is 10 μm or less, preferably 1 μm or less, and the overall particle size is adjusted to be 10 μm or less. More preferably, non-quality silica having an average particle size of 10 μm or less is used as the silicon oxide. By combining this with the firing conditions shown below, it is possible to achieve a crystallization rate of 80% or less of the oxide in the side high resistance layer required in the present invention.

Although oxides are used here as the material for forming the side surface high resistance layer, compounds such as carbonates and hydroxides may be used without being limited to oxides, except for amorphous silica. These compounds are preferably those that convert into oxides at temperatures below 1000°C, preferably below 800°C.

Next, heat this at a heating rate of 40 to 60°C/hr for 1000
The temperature is raised to ~1300°C, preferably 1100-1250°C, held there for 3-7 hours, and cooled to 800°C at a rate of 100-200°C/hr.

In addition, a glass paste made by adding ethyl cellulose, butyl carbitol, n-butyl acetate, etc. as an organic binder to glass powder is placed on the above-mentioned side high-resistance layer. Apply to a thickness of 00 to 300 μm and heat up and cool down in air at a rate of 100 to 200°C.
It is preferable to form the glass layer by heat treatment under the following conditions: /hr, 400 to 600°C for 0.5 to 2 hours.

After that, both end faces of the obtained voltage nonlinear resistor are SjC,
AI■03, diamond etc. #400-2000
Polish with a suitable abrasive using water, preferably oil. Next, after cleaning the polished surface, electrodes made of aluminum or the like are provided on both polished end surfaces by thermal spraying to obtain a voltage nonlinear resistor. The results of measuring various characteristics of the body will be explained.

Example 5: Diameter: 47 Inffl, thickness: 22 mm, prepared by the method described above.
．． V l. at 5 mm. 、． A -200 ~ 230V/m
In order to investigate the effect of changing the crystallization rate of the side high-resistance layer on the moisture resistance and characteristics of the voltage non-linear resistor with a voltage of 1.5 m, sample No. 1 to 6, and Comparative Example No. 1 which does not meet the scope of the present invention in any respect.
7 to 10 were prepared, and the moisture resistance, insulation resistance, and lightning surge resistance of the side high resistance layer were measured. Furthermore, zinc silicate and spinel crystals were observed in the crystalline part of this sample.

The results are shown in Table 1. In Table 1, moisture resistance is determined by ○ if it does not absorb moisture at all under the conditions of penetrating liquid at a pressure of 200 kg/c [and immersion time is 24 hours], △ if it partially absorbs moisture, and × if it completely absorbs moisture. The lightning surge resistance of IOOKA and IIOKA120KA is determined after being left in an atmosphere of 40°C and 100% humidity for 24 hours.
, 130 KA pulse current was applied twice with a current waveform of 4/10 ps, and those that were destroyed are indicated by ×, and those that were not destroyed are indicated by ○. Further, the insulation resistance was measured from the current when a voltage of IOOOV was applied to the element.

Further, the crystallinity rate was determined by quantifying crystals by a quantitative method using X-ray diffraction, and assuming that the remainder was amorphous.

From the results shown in Table 1, it can be seen that the samples of the present invention, in which the crystallization rate of the side high resistance layer is 80% or less, have higher insulation resistance and better lightning surge resistance than the comparative examples. Do you get it.

(Effects of the Invention) As is clear from the above explanation, according to the voltage nonlinear resistor of the present invention, by setting the crystallization rate of the side high resistance layer to 80% or less, moisture absorption of the side high resistance layer is achieved. improve sex,
It is possible to obtain a voltage nonlinear resistor that has improved lightning surge resistance and has good aging (power life) of the element.

Also, good results were obtained regarding the limiting voltage ratio.

Claims (1)

[Claims] 1. In a high-resistance layer formed on the side surface of a voltage non-linear resistor containing zinc oxide as a main component and at least bismuth oxide, the crystallization rate of the oxide forming the high-resistance layer is 80% or less. A voltage nonlinear resistor characterized by: