JPH01202802A - Manufacture of nonlinear voltage resistor - Google Patents

Abstract

PURPOSE:To stabilize various electric characteristic and to improve the quality of a nonlinear voltage resistor by firing a molding obtained by pressure molding in an atmosphere of bismuth oxide, antimony oxide and oxygen respectively having specific partial pressures. CONSTITUTION:A molding obtained by pressure molding is fired in an atmosphere respectively containing bismuth oxide of 0.1-30mmHg of partial pressure, antimony oxide of 0.1-50mmHg of partial pressure, and oxygen of 150mmHg of partial pressure. If the partial pressures of the bismuth oxide and the antimony oxide are less than 0.1mmHg, the bismuth oxide and the antimony oxide are dispersed in the air from an element, while if the partial pressure of the bismuth oxide exceeds 30mmHg or the partial pressure of the antimony oxide exceeds 50mmHg, the bismuth oxide and the antimony oxide is, on the contrary, diffused into the element. thus, the distribution of the bismuth oxide and the antimony oxide in the element becomes inhomogeneous. If the partial pressure of the oxygen is less than 150mmHg, their grain boundary state is not stabilized. In this manner, various electric characteristics are stabilized, and the quality is improved.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a method for manufacturing a voltage non-linear resistor containing zinc oxide as a main component, and particularly relates to a method for manufacturing a voltage nonlinear resistor containing zinc oxide as a main component, and in particular, to This is an attempt to effectively improve the characteristics of the engine.

(Prior Art) Voltage nonlinear resistors useful for protecting electrical systems and electrical equipment are preferably produced by granulating a mixture of zinc oxide, which is the main component, and various additives. It has generally been manufactured through the steps of press-molding powder into a desired shape using, for example, a press mold, firing it under appropriate processing conditions, and then adding electrodes.

However, with voltage nonlinear resistors manufactured according to the conventional method, it is difficult to ensure a predetermined quality over a certain loft even when processed under the same conditions, resulting in a significant decrease in productivity.

In this regard, for example, Japanese Patent Publication No. 62-45681 discloses a technique in which a bismuth oxide atmosphere of 0.05 to 50 mmHg is used as the processing atmosphere during the firing process in manufacturing a nonlinear resistor.

(Problems to be Solved by the Invention) By simply applying the technology disclosed in the above publication, although there is a tendency for characteristics to be improved, it is difficult to avoid variations in quality, and it is difficult to avoid variations in quality. There was a disadvantage that the product could not be obtained stably.

It is an object of the present invention to solve the above-mentioned conventional problems and to propose a manufacturing method that is advantageous in ensuring good electrical characteristics and stable quality.

(Means for Solving the Problem) As a result of various experiments and studies in order to stably manufacture a voltage nonlinear resistor with good electrical characteristics, the inventors found that It has been found that it is extremely effective to adjust the partial pressures of antimony oxide, bismuth oxide, and oxygen to appropriate ranges.

This invention is based on the above knowledge.

That is, this invention produces a voltage nonlinear resistor by adding and mixing additives containing bismuth oxide and antimony oxide to a raw material powder containing zinc oxide as a main component, preferably granulating and press molding, and then firing. For this purpose, the molded body obtained by pressure molding is mixed with bismuth oxide having a partial pressure of 0.1 to 301 HH,
Antimony oxide from 0.1 to 50 mmHg and 150 m
This is a method for manufacturing a voltage nonlinear resistor, which is characterized by firing in an oxygen atmosphere of mHg or higher.

(Function) For the production of voltage nonlinear resistors, the partial pressures of bismuth oxide, antimony oxide, and oxygen during firing should be 0.1 to 30 mmt/g and 0.1 to 50 mmt, respectively.
1g.

The reason why the electrical characteristics of the voltage non-linear resistor can be improved and a certain quality can be ensured by adjusting it to 150 mm t 1 g or more is that in the voltage non-linear resistor, voltage non-linearity occurs in the grain boundary phase. The bismuth oxide partial pressure, antimony oxide partial pressure, and oxygen partial pressure of the firing atmosphere play an important role in the generation and stabilization of the bismuth oxide phase and spinel phase (reaction products of zinc oxide and antimony oxide) that form the grain boundary phase. It is thought that he is doing the following.

Specifically, the partial pressure of bismuth oxide and antimony oxide is 0.
If it is less than 1 mmHg, bismuth oxide and antimony oxide will diffuse into the air from within the element, but if the partial pressure of bismuth oxide exceeds 30 mmHg or the partial pressure of antimony oxide
If it exceeds 0 mmHg, on the other hand, bismuth oxide and antimony oxide will diffuse into the device, and therefore the distribution of bismuth oxide and antimony oxide in the device will become non-uniform. Further, it is considered that these grain boundary phases are not stabilized when the oxygen partial pressure is less than 150 mmHg.

Therefore, a voltage nonlinear resistor with stable electrical characteristics and good quality can only be provided if the three conditions of bismuth oxide partial pressure, antimony oxide partial pressure, and oxygen partial pressure are satisfied within a specific range in the firing atmosphere. It is.

The specific manufacturing procedure according to the present invention will be explained below.

The main raw material of zinc oxide adjusted to a predetermined particle size, additives such as bismuth oxide, cobalt oxide, manganese oxide, antimony oxide, chromium oxide, silicon oxide, nickel oxide, etc. adjusted to a predetermined particle size, and borosilicate preferably containing silver. Mix the prescribed amount of bismuth glass. Next, a predetermined amount of an aqueous polyvinyl alcohol solution and a predetermined amount of an aluminum nitrate solution as an aluminum oxide source are added to these raw material powders. This mixing operation preferably uses an emulsifying machine.

Next, a mixed slurry is obtained by degassing under reduced pressure, preferably at a vacuum level of 200 mmt1 g or less. Here, the water content of the mixed slurry is 3
0 to 35-L%, and the viscosity of the mixed slurry is 10
It is preferable to set it to 0 cP±50.

Next, the obtained mixed slurry is fed to a spray drying device so that the average particle size is 50 to 150 μm, preferably 80 to 120 μm,
Moisture content is 0.5 to 2.0 wt%, more preferably 0.9
-1.5 wt% granulated powder is granulated.

Next, the obtained granulated powder was subjected to a molding process at a molding pressure of 8
00 to 1000 kg/cm" and molded into a predetermined shape.Then, the molded body is heated and cooled at a rate of 50 to 70°C.
The binder is first scattered and removed by calcination under the conditions of 1 to 5 hours at 800 to 1000[deg.] C./hr for 1 to 5 hours.

Then, an SJA edge coating layer is formed on the side surface of the calcined body. Specifically, this insulating coating layer is made of an oxide paste made by adding ethyl cellulose, butyl calpitol, n-butyl acetate, etc. as an organic binder to a predetermined amount of bismuth oxide, antimony oxide, silicon oxide, zinc oxide, etc. is applied to the side surface of the calcined body to a thickness of 100 to 300 μm.

Next, the heating and cooling rate is 30 to 60°C/hr, and the treatment temperature is 1000"C to 1300°C, preferably 1100"C.
~1250°C1 holding time 2 to 7 hours, and the partial pressure of bismuth oxide in the processing atmosphere to 0.1 to 30 mmHg
, preferably 2.0 to 20 mm) Ig, the partial pressure of antimony oxide to 0.1 to 50 mmHg, preferably 5 to 35 m
The main firing is performed under conditions where the partial pressure of oxygen is 150 mmHg or more, preferably 160 mmHg or more.

Here, the atmosphere during firing can be appropriately adjusted by using pellets or bed powder containing these components, or by using their gas medium. To measure the partial pressure, sample a certain amount of the firing atmosphere and quantify the BizO++ 5bzO+i contained therein.
The partial pressure of tzO-J+ 5bzO:+ is determined, and the partial pressure of oxygen is measured using an oxygen meter.

Furthermore, on the above insulating coating layer, ethyl cellulose, butyl calpitol, and acetic acid n are added to the glass powder as an organic binder.
100-300 μm of glass paste with butyl etc.
After applying the coating to a thickness of
It is more preferable to provide a glass layer obtained by heat treatment at 00''C/hr and 400 to 600°C for 0.5 to 2 hours.

Finally, both end surfaces of the obtained element were polished smooth,
An aluminum electrode is provided on that surface by thermal spraying.

(Example) Diameter: 47 mm, thickness: 20 m with the composition shown in Table-1
Voltage nonlinear resistors of m were manufactured according to the present invention under the conditions shown in Table 2, and the electrical characteristics of each element obtained were investigated. Note that the voltage nonlinear index a in Table 2 is
K V” (1: t4 flow, V: pressure, K: proportionality constant)
Based on the values of V, mA and VIO0μA, the lightning surge withstand breakdown rate (%) is 100kA and 120kA.
The breakdown rate after repeatedly applying a current of 4/10 μs 20 times with a current waveform of 4/10 μs, and the switching surge withstand breakdown rate (
%) indicates the percentage of breakdown when a current of 1000 A and 120 OA was repeatedly applied 20 times with a current waveform of 2 ms. The leakage current ratio was determined by charging the obtained device with a current charging rate of 95% at an ambient temperature of 130°C.
Current ratio after 100 hours of power application to that immediately after power application ■. .

It was determined from time 710 hours.

As is clear from Table 2, it was confirmed that the voltage nonlinear resistors (Samples Nos. 091 to 12) manufactured according to the present invention had good electrical characteristics and stable quality.

(Effects of the Invention) According to the present invention, it is possible to stably manufacture a voltage nonlinear resistor having good electrical characteristics such as surge resistance and energized life characteristics.

Patent applicant: Nippon Insulators Co., Ltd.

Claims (1)

[Claims] 1. Additives containing bismuth oxide and antimony oxide are added to raw material powder mainly composed of zinc oxide, mixed, pressure-molded, and then fired to produce a voltage nonlinear resistor. body at a partial pressure of 0.1 to 30 mmH
1. A method for producing a voltage non-direct resistor, the method comprising firing in an atmosphere containing bismuth oxide of 0.3 g, antimony oxide of 0.1 to 50 mmHg, and oxygen of 150 mmHg or more.