JPH02220402A - Voltage non-linear resistor and its manufacture - Google Patents

Abstract

PURPOSE:To improve the voltage non-linear characteristics in a large current region and to improve electro-life and surge-strength by incorporating zinc oxide phase of Zn1+xO (x>=1X10<-5>) into zinc oxide particles in a sintered body. CONSTITUTION:In a sintered body which has a main element of zinc oxide and is provided with voltage non-linear characteristics, zinc oxide phase of Zn1+xO (x>=1X10<-5>) is incorporated into zinc oxide particles. That is, small resistance of each particle and uniform potential barrier among grain boundaries can be realized by incorporating a phase whose oxygen is less than a constant ratio. Thereby, it becomes possible to improve voltage non-linear characteristics in a large current region and to acquire a voltage non-linear resistor of good electro-life and surge strength.

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 and a method for manufacturing the same.

(Prior art) Conventionally, resistors containing zinc oxide (Zn0) as a main component and a small amount of additives such as Bi2O2゜5bzO3+ 5iOz+Co*Oz+Mn0g as subcomponents have widely shown excellent voltage nonlinearity. This property is known to be used in lightning arresters, etc.

Conventionally, in order to improve the nonlinearity in the large current region of this voltage nonlinear resistor whose main component is zinc oxide,
(1) A valence control method for lowering the resistivity of ZnO by diffusing trace amounts of Affi ions, Ga ions, and In ions into a sintered body, (2) ZnO disclosed in JP-A-58-122703. and Al z03+ Gat03. In
A method is known in which ZnO is preliminarily calcined to diffuse Al, Ga, and In ions into ZnO, and then mixed with subcomponents and then shaped and fired.

(Problem to be Solved by the Invention) However, in the above-mentioned valence control method (1), A2 ions, etc. are simply mixed and molded together with the main component ZnO and the subcomponents and sintered. AN,
Ga and In ions were not sufficiently uniformly diffused into the ZnO crystal, and most of them were incorporated into the grain boundary layer and spinel phase. Therefore, the non-linearity in the large current region is not sufficiently improved, the life of the energized material is deteriorated, and the varistor voltage decreases significantly after a lightning surge is applied, resulting in the problem of thermal runaway of the resistor when energized constantly. Ta.

Furthermore, method (2) disclosed in JP-A-58-122703 is more effective than the above-mentioned valence control method (1), but the surge resistance is reduced due to non-uniform grain growth of ZnO. There was a problem.

An object of the present invention is to solve the above-mentioned problems and provide a voltage nonlinear resistor that can improve voltage nonlinearity in a large current range and also has good charging life and surge resistance, and a method for manufacturing the same. It is.

(Means for Solving the Problems) The voltage nonlinear resistor of the present invention contains zinc oxide as a main component,
In the sintered body having voltage nonlinearity, the zinc oxide particles in the sintered body are Zn1. ．． 0 (x≧I Xl0-5).

In addition, the method for manufacturing a voltage nonlinear resistor of the present invention includes adding and mixing a metal oxide to a zinc oxide raw material manufactured by an indirect method of oxidizing zinc vapor, followed by molding and firing. The method is characterized in that a zinc oxide raw material obtained by oxidizing zinc vapor in an atmosphere with an oxygen partial pressure of 120 torr or less is used, and firing is performed in an atmosphere with an oxygen partial pressure of 150 torr or more.

(Function) In the above-described configuration, the voltage nonlinear resistor of the present invention contains Zn, Xo (x≧lX) in the zinc oxide (ZnO) particles.
By including a zinc oxide phase (preferably Therefore, voltage nonlinearity in a large current range can be improved, and a resistor with good various characteristics can be obtained. At this time, it is preferable that the oxygen concentration in the central part of the zinc oxide particles containing the Znl*10 phase is lower than that in the surface part. Further, it is preferable that all the ZnO particles are Zn, , O, but the invention is not necessarily limited to this.

Further, in the method for manufacturing a voltage nonlinear resistor of the present invention, zinc vapor is heated to an oxygen partial pressure of 120 torr or less, preferably 50 torr.
The above-mentioned Zn is oxidized in an atmosphere below rr.
In order to obtain O particles and to manufacture a voltage nonlinear resistor using these ZnO particles, the element body is preferably fired in an atmosphere with an oxygen partial pressure of 150 torr or more.
By carrying out the test at a temperature of 000 to 1300[deg.] C., voltage nonlinearity in a large current range can be improved as described above, and a resistor with good various characteristics can be obtained.

(Example) FIG. 1 is a diagram showing the configuration of an example of an apparatus for implementing the conventionally known method for manufacturing a voltage nonlinear resistor of the present invention. In Figure 1, 1 is metal zinc as a raw material, 2 is a melting furnace for melting metal zinc 1, 3 is a retort furnace for carrying out an oxidation reaction, 4 is a cooling duct, 5 is a collection tank, and 6 is an exhaust gas. Wind fan 7 is a bang filter. In the apparatus configured as described above, the metal zinc l melted in the melting furnace 2 is transferred to the retort furnace 3.
When the zinc in the retort furnace 3 reaches its boiling point (approximately 900°C) and is ejected from the evaporation port, the oxygen partial pressure inside the retort furnace 3 rises to 12
Combustion oxidation is performed in the oxidation chamber 3a maintained at an atmosphere of 0 torr or less. The high-temperature zinc oxide obtained in the oxidation chamber 3a through combustion oxidation is sucked by the suction force of the exhaust fan 6, passes through the cooling duct 4 and is cooled, and then most of the zinc oxide is transferred to the collection tank 5.
A portion of the zinc oxide of the present invention can also be obtained in the bag filter 7.

A method for obtaining a voltage nonlinear resistor from the zinc oxide raw material obtained above is as follows.

To obtain a voltage nonlinear resistor whose main component is zinc oxide,
First, zinc oxide raw material adjusted to a predetermined particle size of 0.1 to 3μ-, bismuth oxide adjusted to a predetermined particle size of 1μ or less,
Cobalt oxide, manganese oxide, antimony oxide, chromium oxide, preferably amorphous silicon oxide, nickel oxide,
A predetermined amount of additives such as boron oxide, oxide, etc. are mixed. In this case, silver nitrate or boric acid may be used instead of silver oxide or boron oxide. Preferably, bismuth borosilicate glass containing silver is used. At this time, a predetermined amount of a polyvinyl alcohol aqueous solution and a predetermined amount of an aluminum nitrate solution as an aluminum oxide source are added to these raw material powders.

Next, deaeration is performed under reduced pressure, preferably at a vacuum level of 200 mm/g or less, to obtain a mixed slurry. Here, the water content of the mixed slurry is 3
0 to 35w tχ, and the viscosity of the mixed slurry is 1
The mixed slurry obtained in the 0th order is preferably set to 00±50cp and is fed to a spray dryer to obtain an average particle size of 50 to 150μ.
m, preferably 80 to 120μ ring, and moisture content is 0.5 to
2.0 iitχ, more preferably 0.9 to 1.5 t
The granulated powder of χ is granulated. Next, the obtained granulated powder is subjected to a molding step and molded into a predetermined shape under a molding pressure of 800 to 1000 kg/C1z. Then, the molded body was heated in air at a heating and cooling rate of 10 to 400 to 600 C/hr.
It is preferable that the binder is removed by scattering for a holding time of 1 to 10 hours at °C.

Next, an insulating coating layer is formed on the side surface of the element body. Incidentally, the element body of the present invention refers to a molded body or a degreased body obtained by heat-treating the molded body under the above conditions. In the present invention, BizOz+ 5l
)z(h+ Ethyl cellulose, butyl calpitol, acetic acid n as an organic binder to a predetermined amount of ZnO, Sing, etc.
An oxide paste containing butyl or the like is applied to the side surface of the element body to a thickness of 60 to 300 μm. In addition, the heating and cooling rate of the element body is 20 to 70°C/hr, 800 to 1000°C1
Holding time: 1 to 5 hours (preferably in an oxidizing or neutral atmosphere during the heating process, and in a neutral atmosphere during the maximum temperature holding and cooling process) After calcination, it is preferable to apply an oxide paste to the side surface. This temperature increase/decrease rate is 20~60°C/h.
r, 1000~1300°C, preferably 1100~
Main firing is performed at 1250° C. for 13 to 7 hours in an atmosphere with an oxygen partial pressure of 150 torr or more, which is a requirement of the present invention. A glass paste prepared by adding ethyl cellulose, butyl calpitol, n-butyl acetate, etc. as an organic binder to glass powder was applied to a thickness of 100 to 300 μm on the above-mentioned insulating coating layer, and the temperature was raised and lowered at a rate of 50 μm in air. ~200°C
It is preferable to form the glass layer by heat treatment under the following conditions: /hr, 400 to 900°C for 0.5 to 2 hours.

After that, both end faces of the obtained voltage nonlinear resistor are Sac,
AI! zOi + diamond etc. 1400~2000
Polishing is performed with a suitable abrasive using water, preferably oil, as the polishing fluid. Next, after cleaning the polished surface, electrodes made of aluminum or the like are provided on both polished end surfaces by, for example, thermal spraying to obtain a voltage nonlinear resistor.

Hereinafter, the results of actually measuring various characteristics of voltage nonlinear resistors within and outside the scope of the present invention will be described.

Implementation ■ According to the method described above, Biz031 Coz04.
Mn01゜5btO,, Crt03. Nto, St
o, respectively 0.1 to 2. Q mol%, 80 zOx O,
Bismuth borosilicate glass containing 0.05 mol% silver.
A varistor with a diameter of 47 m and a thickness of 20 mm was made from a raw material consisting of ZnO produced in an atmosphere with 01 to 0.3 wtχ and the balance having an oxygen partial pressure shown in Table 1 under the firing conditions shown in Table 1. Voltage (V+□) is 200 to 230 V/n
Voltage nonlinear resistors of present invention tests Nα1 to Nα8 and comparative example tests NO, 1 to 3 shown in Table 1 of +s+ were prepared. In addition,
The resistor was fired at 1150° C. for 5 hours in an atmosphere with an oxygen partial pressure shown in Table 1 after degreasing at 400° C. for 5 hours.

In addition, Z
As a result of confirming the amount of zinc in nO particles, Zn, 0 (X≧
IXl0-5).

Conventional method 1 of comparative example test N112 uses zinc oxide powder obtained by oxidizing with zinc vapor in air according to the conventional method, and adds ^1(N(h)s・9HzOo, oos mol%) to the raw material mixture. The method using the valence control method in which 2 ions were diffused by firing, and the conventional method 2 in Comparative Example Test No. 3,
As disclosed in Japanese Patent Application Laid-open No. 58-122703,
Using zinc oxide powder obtained by the conventional method, this and Al
After mixing zOs, we calcined it at 900°C.
Furthermore, both of them show those that were actually fired in the atmosphere.

For the prepared resistors of the present invention and comparative examples, the limiting voltage ratio, ■, □ reduction rate, lightning surge withstand capacity, and switching surge withstand capacity were measured, and the leakage current ratio was determined. The results are shown in Table 1. Here, the limiting voltage ratio is the varistor voltage v1°, and the eVIlIA reduction rate obtained from the ratio of v1□ is 10
It was determined from VIIIA before and after application. The lightning surge resistance is indicated as 8 in 100, 100 KA, and those that were destroyed after applying a current of 120 KA twice with a current waveform of 4710 μs as ×, and those that were not destroyed as O. For the switching surge resistance, the circuits that were destroyed after repeatedly applying currents of 800A, 900^, and 100OA with a current waveform of 211Is 20 times were indicated as ×, and those that were not destroyed were indicated as ○. Furthermore, the ratio of leakage current is
'Charging at C1 charging rate of 95%, charging 1 immediately after charging
Current ratio 11° after 00 hours. Time/1. I asked for it from time. For reference, the average particle size of the ZnO raw material for each test Nα was determined and is also listed in Table 1.

From the results in Table 1, it can be seen that the zinc oxide raw material is composed of Zn1+,0 (x≧l It was found that the resistor of the present invention had better resistance characteristics than the comparative example.

Back m According to Example 1 described above, using zinc oxide produced in a Ni + (h atmosphere) with an oxygen partial pressure of 120 torr or less,
In order to investigate the non-stoichiometry of ZnO particles after firing, Znl+
Resistors in which the value of X in xO was varied were manufactured, and various characteristics were measured in the same manner as in Example 1. The results are shown in Table 2.

From the results in Table 2, the value of X in Zn1+, O is X≧
Tests 1 to 5 of the present invention of lXl0-' are comparative test N
It was found that the characteristics were better compared to α1.2.

(Effects of the Invention) As is clear from the above description, according to the voltage nonlinear resistor and the manufacturing method thereof of the present invention, Zinc vapor is oxidized in an atmosphere with an oxygen partial pressure of 120 torr or less.
By manufacturing a voltage nonlinear resistor using particles with n+*xO (x≧I A voltage nonlinear resistor can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an example of an apparatus for carrying out the method of manufacturing a voltage nonlinear resistor of the present invention. ■... Metallic zinc 2... Melting furnace 3... Retort furnace 3a... Oxidation chamber 4... Cooling duct 5... Collection tank 6... Exhaust fan
7...Bag filter Figure 1

Claims (2)

[Claims] 1. In a sintered body containing zinc oxide as a main component and having voltage nonlinearity, the zinc oxide particles in the sintered body are Zn_1_+_
A voltage nonlinear resistor characterized by containing a zinc oxide phase where xO (x≧1×10^-^5). 2. In a method for manufacturing a voltage nonlinear resistor in which a metal oxide is added to a zinc oxide raw material produced by an indirect method of oxidizing zinc vapor, mixed, molded, and fired, zinc vapor is used as a zinc oxide raw material in an atmosphere with an oxygen partial pressure of 120 torr or less. At the same time, the oxygen partial pressure is 150 torr.
A method for manufacturing a voltage nonlinear resistor, characterized by firing in an atmosphere of r or more.