JPH0494103A - Manufacture of zinc oxide voltage dependent nonlinear resistor - Google Patents

Abstract

PURPOSE:To improve nonlinear voltage dependence in a large current region by adding zinc oxide fine particle with a grain diameter of 1mum or less containing oxide aluminum at specific mole % in terms of Al2O3 to zinc oxide and other metal oxide and by sintering the mixed raw material. CONSTITUTION:As a basic composition, Pr6O11 of 0.5 mole %, CO3O4 of 2.0 mole %, K2O, Cr2O3, MgO and CaO of 0.1 mole %, respectively, and B2O3 of 0.01 mole % are added to zinc oxide. Fine particle zinc oxide whose particle size containing aluminum oxide of 0.2wt.% is in the range of 0.15 to 1mum is used and added in the range of 0.0001 to 0.01 mole % in terms of Al2O3, mixed adequately by a ball mill, formed to slurry by grinding, a binder is combined, dried and formed to grains. Thereafter, a disc of a diameter of 17mm and a thickness of about 2mm is formed. In the process, a formation pressure is adjusted to make a density of 3.1g/cm<3>. Then, it is burnt in air for one hour at 1250 deg.C, silver conductive paste is screen-printed to both sides of a sintered body, and an electrode is formed by burning at 600 deg.C for 5 minutes.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a zinc oxide voltage nonlinear resistor containing zinc oxide as a main component and an oxide such as praseodymium as a subcomponent.

[Conventional technology]

Ceramics made by mixing zinc oxide with various additives and sintering it are known to exhibit voltage nonlinearity in resistance, and as the applied voltage increases, the resistance increases. Because the current decreases rapidly and the current increases significantly, it is widely used as a varistor to suppress abnormal voltage (surge) in electrical circuits.

The voltage-current characteristics of the varistor are expressed by the following approximate equation.

■! -(-)α where I is the current flowing through the varistor, ■ is the applied voltage, C is a constant, and α is the voltage nonlinear index. That is, the varistor characteristics can be expressed by two constants, C and α. Usually, instead of C, the voltage V when a current of 1 mA flows through the varistor is used.

In particular, it is considered important that α, which is an index indicating voltage nonlinearity, has a large value. Zinc oxide varistors exhibit excellent voltage-current characteristics, and also have the characteristic that the characteristics can be adjusted arbitrarily by adjusting the element stiffness.

[Problem to be solved by the invention]

On the other hand, when these zinc oxide varistors are used between lines and ground on the power input side of various electronic devices,
Conventional zinc oxide voltage nonlinear resistors have large characteristic changes in the low current region when voltage is constantly applied, and also have a large rate of change in varistor voltage when large current long-tail surges are applied. However, there was a problem in that it was difficult to improve the performance.

In order to eliminate the drawbacks of conventional zinc oxide voltage nonlinear resistors, it is necessary to suppress the voltage rise particularly in the large current region. In other words, it is necessary to improve the voltage nonlinearity in the input power mi region. To this end, the general method is to add trace amounts of several types of additives to the basic composition of zinc oxide and various metal oxides.
Examples include the addition of oxides and salts of aluminum, gallium and indium.

However, these oxides and salts generally have a coarse particle size of several to several 10 particles (and are extremely difficult to add and disperse as an aqueous solution.Actually, it is difficult to obtain the effect of additives over the entire resistor). Therefore, the amount of addition is 0.01 mol% or more.If the amount added is increased in this way, the nonlinearity in the low current region becomes worse (and the rate of change of the varistor voltage when a long wave tail surge of a large current is applied) becomes worse. Problems also arise in the reliability of the device due to the large thickness.

An object of the present invention is to solve the above-mentioned problems and provide a method for manufacturing a zinc oxide voltage nonlinear resistor that can uniformly disperse additives for improving voltage nonlinearity in a large current region. It is in.

(Means for Solving III) In order to achieve the above object, the method for manufacturing a zinc oxide voltage nonlinear resistor of the present invention includes aluminum oxide in zinc oxide and a plurality of types of other metal oxides. particle size ln
The following zinc oxide fine particles are converted into lJ*os2 and are 0.00
It is added in a range of 1 to 0.005 mol%, and the mixed raw materials are sintered. In addition, the production method of the present invention allows zinc oxide fine particles containing aluminum oxide in zinc oxide and a plurality of types of other metal oxides and having a particle size of 1 or less to be
A step of adding in a range of 0.001 to 0.005 mol% in terms of goz, mixing and pulverizing, a step of granulating the pulverized mixture, a step of molding the granulated granules, and a step of molding the molded object. It shall include a sintering process.

[Effect]

The zinc oxide voltage nonlinear resistor is composed of crystal grains with low resistivity mainly composed of zinc oxide, and grain boundaries and grain boundary layers with high resistivity containing subcomponents.

The smaller the resistance of crystal grains and the larger the resistance near the grain boundaries, the better the nonlinearity is. U, O, ni 1111)
A trace amount of aluminum element of 0.001 to 0.005 mol % is uniformly dissolved in the zinc oxide particles, lowering the specific resistance of the crystal and improving voltage nonlinearity. Further, when fine particles of zinc oxide containing aluminum oxide and having a particle size of 1- or less are used, the dispersibility within the raw material particles is improved compared to when a conventional oxide monosalt and aqueous solution are used.

〔Example〕

The basic composition is zinc oxide with 0.5 mol% pr601+, 2.0 mol% CO5Oa, 0.1 mol% each of KgO+ CrtOs+ Mg' and CaO, and 0.01 mol% B2O2, and aluminum oxide. Using fine particle zinc oxide containing 0.2% by weight and having a particle size in the range of 0.15 to 1n, 0.00% in terms of M2O,
01 to 0.01 mol%, thoroughly mixed in a ball mill, pulverized to form a slurry, blended with a binder (caking thorn), dried and granulated to form a powder with a diameter of 17 cm and a thickness of approx. It was molded into a disk shape with two states. At this time, the density is 3.1g
0th order 125 where the molding pressure is adjusted so that /aj
The sintered body was fired in air for 1 hour, StS conductive paste was screen printed on both sides of the sintered body, and electrodes were formed by firing at 600 °C for 5 minutes, and the error characteristics of the resulting device were measured. . In addition, zinc oxide containing aluminum oxide uniformly can be obtained by mixing aluminum sulfate with zinc oxide powder, or by mixing aluminum sulfate with zinc oxide powder.
Alternatively, it can be obtained by mixing zinc oxide powder and an aqueous aluminum sulfate solution and heating the mixture.

Figure 1 shows the voltage when a current of 40A is passed through the element, ■
,. , and the voltage when a current of 111^ flows through the element, V
16. The ratio of ■4゜A/V 1. Nonlinearity in the large current region represented by A, 0. Figure 2 shows the relationship between the amount of addition and the voltage when a current of 10μ is passed through the element.
V, @IIA and the voltage when a current of 1 mA flows through the element, the ratio of VI + IA, V re D / V + m AZ
The characteristics in the low current region shown are 1□0. The relationship between the amounts added is shown.

It can be seen from FIG. 1 that the nonlinearity in the large current region improves as the amount of M2O added increases. On the other hand, from FIG. 2, the characteristics in the low current region decrease in almost inverse proportion to the amount of Altos added, and if the amount exceeds 0.005 mol %, the characteristics in the low current region will deteriorate.

Figure 3 shows the rate of change of V + @A before and after applying a rectangular wave of width 2 + wsec and 100 A 20 times, ΔV,
The relationship between the long wave tail surge resistance and the amount of M2O3 added is shown.

It can be seen from FIG. 3 that as the amount of AltO added increases, the long wave tail surge resistance deteriorates. As shown in FIGS. 2 and 3, adding a large amount of aluminum oxide worsens nonlinearity in the low current region and increases the rate of change in varistor voltage when a long wave tail surge is applied. It is necessary to suppress the amount of addition as much as possible.

Specifically, AZ, 0° addition amount is 0.001 to 0.
A suitable addition amount is 0.005 mol%.

〔Effect of the invention〕

According to the present invention, by adding aluminum oxide in the form of zinc oxide fine particles containing aluminum oxide to the raw material powder of the zinc oxide voltage nonlinear resistor, the characteristics in the low voltage region and the long wave tail surge resistance are deteriorated. It is possible to uniformly disperse aluminum oxide in M2O3 which does not exceed 0,005 mol% in the resistor, and by adding more than 0,000 mol%, voltage nonlinearity in the large current region can be reduced. It has become possible to produce zinc oxide voltage non-direct yiA resistors.

[Brief explanation of the drawing]

Figure 1 shows the nonlinearity of the zinc oxide voltage nonlinear resistor in the high current range, Figure 2 shows the characteristics in the low current range, and Figure 3 shows the relationship between the long wave tail surge resistance and the amount of klzo3 added. be.

Claims (1)

[Claims] 1) Zinc oxide fine particles with a particle size of 1 μm or less containing aluminum oxide in zinc oxide and a plurality of other metal oxides in an amount of 0.001 to 0.005 mol% in terms of N_2O_3. A method for manufacturing a zinc oxide voltage nonlinear resistor, characterized by adding a range of zinc oxide and sintering the mixed raw materials. 2) Zinc oxide fine particles containing aluminum oxide and having a particle size of 1 μm or less are added to zinc oxide and multiple types of other metal oxides in a range of 0.001 to 0.005 mol% in terms of N_2O_3, and mixed. , a step of pulverizing the pulverized mixture, a step of granulating the pulverized mixture, a step of molding the granulated granules, and a step of sintering the molded body. manufacturing method. 3) heating a mixture of zinc oxide and aluminum sulfate;
3. The method for producing a zinc oxide voltage nonlinear resistor according to claim 1, wherein aluminum oxide-containing zinc oxide fine particles obtained by pulverization are used.