JPS6197905A - Voltage non-linear resistor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a voltage non-conductor which has zinc oxide as a main component and has a high resistance layer formed on the side surface of a sintered body which itself has voltage non-linear resistance characteristics. This relates to a linear resistance element.

[Technical background of the invention and its problems 1 Voltage nonlinear resistors are generally called varistors, and their excellent nonlinear voltage-current characteristics are utilized to create lightning arresters and surge absorbers for voltage stabilization or surge absorption. It is widely used in A typical example is zinc oxide varistor. The main ingredient is zinc oxide, with a small amount of bismuth.

It is constructed by adding oxides such as antimony, cobalt, manganese, chromium, etc., mixing, granulating, and molding, then firing at a high temperature in air, and attaching electrodes to the sintered body. Its non-linear resistance characteristics are very excellent, and the sintered body consists of grain boundary layers formed by zinc oxide particles and additives surrounding them. It is thought that this is caused by the interface with the layer. While these ZnO-based varistors have many advantages such as being able to arbitrarily adjust the voltage-current characteristics to some extent, the use of these ZnO-based varistors as power surge arresters has the following drawbacks. In other words, the rate of change in resistance of a nonlinear resistor is large when a large current pulse is applied, and therefore it is unsuitable for use as an overvoltage protection device that is exposed to voltage pulses or switching surge pulses over a long period of time, and is not stable over a long period of time. There has been a demand for a voltage nonlinear resistor whose main component is a metal oxide and has such electrical characteristics. In order to meet these demands, we have proposed a method of coating the side surface of the sintered body with epoxy resin, and
2. Methods of forming high-resistance layers mainly made of Zn2Si04 have been implemented or developed. However, the epoxy resin coating has poor voltage resistance characteristics and Zny Sb201
2. Although the moisture resistance and other properties of the Zn2Si04-based high-resistance layer have been improved, the problem of a large rate of change in resistance when a large current pulse is applied still remains.

[Object of the Invention] The present invention was made in view of the above-mentioned needs, and provides a voltage mainly composed of a metal oxide, which has good withstand voltage characteristics and whose electrical characteristics hardly deteriorate even when overvoltage pulses are repeatedly applied over a long period of time. A non-linear resistor element is provided.

[Summary of the Invention] According to the present invention to achieve the above object, a high-resistance layer containing at least silicon oxide, titanium oxide, and antimony oxide is formed on the side surface of a sintered body mainly composed of zinc oxide. By providing the layer, it is possible to obtain a voltage nonlinear resistor element that has good high voltage resistance characteristics and a small rate of change in varistor voltage due to large current pulses.

[Embodiments of the invention] The present invention will be explained in detail below with reference to Examples.

FIG. 1 is a cross-sectional view of a voltage nonlinear resistor according to the present invention.
2 is a sintered element body, 2 is a high resistance layer formed on the side surface of this sintered element body 1, and 3 is an electrode provided on both upper and lower surfaces.

The voltage nonlinear resistor having the above structure is manufactured as follows, for example. That is, zinc oxide (ZnO) powder is mixed with bismuth oxide (Bi20a>, cobalt oxide (CO20),
Manganese oxide (MnO), antimony oxide (Sb20i)
) and nickel oxide (Nip) powder at 0.1~
The raw material powders were added in an amount of 5 mol %, and mixed together with water, a dispersant, a binder and a lubricant in a mixing machine. This mixture slurry is granulated using a spray dryer so that the average particle size is, for example, 100 microns, and this powder is pressed to have a diameter of 40 rra.
It was molded into a disk with a thickness of 40 g.

To remove the added dispersant, binder, and lubricant in advance, the element body was fired at 500°C in air and then calcined at 1020°C, and a slurry for forming a high-resistance layer with a different composition ratio prepared in advance was sprayed with a spray gun. It was applied using. The slurry for forming a high resistance layer was prepared as follows. That is, bismuth oxide (B
i203), silicon dioxide (SiO2), titanium oxide (T
i02).

Pure water was added to antimony oxide (Sb 203 ) to make a suitable slurry. At this time, the strength of the coating film was increased by adding about 0.1 wt% of a binder such as polyvinyl alcohol. A slurry such as nickel was applied to the above-mentioned body, and this body was fired at a temperature of 1050 to 1300"C. Both sides of the sintered body thus obtained were ground and polished by the aluminum side. Electrodes were formed to obtain a voltage nonlinear resistor.

The withstand voltage characteristics when a large current pulse is applied to this voltage non-linear resistor (here, a value that does not cause side flashing when applied twice with a 4 x 10 microsecond waveform) and the applied slurry for forming a high resistance layer. The relationship between the composition of the slurry for forming a high-resistance layer and the rate of change in V 10 μA in the opposite direction to the application direction after applying a current of 10 kA 20 times with a waveform of roughly 8 x 20 microseconds. Examples and comparative examples are shown in the table (
I). The values shown are for the firing temperature of 1150
℃.

Also, in Figure 2, 1. tTi 02 /Bi 203 =
1.0, Tt when Bi20a is fixed at 10 mol% 0
2 +SiO2 and Sb 203 and the relationship between the withstand voltage characteristics, and Figure 3 shows the relationship between the withstand voltage characteristics of TiO2 and SiO2 when Bi2O: + and 5b20i are fixed, and Figure 4 shows the relationship between the withstand voltage characteristics of TiO2 and SiO2. 02 /Si 02-1.0.5
The relationship between the amount of 3i 203 added and withstand voltage characteristics when fixed at 15.0 mol % of b203 is shown.

As is clear from Table (I), devices coated with epoxy resin or those without paste coating cause creeping flash at a current of 10 kA or less, whereas the device according to the present invention has much better performance. It can be seen that it has durable voltage characteristics. Also, the conventionally known Zn7Sb20t2/Zn2Si 0
Although the product coated with the composition No. 4-0.25 had voltage resistance characteristics sufficient for practical use, the rate of change in varistor voltage due to pulse application was large. Also, according to Table (I) and Figures 2, 3, and 4, the sum is 100% (1) set a'lJT B! 20340.
3-20 mol%, 3i 02 , Ti 02 is 25-5
It is clear that if Sb 203 is outside the range of 5 to 50 mol %, the desired properties will not be exhibited.

Next, we measured the concentration distribution of the components on the side surfaces of these elements using an X-ray microanalyzer.
The presence of at least Si, 7i, and Sb was confirmed. The amount is located at a depth of 10 μm.
, Ti 02 , and Sb 203 , it was found that the inventive example contained 2.5.2.5 or more than 1 mol %. The role of bismuth oxide is thought to be that it acts as a flux and promotes the diffusion of silicon oxide, titanium oxide, and antimony oxide or the reaction with zinc suboxide.

Then, Si diffused into the element body by bismuth oxide,
Ti.

and sb serve as high resistance layers to improve withstand voltage characteristics and pulse resistance characteristics. It can be seen that the voltage nonlinear resistor obtained according to the present invention has excellent withstand voltage characteristics, has a small rate of change with respect to large current pulses, and exhibits excellent stability. This guarantees extremely high reliability when the device is used in a power surge arrester, etc., and is important from a practical perspective. In the examples of the present invention, an oxide was used as the raw material, but any material that can be sintered to form an oxide may be used; for example, hydroxide, carbonate, oxalate, etc. can also be used to obtain the same effect. Needless to say.

In addition to the additives shown in the examples, other components may be added for the purpose of improving the characteristics of the nonlinear resistor, and in order to further improve the M'S characteristics and withstand voltage characteristics, the voltage nonlinear resistor may be It is desirable to bake glass components etc. on the outside of the glass.

[Effects of the Invention] As described above, according to the present invention, bismuth oxide, silicon oxide, titanium oxide, and antimony oxide are added to the side surface of a sintered body mainly composed of zinc oxide and having voltage nonlinearity.
, 5io2. TiO2゜Sb 0.3-20 mol%, 25-50 mol%, 25-50 respectively in terms of 203
mol%, within the range of 5 to 50 mol%, the total is 100 mol%
A highly reliable resistor with excellent RR4 voltage characteristics and high power pulse characteristics is achieved by applying a material with a composition ratio of It is possible to provide a voltage nonlinear resistor having characteristics.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the structure of a voltage nonlinear resistor according to the present invention, and FIG. 2 is a cross-sectional view showing the structure of a voltage nonlinear resistor according to the present invention, and FIG.
Ti 02 +3 when Bi203 is fixed at 10 mol%
A diagram showing the relationship between i02 and Sb 203 and withstand voltage characteristics. Figure 3 shows the T when Bi2O3°Sb 203 is fixed.
A diagram showing the relationship between iO2 and 5i02 and withstand voltage characteristics, FIG. 4 shows Ti 02 /Si 02 = 1.0.
3i2 when fixed at Sb 20315.0 mol%
FIG. 2 is a diagram showing the relationship between the addition amount of No. 03 and withstand voltage characteristics. 1... Sintered element body, 2... High resistance layer, 3... Electric rod. Applicant's agent Patent attorney Takehiko Suzue No. 10 Figure 2 5b 2030 20 40 60 80
+OO Figure 3 [3iz O3 king-ru 7゜

Claims (1)

[Claims] Bismuth oxide, silicon oxide, titanium oxide, and antimony oxide are added to the side surface of a sintered body mainly composed of zinc oxide, which itself has voltage nonlinear characteristics.Bi_2O_3, SiO_2, TiO_2, Sb_2O
_3 converted to 0.3 to 20 mol%, 25 to 5 respectively
A substance with a composition ratio of 0 mol%, 25 to 50 mol%, and 5 to 50 mol% with a total composition ratio of 100 mol% is applied and then sintered to form a high-resistance layer on the side surface of the nonlinear resistor. A voltage nonlinear resistor characterized by: