JPS5852802A - Zinc oxide nonlinear 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 The present invention relates to a nonlinear resistor containing zinc oxide as a main component.

As is well known, surge absorbers, lightning arresters, and the like are used to protect power equipment from abnormal high voltages such as lightning and switching surges. This K is generally a voltage expressed by the following formula -
A nonlinear resistor with current characteristics is used.

Here, ■ is an applied voltage, ■ is a current, C is a quantity corresponding to the resistance value of a normal resistor (nonlinear resistance), and α is a nonlinear index.

In lightning arresters, it is desirable that the nonlinearity index (CQ) is large, and as a characteristic element, there is a tendency for ZnO-based nonlinear resistors to be used in place of conventional SiC-based nonlinear resistors. This ZnO-based nonlinear resistor has a steep nonlinear characteristic in the small current region and a sharp rise up to the large current region, and does not require a gap, making it possible to manufacture small and excellent lightning arresters. Pointed.

Incidentally, in recent years, there has been a trend toward ultra-high voltage in electric power systems, and with this ultra-high voltage, the increase in the size of equipment has become a frequent problem.

In order to reduce the size of equipment, reinforcing the insulation using insulating materials with high dielectric strength may be considered, but this is also one way to lower the protection level of equipment using lightning arresters. That is, there is no need to take a large safety factor into account, and the equipment can be made smaller. To achieve this, strict duties are required of the lightning arrester, and it is necessary to keep the voltage level low, especially in the high current region. In other words, an excellent limiting voltage ratio (generally the voltage between the terminals of a non-linear resistor when 1 mA flows (V%) and the voltage between the terminals of the same non-linear resistor when a current of another value flows) A nonlinear resistor with a ratio of

The present inventors have undertaken research to meet the above-mentioned demand for improved characteristics. In order to improve the limiting voltage ratio characteristics of ZnO-based nonlinear resistors, there is a method of changing the composition of additive components to the ZnO main raw material, for example, adding a small amount of a specific component, or increasing or decreasing the amount of a specific component. Although it is
First, the structure and characteristics of the ZnO-based nonlinear resistor will be considered.

A ZnO-based nonlinear resistor is a sintered body obtained by adding bismuth oxide, cobalt oxide, manganese oxide, antimony oxide, chromium oxide, silicon dioxide, nickel oxide, etc. to zinc oxide and sintering it at 1000°C or higher. The inside thereof consists of crystal grains mainly composed of zinc oxide, a grain boundary layer containing other additive components, and a spinel layer containing various components. The voltage nonlinearity of this nonlinear resistor is thought to be mainly based on the electrical properties at the interface between the ZnO crystal grains and the grain boundary layer, and what kind of atoms (
Nonlinearity is affected by whether or not ions are included. Further, a large amount of Zn ions diffused from the crystal grains during sintering are present in the spinel layer and the grain boundary layer', and the behavior of the Zn ions therebetween is thought to affect the nonlinear resistance value and nonlinearity.

ρ On the other hand, in the current region, the non-linear resistance at the interface of the grain boundary layer gradually becomes negligible, and a voltage rise can be seen due to the specific resistance of the ZnO particles.

Based on this consideration, we arrived at the idea to reduce the voltage rise.

Therefore, in the present invention, we focused on AtR4, which has the effect of lowering the resistivity by selectively dissolving into ZnO particles, and by adding and mixing the required amount as an aqueous solution, salt, or oxide, we achieved an excellent restriction. The present invention aims to provide a zinc oxide nonlinear resistor having voltage ratio characteristics.

Hereinafter, the present invention will be explained in detail based on examples. Example M [995% or more ZnO, 95.0 mol% Bi,
O, 05 mol%, CO! 0.5 mol% of 03, Mn
O, 0 mole, Sb, O, 1.0 mol%, Cr1
O1 to 0.5 mol%, 5in1 to 1.0 mol, NiO
A predetermined amount of an aqueous solution of aluminum nitrate was added thereto and mixed in a ball mill to form a slurry. After drying and granulating this mixed slurry, it was pressure-molded into a disk and fired at 1100 to 1300°C to obtain a sintered body (diameter-diameter). After polishing this to a thickness of 5 mK, a silver electrode with a diameter of ■ was baked onto it.

The above ZnO elements were manufactured by varying the amount of aluminum added, and the nonlinear index (α) with respect to the amount of aluminum added was determined.
(Fig. 1), change in limiting voltage ratio (Fig. 2), and change in free electron density within the ZnO particles calculated from measurement of infrared reflection (Fig. 3) were measured.

As shown in FIG. 1, the nonlinearity index (α) decreases in approximately inverse proportion to the amount of aluminum added, and adding a large amount of aluminum worsens the nonlinearity. On the other hand, as shown in FIG. 2, the value of the limiting voltage ratio decreases as the amount of aluminum added increases, and it is clear that the characteristics are improved. The change in free electron density shown in FIG. 3 confirms that this property improvement is due to a decrease in the specific resistance of the ZnO particles. That is, as the amount of aluminum added increases, the free electron density increases (an increase in free electron density means a decrease in specific resistance).

As described above, the addition of aluminum has a great effect on improving the limiting voltage ratio characteristics, but it also has the unfavorable aspect of reducing the -plane nonlinearity index (α), and it is important to balance the two. If the value of the non-linearity index (α) is small, the leakage current will increase with constant voltage application, which will increase the element temperature and shorten the element life. Therefore, it is desirable that α>20. It is desirable that the value is smaller than 20 to 9 in order to protect the device in the event of a surge. As a result, it is appropriate to add aluminum in a weight ratio of 5 to 50 ppm.

In the above explanation, aluminum is added in the form of an aqueous solution of nitrate, but the same effect can be achieved even if aluminum is added in the form of other salts or oxides.

As described above, according to the present invention, by adding a predetermined amount of aluminum, the zinc oxide nonlinear resistor is capable of improving the limiting voltage ratio characteristics while maintaining the required value of the nonlinear index (α). can be provided.

[Brief explanation of the drawing]

The drawings are for explaining the influence of the additive (aluminum) on the characteristics of the zinc oxide nonlinear resistor according to the present invention, and Figure 1 shows the change in the nonlinear index (α) with respect to the amount of aluminum added. Figure 2 is a diagram showing the change in limiting voltage ratio with respect to the amount of aluminum added, and Figure 3 is a diagram showing the relationship between the amount of aluminum added and the free electron density in ZnO particles calculated from infrared reflection measurements. be. Figure 3 AtA dispute Pm) Procedural amendment written by) 1985 1n 31 Dear Commissioner of the Japan Patent Office 1 Indication of the case 1986 Patent No. 16 Part 11 No. 2 Name of the invention Zinc oxide nonlinear resistor 3. Relationship with the case of the person making the amendment Applicant (-10) Meidensha Co., Ltd. 4, Agent Address: 1-29 Akashi-cho, Chuo-ku, Tokyo 104, Suiseikai Building Telephone: 03 (
545) 2251 (Representative) Patent Attorney (6219) Fujiya Shiga 5, Detailed explanation from O of the specification to be amended - Column O ◎ a Contents of the amendment (1) Page 8 of the specification, from line 8 to line I ``This ZnO-based non-linear resistor has...'' and ``This ZnO-based non-linear resistor has excellent non-linear characteristics in a small current region and can reach a large current region. 0 (2) Delete ``It is possible to think about it again.'' from page 5, line 12 to line 16. (3) "Free electron concentration" stated on page 6, line 7 of the same
Free electron density” @

Claims (2)

[Claims] (1) Zinc oxide is the main component, and bismuth, cobalt, manganese, antimony, chromium, silicon, and nickel are added as additive components, B: L, O, Co=O, respectively.
,Mn01,S'b,O,,cr,o,,S10. and 0.1 to 3.0 mol%, respectively, in terms of NiO form.
, 0.05-3.0 mol%, α05-3 mol, 0.1
~5 mole, 0.02 to 3.0 mole%, 0.05 to 5 mole, and 0.1 to 5 mole% of the raw materials blended, the amount containing 5 to 501) pm in weight ratio in the sintered body. A zinc oxide non-linear resistor made by adding aluminum as an oxide and salt as an aqueous solution, then firing. (2) The zinc oxide nonlinear resistor according to claim 1, wherein the firing is performed at 1100 to 1300°C.