JPH04299504A - Manufacture of voltage dependent nonlinear resistor - Google Patents

Abstract

PURPOSE:To develope the title manufacturing method of a voltage dependent nonlinear resistor capable of lowering the limited voltage in high current region for displaying the stabilized electric characteristics. CONSTITUTION:The title voltage dependent nonlinear resistor can be manufactured by the steps mentioned as follows: the material powder containing zinc oxide as the main component and 0.1-0.4mol% of bismuth in terms of Bi2O3; 0.1-0.4mol% of antimony in terms of Sb2O3; 0.05-0.2mol% of chromium in terms of Cr2O3; 0.1-0.4mol% of nickel in terms of NiO as the sub-components is blended, formed and baked to be cooled down at the cooling rate not exceeding 15 deg.C/hour.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a voltage nonlinear resistor containing zinc oxide as a main component and at least one kind of additive exhibiting voltage nonlinearity as a subcomponent.

0002

2. Description of the Related Art Voltage nonlinear resistors containing zinc oxide as a main component are widely used in lightning arresters and surge absorbers for the purpose of voltage stabilization or surge absorption due to their excellent nonlinear voltage-current characteristics. This voltage nonlinear resistor is
A predetermined amount of oxides such as bismuth, antimony, chromium, nickel, etc. that exhibit voltage nonlinearity are added to the main component zinc oxide, mixed, granulated, molded, and then fired to preferably form a side high-resistance layer. Therefore, it can be manufactured by applying an inorganic substance, firing it again, and attaching an electrode to the sintered body. In recent years, there has been a desire to obtain more stable electrical characteristics of the voltage nonlinear resistor obtained in this way, and a desire to reduce the limiting voltage in a large current region. As a method to obtain stable electrical characteristics, the temperature decreasing process of the firing process is lowered from a temperature higher than 500°C to 40°C.
A method of slow cooling at a cooling rate slower than 1 hour was disclosed in Japanese Patent Application Laid-open No. 5
It is disclosed in Japanese Patent No. 7-114204.

0003

[Problems to be Solved by the Invention] However, the voltage nonlinear resistor obtained by this method has problems in the large current range because the additive wraps around the zinc oxide particles to form a three-dimensional network structure after firing. The problem was that the limiting voltage was still high.

The object of the present invention is to ensure that the limiting voltage in the large current range is not limited to the resistance of the zinc oxide particles in the voltage nonlinear resistor, but also
Based on the inventor's knowledge that it depends on the resistance of the grain boundary phase forming a dimensional network structure, the above-mentioned problems can be solved and the limiting voltage in the large current region can be reduced and stable electricity can be achieved. The purpose of this invention is to provide a method for manufacturing a voltage nonlinear resistor that can obtain ideal characteristics.

[0005]

[Means for Solving the Problems] The method for manufacturing a voltage nonlinear resistor of the present invention uses zinc oxide as a main component and bismuth as a subcomponent in an amount of 0.1 to 0.4 mo converted to Bi2O3.
l%, antimony converted to Sb2O3 is 0.1-
0.4 mol%, 0 when converting chromium to Cr2O3
．． Mix raw material powder containing 05-0.2 mol%, 0.1-0.4 mol% in terms of nickel as NiO,
After molding and firing, it is characterized by cooling at a cooling rate of 15° C./hour or less.

[0006]

[Function] In the above structure, even if the total amount of additives added as subcomponents, especially the amount of bismuth added, is reduced, if the cooling rate in the cooling process in which the grain boundary phase is formed is set to 15°C/hour or less, A grain boundary phase in which bismuth is uniformly precipitated can be obtained, and as a result, a voltage nonlinear resistor with good electrical characteristics in a large current region can be obtained.

[0007] Here, the amount of bismuth added is 0.1-0.4 mol% in terms of Bi2O3, the amount of antimony added is 0.1-0.4 mol% in terms of Sb2O3,
The amount of chromium added is converted to Cr2O3 and is 0.05-0.
2 mol%, nickel addition amount converted to NiO 2 is 0.
1-0.4 mol% and the cooling rate after firing was 15℃/
The reason why the limiting voltage ratio and the rate of change were significantly reduced by limiting the voltage to less than the time is as follows. In the above composition range, a three-dimensional network structure is not formed because there are few grain boundary constituents. Therefore, compared to a composition with many grain boundary constituents and a three-dimensional network structure, the limiting voltage in the large current region is smaller and the limiting voltage ratio is reduced. Furthermore, if the grain boundary constituents are small and the cooling rate is fast, variations occur in the precipitation of bismuth at the grain boundaries of zinc oxide. However, if the cooling rate after firing is set to 15°C/hour or less, there will be no variation in bismuth precipitation and the microstructure will be uniform, so the limiting voltage ratio
It is thought that both the rate of change will be reduced.

[0008]

[Example] An actual example will be explained below. Example: Zinc oxide is the main component, and additives for developing voltage nonlinearity include Bi2O3, Sb2O3, Cr2O3.
, NiO 2 is added in the ratio shown in Table 1, and Co
O 2 and MnO 2 were added, and an organic binder, a dispersant and water were added thereto to form a slurry. After drying this slurry with a spray dryer and granulating it, the diameter of the slurry is 60 mm.
A molded body was obtained by molding it into a disc shape. The obtained molded body was
After degreasing by heat treatment at 00℃, 800-950
Preliminary firing was performed at a temperature of 1200°C, and an inorganic material was applied in the form of a paste to form a high resistance layer on the side surface.
Baked for an hour. In this firing, the cooling rate was varied as shown in Table 1. Thereafter, both end surfaces of the obtained sintered body were polished and aluminum sprayed electrodes were applied to the polished surfaces to obtain a voltage nonlinear resistor.

The voltage nonlinear resistor thus obtained has a limiting voltage V1m per unit thickness when a current of 1mA is applied.
A, nonlinear index α calculated from current 0.1 mA and limited voltage when 1 mA is applied, limiting voltage ratio calculated from V1 mA and limited voltage per unit thickness when 40 KA current is applied, and current 100 KA with 4/10 μs waveform The rate of change calculated from the difference in V1mA before and after the application of the voltage was applied twice was measured. The results are shown in Table 1.

0010

[Table 1]

In Table 1, Bi2O3 is set to 0.
．． 4 mol%, Sb2O3 0.4 mol%, C
0.2 mol% r2O3, 0.4 mo NiO
When added in excess of 1%, the limiting voltage ratio was large in all cases. If Bi2O3 is less than 0.1 mol%, varistor characteristics cannot be confirmed, and if Sb2O3 is less than 0.1 mol%,
%, the limiting voltage ratio and rate of change were large. Also,
When Cr2O3 was less than 0.05 mol%, the rate of change was large, and when NiO was less than 0.1 mol%, the limiting voltage ratio and the rate of change were large. The composition range of the present invention other than the above, that is, Bi2O3 is 0.1-0.4 mol%,
0.1-0.4 mol% Sb2O3, Cr2O3
0.05-0.2 mol%, NiO 0.1-0
．． At 4 mol%, at least one of the limiting voltage ratio and the rate of change is reduced by slowing the cooling rate after firing, and especially in this composition range, the cooling rate after firing is set to 15°C/hour or less of the present invention. As a result, both the limiting voltage ratio and the rate of change were significantly reduced. That is, remarkable effects were obtained by defining the composition and cooling rate within the range of the present invention.

0012

As is clear from the above description, according to the present invention, the total amount of additives added as subcomponents, especially the amount of bismuth added, can be reduced, and the cooling process during which grain boundary phases are formed can be reduced. If the speed is 15° C./hour or less, a grain boundary phase with uniform bismuth precipitation can be obtained, and as a result, a voltage nonlinear resistor with good electrical characteristics in a large current region can be obtained.

Claims (1)

[Claims] [Claim 1] Zinc oxide is the main component, and bismuth is 0.1-0.4 mo converted to Bi2O3 as a subcomponent.
l%, antimony converted to Sb2O3 is 0.1-
0.4 mol%, 0 when converting chromium to Cr2O3
．． 05-0.2 mol%, 0.1-0.4 mol% in terms of nickel as NiO. A method for manufacturing a voltage nonlinear resistor.