JPH04245601A - Nonlinearly voltage-dependent resistor - Google Patents

Abstract

PURPOSE:To reduce the rate of change of varistor voltage, and improve surge durability, charging life, etc., by adopting a specified composition. CONSTITUTION:Bismuth of 0.3-1.2mol% converted into Bi2O3, antimony of 0.3-1.5mol% converted into Sb2O3, chromium of 0.3-1.5mol% converted into Cr2O3, and manganese of 0.2-0.8mol% converted into MnO2 are contained. Further silicon of 4.0-10.0mol% converted into SiO2, aluminum of 0.002-0.02mol% converted into Al2O3, and boron of 0.0001-0.05mol% converted into B2O3 are contained. Silver of 0.0001-0.05mol% converted into Ag2O3, and at least either potassium of 0.0005-0.015mol% converted into K2O or sodium of 0.0005-0.015mol% converted into Na2O are contained. The residual is formed of zinc oxide.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage nonlinear resistor used in overvoltage protection equipment.

0002

[Prior art] Bi2O3, Sb2O3, SiO2, Co2 with zinc oxide (ZnO) as the main component
Resistors containing small amounts of metal oxides such as O3 and MnO2 as subcomponents are widely known to exhibit excellent voltage nonlinearity, and are used in lightning arresters and the like by taking advantage of this property.

As such voltage nonlinear resistors used in power equipment, those having the composition disclosed in, for example, Japanese Patent Application Laid-Open No. 63-136603 are suitable. However, even if these compositions were adopted, there still remained a drawback that the rate of change ΔV1mA of the varistor voltage V1mA after application of a lightning surge was large.

[0004] For this reason, when designing a lightning arrester, it is necessary to take into account the rate of change in V1mA in advance. On the other hand, as a method of suppressing the deterioration itself caused by surges, it is known to perform heat treatment at a temperature of 600°C or higher after firing the voltage nonlinear resistor, but this method reduces the varistor voltage of the voltage nonlinear resistor. This has the disadvantage that the limiting voltage ratio V40KA/V1mA increases.

[0005]

[Problems to be Solved by the Invention] An object of the present invention is to provide a voltage nonlinear resistor that has a small rate of change ΔV1mA of varistor voltage after a surge is applied, has a limited voltage ratio V40KA/V1mA, has excellent surge resistance, and has an excellent energized life. It is to provide.

[0006]

[Means for solving the problems] The present invention uses bismuth.
0.3 to 1.2 mol% in terms of Bi2O3,
Antimony converted to Sb2O3 is 0.3 to 1.5
mol%, chromium converted to Cr2O3 0.
3-1.0 mol%, cobalt converted to Co2O3 0.3-1.5 mol%, manganese M
0.2 to 0.8 mol% in terms of nO2, 4.0 to 10.0 mol in terms of silicon as SiO2
%, 0.3 to 2.5 when converting nickel to NiO
mol%, aluminum converted to Al2O3
0.002-0.02 mol%, boron B2O3
0.0001-0.05 mol% in terms of silver, 0.0001-0.05 mol% in terms of silver
l%, and 0.0005 to 0.0 in terms of K2O.
015 mol% of potassium and 0.0005 to 0.015 mol% of sodium in terms of Na2O, the remainder being zinc oxide. .

[0007]

[Operation] According to the present invention, by employing the above-mentioned specific composition, the rate of change Δ of the varistor voltage after application of a surge is
V1mA is low, limiting voltage ratio V40KA/V1mA
It is possible to provide a voltage nonlinear resistor with excellent surge resistance and energized life.

[0008] Bismuth has a value of 0.0 in terms of Bi2O3.
3 to 1.2 mol% is used. Bismuth forms a grain boundary layer between zinc oxide particles, and is an important additive thought to be involved in the formation of a Schottky barrier that is related to the development of varistor properties. This is 0.3 mol
%, ΔV1mA, V40KA/V1m
A increases, and surge resistance deteriorates. On the other hand, if this exceeds 1.2 mol%, ΔV1
mA increases, and surge resistance deteriorates.

Antimony and chromium are each Sb
In terms of 2O3 and Cr2O3, Sb2O3
0.3-1.5 mol%, Cr2O3 0.3
~1.0 mol% is used. Antimony and chromium react with zinc oxide to form a spinel phase, thereby suppressing abnormal grain growth of zinc oxide particles and improving the uniformity of the sintered body. The amount converted to Sb2O3 is
If it is less than 0.3 mol%, ΔV1mA increases, the surge resistance deteriorates, and this
If it exceeds ol%, surge resistance deteriorates. Also, Cr
If the amount converted to 2O3 is less than 0.3 mol%, ΔV1mA becomes large and the charging life deteriorates, and if it exceeds 1.0 mol%, ΔV1mA increases.
becomes larger, and V40KA/V1mA also becomes larger.

[0010] Cobalt has a value of 0.0 in terms of Co2O3.
3 to 1.5 mol% is used. Also, manganese is M
0.2 to 0.8 mol% is used in terms of nO2. Part of cobalt and manganese is dissolved in zinc oxide particles as a solid solution, and part of it is precipitated in the grain boundary layer, thereby having the effect of increasing the height of the Schottky barrier. It is also thought to be related to the stability of the barrier. C
If the amount converted to o2O3 is less than 0.3 mol%, ΔV1mA becomes large, which is 1.5 mol%.
If it exceeds ΔV1mA, it also becomes large. Also,
If the amount converted to MnO2 is less than 0.2 mol%, the charging life will deteriorate, and if it exceeds 0.8 mol%,
As expected, the charging life will deteriorate.

[0011] It is preferable that the cobalt raw material contains Co3O4 in terms of improving properties, but in reality Co2
It is also possible to use mixtures of O3 and Co3O4.

[0012] Silicon is 4.0 in terms of SiO2
~10.0 mol% is used. Silicon precipitates in the grain boundary layer and has the effect of suppressing grain growth of zinc oxide particles. It is preferable to use amorphous silica because it improves reactivity and improves properties. The amount converted to SiO2 is 4.0 mo
If it is less than 1%, V40KA/V1mA also becomes large and the surge resistance deteriorates. This is 10.0 mol
%, ΔV1mA, V40KA/V1mA
becomes larger.

[0013] Nickel is converted to NiO from 0.3 to
2.5 mol% is used. The amount converted to NiO is
If it is less than 0.3 mol%, V40KA/V1mA
increases, and surge resistance deteriorates. If this exceeds 2.5 mol%, ΔV1mA
and V40KA/V1mA increase.

[0014] Aluminum is converted into Al2O3
0.002 to 0.02 mol% is used. Al2O
If the amount converted to 3 is less than 0.002 mol%, V40KA/V1mA becomes large and the surge resistance deteriorates. If this exceeds 0.02 mol%,
ΔV1mA increases.

[0015] Boron is 0.0 in terms of B2O3
001 to 0.05 mol% is used. B2O3
If the conversion amount is less than 0.0001 mol%, the energized life will deteriorate, and if it exceeds 0.05 mol%, ΔV1mA and V40KA/V1mA will increase. Silver is 0.0001 to 0.00 in terms of Ag2O.
05 mol% is used. The amount converted to Ag2O is 0.
If it is less than 0001 mol%, V40KA/V1
mA increases, and surge resistance deteriorates. This is
When it exceeds 0.05 mol%, ΔV1mA increases.

Both boron and silver have the effect of stabilizing the grain boundary layer. It is preferable to add silver-containing bismuth borosilicate glass because it improves the charging life. Note that the glass may also contain other metal oxides such as zinc oxide.

[0017] 0.0005 to 0.01 converted to K2O
5 mol% potassium and 0.0 in terms of Na2O
005 to 0.015 mol% of sodium is used. It has been found that these additions greatly affect the varistor characteristics. Whether adding only one or both of potassium and sodium, the amount of each added is 0.0005 to 0.015 m
Must be within the range of ol%. This addition amount is 0.
If it is less than 0.005 mol%, ΔV1mA becomes large, and if it exceeds 0.015 mol%, V40KA
/V1mA increases, and surge resistance deteriorates. If this total amount is 0.002 to 0.005 mol%, ΔV1mA becomes even smaller. Further, when one of them is added alone, ΔV1mA is smaller when sodium is added than when potassium is added. When both are added at the same time, ΔV1mA becomes smaller, but V40KA/V1mA becomes slightly larger than when added alone.

[0018]

[Example] To obtain a voltage nonlinear resistor containing zinc oxide as the main component, firstly, a zinc oxide raw material adjusted to a predetermined particle size, bismuth oxide, cobalt oxide (preferably Co3O4) and oxide manganese, antimony oxide,
A predetermined amount of additives such as chromium oxide, silicon oxide (preferably amorphous), nickel oxide, boron oxide, silver 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. Alternatively, the additive may be calcined at 800 to 1000°C, then pulverized and adjusted to a predetermined particle size, and mixed with the zinc oxide raw material. At this time, a predetermined amount of a binder (for example, an aqueous polyvinyl alcohol solution), a dispersant, and the like are added to these raw material powders. Aluminum is also preferably added in the form of an aluminum nitrate solution.

In order to incorporate sodium or potassium into the voltage nonlinear resistor, for example, an aqueous solution of sodium or potassium carbonate or nitrate is added to the raw material, or a glass containing sodium or potassium is added to the raw material. Good to add.

[0020] Next, vacuum degassing is preferably performed at a vacuum degree of 200 mmHg or less, and the water content of the mixed slurry is 30 to 35 mmHg.
wt%, and the viscosity of the mixed slurry is 100±5
It is preferable to set it to 0 cp. Next, the obtained mixed slurry was fed to a spray dryer to obtain an average particle size of 50 to 150 μm.
Preferably 80 to 120 μm and moisture content of 0
．． 5-2.0 wt%, more preferably 0.7-1.
Granulate 2wt% granulated powder. Next, the obtained granulated powder is subjected to a molding process under a molding pressure of 400 to 1000 kg.
/cm2 into a predetermined shape.

Next, the molded body is heated and cooled at a rate of 10 to 10
Organic components are removed by scattering at a temperature of 400 to 700° C./hr to obtain a degreased body. Next, the degreased body was heated at a rate of 30
~70℃/hr 800~1000℃, holding time 1~
It is fired for 5 hours to obtain a calcined body.

Next, a high resistance layer is formed on the side surface of the calcined body. In this example, bismuth oxide, antimony oxide, zinc oxide,
An insulating coating mixture paste prepared by adding an organic binder such as ethyl cellulose, butyl carbitol, or n-butyl acetate to a predetermined amount of silicon oxide or the like is applied to the side surface of the calcined body to a thickness of 30 to 300 μm.

Next, this temperature is raised and lowered at a rate of 20 to 100°C.
The main firing is carried out under the following conditions: /hr, maximum holding temperature of 1000 to 1300°C, preferably 1050 to 1250°C, for 3 to 7 hours.

[0024] Thereafter, a glass paste prepared by adding ethyl cellulose, butyl carbitol, n-butyl acetate, etc. as an organic binder to glass powder was applied to the high-resistance layer on the side surface for 50 minutes.
It is preferable to form a glass layer by applying the glass layer to a thickness of ~300 μm and heat-treating it in air at a temperature increase/decrease rate of 50-200° C./hr and a holding time of 0.5-2 hours at 400-550° C.

[0025] Thereafter, both end faces of the obtained voltage nonlinear resistor are polished with a diamond grindstone or the like. 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.

Next, according to the above manufacturing method, voltage nonlinear resistors having the compositions shown in the table below were manufactured. This resistor has a disk shape with a diameter of 47 mm and a width of 22.5 mm. However, amorphous silica was used for silicon, vitrified boron and silver, Co3O4 was used as a cobalt source, and aluminum nitrate solution was used for aluminum. V1mA per unit width is 330 to 500V/mm
is preferable, and 400 to 450 V/mm is more preferable. Further, V1mA/V10μA is preferably 1.5 or less.

Among the characteristics of the voltage nonlinear resistor, V10μ
A, V1mA, and V40KA indicate the limiting voltages generated between the electrodes on both end faces when currents of 10 μA, 1 mA, and 40 KA flow through the disc-shaped resistor, respectively. ΔV1mA is lightning surge (4/10μs,
Reverse direction V1mA change rate after application of 120KA, 2 times) (
%). Regarding surge resistance, lightning surge (4/
10μs, 120KA, 2 times) Pass rate after application (
%). Regarding the charging life, the temperature is 130℃,
Existence of thermal runaway after applying electricity for 1000 hours at a charging rate of 95% (
×), none (〇).

[0028]

[Table 1]

[0029]

[Table 2]

[0030]

[Table 3]

[0031]

[Table 4]

[0032]

Effects of the Invention As is clear from the above results, by following the present invention, the rate of change ΔV1mA of the varistor voltage after lightning surge application is small (less than 10%), and the limiting voltage ratio V40KA/V1mA (2 It is possible to provide a voltage nonlinear resistor with a small resistance (less than .1) and excellent surge resistance and energized life. This allows the lightning arrester to be made even more compact and lightweight.

Claims (1)

[Claims] [Claim 1] Bismuth converted into Bi2O3
0.3-1.2 mol%, antimony Sb2O
0.3 to 1.5 mol% in terms of chromium
0.3 to 1.0 mol% in terms of Cr2O3,
Cobalt converted to Co2O3 is 0.3 to 1.5
mol%, manganese converted to MnO2 0.
2 to 0.8 mol%, silicon converted to SiO2 4.0 to 10.0 mol%, nickel converted to NiO
Converting to 0.3-2.5 mol%, converting aluminum to Al2O3 0.002-0.02
mol%, boron converted to B2O3 0.000
1 to 0.05 mol%, 0.0001 to 0.05 mol% in terms of silver as Ag2O, and K2O
0.0005 ~ 0.015 mol% potassium and Na2O 0.0005 ~
1. A voltage nonlinear resistor, characterized in that it contains at least one of 0.015 mol% of sodium, and the remainder is zinc oxide.