JPH0576761B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a voltage-current non-linear resistor made of a sintered body containing zinc oxide (ZnO) as a main component, and particularly to a voltage-current non-linear resistor that has excellent life characteristics when DC current is applied. . [Technical background of the invention and its problems] Various voltage-current non-linear resistors (oxide varistors) have been studied, but one of them is
Some use a sintered body containing ZnO as the main component.
In products using this sintered body mainly composed of ZnO, attempts have been made to add various subcomponents to obtain desired characteristics. Recently, research and development on DC power transmission has been carried out.
Unlike in the case of AC power transmission, a unidirectional electric field is always applied to a nonlinear resistor, resulting in extremely harsh conditions. At present, a voltage-current nonlinear resistor with excellent DC life characteristics that can withstand such harsh conditions has not been obtained. For example, Bi ₂ O ₃ , CoO, Sb ₂ O ₃ ,
Those with NiO and MnO added, those with B and Bi added to ZnO shown in Japanese Patent Publication No. 46-19472,
A method in which glass containing boron oxide is added to ZnO is known, as shown in Japanese Patent Publication No. 56-33842, but none of them have sufficient properties. For example, leakage current when applying DC voltage increases with time,
Thermal runaway occurred and the DC life characteristics were poor. Furthermore, as power transmission has become increasingly high voltage (UHV) in recent years, the required characteristics, such as voltage-current nonlinear characteristics and life characteristics, have become more severe. As described above, the demand for improvements in various properties such as life characteristics and nonlinearity is increasing year by year, and research is being conducted in various places to satisfy these demands. [Object of the invention] The present invention has been made in consideration of the above points, and
The purpose of the present invention is to provide a voltage-current nonlinear resistor with excellent DC life characteristics. A further object of the present invention is to provide a voltage-current nonlinear resistor with excellent voltage-current nonlinear characteristics. [Summary of the Invention] The present invention provides a voltage-current nonlinear resistor characterized in that non-stoichiometric bismuth oxide is contained in a sintered body containing zinc oxide as a main component and at least bismuth oxide as a subcomponent. It is. Nonstoichiometric bismuth oxide has a composition deviating from Bi ₂ O ₃ in stoichiometric ratio, and Bi ₂ O _2.33 and Bi ₂ O _2.75 are known. This sintered body mainly composed of zinc oxide and containing non-stoichiometric bismuth oxide has excellent varistor properties such as nonlinearity and life characteristics. The non-stoichiometric bismuth oxide in the voltage-current non-linear resistor according to the present invention is produced by a firing process, a heat treatment process,
The proportion of bismuth in total bismuth oxide changes depending on manufacturing conditions such as firing atmosphere, heat treatment atmosphere, and composition. However, due to the small amount of the non-stoichiometric compound and the close interplanar distance to other phases of bismuth oxide,
It is difficult to distinguish the non-stoichiometric phase by line diffraction, so identification was done by electron beam diffraction. Therefore, it is not possible to quantitatively determine the ratio of non-stoichiometric bismuth oxide to the total amount of Bi ₂ O ₃ , but when we investigated the relationship between the presence or absence of non-stoichiometric bismuth oxide and non-linear characteristics, AC and DC life characteristics in various compositions, we found that it is variable. Those containing specific bismuth oxide showed superior properties compared to those containing no specific bismuth oxide. Sub-components of the sintered body include MnO, NiO,
_Co2O3 , _{Sb2O3 , MgO ,} BaO, _Fe3O4 , _{B2O3 ,}
There are various materials such as Al ₂ O ₃ , SnO ₂ , SiO ₂ , Ag ₂ O, etc., but the following compositions are particularly preferred because they have excellent varistor properties. That is, bismuth, cobalt, manganese, antimony, and nickel are added as subcomponents.
Bi ₂ O ₃ , Co ₂ O ₃ , MnO, Sb ₂ O ₃ and 0.1 to 5 mol% in terms of NiO, respectively, and at least one selected from aluminum, indium and gallium is Al ³⁺ , In ³⁺ , 0.0001 to 0.05mol converted to Ga ³⁺
% and further contains boron as an accessory component of 0.001 to 1wt% in terms of B ₂ O ₃ with respect to the basic component including zinc oxide and the above-mentioned accessory components. It is the body. Since the voltage-current nonlinear resistor having such a composition is excellent in various varistor characteristics, it becomes even more excellent by including the non-stoichiometric bismuth oxide according to the present invention. Bi ₂ O ₃ , Co ₂ O ₃ , MnO, Sb ₂ O ₃ , NiO 0.1 to 5 mol% each, Al ³⁺ , Ga ³⁺ , In ³⁺ 0.0001 to 5 mol%
The reason why B ₂ O ₃ was set at 0.05 mol % and 0.001 to 1.0 wt % is because, outside this range, the deterioration of each property becomes large and the effect of containing non-stoichiometric bismuth oxide is not manifested. Each of the above components is a converted value, and can be added in various forms such as carbonate. For example, various types of boron can be added, such as B ₂ O ₃ ,
H ₃ BO ₃ , HBO ₂ , B ₂ (OH) ₄ , ZnB ₄ O ₇ , AgBO ₂ ,
Ag ₂ , B ₄ O ₇ , BaB ₄ O ₇ , Mg(BO ₂ ) ₂・8H ₂ O,
_MnB4O7・_8H2O , _{BiBO3 , Ni3} ( _BO3 ) ₂ ,
Examples include Ni ₂ B ₂ O ₅ and the like. Considering uniform mixing of raw materials, it is preferable to use a boron component that is easily soluble in water and to mix it as an aqueous solution. For example H ₃ BO ₃ , HBO ₂ , B ₂
(OH) ₄ , ZnB ₄ O ₇ , ammonium boron, AgBO ₂ ,
Ag ₂ B ₄ O ₇ etc. are listed as easily soluble in water. Al ³⁺ , In ³⁺ , and Ga ³⁺ exhibit their effects in a range of 0.05 mol% or less. Al ³⁺ etc. can be effective when added in a trace amount, but especially when added in an amount of 0.0001 mol % or more, excellent effects are achieved. Moreover, if there is too much of it, the characteristics will deteriorate on the contrary. In particular, the effect of containing Al ³⁺ etc. on nonlinear characteristics is significant. In this case as well, as described above, since the effect of improving properties can be obtained with a very small amount, it is preferable to mix and add a compound easily soluble in water, such as a nitrate, as an aqueous solution. [Effects of the Invention] As explained above, according to the present invention, a voltage-current nonlinear resistor with excellent DC life characteristics can be obtained. The resistor of the present invention also has excellent nonlinear characteristics and AC life characteristics. Therefore, it is effective as a lightning arrester as a surge absorber for DC high voltage power transmission. It is also effective for AC power transmission. It is particularly suitable for UHV applications. or,
Since both direct current and alternating current applications can be manufactured on the same line, there are great manufacturing advantages such as cost reduction. In addition, because it has excellent characteristics,
It is also effective as a consumer device. [Embodiments of the Invention] Examples of the present invention will be described above. Bi ₂ O ₃ , Co ₂ O ₃ , MnO,
Sb ₂ O ₃ , NiO, Al(NO ₃ ) _{3.9H 2} O are prepared in a desired composition ratio, an aqueous solution in which H ₃ BO ₃ is dissolved in a desired ratio as a B-containing compound is added, and after mixing, PVA was added as a binder, granulated, and formed into a disc-shaped plate. After drying this plate material, the firing conditions and heat treatment conditions were varied to create plates of various compositions, with and without non-stoichiometric bismuth oxide. Both sides of the obtained sintered body were polished to a diameter of 25 mm and a thickness of 2.5 mm.
And so. Electrodes were provided on both sides of this sample by Al spraying to form a voltage-current nonlinear resistor, and various characteristics were measured. The results are shown in Table 1. In Table 1,
The voltage-current nonlinear characteristics are V _2KA /V _1nA , and the life characteristics are
Shown as L ₄₀₀ . Moreover, the amount of B was converted into B ₂ O ₃ and expressed as a weight ratio to the basic components. V _2KA /V _1nA = V (voltage when 2KA current is applied) / V (voltage when 1mA current is applied) L ₄₀₀ = I (400) / I (0) I (400) is the ambient temperature of 95°C, and the DC If
This is the leakage current measured at room temperature after applying a voltage of 0.75×V _1nA for 400 hours, and in the case of AC, it is 0.85×
This is the leakage current measured at room temperature after applying a voltage of V _1nA for 400 hours. I(0) is the initial value,
L ₄₀₀ was expressed as the ratio of I(400) and I(0). Identification of non-stoichiometric bismuth oxide was performed by electron diffraction, using ASTM cards 27-49 (Bi ₂ O _2.75 ), 27-51.
(Bi ₂ O _2.33 ) was used. However, since bismuth oxide dissolves other subcomponents in solid solution, the value of the distance between the two is
Does not necessarily match the ASTM card value, ±3%
There is a range of degrees. Note that Table 2 shows the manufacturing conditions for each sample. Third
The table is a table that proves the symbols in Table 2. If the temperature increase/decrease rate is made faster than the normal rate,
Non-stoichiometric compounds exist. Also, non-stoichiometric compounds are likely to be produced when the oxygen partial pressure is low, but when the oxygen partial pressure is low, the characteristics themselves deteriorate.

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[Table] As is clear from Table 1, the sintered body containing non-stoichiometric bismuth oxide has a higher
It can be seen that the nonlinear characteristics and AC and DC life characteristics are excellent. Although numerically small, the effect is enormous. In addition to bismuth as the above-mentioned subcomponents, cobalt,
Although manganese, antimony, nickel, aluminum, and boron were selected, the effect of improving properties by non-stoichiometric bismuth oxide is the same in the case of combinations of other subcomponents.

Claims (1)

[Claims] 1 Bi ₂ O _2.33 in a sintered body containing zinc oxide as a main component and at least bismuth oxide as a subcomponent.
and Bi ₂ O _2.75 . 2 The sintered body contains bismuth, cobalt, manganese, antimony, and nickel as subcomponents.
0.1 to 5 mol% in terms of Bi ₂ O ₃ , Co ₂ O ₃ , MnO, Sb ₂ O ₃ and NiO, respectively, and at least one selected from aluminum, indium and gallium is Al ³⁺ , In ³⁺ , 0.0001~ converted to Ga ³⁺
It contains 0.05mol%, and in addition to the basic component including zinc oxide and the above-mentioned subcomponents, boron is added as a subcomponent.
The voltage-current nonlinear resistor according to claim 1, characterized in that the content is 0.001 to 1 wt% in terms of B ₂ O ₃ .