JPH0354441B2 - - 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 in particular 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 (varistors) have been researched in the past, and one of them uses a sintered body mainly composed of ZnO. There is. this
In products using sintered bodies containing ZnO as a main component, attempts have been made to obtain desired characteristics by adding various subcomponents. Recently, research and development on direct current power transmission has been carried out, but unlike in the case of alternating current 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, JP-A-49-
Bi ₂ O ₃ , CoO, ZnO shown in No. 119188
Added Sb ₂ O ₃ , NiO, MnO, Special Publication 1977-
19472, in which B and Bi are added, and ZnO, shown in Japanese Patent Publication No. 56-33842, in which glass containing boron oxide is added, etc., but both are sufficient. characteristics have not been obtained. For example, leakage current increases with time when direct current is applied, resulting in thermal runaway and poor direct current life characteristics. 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 uses zinc oxide as a main component, and bismuth, cobalt, manganese, antimony, and nickel as subcomponents, respectively Bi ₂ O ₃ , Co ₂ O ₃ , MnO, Sb ₂ O ₃ ,
In terms of NiO, Bi ₂ O ₃ 0.1-5 mol%, Co ₂ O ₃ 0.1-5 mol%, MnO 0.1-5 mol%, Sb ₂ O ₃ 0.1-5 mol%, NiO 0.1-5 mol%, and aluminum, indium and potassium, at least one selected from Al ³⁺ , In ³⁺ ,
For the basic composition containing 0.0001 to 0.05 mol% or less in terms of Ga ³⁺ , boron is included in terms of B ₂ O ₃ .
This is a method for manufacturing a voltage/current nonlinear resistor, characterized in that glass containing boron is added and sintered so that the glass contains boron in an amount of 0.001 to 1 wt%. As mentioned above, Bi ₂ O ₃ , Co ₂ O ₃ , MnO, Sb ₂ O ₃ ,
By adopting a composition in which glass containing B is added to NiO as a basic component containing at least one of Al, In, and Ga, the DC life characteristics are significantly improved. It also has excellent life characteristics and nonlinear characteristics when AC is applied. In the present invention, Bi ₂ O ₃ , Co ₂ O ₃ , MnO,
Sb ₂ O ₃ and NiO were set at 0.1 to 5 mol% each because
This is because if it deviates from this range, the nonlinear characteristics and life characteristics will deteriorate. Al ³⁺ , In ³⁺ , Ga ³⁺ is 0.0001mol%~0.05mol
Effective within a range of %. 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. 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. By adding glass containing B to this basic composition, various properties are improved, and in particular, the DC life is significantly improved. In other words, if only the basic composition is used, the leakage current will increase over time when DC voltage is applied, causing thermal runaway, and it is impossible to use it for _{DC applications} . %, the change in leakage current over time is reduced, and the DC life characteristics are dramatically improved.
If the amount is less than 0.001 wt%, the effect of adding B-containing glass will not appear, and if it is added at 0.001 wt% or more, the DC life characteristics will be particularly improved. If it exceeds 1wt%, it not only deteriorates the DC life characteristics, but also deteriorates the AC life and non-linear characteristics.
Even in the case where Al etc. are not included, the DC life can be improved to some extent by adding B-containing glass, but this not only deteriorates the non-linear characteristics but also leads to a significant decrease in discharge capacity. When a voltage nonlinear resistor is used in a device intended to absorb large surges, such as a power surge arrester, it is particularly required to have an excellent energy handling capacity per unit volume. Generally, in order to express the energy handling capacity of a voltage nonlinear resistor with a specific numerical value, a 2 ms current rectangular wave is applied and the rectangular wave discharge capacity per unit volume is used. (For test methods, see JEC-
203P.43) In other words, if the discharge withstand capacity is small, applying a large current impulse to a voltage nonlinear resistor will cause creeping flash or through-breakage, and the original purpose of surge absorption will not be achieved. In addition, the performance of lightning arresters etc. will be greatly reduced. In a system that does not contain Al, In, or Ga, this discharge withstand capacity becomes small. [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 voltage 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 below. Bi ₂ O ₃ , Co ₂ O ₃ , MnO,
Glass containing Sb ₂ O ₃ , NiO, Al(NO ₃ ) _{3.9H 2} O and B is prepared and mixed in the desired composition ratio, then PVA is added as a binder, granulated, and formed into a disc-shaped plate. did. After drying this plate material 1100~1300℃ 2 hours
After firing to a certain degree, both sides were polished to form a sintered body with a diameter of 20 mm and a thickness of 2 mm. The glasses used are shown in Table 1. Electrodes were provided on both sides of this sample by Al spraying to form an electrode current nonlinear resistor, and various characteristics were measured. The results are shown in Table 2. In Table 2, compositions outside the scope of the present invention are also shown as comparative examples. In Table 2, the voltage-current nonlinear characteristics are shown as 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 90°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). Note that the x mark in the table indicates that thermal runaway occurred within 400 hours.
In addition, the glass types shown in Table 1 in Table 2
No. was used.

【table】

【table】

[Table] As is clear from Table 2, in the examples of the present invention, DCI(400)/I(0) is small and the DC life is excellent. Other characteristics are
AC life ACI(400)/I(0), nonlinearity V _2KA /
It can be seen that both V _1nA are also excellent. As is clear from the comparative examples (Samples No. 38 and 39), if the amount of glass added is small, the DC life will be inferior.
If it is too large, not only the DC life but also the AC life and nonlinearity will deteriorate. Furthermore, as is clear from the comparative examples (sample Nos. 40 and 41), even when a suitable amount of glass is contained, Al
If the amount is outside the range, the nonlinear characteristics will be greatly degraded, and especially if the amount of Al is too large, thermal runaway will occur in both AC and DC applications. Furthermore, when Al is low, the life characteristics are inferior, although this is not as noticeable as when Al is high. Furthermore, if the amount of Al is outside the range, the discharge withstand capacity will be significantly degraded. Table 3 shows Al in the composition system of sample No. 16.
Shows the discharge capacity when changing the amount. Similarly, FIG. 1 shows a discharge withstand characteristic diagram. As is clear from Table 3 and Figure 1, it is about 250J/ ^cm3 within the scope of the present invention, but if it is outside the range.
Extremely poor, at around 200J/cm3 or ^less .

[Table] The same effect as Al could be obtained with In and Ga. The results are shown in Table 4. The manufacturing method is the same as described above.

【table】

[Table] As is clear from Table 4, In and Ga are similar to Al, and by adding glass containing B, a varistor with particularly excellent DC life can be obtained. Bi ₂ O ₃ in voltage-current nonlinear resistor according to the invention
When we examined the crystal structure of this material, we found that an α phase (orthorhombic system) was formed. The ratio of this α phase in the total Bi ₂ O ₃ changes depending on manufacturing conditions such as temperature and composition.
We investigated the change in characteristics depending on the ratio of α phase and found that if the amount of α phase (Rα) in the total amount of Si ₂ O ₃ is 10% or more, more preferably 30% or more, especially 50% or more, the DC life characteristics will be affected. It turned out to be excellent. This tendency is the same in the composition range of the present invention,
The same was true for Al ³⁺ , In ³⁺ , and Ga ³⁺ . However, when the basic components were different, the α phase did not occur. For example, ZnO−Bi ₂ O ₃ −Co ₂ O ₃ −MnO−
Even when B ₂ O ₃ was added to the basic component of NiO−Sb ₂ O ₃ plus Cr ₂ O 3 and SiO ₂ , α phase did not occur, and _neither nonlinearity nor life characteristics were improved. Nakatsuta. Moreover, this α phase changes into another phase by heat treatment. Therefore, it is desirable not to add a process that includes heating to an extent that changes this crystal phase. Particularly in the case of DC application, L ₄₀₀ is improved at Rα10, and settles to a nearly constant value at Rα30, especially Rα50. If Rα is small, thermal runaway will occur. B
When no glass is added, Rα=0,
With the addition of B-containing glass, an α phase begins to form. Table 5 shows the relationship between the amount of α phase in the sample and the properties. The amount of α phase was defined by Rα shown below. Rα≡I(α)/I(α)+I(β)+I(γ)+I(
δ)×100 (I(α): Maximum intensity by X-ray diffraction I(β): 〃 I(γ): 〃 I(δ): 〃 α (orthorhombic system), β (tetragonal system) γ( body-centered cubic system), δ (face-centered cubic system))

[Table] Similarly, ACL ₄₀₀ due to changes in Rα (dashed line), D.
Figure 2 shows the change in CL ₄₀₀ (solid line). As is clear from the figure, thermal runaway occurs when DC is applied in a region where Rα is less than 10. At about Rα30
ACL ₄₀₀ is stable, and DCL ₄₀₀ is also stable at around Rα50.

[Brief explanation of drawings]

Figures 1 and 2 are characteristic curve diagrams.

Claims (1)

[Claims] 1 Main component is zinc oxide, and subcomponents are bismuth, cobalt, manganese, antimony, and nickel, respectively Bi ₂ O ₃ , Co ₂ O ₃ , MnO, Sb ₂ O ₃ , and NiO
In terms of, Bi ₂ O ₃ 0.1-5 mol%, Co ₂ O ₃ 0.1-5 mol%, MnO 0.1-5 mol%, Sb ₂ O ₃ 0.1-5 mol%, NiO 0.1-5 mol%, and further aluminum, indium and At least one selected from gallium is Al ³⁺ , In ³⁺ ,
While the basic component contains 0.0001 to 0.05 mol% in terms of Ga ³⁺ , boron contains 0.001 to 0.001 in terms of B ₂ O ₃ .
A method for manufacturing a voltage/current nonlinear resistor, which comprises adding glass containing boron to a content of 1 wt% and sintering the glass.