JPS6329801B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a voltage nonlinear resistor made of an oxide semiconductor. One of the circuit elements using semiconductors is a voltage nonlinear resistor, and a typical example is a varistor made of a sintered body of ZnO with various oxides added thereto. This type of varistor has non-linear voltage-current characteristics, and as the voltage increases, the resistance rapidly decreases and the current increases significantly, so it is widely used for absorbing abnormal overvoltages and stabilizing voltage. It is put into practical use. By the way, the characteristics of a voltage nonlinear resistor are generally evaluated using the voltage-current characteristics expressed by the following approximate expression. I=(V/C)〓 (where I is the current flowing through the varistor, V is the applied voltage, C is a constant, and α is a nonlinear coefficient) Therefore, the general characteristics of a varistor can be expressed using two constants, C and α. can be used, usually instead of C.
It is expressed as a voltage V of _1nA at 1mA, and emphasis is placed on a large α value, which is an index indicating voltage nonlinear characteristics. The above-mentioned ZnO-based varistor (voltage nonlinear resistor) has the above-mentioned characteristics of good voltage-current characteristics, and furthermore, the voltage-current characteristics can be arbitrarily adjusted by controlling the thickness of the element. But on the other hand these
When using ZnO-based varistors as power surge arresters, there are the following drawbacks. That is, in the conventional ZnO-based voltage nonlinear resistor, the characteristics change greatly in the small current region when constantly energized, and the rate of change of the varistor voltage is large when an impact current is applied. Furthermore, the nonlinearity in the large current region was insufficient and could not be said to be satisfactory. In order to eliminate the drawbacks of conventional ZnO-based nonlinear resistors, it is generally necessary to add several oxides to the basic composition of ZnO with various oxides added. , methods of adding various glass components have been adopted. However, even if the nonlinearity in the large current range is improved by adding oxides, the characteristics in the small current range due to constant current application or impact current are large, resulting in a lack of reliability. Furthermore, improving characteristics using various glass components is effective in changing characteristics in the small current region due to constant voltage application, but
With regard to shock current characteristics and nonlinearity in a large current range, it is ineffective or even has an adverse effect, and cannot be said to be sufficient for use as a power surge arrester. The present inventors conducted various studies in view of these points, and as a result, ZnO was used as the main component, and as a subcomponent,
Bi ₂ O ₃ , Co ₂ O ₃ , Sb ₂ O ₃ , MnO, Cr ₂ O ₃ , SiO ₂ and
By adding at least one of K ₂ O and Ag ₂ O to the basic composition system consisting of at least one of NiO and Al ₂ O ₃ , it is highly reliable.
We have discovered that an oxide voltage nonlinear resistor with excellent nonlinearity in a large current range can be obtained. Hereinafter, the details of the present invention will be explained with reference to Examples. Example 1 ZnO contains 1.0 mol% each of Bi ₂ N ₃ and Sb ₂ O ₃ , 0.5 mol% each of Co ₂ O ₃ , SiO ₂ , NiO, MnO, Cr ₂ O ₃ , and 0.01 mol % of Al ₂ O ₃ % as the basic composition, at least one of K ₂ O and Ag ₂ O is added and blended thereto in a ratio of 0.05 to 5 mol %, and thoroughly mixed in a ball mill to obtain a prepared powder. Polyvinyl alcohol was blended with the thus obtained prepared powder as a binder, and each was molded into a disk shape with a diameter of 55 mm at a pressure of 1 ton/cm, and these molded bodies were fired at 1200°C in an air atmosphere to obtain a sintered body. Ta. Both main surfaces of the thus obtained sintered bodies were polished parallel to each other to a thickness of 20 mm, and then Al was sprayed onto the polished surfaces to obtain a voltage nonlinear resistor equipped with electrodes. The nonlinearity in the large current range of the voltage nonlinear resistor thus obtained is determined by the voltage when a current of 10KA is passed through the element (V _10KA ) and the voltage when a current of 1mA is passed through the element (V _1nA ). Figure 1 shows the relationship between the amounts of K ₂ O and Ag _{2 O} added to _the basic composition. Furthermore, Fig. 2 shows the change in characteristics in the small current range due to the impact current. The rate of voltage change was expressed as the rate of change before and after application of an impulse current of voltage V _{10 nA} when a current of 10 mA was passed through the element. In addition, the impact current is 8 x 20μS
10KA was applied 10 times at 30 second intervals. Furthermore, Figure 3 shows the change in characteristics in the small current region when constant voltage is applied.
The voltage of ×V _1nA is shown as the rate of change of V _10nA before and after 500 hours of application. In Figures 1 to 3, curve a is for the case where Ag ₂ O is added to the basic composition, curve b is for the case when K ₂ O is similarly added, and curve C is for the case where Ag ₂ O and K ₂ O are added. This is a case where O is added in a composite manner at a molar ratio of 1:1. As is clear from FIG. 1, when at least one of Ag ₂ O and K ₂ O is added to the basic composition, the nonlinearity in the large current range is significantly improved. Furthermore, from Fig. 2, the stability of the characteristics in the small current region due to the application of an impulse current is significantly improved, and as is clear from Fig. 3, the stability of the characteristics in the small current region when the current is constantly applied is improved. has also been significantly improved. These remarkable improvements in nonlinearity, shock current characteristics, and constant charging characteristics in the large current range are essential elements when applying nonlinear resistors to lightning arresters, etc., and the voltage nonlinear resistor of this example These factors are fully satisfied. Note that the effect of this example is the first
As is clear from Fig. 3, at least one of K ₂ O and Ag ₂ O is added to the basic composition by 0.05 to 5.
This is always exhibited when the compound is added in mol%. Example 2 Bi ₂ O ₃ and Co ₂ O ₃ , MnO, Cr ₂ O ₃ were added to ZnO in an amount of 0.05 to 2 mol %, and Sb ₂ O ₃ was added in an amount of 0.1 to 3 mol %.
0.05-5 mol% of SiO ₂ , 0.05-2 mol% of at least one of NiO and Al ₂ O ₃ , 0.001-2 mol% each
For the basic composition system containing 1 mol% addition,
At least one of Ag ₂ O ₃ and K ₂ O, respectively
Addition of 0.5 mol % was carried out under the same conditions as in Example 1 to obtain 27 types of voltage nonlinear resistors, including reference examples. The nonlinearity and impact current characteristics in the large current range of the voltage nonlinear resistor thus obtained, and the small current range characteristics after constant voltage application are shown in Table 1 together with the composition ratio. Table 1 shows V _10KA /V _1nA and the rate of change in V 10nA due to impulse current application, and the rate of change in V _10nA due to constant voltage application.
The rate of change in V _10nA was measured based on the conditions described in Example 1.

[Table] As is clear from Table 1, in all of these examples, the nonlinearity in the large current range and the stability of the characteristics in the small current range during application of shock current and constant voltage application are significantly improved. . In other words, the basic composition is ZnO as the main component,
Bi ₂ O ₃ and Co ₂ O ₃ , MnO, Cr ₂ O ₃ respectively
0.05-2 mol%, Sb ₂ O ₃ 0.1-3 mol%, SiO ₂
At least one of K ₂ O and Ag ₂ O is added even when changing 0.05 to 5 mol % and at least one of NiO and Al ₂ O ₃ to 0.05 to 2 mol % and 0.001 to 1 mol %, respectively. By blending, the effects of the present invention are always exhibited. As described above, according to the present invention, it is possible to obtain an oxide nonlinear resistor that has excellent nonlinearity in a large current range and also has excellent reliability during application of an impact current and constant voltage application.

[Brief explanation of drawings]

1 to 3 are curve diagrams showing characteristic examples of the oxide voltage nonlinear resistor according to the present invention.

Claims (1)

[Claims] 1. Zinc oxide as the main component, at least one of nickel and aluminum as subcomponents, and bismuth, cobalt, antimony, manganese, chromium and silicon, respectively NiO, Al ₂ O ₃ and Bi ₂ O ₃ ，
In terms of Co ₂ O ₃ , Sb ₂ O ₃ , MnO, Cr ₂ O ₃ and SiO ₂ , NiO 0.05-2 mol% Al ₂ O ₃ 0.001-1 mol% Bi ₂ O ₃ 0.05-2 mol% Co ₂ O ₃ 0.05 to 2 mol% MnO 0.05 to 2 mol% Cr ₂ O ₃ 0.05 to 2 mol% Sb ₂ O ₃ 0.1 to 3 mol% SiO ₂ 0.05 to 5 mol% The raw material contains at least potassium and silver. Converting one type to K ₂ O and Ag ₂ O is 0.05~
An oxide voltage nonlinear resistor characterized by being formed by sintering a composition containing 5 mol%.