JPS58220403A - Method of producing voltage nonlinear resistor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to voltage non-linear resistors, particularly nickel oxide (Nip
) as one of the additive components.

A zinc oxide sintered voltage nonlinear resistor containing small amounts of Bi2O3 and Co2O3° in zinc oxide powder is obtained.

It is well known that the characteristics of these voltage nonlinear resistors are approximately expressed by the following equation.

However, a is a nonlinear index, and C is a nonlinear resistance value, which is usually expressed as a voltage when a certain DC current is passed through an element having a thickness of 1+o+. For example, when a current of 1 mA is applied, the voltage between the two poles of the element is expressed as v, nlmA,
The voltage between both electrodes when a current of 40A flows is v4oA
It is expressed as

Voltage nonlinear resistors that exhibit these characteristics are used not only for voltage stabilization, but also for surge absorption, such as absorbing high voltage surges that enter power supply circuits and protecting other electronic components from them. There is a use as. When used for the latter purpose of absorbing surges, nonlinear characteristics especially in the high current range become important.

The nonlinear characteristics of the zinc oxide sintered nonlinear resistor are believed to be due to the thin high-resistance layer formed between the Zn sheets within the sintered body. That is, when a voltage is applied to the element,
Almost no electric field is applied to ZnO, which is a material with good electrical conductivity, and the electric field is concentrated on the thin high-resistance layer between ZnO fi elements, and due to the high electric field, the voltage-current characteristic has a remarkable non-linear characteristic. appears.

However, when a particularly large current, such as a surge current, attempts to flow through the element, the resistance within the ZnO particles, which was hardly a problem in the low current range, becomes extremely non-negligible as the total resistance within the element. The electric field is applied not only to the grain boundary layer but also to the ZnO particles.

If the resistance value of ZnO is large, non-linear resistance characteristics in a high current range will be impaired. It is believed that the drowsy conductivity of ZnO particles appears as a result of an imbalance between the numbers of Zn atoms and zero atoms in the ZnO crystal. In this case, extra Zn atoms interstitialize between the lattice points consisting of Zn atoms and O atoms, and one child provided by the Zn atoms circulates within the crystal, thereby
It is said that O crystal is an n-type semiconductor. Therefore, the drowsiness conductivity of this ZnO crystal depends on the number of interstitial Zn atoms, and the higher the number, the higher the drowsiness conductivity.

Now, when considering the ZnO crystal in a zinc oxide sintered voltage nonlinear resistor, in order to have excellent voltage nonlinear characteristics in a high current range, the number of 0 atoms must be proportional to the number of Zn atoms. It can be said that it is desirable to have a slightly smaller amount. CO atom,
It is thought that the same concept can be applied to the ZnO crystal phase in a practical sintered body in which Mn atoms and the like are dissolved. Therefore, an important issue is how to obtain a sintered body having a ZnO crystal phase that is slightly deficient in zero atoms as described above.

The present invention meets the above requirements and provides a method for manufacturing a zinc oxide sintered voltage non-linear resistor for obtaining a sintered body with excellent voltage non-linear resistance characteristics in a high current range.

That is, the present invention aims to provide a method for obtaining a zinc oxide sintered body having a substituent oxide crystalline phase and a low resistance value. Here, there are various methods to lower the resistance of the ZnO crystal phase in the zinc oxide sintered body.
Also, the present invention relates to a zinc oxide sintered body to which N i O is added as one of the additives, and is intended to reduce the resistance of the ZnO crystal phase within the sintered body. This was achieved by pre-treating the additive N i O powder.Hereinafter, the manufacturing method of the present invention will be described by way of examples and comparative examples.

<Example 1> A commercially available nickel oxide (Nip) reagent was heated at 30'O
°C, 5001:, 600 °C, 7oO °C.

After heat treatment at each temperature of 800° C. for 2 hours and cooling with O, pulverization was performed to prepare six types of Ni bodies.

Next, 97 mol of zinc oxide (ZnO) powder, a commercially available reagent,
Add 0.5 molt of nickel oxide (NiO) heat-treated at 30C) to 0.5 molt of bismuth oxide (Bt203) o, s molt, acid □), mix well, and form a mixture with a thickness of 1. 2 ttan and a diameter of 23 mm, and sintered in air at 1360° C. for 1 hour. The temperature increase rate and temperature decrease rate were each ±100°C/hour. Silver electrodes having an area of 2.3 C were baked onto both the front and back surfaces of the sintered body thus obtained.

For the sample obtained as above, measure the values of v and rnA using a DC constant current power supply, then measure the value of v4°A using a nozzle power supply, and then calculate v4oA/v1tn.
The value of A was determined. Same procedure at 400℃.

A sintered body was made using N i O powder heat-treated at temperatures of 500°C, 600°C, 7oO°C, and 8oO°C, and v
The value of 4oA/v1mA was determined.

Figure 1 shows the heat treatment temperature and limiting voltage ratio for NiO.
4°A/vlmA is shown. As is clear from this figure, the value of v4°A/vlmA decreases when the heat treatment temperature for NiO is 400°C or higher, and is 6o.

Minimum at °C. Further, as the heat treatment temperature of NiO becomes higher, the value increases. Note that NiO without heat treatment
When using , the value of v4゜A/v4mA is 2.30
Met.

<Example 2> Page 7 A commercially available nickel oxide (Nip) reagent was prepared in advance at 300°C, 400°C, 500°C, and 600 Tl in N2 gas.
700111: Heat treated at each temperature of 800°C for 2 hours, cooled, and crushed to prepare 6 types of Ni bodies. Using these two NiO powders, the same procedure as in Example 1 was carried out. Make a sintered body, and its limiting voltage ratio ■4oA/v,
n1mA was determined. FIG. 2 shows the relationship between the heat treatment temperature applied to NiO and the limiting voltage ratio. As is clear from the figure,
As in Example 1, from 400°C to v4°A/v4m
The value of A decreases and reaches a minimum at 600°C, and increases as the temperature rises further. The tendency is similar to that in Example 1.

<Comparative example> A commercially available nickel oxide (Nip) reagent was pre-incubated in air for 30 min.
0'C, 400℃, 500℃, 6oO℃.

After heat treatment at 700° C. and 800° C. for 2 hours, the mixture was cooled and pulverized to obtain six types of nickel oxide (Nip) powders. Using these nickel oxide (Nip) powders, the same procedure as in Example 1 was carried out in the same manner as in JP-A-58-220403.
(3) Create zinc oxide sintered bodies with the same composition ratio, and set the limiting voltage ratio v
4°A/v1mA was determined. Figure 3 shows heat treatment temperature and v4
The relationship with the value of °A/V1mA is shown. As is clear from the figure, although the value of v4oA/■1mA reaches its minimum at 600°C, its effect is smaller than that of the above embodiment.

Based on the above examples and comparative examples, we have explained how the heat treatment applied to nickel oxide in advance affects the limiting voltage ratio of the zinc oxide sintered body.
N in atmospheres with different composition ratios of mixed gases of and 02
As a result of examining the effect of iOO heat treatment, we found that even if Nio is heat treated in a weakly oxidizing atmosphere,
It was found that the same effect as mentioned above was obtained.

In addition, in the Examples and Comparative Examples, zinc oxide sintered bodies were made according to the same compounding ratio in order to compare data with each other, but of course, the heat treatment effect on NiO appears only in the case of this compounding ratio. However, it is not impossible to obtain zinc oxide sintered bodies even when producing zinc oxide sintered bodies with other blending ratios.

Heat treatment temperature attached to N i O from 400℃ to 600℃
As the power is increased, the value of ■4oA/■4mA tends to decrease. This is due to the increase in temperature.

As a result of the gradual removal of adsorbed oxygen or structural oxygen,
This is thought to be because the resistance value of zinc oxide in the zinc oxide sintered body became low. However, the reason why the value of 4oA/v1mA becomes large due to heat treatment at a temperature higher than 600° C. is currently not clear.

As explained above, the method according to the present invention is characterized in that nickel oxide powder as a raw material is previously subjected to heat treatment at 400°C to 700'C in a neutral, weakly reducing, or weakly oxidizing atmosphere. shall be. This method is effective in lowering the electrical resistance of the zinc oxide crystal phase in the zinc oxide sintered body, improving the nonlinear resistance characteristics of the device in the large current range, and preventing surge current absorption. Therefore, it is possible to obtain a device with excellent characteristics.

[Brief explanation of the drawing]

1 and 2 are NiO
FIG. 3 is a diagram showing the relationship between the heat treatment temperature applied to NiO and the limiting voltage ratio to explain the effect of the comparative example. Name of agent: Patent attorney Toshio Nakao and 1 other person
1 Fig. 1 processing IFX (・to 1 Fig. 2 1 place grip

Claims (1)

[Claims] When manufacturing a sintered non-linear resistor mainly composed of zinc oxide containing nickel oxide (NIP), the raw material oxidation-7 Kel is preheated at 400°C to 400°C in a weakly reducing, neutral or weakly oxidizing atmosphere. A method for manufacturing a voltage nonlinear resistor, the method comprising performing heat treatment at a temperature within a range of 700°C.