JPS60169106A - 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 Technical Field The present invention relates to a voltage nonlinear resistor containing zinc oxide as a main component.

BACKGROUND ART Voltage nonlinear resistors (hereinafter referred to as "rZnO elements") mainly composed of zinc oxide (ZnO) have excellent nonlinearity, so they can be used in semiconductor devices such as transistors and thyristors, or electrical devices. Used in equipment surge absorbers, etc. This type of ZnO element is usually obtained by mixing ZnO as a main component with several types of additives including bismuth oxide (B12o3) as subcomponents, and molding and sintering the mixture. Here, 8420 g is added to promote crystal growth of ZnO particles by liquid phase sintering, since it has a lower melting point than ZnO.

Conventionally, in order to fully exhibit its function, 20 g of Bi was used in a large amount of 0.3 mol 9 or more based on the total components.

On the other hand, when manufacturing a ZnO element, a heat treatment step of 400 to 900° C. is required after sintering in order to improve the life characteristics of the ZnO element and to form an insulating coating on the outer periphery of the ZnO element.

However, due to such heat treatment, the crystal structure of Bi2O5 was changed, and the electrical characteristics of the ZnO element were significantly deteriorated.

The degree of the decrease is greater as the heat treatment temperature is higher. Such conventional ZnO elements have a satisfactory α (nonlinear index) of 20 or more in a certain current range (for example, 100 μA to IA), but have the disadvantage that α drops extremely outside the above range. was there.

Further, as mentioned above, although a large amount of 8120 g is used as an additive, the number of cracks of bismuth (Bi) element is 2×10 5, and BizOs is extremely scarce in terms of resources.

Purpose of the Invention The present invention has been made in view of the above-mentioned conventional problems, and provides a long-life voltage nonlinear resistor that can be manufactured without using BizOs, which is a scarce resource, and has excellent electrical characteristics. The purpose is to

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention has been developed by using manganese oxide (PJinOz) 0.1 to 5 mol%, antimony oxide (5bzOz) 0.1 to 5 mol%, chromium oxide (
CrzOa) 0.1 to 5 mol% and the balance ZnO, CrzOs, ZnO, cobalt oxide (C
Adding 0.2 to 20% by weight of a second component obtained by calcining a mixture of 1 m or more of O2O3) and Seed02, lead oxide (pbo) and 5b20a,
It is sintered to form a ZnO element.

Example Hereinafter, one embodiment of the present invention will be described in detail.

First, a predetermined amount of each powder (PbO, CrxOs, 5bzOa cr) was weighed in a ratio of 4:1:1, and the weighed powders were sufficiently mixed in a centrifugal ball mill to obtain a mixed powder. Thereafter, the calcined body of this mixed powder was ground with a centrifugal ball mill to obtain a reaction product as a second component.

On the other hand, as the first component, Zn0 98.5 mol%, Mn
0g Q, 5mol%, 5bzOa 0.5mol, TI/
A predetermined amount of Cr gos O, 5% was weighed.

Then, 2% by weight of the above reaction product was added to this first component, and then thoroughly mixed in a rotary ball mill and formed into a disk shape.

Next, this molded body was fired in air at a firing temperature of 1100°C for 6 hours, then both end faces of the obtained sintered body were polished, silver (Ag) electrodes were applied to both end faces, and a temperature of 590°C was applied. A voltage nonlinear resistor (ZnO
(Sakuko) was obtained.

Coconi, PbO, Cr20a, Sb 20B (1)
When X-ray diffraction was performed on the reaction product obtained by calcining the mixed powder, the X-ray diffraction pattern was as shown in Figure 1.As a result of assigning the signals in Figure 1, it was found that the reaction product was It was found that the main component of the product was pyrochlore crystal py.

FIG. 2 is a graph showing the voltage-current characteristics of the ZnO element of this example, with the horizontal axis representing the current and the vertical axis representing the voltage. In FIG. 2, solid line 1 shows the characteristics of the ZnO device of this example, and solid line 2 shows the characteristics of the conventional ZnO device containing Bi20a as the main additive. , the slope of solid line 1 is smaller than the slope of solid line 2. Here, the smaller the slope of the solid line in FIG. 2, the larger α is, so the Zn of this example
It can be seen that the O element has better nonlinear characteristics than the conventional ZnO element.

Furthermore, FIG. 3 is a graph showing the relationship between each heat treatment temperature and the rate of change in Vll/mrx and α before and after the heat treatment when the temperature of the heat treatment, which is the final stage in the ZnO element manufacturing process, is varied. , the horizontal axis shows the heat treatment temperature, and the vertical axis shows each rate of change.

Note that the heat treatment time was 1 hour at each temperature.

Here, ■1rrIA/IIm is Z with a thickness of 11111
It is the voltage across both ends when a current of 1 mA is passed through the nO element, and α is an index of V (v) when a current of 1 mA of ZnO is passed. K is a nonlinear resistance. Also, although this α varies depending on the current value, generally Q,
Values obtained when a current in the range of 1 mA to 1 mA is applied are often used (hereinafter, values within this range will be adopted).

In FIG. 3, solid lines 3 and 4 show the α and VxmA/ms characteristics of the ZnO device of this example, respectively, and solid lines 5 and 6 show the α and VxmA/ms characteristics of the conventional ZnO device containing Bi2O3 as the main additive, respectively. This shows the characteristics of VsmA/U, and in conventional ZnO elements, α and V
The heat treatment temperature for both xm^/yartr is approximately 500℃.
As the temperature increases, the characteristics rapidly decrease as the temperature rises. On the other hand, it can be seen that in the ZnO element of this example, the characteristics of both α and Vtm hardly change due to heat treatment.

Furthermore, Fig. 4 shows that ■
This is a graph showing the rate of increase in leakage current when a DC voltage of 85% of 1 mh/mm is applied, with the horizontal axis representing the voltage application time and the vertical axis representing the rate of increase in leakage current.

In FIG. 4, a solid line 7 shows the characteristics of the ZnO element of this example, and a solid line 8 shows the characteristics of a conventional ZnO element containing BizOa as the main additive.
It can be seen that the element has a lower leakage current increase rate and better life characteristics than the conventional ZnO element.

On the other hand, the following table shows the above Mn0z, 8b, which is a component of the additive.
This shows the results of V1fnA/mlK and α when all of 20s, CrzOz and the reaction product were added, and when any one component of MnO2, 5bzOi, CrzOs or the reaction product was added. be. The ZnO elements with each composition were manufactured in the same manner as in the above example, and the first component in the table, ZnO1Mr+02.5bzOa and CrzOs
The composition of each component is expressed in mol %, and the reaction product as the second component is expressed in weight % relative to the first component.

Table From this table, the reaction product or 5bzOa as an additive
V1m/+u is extremely small, and My
) 02, Sb 203, Cr2O5 or the reaction product, the value of α is extremely small. In contrast, Example 1 (main Fy
l) As shown in (PJnOz, 5bzOs, CrzOa, when all four components of the reaction product are added, V om /m
It can be seen that both x and α have large values and exhibit good characteristics. That is, it can be said that the characteristics deteriorate if any one of the above four components is removed.

From Fig. 5 to Fig. 8, MnO2 and 8b20 are respectively shown.
This is a graph showing how V1m/dragon and α change when the content ratios of s, Cr xoa, and reaction products are changed. The horizontal axis shows the content ratio of each component, and the vertical axis shows Vx
mA/mti and α are taken. In each figure, solid lines A1 to A4 indicate the characteristics of Vxm/force, and solid lines 81 to
B4 shows the characteristic of α. Here, as shown in Figures 5 to 7, when the content ratio of one of the three components MnO2, 5b203, and CrzOs is changed, each of the other two of the three components is changed. The content ratios are each fixed at 0.5 mol%, the ZnO content is increased or decreased, and the reaction product content is fixed at 2% by weight. In addition, the one shown in Fig. 8 is ZnO98,5 mo/l.
/%, Mn0z □, 5 mol%, 5bzOs 0.5
The first component consisting of mol%, CBQa O, 5% A/% is fixed, and the content ratio of the reaction product to this first component is varied.

As shown in FIGS. 5 to 8, in order to obtain good characteristics for both VtmA/mu and α, Mn0z must be 0.
．． 1 to 5 mol%, 0.1 to 5 mol% of 5b20s, Cr
*Os is 0.1-5 mol%, reaction product is 0.2-2
It is necessary that each content be within the range of 0% by weight. In addition, in FIG. 8, PbO, which is a constituent component (second component) of the reaction product, is not shown as a reaction product.
The chain line shows the characteristics when each component is mixed and used without reacting 5bzOa and CrzOs. The dashed line A5 shows the characteristics of V+mi7'mrn, and the dashed line B5 shows the characteristics of α. As shown in FIG. 8, PbO1Sb20a, Crab
If the components are simply mixed together without reacting s, no pyrochlore crystals will be produced, making it impossible to obtain good properties.

In addition, in the above examples, the blending ratio of the reaction products was Pb
O: 5b20s: Cr20g = 4: 1
1, but the present invention is not limited to such embodiments. In other words, it is sufficient that the blending ratio is such that pyrochlore crystals are generated after calcination. Also, regarding the ingredients, p.
bo, 5bzOa, CrzOs (i) Not limited to combinations, Cr20a, ZnO, CO2O3 and M+1
02 (Any one or more of Q and PbO and Sb
Pyrochlore crystals are produced even when using any combination with 203, and the same effect can be obtained. Furthermore, the calcination temperature and time in the calcination step to obtain the reaction product are 800 to 1100°C and 1 to 10°C, respectively.
Preferably a range of hours. Calcining temperature is 800℃
If the calcination time is less than 1,100°C, the reaction will be slow; if the calcination time exceeds 1100°C, a large amount of PbO will volatilize; if the calcination time is less than 1 hour, the reaction will be insufficient; if it exceeds 10 hours, the PbO will evaporate.
This is because the degree of volatilization of bO becomes large.

On the other hand, the firing temperature and firing time in the firing step after mixing the first component and the second component (reaction product) are preferably in the range of 1000 to 1300°C and 1 to 20 hours, respectively. If the firing temperature is less than 1000°C, a dense sintered body will not be obtained, if it exceeds 1300°C, PbO will volatilize and the nonlinear characteristics will deteriorate, and if the firing time is less than 1 hour, it will not be possible to obtain a dense sintered body. This is because a uniform sintered body cannot be obtained, and if the time exceeds 20 hours, PbO near the surface will volatilize, resulting in poor nonlinear characteristics.

Moreover, it is preferable that the heat treatment temperature of the sintered body is in the range of 500 to 850°C. This is because if the heat treatment temperature is less than 500°C, the life characteristics of the obtained ZnO element will be poor, and if it exceeds 850°C, the nonlinear characteristics will be poor.

In addition, in the above example, a centrifugal ball mill, an aluminium crucible, etc. were used to manufacture the ZnO element, but the types of these devices may be varied as long as they meet the purpose, and are limited to the devices used in the above example. It's not a thing.

Effects of the Invention As described above, according to the present invention, since Bi2O3, which has conventionally been used in large quantities as an additive, is not used at all, the nonlinear characteristics do not deteriorate due to heat treatment. The nonlinear index in the micro current region and large current region is larger than that of conventional products.
In particular, since the nonlinear index is large in the microcurrent region, the leakage current during power application is small. Furthermore, since the increase in leakage current due to long-term energization is small, a surge absorbing element with a long life can be obtained. Furthermore, instead of Bi20g, which has a resource-poor number of 2×10, Clark number is 1.5×10.
Since it uses PbO, etc., it has advantages such as being advantageous in terms of resources.

[Brief explanation of drawings]

Figure 1 is an X-ray diffraction diagram of a reaction product used in an example of the present invention, Figure 2 is a voltage-current characteristic diagram of a ZnO device according to an example of the present invention, and Figure 3 is a heat treatment diagram of a ZnO element. Graph showing changes in l/1mA/Hx and α with respect to warm foothills,
Figure 4 is a graph showing the rate of increase in leakage current with respect to the electrification time of the ZnO element, and Figures 5 to 8 are graphs showing V1 when the content ratio of each component of the additive of the ZnO element is changed.
It is a graph showing mA/Hz and α. Figure 2: Den 5 (A) Figure 3: Pretreatment formula j! Jl ('C) Figure 5 Mno2 Nejihamatomi 1? : (mol 10) Figure 6

Claims (1)

[Claims] (1) il! Manganese oxide 0.1-5 mol%, antimony oxide 0.1-5 mol%, chromium oxide 0.1-5 mol%
, chromium oxide,
0.2 to 20% by weight of a second component obtained by calcining a mixture consisting of at least one of zinc oxide, cobalt oxide, and manganese oxide, and antimony oxide and antimony oxide.
In addition, a voltage nonlinear resistor characterized by being made by sintering.