JPS6115303A - Method of producing oxide 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 of the Invention] The present invention relates to a method for manufacturing an oxide voltage nonlinear resistor, and in particular to an improvement in a method for mixing raw materials for a zinc oxide (ZnO)-based voltage nonlinear resistor. .

[Technical background of the invention and its problems]

A voltage non-linear resistor, that is, a varistor, has non-linear voltage-current characteristics, and as the applied voltage increases, its resistance rapidly decreases and the flowing current increases significantly, so it is difficult to absorb abnormally high voltage. It is also widely used for voltage stabilization.

Part 2. A varistor using a ZnO-based sintered body is known as a typical example.

Such a ZnO-based voltage nonlinear resistor is generally manufactured by the following method. That is, first, ZnO powder, which is the main component raw material, and bismuth oxide (B
i203) l Antimony oxide (Sb2()5) r Fine powder of metal oxides such as cobalt oxide (CoO) and muffin oxide (MnO) are blended in a predetermined ratio, and this is mixed and crushed in a grinder. For example, using Norconia balls to mix and
After pulverizing, an appropriate binder is added to granulate the powder to a predetermined particle size.

Next, after filling this granulated powder into a predetermined mold, it is compacted to form a compact (for example, a pellet), and the obtained compact is fired at a temperature of, for example, about 1100 to 1350°C. By doing this, a ZnO yarn sintered body is obtained.

In the obtained sintered body, the main component, ZnO, usually has a thickness of several μm.
The metal oxide, which is a subcomponent, constitutes a relatively large crystal powder component ranging from m to several tens of μm, and forms a grain boundary layer component that thinly covers the ZnO crystal grains and is interposed in a layered manner on the contact surface between the crystal grains. It consists of

In a ZnO-based varistor having such a microstructure, the structural uniformity of each component acts as an important factor for stabilizing and improving varistor characteristics such as voltage nonlinearity, life characteristics, and surge energy resistance.

However, in conventional manufacturing methods, attempts have been made to improve the structural uniformity by using ZnO powder bundles as the main component raw material and metal oxide powders as the subcomponent raw materials with fine particle diameters. However, it was extremely difficult to achieve the desired effect. In addition, since the amount of subcomponent raw materials added is generally extremely small compared to the amount of ZnO powder, mixing of the two becomes insufficient, and it is particularly difficult to interpose grain boundary layer components with uniform thickness and composition between ZnO crystal grains. is extremely difficult.

Therefore, conventional manufacturing methods have the disadvantage that not only the varistor characteristics themselves deteriorate, but also the characteristics vary widely between or within manufacturing lots, leading to a decrease in quality stability.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a method for manufacturing an oxide voltage nonlinear resistor having excellent characteristics with stable quality.

[Summary of the invention]

The present inventors discovered that when raw material powders are mixed as in the conventional manufacturing method, the subcomponent raw materials form aggregates, making it impossible to form grain boundary layer components with uniform thickness and composition. I found out. In order to form a grain boundary layer component with a uniform thickness and composition, we have conducted intensive research on mixing methods of raw materials, and have found that by slurrying the raw materials and mixing them in stages, the formation of aggregates can be significantly reduced. Moreover, it was found that the varistor properties of the sintered body were improved.

That is, the method for manufacturing an oxide voltage nonlinear resistor of the present invention includes a step of making a slurry of at least a part of the subcomponent raw material and a part of zinc oxide, which is the main component raw material, and finally forming the slurry with the slurry. The method is characterized by comprising a step of mixing the remaining raw materials.

In the present invention, the sub-component raw material may be any material as long as it imparts varistor properties to the sintered body and improves its performance when the sintered body is produced by blending it with the main component raw material, zinc oxide. Such subcomponent raw materials include antimony (
Sb), bismuth (Bi), chromium (Cr), :+pult ('coL Mangano (Mn), nickel (Ni)
), silicon (Si).

At least one of oxides such as aluminum (Al), boron (B), silver (Ag), and other compounds may be used.

In the method of the present invention, first, some or all of the subcomponent raw materials and a part of the main component raw material, zinc oxide, are dispersed in mixed drained water to form a slurry, or the slurry products are mixed together. In some cases, it is made into a slurry. Next, this slurry is mixed with a slurry of the remaining raw materials (the main component raw material and the subcomponent raw material or only the main component raw material).

Note that the slurry of the remaining raw materials may be divided into multiple portions and mixed. Furthermore, an appropriate dispersant or binder may be added when preparing the slurry.

By slurrying the raw materials and mixing them in stages, it is possible to prevent the subcomponent raw materials from agglomerating.If the slurry is dried, then granulated, and a sintered body is manufactured, the internal The grain boundary layer component has a uniform thickness and composition, and good varistor properties can be obtained, and variations in properties between lots and within lots are also extremely small.

In addition, ZnO is the main component and B+703 r Coo +
Sb2Sb203r and NiO each from 0.1 to
A system containing approximately 1% of B + Ag r (containing other components such as Cr2O3 as necessary) has excellent nonlinear characteristics and life characteristics, but especially B + Ag r of approximately 0.1% by weight or less.
By adding a small amount of a compound such as Si, the properties are further improved.

In particular, the method of the present invention is effective for the uniformity of such small amounts of added components of about 0.1 weight or less, and examples of subcomponents that are effective in such small amounts of addition include
Examples include compounds such as I Ag + Si.

[Embodiments of the invention]

Examples 1 to 9 and Comparative Example 1 1. Bi2O30.75 mol% as a subcomponent raw material.

Coo 0.5 mol%, MnO 0.5 mol%,
5b2o51.0 mol% l Cr2030.5 mol,
%, NiO1,Omolti.

Al(No3) 50.01% by weight, and 5i020.01% by weight, 82030.02% by weight as trace components (components added at about 0.1% by weight or less) among the raw materials for subcomponents.
.

0.02% by weight of Ag2O, the balance being Zn which is the main component raw material
Each component was weighed out so that the composition consisted of O.

Next, the total amount of trace components among the subcomponents and the amount (wt%) shown in the first column in Table 1 below of the total amount of ZnO, which is the main component raw material, and the subcomponent raw materials other than trace components, are determined by a predetermined amount. of water for a predetermined period of time to form a slurry. Continuing,
The remaining raw materials (consisting of ZnO, which is the main component raw material, and subcomponent raw materials other than trace components) are slurried in the same manner as above,
Slurries corresponding to the amounts (wt%) shown in the second and subsequent times in Table 1 below were combined with the first slurry and mixed for a total of 20 hours.

The total amount of water used is 2.2% of the total amount of raw materials by weight.
It was distributed 5 times in weight ratio each time. Further, for Examples 1 to 4, the first mixing time was 5 hours, and for Examples 5 to 9, the mixing time before the final time was 2 hours each.

Furthermore, in Comparative Example 1 in Table 1 below, the above components were mixed all at once as in the conventional method.

Table 1 Examples 10 to 18 and Comparative Example 2 First, Bi2O3Q, 75% Yachi, was used as a subcomponent raw material.

Co00.5 mol%, MnO0.5 mol%, 5
b2o31.0mo/L'%! 5i020.5 mol%, Cr2O30.5 mol%.

Each component was weighed out so that the blended composition consisted of 01.0 mole of Ni and 30.01 mole of A/(NO3), with the remainder being ZnO, which was the main raw material.

Next, the total amount of the subcomponents and the amount of ZnO, which is the main component raw material, shown in the first batch in Table 2 below (% of mold needles) were mixed together with a predetermined amount of water for a predetermined time to form a slurry. Continuing,
The remaining raw material (consisting of ZnO, which is the main component raw material) was made into a slurry in the same manner as above, and the slurry corresponding to the amount (wt%) shown from the second time onwards in Table 2 below was combined with the first slurry to make a total of 20. Time mixing was performed.

The total amount of water used is 2 times the total amount of raw materials by weight.
．． 5 times, and distributed each time by weight ratio. In addition, for Examples 10 to 13, the first mixing time was 5 hours,
For Examples 14 to 18, the mixing time before the final round was 2 hours each.

Furthermore, in Comparative Example 2 in Table 2 below, the above components were mixed all at once as in the conventional method.

Table 2 After all the raw materials were mixed as described above, the slurry was dried, and an appropriate amount of polyvinyl alcohol (PVA) was added for granulation. Subsequently, the obtained granulated powder was filled into a mold having a predetermined size and shape and press-molded. Then,
Obtained L/W 1'2 at 100℃~13oo℃
Firing was performed for an hour to obtain a disk-shaped sintered body with a diameter of 20 mm and a thickness of 2 mm. Aluminum electrodes were thermally sprayed on both sides of this sintered body to prepare a sample for measuring characteristics.

The performance of these samples was investigated as follows.

1) Life characteristics Each sample was placed in a constant temperature bath at 90℃, and each sample was heated to 1mA,
Initial voltage value v1mA when a current of 10/jA flows
, v1o, and further applied a voltage of 95- of these voltages for 200 hours: (vlmA)200
Measure r (v10μA)2'OO and calculate the rate of change from these values: ((VlmA)2oo VlmA:)/
V1m* + [(v10μA) 200-v10μm]
/v1oμA was calculated. The smaller this rate of change is, the smaller the characteristic deterioration is. These results are shown in Table 3 below.

2) Nonlinearity and surge energy tolerance 10 for each sample
The voltage value when a current of kA was passed: vlokA was measured and X''10kA/vlmA was calculated.The smaller the limiting voltage ratio, the better the nonlinearity.

In addition, the surge energy resistance is JEC'-203,4
According to the method described on page 3, 2 m5e was added to the sample.
By applying a current rectangular wave of c, the unit volume of the sample Ccrn3)
It is shown as the rectangular wave discharge withstand capacity (Joul). These results are shown in Table 4 below. 3) Product quality stability Examples 2 and 11 10 lots of 10 pieces were manufactured, and the v 1 mA of all the pieces was measured to examine the variation. The results are shown in FIG. 1 (Example 2) and FIG. 2 (Example 11), respectively. Further, for comparison, the variation between each lot was similarly investigated for Comparative Examples 1 and 2, and the results are shown in FIG. 3 (Comparative Example 1) and FIG. 4 (Comparative Example 2), respectively.

Table 3 Table 4 As is clear from Table 3, the varistors of Comparative Examples 1 and 2 had a large rate of change in voltage and had large characteristic deterioration, whereas the varistors of Examples 1 to 18 all had a change in voltage. The ratio is small, and the deterioration of characteristics is small. Furthermore, as is clear from Table 4, the varistors of Comparative Examples 1 and 2 have poor nonlinearity and low surge energy resistance, whereas the varistors of Examples 1 to 18 all have excellent nonlinearity, It also has high surge energy resistance. Furthermore, as is clear from Figures 1 to 4, the varistors of Comparative Example 1 (Figure 3) and Comparative Example 2 (Figure 4) have large variations in varistor voltage between manufacturing lots and within lots. , Example 2 (Figure 1) and Example 11
The quality of the varistor shown in (Fig. 2) is stable.

〔Effect of the invention〕

As detailed above, the method of the present invention has excellent nonlinearity, high surge energy resistance, and good life characteristics.
Furthermore, it is possible to manufacture an oxide nonlinear resistor with excellent quality stability between lots and within a lot during manufacturing.

[Brief explanation of drawings]

1 to 4 are diagrams showing variations in varistor voltage between lots and within lots of varistors obtained by the methods of Example 2, Example 11, Comparative Example 1, and Comparative Example 2, respectively. Applicant's Representative Patent Attorney Takeshi Suzue Syllable 1 Figure Lot Fragrance Figure 2 Rosito Scent

Claims (3)

[Claims] (1) In manufacturing an oxide voltage nonlinear resistor whose main component is zinc oxide, there is a step of slurrying at least a part of the subcomponent raw material and a part of the main component raw material, zinc oxide, and a final step. A method for manufacturing an oxide voltage nonlinear resistor, comprising the steps of: mixing the slurry with the remaining raw material made into a slurry. (2) The method for manufacturing an oxide voltage nonlinear resistor according to claim 1, characterized in that the remaining slurry-formed raw material is mixed in multiple batches. (3) The method for manufacturing an oxide voltage nonlinear resistor according to claim 1, wherein a part of the subcomponent raw material contains at least one of Si, Ag, or B compounds.