JPS5992504A - 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 a method for manufacturing a voltage non-linear resistor containing zinc oxide as a main component and a metal oxide such as bismuth oxide.

Voltage nonlinear resistors are surge absorbing elements, voltage stabilizing elements,
It is widely used in lightning arresters, etc., and in recent years, a voltage nonlinear resistor made of oxide sintered body containing zinc oxide as a main component has been developed. This voltage nonlinear resistor is generally made of zinc oxide and trace additives such as bismuth oxide, cobalt oxide, and chromium oxide.
After mixing with antimony oxide etc. and press molding/100
-%-/:! It is made by attaching electrodes to something sintered at 0θ℃. Details such as its composition and manufacturing method can be found in, for example, the Japanese Journal of Applied Physics (MoMatsuoka, “Nonohmic Pr.
operations of ZincOxde Cer
amics” *Jap, J, Appl, Phys
,,tO,73g(tqqt)).

In this method, the raw materials are generally mixed as powders (hereinafter referred to as powder mixing method), so some degree of non-uniformity remains in the component distribution of the resulting device (such non-uniform voltage It is known that resistors are susceptible to deterioration due to continuous DC energization.) Therefore, when adding additive components to zinc oxide powder to obtain a voltage nonlinear resistor, it is necessary to use a salt solution of the additive (additive component) that does not react with each other to form a solid phase (even if an organic solvent is used). A production method (hereinafter referred to as the solution mixing method) has been proposed in which zinc oxide powder is immersed in a liquid with a liquid temperature of /fffi or higher, and the powder obtained by evaporation to dryness or filtration is dried, molded, and sintered. (Special Publication Showa Ig
-qg3'ys publication).

In this method, a solid phase is not formed when the salt solution of the additive is prepared, but there is a drawback that a solid phase is formed when the zinc oxide powder is immersed. Namely, a nitric acidic aqueous solution of bismuth oxide (cobalt.

When a dough (containing salts such as chromium and manganese) is prepared and the dough is immersed in zinc oxide powder, the nitric acid and zinc oxide react and the acidity decreases, producing solids such as bismuth oxide or bismuth hydroxide. .

In addition, when using an ethanol solution of bismuth chloride, an aqueous solution must be used because the salts of other additives do not dissolve in ethanol, and when zinc oxide powder is immersed, two kinds of alcohol solutions and aqueous solutions are mixed. In the presence of water, bismuth chloride decomposes to form a solid phase of bismuth (chemical formula unknown). That is, even if a salt solution of the additive is used, the method of simultaneous mixing of the salt solution has the disadvantage that a solid phase is generated which is no different from conventional powder mixing.

This invention was made in order to eliminate the above-mentioned drawbacks of the conventional technology. By sequentially adding salt solutions of one or more types of additives, a solid-liquid mixture is created, resulting in high uniformity and excellent current and voltage characteristics. The object of the present invention is to obtain a voltage nonlinear resistor that exhibits little deterioration even when continuously energized.

The feature of this invention is that when adding additive components to zinc oxide powder to obtain a voltage nonlinear resistor, solutions of the additive do not react with each other to form a solid phase, and the zinc oxide powder Prepare several salt mixed solutions of additives that do not form a solid phase even when immersed (organic solvents are also acceptable), and repeat the process of immersing the mixed solutions in zinc oxide powder and evaporating to dryness for the number of types of salt mixed solutions. After that, the obtained powder is dried, pyrolyzed, and shaped.

(3) A method for manufacturing a sintered voltage nonlinear resistor. By this molding method, it is possible to uniformly mix the additive components into the zinc oxide powder by bringing the salt mixed solution of the zinc oxide powder W additive into contact with the zinc oxide powder.

The salt of the additive may form a salt by reacting with the additive solution, but it is necessary that the relationship is such that no precipitation occurs.

However, if precipitation occurs, it may be added to a separate solution, and the above conditions are not essential.

Other conditions are heating 1 (thus, salts that easily become oxides, such as nitrates, chlorides, sulfates, etc., are soluble in water or organic solvents, or the anion is a weak acid or weak alkaline). and water-soluble ones.

This salt is weighed in terms of oxide and prepared into a mixed solution of several salts that do not cause precipitation. Zinc oxide powder was mixed in suspension in one mixed solution and evaporated to dryness until the solvent disappeared. Next, the zinc oxide powder is suspended and mixed and evaporated to dryness, then suspended and mixed in a salt mixed solution of another additive, and evaporated to dryness again (1). Repeat this for the number of additive salt mixture solutions.

In addition, each salt is separately suspended and mixed with the zinc oxide powder in the suspension mixture of the mixed solution and the zinc oxide powder.

The powder thus obtained is thermally decomposed to turn the additives into oxides, and then crushed, molded, and sintered using conventional methods. Therefore, there is a need for a voltage nonlinear resistor element with highly uniform and precise current/voltage characteristics.

The present invention will be explained below with reference to Examples.

Example l Table 1 shows the composition of the solution used as a raw material.

Solution 1 was mixed with zinc oxide lθθg and mixed in a ball mill for 1 hour. Pour this mixture into an evaporating dish at 9θ~9! r℃, 6
Heated for ~/j hours. The dry powder was mixed with the solution and mixed in a ball mill for 1 hour.

Same as above, 9θ~? The sample was dried by heating at 3°C. The obtained powder was thermally decomposed by heating at 100° C. for 2 hours, and then pulverized using a Laikai machine, and an aqueous polyvinyl alcohol solution (3%) was added as a binder and molded. Acid pressure 300~,
The sample was in the shape of a disk, had a diameter of 10 mm, and had a thickness of Am. Aluminum was sprayed on both sides of the sintered body to form electrodes (elements).

t [In this example, since precipitation occurs when solution 1 and solution - are mixed, they are mixed with zinc oxide in two parts.

Example Table 1 shows the composition of the solution used as a raw material.

Table 2 (However, tartaric acid in solution a was used to externally dissolve antimony oxide.) 100 g of zinc oxide was mixed with solution / and solution co at the same time,
After drying, solution 3 was mixed and then dried, and the resulting powder was used as an electrode in the same manner as in Example 1.

Although there are three types of solutions in this example, precipitation does not occur even if solutions 1 and 2 are mixed, and there is no problem even if they are mixed with zinc oxide at the same time. Solutions 1 and 2 are simply separated for convenience in order to dissolve the salt, and may be mixed after they have been dissolved.

Here, solutions 1 and 2 were simultaneously mixed and dried, and then solution 3 was mixed.

Comparative Example Powders obtained by the conventional solution mixing method and powder mixing method were made into electrodes in the same manner as in Example 1.

In the solution mixing method, zinc oxide, solution/and solution compounds shown in Table 1 of Example 1 were used, and in the powder mixing method, zinc oxide lθθg, bismuth oxide + xJ (antimony oxide 3.ty, charcoal WIR manganese θ Kuda g, cobalt oxide 2 1g, chromium oxide θ?gy, nickel oxide 4?A
F was used.

Table 3 shows a comparison of the apparent densities of the device obtained by the present invention and the device obtained by the conventional manufacturing method.

(t') As can be seen from Table 3, the density is somewhat better in the conventional solution mixing method than in the conventional powder mixing method, but in the example of the present invention, the density is much higher than that. It becomes. That is, it can be said that the device obtained by the present invention has high uniformity and is dense.

Next, FIG. 1 shows the results of measuring the current/voltage characteristics of the device manufactured in the example and the device manufactured by the conventional method. Curve l is the value of the device manufactured in Example 1 and Example C of the present invention (both results were almost the same), curve C is the value of the device manufactured by the conventional solution mixing method, and curve 3 is the value of the device manufactured by the conventional powder mixing method. The values of elements manufactured by the mixing method are shown. The firing temperature was 1000°C in all cases. The smaller the change in voltage with respect to the change in current, the better the characteristics. As can be seen from the figure, the device obtained according to the present invention exhibits excellent current/voltage characteristics over the entire current range. However, the devices obtained using the conventional solution mixing method showed inferior characteristics in the low current region, and the devices obtained using the conventional powder mixing method showed poor characteristics in the low current region.
It is inferior in both the low current region and the high current region. In the conventional solution mixing method, the uneven distribution of bismuth in the solid phase during mixing leads to deterioration of characteristics in the low current region.
It is believed that non-uniformity of additives gave the worst results in conventional powder mixing methods.

Figure 2 shows the ambient temperature/30°C using the same sample as in Figure 1.
, charging rate (AC applied voltage/V/mA) = Or! The results of measuring the change in leakage current outside the resistor over time at r are shown. In the figure, curve 1 is the value of the device according to Examples 1 and 2 of the present invention, curve C is the value of the device according to the conventional solution mixing method, and the curve ? indicates the value of the element obtained by the conventional powder mixing method. The firing temperature was 1000°C in all cases.

In the figure, the closer the curve is to the upper right, the more easily the element deteriorates due to energization. As can be seen from the figure, the element obtained by the present invention has the smallest increase in leakage current outside the resistor, and it is clear that it is less likely to deteriorate due to continuous energization than the conventional manufacturing method.

In addition, in the above examples, zinc oxide powder was used as the raw material, but a mixed system using a salt such as zinc nitrate, which is soluble in water or an organic solvent and easily becomes an oxide when heated, is used as the raw material. The entire solution may be used as a solution, and the same effect as in the above example can be seen.

In addition, although the above example uses an ethanol solution of bismuth chloride, other organic solvents may be used, and other bismuth salts soluble in organic solvents may also be used, and the same solution as in the above example may be used. You can see the effect.

As described above, according to the present invention, in order to avoid the formation of a solid phase when mixing the zinc oxide powder and the additive salt solution, the additive salt solution is suspended and mixed in stages to completely remove all the additives. Since the mixture is mixed as a solution, it is possible to obtain a voltage nonlinear resistor that is highly uniform, dense, has excellent current/voltage characteristics, and is resistant to deterioration even when continuously energized.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the current/voltage characteristics of an element manufactured by the method of the present invention and an element manufactured by the conventional method, and Fig. 1 shows the change over time in the leakage current outside the resistance for the same sample as in Fig. 1. It is a diagram. Agent Makoto Kuzuno - Party 1 Figure 2, Commissioner of the Japan Patent Office 1. Indication of the case Patent application No. 371-0411JII
No. 2, Name of the invention Method for manufacturing a voltage nonlinear resistor 3, Relationship with the case of the person making the amendment Patent applicant address 2-2-3 Marunouchi, Chiyoda-ku, Tokyo Name (601,) Mitsubishi Electric Corporation Representative: Hitoshi Katayama 4, Agent address: Mitsubishi Electric Corporation, 2-2-3 Marunouchi, Chiyoda-ku, Tokyo Subject of amendment (1) Column for detailed explanation of the invention in the specification Contents of amendment +11 7th line from the bottom of page 1 of the specification “electrode” is changed to “element”
Correct to.

Claims (2)

[Claims] (1) In a method of manufacturing a voltage nonlinear resistor using zinc oxide as the main component and adding additive components, a solution of the additive is prepared, a mixed solution of one or more types is prepared in a combination that does not produce a solid phase, and the mixture is When the solution and zinc oxide powder are mixed in suspension, the suspension mixing and drying of the mixed solution and zinc oxide powder are repeated in order to form a solid-liquid mixture, and the obtained powder is pulverized, pyrolyzed, molded, A method for manufacturing a voltage nonlinear resistor, characterized by sintering. (2) The method for manufacturing a voltage nonlinear resistor according to claim 7, wherein an organic solvent solution of bismuth chloride is used for suspension mixing of the mixed solution and zinc oxide powder. A method for manufacturing a voltage nonlinear resistor according to claim 1.