JPH01276704A - Manufacture of oxide voltage-nonlinear resistor - Google Patents

Abstract

PURPOSE:To stabilize quality and to improve varistor characteristics by dissolving metallic salt of additive composition containing Mn which is dissolved by polyatomic alcohole into alcohole and by sintering material powders which is added into zinc oxide alcohole slurry and hydrolyzed. CONSTITUTION:Among metallic salt of additive component, at least metallic salt of Mn is dissolved by polyatomic alcohol, and metallic salt or metallic salt solution of additive component containing this solution is dissolved by alcohole solution and then added into zinc oxide alcohol slurry. It is then hydrolyzed to acquire sediment which is homogeneously diffused and attached on a surface of ZnO powders at an order of atomic level. Fine structure where oxide of a number of additive components is interposed as a homogeneous intergranular phase among ZnO powders can be acquired by eliminating solvent from the sediment to prepare material powders and by burning them. Quality can be stabilized in this way, and varistor characteristics can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a method for manufacturing an oxide voltage nonlinear resistor.

(Prior art) A zinc oxide voltage nonlinear resistor made of a sintered body containing ZnO as a main component and additive components such as B12O3 has nonlinear voltage-current characteristics, and its characteristics change as the applied voltage increases. Because resistance rapidly decreases and current increases rapidly, it is widely used in lightning arresters and surge absorption elements that absorb abnormally high voltages.

The zinc oxide voltage nonlinear resistor described above has conventionally been manufactured by the following method. First, zinc oxide (ZnO) powder, which is the main component, and fine powder of metal oxides, such as bismuth oxide (Bl 203 ) and manganese oxide (MnO), which are additive components, are mixed in a predetermined ratio. are mixed and crushed using a medium (for example, zirconia balls) in an appropriate mixing/pulverizer, and then granulated with an appropriate binder. Subsequently, this granulated material is filled into a mold, pressure-molded to form pellets, and then fired in a temperature range of 1,100 to 1,350° C. to produce a zinc oxide voltage nonlinear resistor. In the zinc oxide voltage nonlinear resistor manufactured by this method, ZnO, which is the main component, usually constitutes relatively large grains of several μm to several tens of μm, and most of the additive components are located at the grain boundaries of the ZnO particles. The grain boundary phase is formed by intervening in the grain boundary phase. In a zinc oxide voltage nonlinear resistor having such a fine structure, the structural uniformity of each component acts as an important factor for improving the stability of the nonlinear resistor for the purpose of absorbing surges.

However, in conventional manufacturing methods, it is difficult to uniformize the particle size of ZnO powder used as a raw material and powder of additive components, and in general, the amount of additive components added is
Since the amount is extremely small compared to the amount of nO powder, the additive component and the ZnO powder tend to be mixed non-uniformly. As a result, it becomes difficult to obtain a zinc oxide voltage nonlinear resistor with a uniform microstructure. This not only increases the variation in characteristics between manufacturing lots or within a loft, leading to a decrease in quality stability, but also causes problems such as voltage nonlinearity, life characteristics, surge energy resistance, etc. of the obtained zinc oxide voltage nonlinear resistor. This results in a deterioration of the varistor characteristics themselves.

On the other hand, a coprecipitation method is known as a method for obtaining powder with fine particle size and relatively uniform particle size. A method for producing raw material powder using this coprecipitation method is disclosed in Japanese Patent Application Laid-Open No. 58-22580.
There is a method disclosed in No. 4 in which Zn salt and Bl salt are co-precipitated in an aqueous solution. However, with this method, it is difficult to co-precipitate the many components added to improve the various properties of the zinc oxide voltage nonlinear resistor according to the desired composition, and there is a limit to the concentration of the solution. There were many problems in manufacturing, such as the large amount of solution to be handled and the difficulty of molding because the particle size of the zinc component produced by coprecipitation was extremely small.

(Problems to be Solved by the Invention) The present invention was made to solve the above-mentioned conventional problems, and it makes it possible to uniformly mix a large number of additive components, form a uniform microstructure, and achieve quality. The present invention aims to provide a method for easily producing an oxide voltage nonlinearity-low antibody that achieves stabilization of varistor characteristics and improved varistor characteristics.

[Structure of the Invention] (Means for Solving the Problems) The present invention comprises a first step of making a solution of at least a Mn metal salt among the metal salts of additive components with a polyhydric alcohol, and an additive component containing this solution. a second step of dissolving the metal salt or metal salt solution in an alcohol solution, a third step of adding the solution obtained in the second step into the zinc oxide alcohol slurry, and hydrolyzing this solution. An oxide voltage nonlinear resistance characterized by sintering a raw material powder prepared by a method comprising: a fourth step of producing a precipitate; and a fifth step of removing a solvent from the precipitate. It is a method of manufacturing the body.

The present invention will be explained in detail below.

In the first step, at least Mn of the metal salt as an additive component is added.
This is a process in which a metal salt containing (for example, manganese nitrate) is dissolved in a polyhydric alcohol. In addition to the above-mentioned Mn, the additive components used here include B1, Sbs Cos Nl, and Cr.
, Sl, etc. Examples of these metal salts include nitrates, chlorides, metal alkoxides, acetylacetone salts, and the like. Further, among these additive components, in addition to the above-mentioned Mn, a metal salt of B1, etc. may be dissolved in a polyhydric alcohol. Examples of the polyhydric alcohol include ethylene glycol and glycerin.

The second step is a step of dissolving the metal salt or metal salt solution of the additive component, including the solution obtained in the first step, in alcohol. Examples of the alcohol used here include ethyl alcohol, methyl alcohol, propyl alcohol, butyl alcohol, and the like.

The third step is a step of adding the solution obtained in the second step to the alcohol slurry of zinc oxide. This slurry is prepared by dispersing zinc oxide powder in an alcohol such as ethyl alcohol. Regarding the particle size of zinc oxide in this slurry, if it is too large, the activity will decrease and it will be impossible to achieve sintering and increase the density of the body, but if it is too small, it will be difficult to mold, so it is 0.3~ It is preferable to set it to about 0.7 μm.

In addition, in the case of B1, the amount of metal salt as an additive component to the slurry is 0.1 to 2.0 in terms of Bl oxide.
rBo1%, other Mn, 5bSCo, Nl, C
In the case of r, St, etc., it is desirable that the total amount is 3 to 5 mo1% in terms of their oxides.

In the fourth step, the solution (Zn
This is a step in which a precipitate is produced by hydrolyzing an alcoholic solution of mixed metal ions containing O. Hydrolysis is carried out by dropping ammonia water with adjusted concentration (for example, ammonia water diluted to 1150 with water) into the alcohol solution of the mixed metal ion containing ZnO, and the entire solution is brought to a pH of 7 to 8.
to a certain degree.

In addition to ammonia water, an alkaline solution such as KOH may be used. All the metal ions in the alcohol are almost completely precipitated when the pH is about 7 to 8, but since the metal ions that precipitate differ depending on the pH in the low pH region, this is a point of view to prevent problems due to shifts in the precipitation timing. It is desirable to sufficiently stir the alcohol solution of mixed metal ions containing ZnO in order to accelerate the hydrolysis. Due to this hydrolysis, the added component hydroxide (
metal hydroxides) are uniformly dispersed and precipitated. The generated metal hydroxide is uniformly dispersed and attached on the ZnO powder surface on an atomic level order. Such dispersion of metal hydroxide into ZnO powder on the order of the atomic level cannot be achieved by conventional mechanical mixing methods of powders.

The fifth step is a step of filtering, washing, and heating the precipitate produced in the fourth step. Alcohol, water, aqueous ammonia, polyhydric alcohol, etc. are mixed in the precipitate filtered from the hydrolyzed solution in the fourth step, and when trying to remove the alcohol etc. by directly heating it, the precipitate contains alcohol, water, aqueous ammonia, polyhydric alcohol, etc. A dark powder adheres to the surface of the precipitate powder due to the carbon contained therein. To prevent the adhesion of such powder,
After the hydrolysis, the precipitate is filtered and washed with pure water about three times, and the mixed water is evaporated while stirring with a stirrer to prevent separation due to the specific gravity of the precipitated components. The raw material powder obtained by such washing and heating evaporation is
No peaks other than ZnO were observed in the line diffraction test, and it was confirmed that each metal hydroxide existed in an amorphous state and was very active.

Next, an appropriate binder is added to the raw material powder prepared in the fifth step, molded, and fired to produce an oxide voltage nonlinear resistor. In this firing, since the raw material powder has high activity, it is possible to sinter at a lower temperature than in conventional powder sintering. Alternatively, instead of directly sintering the raw material powder, it may be calcined in advance at 400 to 700°C to convert all compounds in the raw material powder into oxides, and then fired. However, in general, calcination at a higher temperature is not preferable because the activity of the powder decreases and agglomeration of powders becomes more likely to occur, but calcination may be preferable for varistor characteristics such as nonlinearity.

(Function) According to the present invention, at least M
ZnO A precipitate is obtained that is uniformly dispersed and adhered to the powder surface on the order of the atomic level. Therefore, by removing the solvent from the precipitate to prepare a raw material powder and firing it, a fine structure in which the oxides of many additive components are interposed as a uniform grain boundary phase between the ZnO powders is obtained. It is possible to manufacture an oxide voltage nonlinear resistor with stable quality and improved varistor characteristics through a simple process.

(Example) Examples of the present invention will be described in detail below.

First, Mn (NO3) 2 , Bl (NO3)
3 ・5H20 is converted to metal oxide and is 0.5 respectively.
They were weighed to give a mol% of 0.25 mol%, dissolved in a small amount of ethylene glycol, and then dissolved in ethyl alcohol. Next, Z
nO powder (average particle size 0.4 μm) 10! A ZnO ethyl alcohol slurry was prepared by mixing iF and 30 g of ethyl alcohol using a mixer/pulverizer for about 1 hour to disperse ZnO in ethyl alcohol. Subsequently, an ethyl alcohol solution of Mn5Bi nitrate dissolved in ethylene glycol was added dropwise to the ZnO ethyl alcohol slurry and mixed for about 1 hour.Next, ammonia diluted with water to about 1150 was added to the mixed solution. Add water to perform hydrolysis and bring the overall pH to 7.
Adjusted to ~8. The precipitate produced by such hydrolysis was filtered, washed three times with pure water, and the solvent water was removed by heating to obtain a raw material powder.

Next, polyvinyl alcohol was added to the raw material powder and granulated, and then the granulated product was filled into a mold having a predetermined shape and press-molded. The obtained pellets were fired at 1100°C for 2 hours to produce a varistor sintered body.

Comparative Example Varistor firing was carried out in the same manner as in the example except that Bi2O3 and MnO were added to the ZnO powder to have the same composition as in the example, mixed and ground in a bot mill, and further dried to obtain a raw material powder. A body was produced.

The relative densities of the varistor sintered bodies of this example and comparative example were measured. Also, after polishing both sides of each sintered body, AJ! The electrodes were deposited and the voltage change rate (V 2 change rate) and I/Io were measured.

mA These results are shown in Table 1 below. Note that the voltage change rate is the change in (2) expressed as a percentage after applying an 8/10 μs impact current at 100 A/d 1000 times to the varistor sintered body through an AI electrode. In addition, mA 1/Io is the initial mA current (process 0) when the varistor sintered body is placed in a constant temperature oven at 120°C and a voltage of 85% of V is applied, and the current (I) after 500 hours. It is expressed as a ratio.

Table 1 As is clear from Table 1 above, the varistor sintered body of this example has a higher density than the same sintered body of the comparative example, has a lower rate of change of It can be seen that the rate of change in leakage current (I/I o ) is small and good.

Further, when the voltage-current characteristics of the varistor sintered bodies of the present example and the comparative example were investigated, the characteristic diagram shown in FIG. 1 was obtained. In addition, A in FIG. 1 shows the characteristic line of the varistor sintered body of this example, and B shows the same characteristic line of the comparative example. As is clear from FIG. 1, it can be seen that the varistor sintered body of this example has significantly superior nonlinearity compared to the same sintered body of the comparative example.

[Effects of Gyomei] As detailed above, according to the present invention, there is no need for a pulverization process, which simplifies the process and prevents contamination of impurities, and by making the raw material powder fine and activating it, it can be made dense by firing at a relatively low temperature. It has a fine structure in which the oxides of many additive components are interposed as a uniform grain boundary phase between ZnO powders, and has excellent nonlinearity, large surge energy resistance, and good life characteristics. It is possible to provide a method for manufacturing an oxide voltage nonlinear resistor that has various effects such as achieving quality stability.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing voltage-current characteristics of varistor sintered bodies of examples of the present invention and comparative examples. Applicant's agent Patent attorney Takehiko Suzue

Claims (1)

[Claims] A first step of dissolving at least Mn metal salt among the metal salts of the additive component in a polyhydric alcohol, and a second step of dissolving the metal salt of the additive component or the metal salt solution containing this solution in an alcohol solution. , a third step of adding the solution obtained in the second step to the zinc oxide alcohol slurry, a fourth step of hydrolyzing this solution to produce a precipitate, and removing the solvent from the precipitate. A method for manufacturing an oxide voltage nonlinear resistor, comprising: sintering raw material powder prepared by a method comprising: a fifth step of removing;