JPH0828285B2 - Method of manufacturing voltage non-linear resistor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a voltage nonlinear resistor containing zinc oxide as a main component.

(Prior Art) Bi ₂ O ₃ , Sb ₂ O ₃ , S containing zinc oxide (ZnO) as a main component
It is widely known that resistors containing a small amount of additives such as iO ₂ , Co ₂ O ₃ , and MnO ₂ as an auxiliary component show excellent voltage nonlinearity. Is used for.

In order to improve the non-linearity in a large current region, the voltage non-linear resistor containing zinc oxide as the main component has been conventionally (1) diffused a small amount of Al ions, Ga ions and In ions during sintering. Valence control method to lower the specific resistance of ZnO,
(2) ZnO and Al ₂ disclosed in JP-A-58-122703
A method is known in which O ₃ , Ga ₂ O ₃ and In ₂ O ₃ are preliminarily calcined to diffuse Al, Ga and In ions into the sintered body, and then mixed with auxiliary components and molded. .

(Problems to be Solved by the Invention) However, in the valence control method (1) described above, only a small amount of ZnO or a sub-component, Al ion, etc. is simply mixed and molded and sintered. Al, Ga and In ions were not sufficiently dispersed in the ZnO crystal, and most of them were incorporated into the coarse boundary layer and spinel phase. Therefore, there is a problem that the improvement of the non-linearity in the large current region is insufficient, the charging life is deteriorated, and the rate of change of V _{1 mA} after application of a lightning surge becomes large.

Further, the method (2) disclosed in JP-A-58-122703 is more effective than the valence control method (1) described above, but the surge resistance is lowered because ZnO grows nonuniformly. There was a problem.

An object of the present invention is to solve the above-mentioned problems and to provide a manufacturing method capable of improving voltage nonlinearity in a large current region, and obtaining a voltage nonlinear resistor having a good voltage-carrying life and surge resistance. It is what

(Means for Solving the Problems) A method for producing a voltage nonlinear resistor according to the present invention is a method for producing a voltage nonlinear resistor containing a zinc oxide raw material as a main component produced by an indirect method of oxidizing zinc vapor, As the zinc oxide raw material, zinc oxide obtained by oxidizing zinc vapor in an atmosphere containing at least aluminum, indium, or gallium, in which the metal element is in solid solution, is used.

(Operation) In the above-described structure, since zinc vapor is oxidized in an atmosphere containing at least aluminum, indium, or gallium, aluminum, indium, or gallium is sufficiently dissolved in zinc oxide in the process in which zinc becomes zinc oxide. If a non-linear voltage resistor is manufactured using this zinc oxide raw material by the same method as the conventional method, the voltage non-linearity in the large current region can be improved, and the voltage non-linearity also has good voltage life and surge withstand capability. A resistor can be obtained.

At this time, preferably, a solution containing aluminum ions, indium ions, or gallium ions, that is, an aqueous solution of aluminum nitrate or the like is dispersed as fine mist with an ultrasonic atomizer or the like, and is oxidized in a vaporized atmosphere at a high temperature of 1200 to 1300 ° C. As a result, a preferable voltage non-linear resistor can be obtained.

Further, by oxidizing in a gas containing a gas containing aluminum, indium or gallium, that is, a gas such as bromide or iodide, a better voltage non-linear resistor can be obtained.

Here, the oxygen partial pressure in these atmospheres is preferably 0.2 atm or more. The amount of aluminum, indium, and potassium in the atmosphere is 0.00001 to 0.0 in total as Al, In, and Ga.
1 g / is preferred. Incidentally, if less than 0.00001 g /, aluminum, indium, the effect of solid solution of gallium is not sufficiently expressed, and if more than 0.01 g / does not dissolve, the amount attached to the surface of ZnO particles significantly increases, This is not preferable because it adversely affects the device characteristics.

Furthermore, when obtaining ZnO powder raw material, high temperature, for example, 400 ℃
It is preferable to use a material obtained by gradually cooling the above ZnO, because it is possible to prevent the generation of needle crystals due to rapid cooling.

Further, in order to completely remove deposits such as aluminum oxide which do not form a solid solution and adhere to the surface of the generated ZnO particles, the generated ZnO powder may be oxidized and washed with aluminum.

(Embodiment) FIG. 1 is a diagram showing a configuration of an example of an apparatus for carrying out a conventionally known method of manufacturing a voltage nonlinear resistor according to the present invention.
In FIG. 1, 1 is metallic zinc as a raw material, 2 is a melting furnace for melting metallic zinc 1, 3 is a retort furnace for carrying out an oxidation reaction, 4 is a cooling duct, 5 is a collection tank, and 6 is a discharge tank. The air blower, 7 is a bag filter. In the apparatus having the above-mentioned structure, when the metallic zinc 1 melted in the melting furnace 2 is put into the retort furnace 3 and heated to about 1300 to 1400 ° C from the outside, the zinc in the retort furnace 3 reaches the boiling point (about 900 ° C), It is jetted from the evaporation port and burns and oxidizes with oxygen in the air introduced in the oxidation chamber 3a in the retort furnace 3. The high temperature zinc oxide obtained by combustion and oxidation in the oxidation chamber 3a is sucked by the suction force of the exhaust fan 6, passes through the cooling duct 4 and is cooled, and then most of it is in the collection tank 5. In addition, a part of them can be obtained by zinc oxide in the bag filter 7.

At this time, in the present invention, in the air introduced into the oxidation chamber 3a of the retort furnace 3, aluminum nitrate, indium nitrate,
Included each gallium nitrate aqueous solution, etc. made into a fine mist with an ultrasonic atomizer, and aluminum bromide or aluminum iodide gas etc. as the amount of Al, In, Ga 0.0000
1 to 0.01 g / quantity It is included in the atmosphere. Further, ZnO is provided with a cooling duct 4 and is configured to be gradually cooled in the duct 4 to obtain zinc oxide as crystals having a grain size of about 0.5 μm.

The method for obtaining the voltage nonlinear resistor from the zinc oxide raw material obtained as described above is as follows.

In order to obtain a voltage nonlinear resistor containing zinc oxide as a main component, first, a zinc oxide raw material adjusted to a predetermined particle size and bismuth oxide, cobalt oxide, manganese oxide, antimony oxide, chromium oxide adjusted to a predetermined particle size, preferably Is mixed with a predetermined amount of an additive such as amorphous silicon oxide, nickel oxide, boron oxide or silver oxide. In this case, silver nitrate or boric acid may be used instead of silver oxide or boron oxide. Bismuth borosilicate glass containing silver is preferably used. At this time, a predetermined amount of polyvinyl alcohol aqueous solution or the like is added to these raw material powders.

Next, vacuum degassing is preferably performed at a vacuum degree of 200 mmHg or less to obtain a mixed sludge. The water content of the mixed slurry is 30-35 wt.
%, And the viscosity of the mixed slurry is preferably 100 ± 50 cp. Next, the obtained mixed sludge is supplied to a spray dryer to have an average particle size of 50 to 150 μm, preferably 80 to 120 μm.
And the water content is 0.5 to 2.0 wt%, more preferably 0.9 to 1.5 wt
Granulate% granulated powder. Next, the obtained granulated powder is molded into a predetermined shape under a molding pressure of 800 to 1000 kg / cm ^{2 in} a molding step. Then, the molded body is heated / cooled at a temperature of 50 to 70 ° C.
Firing is performed under the conditions of 800 to 1000 ° C./hr and a holding time of 1 to 5 hours. In addition, the temperature rising / falling rate of the molded body is 10 to 10 before the calcination.
It is preferable to remove the binder by scattering at 400 to 600 ° C. at 0 ° C./hr and a holding time of 1 to 10 hours.

Next, an insulating coating layer is formed on the side surface of the calcined body that has been calcined. In the present invention, an oxide paste obtained by adding ethyl cellulose, butyl carbitol, n-butyl acetate or the like as an organic binder to a predetermined amount of Bi ₂ O ₃ , Sb ₂ O ₃ , ZnO, SiO ₂ or the like is used in an amount of 60 to 30.
The thickness of 0 μm is applied to the side surface of the calcined body. Next, the temperature rising / falling rate is 20 to 60 ° C / hr, 1000 to 1300 ° C, preferably 1100.
Main-baking is performed under the conditions of ~ 1250 ° C and 3-7 hours. In addition,
A glass paste obtained by adding ethyl cellulose, butyl carbitol, n-butyl acetate, etc. as an organic binder to glass powder is applied on the above-mentioned insulating coating layer to a thickness of 100 to 300 μm, and the temperature rising and falling speed is 50 to 200 ° C. in air. It is preferable that the glass layer is formed by heat treatment under the conditions of / hr and 400 to 900 ° C. holding time of 0.5 to 2 hours.

After that, both end surfaces of the obtained voltage nonlinear resistor are
Polishing is performed with water, preferably oil, as a polishing liquid with an abrasive corresponding to # 400 to 2000 such as ₂ O ₃ and diamond. Next, after cleaning the polished surface, a voltage non-linear resistor is obtained by, for example, spraying a metallikon electrode made of, for example, aluminum metallikon on the polished both end surfaces.

Hereinafter, the results of actually measuring various characteristics of the voltage nonlinear low antibody within and outside the range of the present invention will be described.

Examples Bi ₂ O ₃ , Co ₃ O ₄ , MnO ₂ , Sb ₂ O ₃ , Cr ₂ according to the method described above
ZnO produced in an atmosphere containing 0.1 to 2.0 mol% of O ₃ , NiO, and SiO ₂ , 0.01 to 0.3 wt% of bismuth borosilicate glass containing silver, and the balance of Al, In, and Ga shown in Table 1. Inventive sample No. 1 shown in Table 1 having a diameter of 47 mm and a thickness of 22.5 mm and a varistor voltage (V _{1 mA} ) of 200 to 230 V / mm.
5 and Comparative Example Sample Nos. 1 and 2 were prepared.

The conventional method 1 of the comparative example 1 uses zinc oxide powder obtained by the conventional method to add 0.01 mol% of Al (NO ₃ ) ₃ .9H ₂ O to the raw material mixture, and burns the Al ions to diffuse the atoms. The value control method and the conventional method 2 of Comparative Example 2 are disclosed in
As disclosed in JP-A-58-122703, zinc oxide powder obtained by a conventional method is used, and this is mixed with Al ₂ O ₃ and then calcined at 900 ° C. The average particle size of ZnO used and the amounts of Al, In and Ga in the sintered body are shown in Table 1. In this example, air was sent into the oxidation chamber.

With respect to the prepared low antibodies of the present invention and the comparative example, the control voltage ratio, V _1mA decrease rate, lightning surge withstand capability and switching surge withstand capability were measured, and the leakage current ratio was determined. The results are shown in Table 1. Here, the limiting voltage ratio is the varistor voltage V
_It was calculated from the ratio of _10KA and V _1mA . The V _1mA decrease rate was obtained from V _1mA before and after applying a current of 30 KA with a current waveform of 8/20 μs 10 times. Lightning surge withstand current of 130KA and 150KA is 4/10
A sample which was destroyed after being applied twice with a current waveform of μs was marked with X, and a sample which was not broken was marked with ◯. The switching surge resistance is indicated by x when the current of 800 A and 1000 A was repeatedly applied 20 times with a current waveform of 2 mS and was broken, and when it was not broken, it was marked as o. Further, the ratio of the leakage current was obtained from the current ratio I ₁₀₀ hours / I ₀ hours immediately after the power was applied 100 hours after the power was applied to the element at an ambient temperature of 130 ° C. and a charge rate of 95%.

From the results shown in Table 1, it can be seen that the resistor of the present invention using the zinc oxide raw material obtained by the oxidation in the predetermined atmosphere has various excellent properties as compared with the comparative example.

(Effects of the Invention) As is apparent from the above description, according to the method for producing a voltage-ratio linear resistor of the present invention, by using a zinc oxide raw material obtained by oxidizing zinc vapor in a predetermined atmosphere, It is possible to obtain a voltage non-linear resistor which can improve the voltage non-linearity in a large current region and also have a good electric charge life and surge withstand capability.

[Brief description of drawings]

FIG. 1 is a diagram showing the configuration of an example of an apparatus for carrying out the method of manufacturing a voltage nonlinear resistor according to the present invention. 1 ... Metal zinc, 2 ... Melting furnace, 3 ... Retort furnace, 3a ... Oxidizing chamber, 4 ... Cooling duct, 5 ... Collection tank, 6 ... Fan, 7 ... Bag filter

Claims (1)

[Claims] 1. A method for producing a voltage non-linear resistor containing a zinc oxide raw material as a main component, which is produced by an indirect method of oxidizing zinc vapor, in an atmosphere containing at least aluminum, indium or gallium as the zinc oxide raw material. A method for producing a voltage non-linear resistor, characterized in that zinc oxide in which the metal element is formed as a solid solution is used, which is obtained by oxidizing in a medium.