JPH07109805B2 - Voltage nonlinear resistor and method of manufacturing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a voltage nonlinear resistor containing zinc oxide as a main component and a method for manufacturing the same.

(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, in the voltage non-linear resistor containing zinc oxide as a main component, (1) a small amount of Al ions, Ga ions, and In ions are conventionally added to the sintered body. Valence control method to diffuse and reduce the specific resistance of ZnO,
(2) ZnO and Al ₂ disclosed in JP-A-58-122703
_{O 3, Ga 2 O 3,} In 2 O 3 to be pre Ji because calcining Al, Ga, ZnO and In ions
A method is known in which, after diffusing into the inside, mixing with auxiliary components and molding and firing are carried out.

(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 diffused into the ZnO crystal, and most of them were taken into the grain boundary layer and spinel phase. Therefore, the non-linearity of the large current region is not sufficiently improved, the life of the voltage is deteriorated, and the varistor voltage after the lightning surge is applied is greatly reduced. It was

In addition, the method (2) disclosed in JP-A-58-122703
Then, although it is more effective than the valence control method (1) described above, there is a problem that the surge resistance is lowered because ZnO grows nonuniformly.

An object of the present invention is to solve the above-mentioned problems and to provide a voltage non-linear resistor which can improve voltage non-linearity in a large current region, and which also has good voltage-applied life and surge withstand capability, and a method for manufacturing the same. Is.

(Means for Solving the Problems) The voltage nonlinear resistor of the present invention contains zinc oxide as a main component,
In a sintered body having voltage non-linearity, zinc oxide particles in the sintered body contain a zinc oxide phase of Zn _{1 + x} O (x ≧ 1 × 10 ⁻⁵ ). .

The method for producing a voltage non-linear resistor of the present invention is a method for producing a voltage non-linear resistor in which a zinc oxide raw material produced by an indirect method of oxidizing zinc vapor is mixed with a metal oxide, and then molded and fired. A zinc oxide raw material obtained by oxidizing zinc vapor in an atmosphere having an oxygen partial pressure of 120 torr or less is used, and is fired in an atmosphere having an oxygen partial pressure of 150 torr or more.

(Operation) In the above-described structure, in the voltage nonlinear resistor of the present invention, Zn _{1 + x} O (x ≧ 1 × 10 ^−5, preferably x ≧ 1 × 10 ⁻⁴ ) in zinc oxide (ZnO) particles. By including a zinc oxide phase, that is, a phase in which oxygen is less than a stoichiometric ratio, the resistance of each particle can be reduced and the potential barrier between each grain boundary can be made uniform. The linearity can be improved and various specially manufactured resistors can be obtained. At this time, it is preferable that the oxygen concentration in the central portion of the zinc oxide particles containing the Zn _{1 + x} O phase is lower than that in the surface portion. Also,
Although it is preferable that all the ZnO particles are Zn _{1 + x} O, it is not necessarily limited thereto.

Further, in the method for manufacturing a voltage non-linear resistor of the present invention, the ZnO particles described above can be obtained by oxidizing zinc vapor in an atmosphere having an oxygen partial pressure of 120 torr or less, preferably 50 torr or less, and further using the ZnO particles. In order to manufacture a voltage non-linear resistor, the oxygen partial pressure is 150 torr for firing the element body.
By carrying out in an atmosphere of r or higher, preferably at 1000 to 1300 ° C., it is possible to improve the voltage non-linearity in the large current region as described above, and obtain a resistor having various excellent characteristics.

(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 configuration, the metal zinc 1 melted in the melting furnace 2 is retort furnace 3
When heated to about 1300 to 1400 ° C from the outside, zinc in the retort furnace 3 reaches the boiling point (about 900 ° C), ejects from the evaporation port, and is maintained in an atmosphere with an oxygen partial pressure of 120 torr or less in the retort furnace 3. Combustion oxidation is performed in the oxidation chamber 3a. 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. Further, a part of the zinc oxide can be obtained in the bag filter 7 as the zinc oxide of the present invention.

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

To obtain a voltage nonlinear resistor whose main component is zinc oxide,
First, zinc oxide raw material adjusted to a predetermined particle size of 0.1 to 3 μm and bismuth oxide, cobalt oxide, manganese oxide, antimony oxide, chromium oxide, preferably amorphous silicon oxide, nickel oxide adjusted to a predetermined particle size of 1 μm or less. A predetermined amount of an additive such as boron oxide, silver oxide, etc. is mixed. 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 and a predetermined amount of aluminum nitrate solution as an aluminum oxide source are added to these raw material powders.

Next, source pressure 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 30-35wt%
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,
Water content is 0.5-2.0wt%, more preferably 0.9% -1.5wt%
Granulate the granulated powder of. 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 temperature rise / fall rate of the molded body in air is 10
It is preferable to remove the binder by scattering at 400 to 600 ° C. at a temperature of 100 ° C./hr and a holding time of 1 to 10 hours.

Next, an insulating coating layer is formed on the side surface of the element body. The element body of the present invention means a molded body or a degreased body obtained by heat-treating the molded body under the above conditions. In the present invention, Bi ₂ O ₃ , Sb ₂ O ₃ , ZnO, Si
An oxide paste obtained by adding ethyl cellulose, butyl carbitol, butyl acetate or the like as an organic binder to a predetermined amount of O ₂ or the like is applied to the side surface of the element body to a thickness of 60 to 300 μm. The temperature of the element body is maintained at 20 to 70 ℃ / hr, 800 to 1000 ℃, and the holding time is 1 to 5 hours (preferably the heating process is oxidizing or neutral atmosphere, the maximum temperature holding and cooling process are neutral) (Atmosphere) After calcination, it is preferable to apply an oxide paste to the side surface. Next, this is heated / cooled at a rate of 20-60 ℃ / hr, 1000-1
Main calcination is performed at 300 ° C., preferably 1100 to 1250 ° C. for 3 to 7 hours in an atmosphere having an oxygen partial pressure of 150 torr or more, which is a requirement of the present invention. It should be noted that a glass paste obtained by adding ethyl cellulose, butyl carbitol, n-butyl acetate, etc. as an organic binder to glass powder is applied to the insulating coating layer in the range of 100 to 300.
It is applied to a thickness of μm and the temperature rising / falling rate is 50-200 ℃ / h in air.
It is preferable that the glass layer is formed by heat treatment under the conditions of r, 400 to 900 ° C., holding time 0.5 to 2 hours.

After that, both end surfaces of the obtained voltage non-linear resistor are covered with SiC, Al ₂ O.
_3. Polishing is carried out with water, preferably oil, as a polishing liquid with a polishing agent corresponding to # 400 to 2000 such as diamond. next,
After cleaning the polished surface, an electrode made of, for example, aluminum is provided by thermal spraying on both polished surfaces to obtain a voltage non-linear resistor.

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

Example 1 According to the method described above, Bi ₂ O ₃ , Co ₃ O ₄ , MnO ₂ , Sb ₂ O ₃ , Cr
₂ O ₃ , NiO, SiO ₂ 0.1-2.0 mol% each, Al ₂ O ₃ 0.005 mol%, bismuth borosilicate glass containing silver 0.01-0.3 wt%
%, And the balance is ZnO produced from an atmosphere with an oxygen partial pressure shown in Table 1, and the varistor voltage (V _1mA ) is 47 mm in diameter and 20 mm in thickness under the main firing conditions shown in Table _1.
The voltage non-linear resistors of the present invention tests No. 1 to 8 and the comparative example tests No. 1 to 3 shown in Table 1 of 200 to 230 V / mm were prepared. In addition,
The resistor was fired at 400 ° C. for 5 hours and then degreased at 1150 ° C. for 5 hours under an oxygen partial pressure atmosphere shown in Table 1.

The resistance of the resistor was changed to Zn by the X-ray diffraction method.
As a result of confirming the amount of zinc in the O particles, Zn _{1 + x} O (x ≧ 1 × 10
^-5 ).

Conventional Method 1 of the comparative example Test No.2 is, Al (NO ₃₎ the raw material mixture using a zinc oxide powder obtained by oxidizing zinc vapor in air by conventional means 3 _· 9H ₂ O0.005 moles % By the valence control method in which Al ions are diffused by firing, and the conventional method 2 of the comparative example test No. 3 is the conventional method as disclosed in JP-A-58-122703. The zinc oxide powder obtained in Example ₁ was mixed with Al ₂ O ₃ and then calcined at 900 ° C., and both were calcined in the air.

With respect to the prepared resistors of the present invention and the comparative example, the limiting voltage ratio, the V _{1 mA} reduction rate, the lightning surge withstand capability and the 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 _1OKA 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 100KA, 110KA, 120KA is 4/1
A sample that was destroyed after being applied twice with a current waveform of 0 μs was shown as x, and a sample that was not destroyed was shown as ◯. The switching surge resistance is indicated by x when the current of 800 A, 900 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 indicated by ◯. Further, the ratio of the leakage current was obtained from the current ratio I ₁₀₀ hours / I _O hours 100 hours after the power was applied to the element immediately after the power was applied, with the element being charged at an ambient temperature of 130 ° C. and a charging rate of 95%.
For reference, the average particle size of the ZnO raw material of each test No. was determined and is also shown in Table 1.

From the results of Table ₁ , Zn _{1 + x} O (x ≧ 1 × 10 ⁻⁵ ) obtained by using a zinc oxide raw material in an atmosphere having a predetermined oxygen partial pressure and firing at a predetermined oxygen partial pressure It has been found that the resistor of the present invention composed of particles has better various characteristics than the comparative example.

Example 2 N ₂ with an oxygen partial pressure of 120 torr or less according to Example 1 described above.
Zn oxide after firing using zinc oxide generated in + O ₂ atmosphere
In order to investigate the non-stoichiometry of O particles, resistors having different values of x in Zn _{1 + x} O were prepared, and various characteristics were measured as in Example 1. The results are shown in Table 2.

From the results in Table 2, the value of x in Zn _{1 + x} O is x ≧ 1 × 10
It was found that Test Nos. 1 to ⁵ of the present invention of No. ^-5 had better various characteristics than Comparative Examples Test Nos. 1 and 2.

(Effects of the Invention) As is apparent from the above description, according to the voltage nonlinear resistor and the method for manufacturing the same of the present invention, zinc vapor is converted into oxygen partial pressure.
Zn _{1 + x} O by oxidizing in an atmosphere of 120 torr or less
By manufacturing voltage non-linear resistors using particles with (x ≧ 1 × 10 ⁻⁵ ), voltage non-linearity in a large current range can be improved, and a voltage with a good voltage life and surge withstand capability can be obtained. A non-linear resistor can be obtained.

[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 (2)

[Claims] 1. In a sintered body containing zinc oxide as a main component and having voltage non-linearity, zinc oxide particles in the sintered body are Zn _{1 + x} O 2.
A voltage nonlinear resistor comprising a zinc oxide phase of (x ≧ 1 × 10 ⁻⁵ ). 2. A method for producing a voltage non-linear resistor, comprising adding and mixing a metal oxide to a zinc oxide raw material produced by an indirect method of oxidizing zinc vapor, followed by molding and firing, and using zinc vapor as the zinc oxide raw material and oxygen content. A method for producing a voltage non-linear resistor, which comprises using a material obtained by oxidation in an atmosphere having a pressure of 120 torr or less and firing the material in an atmosphere having an oxygen partial pressure of 150 torr or more.