JP2002305104A - Voltage nonlinear resistor and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method which can simply obtain a voltage nonlinear resistor, in which long service life and high durability are realized, without giving adverse effects on the environment. SOLUTION: In a method for manufacturing the voltage nonlinear resistor where zinc oxide is main component, at least bismuth oxide and antimony oxide are contained as additive, mixed powder of bismuth oxide and antimony oxide is calcinated. Composition, composed of the mixed powder, zinc oxide and other additive, is heated and sintered at 700-1,000 deg.C and cooled down to room temperature. After that, this sintered member is subjected to heat treatment again in the range of 600 deg.C to 750 deg.C. As a result, at least 80% of the whole bismuth oxide contained in the sintered member is inverted to γ-Bi2 O3 of body-centered cubic lattice.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage nonlinear resistor made of a sintered body containing zinc oxide as a main component and suitable for use in, for example, a lightning arrester or a surge absorber, and a method of manufacturing the same.

[0002]

2. Description of the Related Art FIG. 2 is a schematic view showing a form of a conventional general zinc oxide voltage non-linear resistor, and FIG. 3 is a cross-sectional view for explaining the structure of the resistor. Conventionally, lightning arrester,
Voltage non-linear resistors mainly composed of zinc oxide used for surge absorbers, etc.
A side surface of the sintered body 1 obtained by mixing a composition containing an additive effective for improving electric characteristics, including bismuth oxide, which is indispensable for the expression of voltage non-linearity, and passing through each step of granulation, molding, and firing. This is constituted by providing a side surface high resistance layer 2 and metal electrodes 3 (upper and lower surfaces) made of metal aluminum sprayed or the like.

FIG. 4 is a schematic diagram showing a fine structure of a part of the crystal structure of a conventional general zinc oxide voltage non-linear resistor. 4 is a spinel particle containing zinc and antimony as main components, 5 is a zinc oxide particle, 6 is a bismuth oxide main component phase, 7
Is the twin boundary in the zinc oxide crystal grains. That is, the spinel particles mainly composed of zinc and antimony have two kinds of existing states, one existing around the inside of the zinc oxide particles 5 and the other existing near the triple point (multiple point) of the zinc oxide particles. In some cases, a part of the bismuth oxide main component phase 6 exists not only at multiple points but also at the boundaries of the zinc oxide particles 5.

[0004] The crystal phase of bismuth oxide detected by X-ray diffraction, which will be described later, mainly consists of triple points (multipoints) of zinc oxide particles.
This crystal structure plays an important role in the lifetime of the device. The spinel particles 4 are insulating particles themselves, but are involved in determining the size of the zinc oxide particles 5.

[0005] The main baking step of the conventional manufacturing method generally requires a temperature around 1200 ° C. This is because the density of the sintered body becomes sufficiently high and it is necessary to obtain appropriate voltage non-linearity and varistor voltage (normally, a voltage for flowing a current value of about 1 mA). It is also known that bismuth oxide contained in the device is converted into body-centered cubic bismuth oxide (γ-Bi ₂ O ₃ ) by heat treatment at an appropriate temperature after firing, and the life characteristics are improved at this time. (Tokuhei 5-22362
Publication: Reference 1). In Reference 1, usually 500 to 6
It is shown that the heat treatment at about 00 ° C. contained 20 to 80% of body-centered cubic bismuth oxide, and at that time the life characteristics were improved.

FIG. 5 is a characteristic diagram showing annealing (reheating) conditions of a conventional zinc oxide voltage non-linear resistor and a change in current with time. Bismuth oxide 0.5 mol%, antimony oxide 1.0 mol%, manganese oxide, cobalt oxide, nickel oxide 0.5 mol% each, boron oxide 0.04
mol%, 0.004 mol% of aluminum nitrate, and the balance of zinc oxide, these were prepared by a normal ceramic process, and a sintered body fired at 1200 ° C for 5 hours in air was annealed at a temperature of 480 ° C to 600 ° C, The conversion of bismuth oxide to body-centered cubic is also shown in the figure. The optimum annealing condition is a temperature range of about 480 ° C. to 520 ° C., a relatively narrow temperature range, and a conversion to a body-centered cubic crystal is at most about 50%.

FIG. 6 is a characteristic diagram showing the relationship between the annealing conditions of a conventional zinc oxide voltage non-linear resistor and the amount of formation (conversion) of a body-centered cubic crystal determined by X-ray diffraction. As-baked, either tetragonal or simple cubic, it is a mixed crystal of tetragonal and simple cubic, but the conversion starts from about 500 ° C to body-centered cubic, and reaches 900 ° C through the maximum value of 700-800 ° C. Annihilation (conversely, a change from body-centered cubic to a mixed crystal of tetragonal and simple cubic, or to tetragonal or simple cubic). The life stabilizing region is between 30% and 60% as apparent from FIG. 6 when viewed from the body-centered cubic bismuth oxide amount. In addition, an element having a different composition such as the addition of a rare earth oxide to
It has been experimentally confirmed that if the sintering is performed at about 0 ° C., substantially the same conversion ratio and life stabilizing region are exhibited.

In recent years, a part of additives, such as bismuth oxide, to be added in small amounts are preliminarily calcined (partially calcined) at a temperature of about 400 to 700 ° C., and finally calcined (Zinc oxide) by adding to the main component zinc oxide. It has been clarified that the temperature of the main firing can be lowered to 1000 ° C. or lower to around 900 ° C. For example, this method is disclosed in Japanese Patent Application Laid-Open No. 9-67161 (Cited Document 2). However, since the main firing temperature can be reduced by this method, energy saving at the time of element production and electrical characteristics due to a reduction in zinc oxide defects are reduced. The effect of stabilization, reduction of the evaporation of bismuth oxide and improvement of the environment resulting therefrom can be expected, which can be a very useful method in the industry.

Regarding this, for example, Atsushi Iga, “Mechanism of low-temperature sintering (850-950 ° C.) of ZnO varistors”
And "Electrical Properties of ZnO Varistor" Powder and Powder Metallurgy Vol. 44 No. 12 p1069-1077
(1997) (Cited Documents 3 and 4), but in the present specification, a calcination method capable of lowering the calcination temperature by additive calcination is a low-temperature calcination (method). The element manufactured by the manufacturing method is referred to as a low-temperature firing element.

[0010]

It has also been found that the low-temperature fired zinc oxide device manufactured in this way has no inferior in the sintered density and VI characteristics as compared with the conventional device fired at around 1200 ° C. However, when applied to a gapless surge arrester, a voltage is constantly applied to the element, so that the so-called change in leakage current with time (lifetime characteristic) is an extremely important evaluation item like the conventional element.

As described above, in the conventional device, the solution of this point is regarded as optimization of the annealing treatment after firing, that is, conversion into body-centered cubic bismuth oxide, and it is shown that the life characteristics can be improved. However, the life of the important low-temperature fired device, that is, the change over time of the leakage current under a constant voltage stress, has not yet been sufficiently studied as compared with the conventional device, and there is little knowledge about the optimal conditions or information on bismuth oxide. At present, there is no such thing.

Generally, the heat treatment conditions for improving the life characteristics greatly depend not only on the special composition of the device but also on the device manufacturing method, and it is necessary to optimize the condition. That is, the same conditions as those of the conventional element are not always applicable to the low-temperature fired element, and a new study is required.

On the other hand, by forming an appropriate high-resistance layer on the side surface of the element, it is possible to prevent flashover on the side surface portion. Conventionally, a polycrystalline high-resistance layer made of spinel and zinc silicate is provided, and furthermore, By forming a glass layer thereon, the withstand capacity (surge energy absorbing ability) of the element has been improved.

It has been found that the provision of a single glass layer as the side layer can sufficiently improve the resistance, and therefore, it is necessary to simultaneously perform appropriate heat treatment and glass layer formation on the conventional element to extend the life. Has been proposed to simplify the process (Japanese Patent Publication No. 4-4723; cited document 5).

In short, it is important for the simplification of the process and the energy saving to match the heating conditions at the time of annealing with the heating conditions required for forming the glass layer and for forming the baking type electrode.

[0016] In addition, since a device manufactured by firing at about 1200 ° C according to the conventional method had annealing conditions corresponding to a long life at about 500 ° C, a lead component was inevitably required to enable sealing at a low temperature. It is necessary to use glass containing a large amount. For this reason, the expansion coefficient increases, and the glass itself has a complicated composition, such as the necessity of adding a filler having a low expansion coefficient to reduce this value. In addition, it is needless to say that the material is not desirable for the environment because of a large amount of lead.

An object of the present invention is to provide a manufacturing method capable of obtaining a voltage non-linear resistor realizing a long life and high withstand voltage easily and without adversely affecting the environment.

[0018]

According to a first aspect of the present invention, there is provided a method for manufacturing a voltage non-linear resistor comprising zinc oxide as a main component and at least bismuth oxide and antimony oxide as additives. Is calcined, the composition comprising the mixed powder, zinc oxide and other additives is heated and sintered at 700 to 1000 ° C., and cooled to room temperature.
By performing a reheating treatment in the range of 750 ° C., 80% or more of the total bismuth oxide contained in the sintered body is converted into body-centered cubic γ-Bi ₂ O _3. This is a method for manufacturing a linear resistor. The invention according to claim 2 is characterized in that, during the reheating treatment, an insulating layer is formed by simultaneously baking a sintered body and a glass material having an expansion coefficient within a range of ± 20% on side surfaces of the sintered body. The method for manufacturing a voltage non-linear resistor according to claim 1. The invention according to claim 3 is characterized in that the glass material to be baked on the side portion is zinc borosilicate glass, bismuth borosilicate glass, alkali borosilicate glass or zinc borate glass, and the thickness obtained after baking is at least 20 μm or more. The method for manufacturing a voltage non-linear resistor according to claim 1 or 2. According to a fourth aspect of the present invention, in any one of the first to third aspects,
It is a voltage non-linear resistor manufactured by the manufacturing method of item.

According to the above configuration, since the heating temperature at the time of the reheating treatment is set to the specific range, the conversion range of the body-centered cubic bismuth oxide can be determined, and the voltage nonlinearity having excellent life characteristics can be determined. A resistor can be obtained. In addition, since the glass insulating layer on the side surface of the sintered body can be provided at the same time as the reheating treatment, a manufacturing method excellent in productivity can be provided.

FIG. 7 is a sectional view of an example of the voltage non-linear resistor thus manufactured. Although the structure of the resistor itself is the same as that of the related art (FIG. 3), there is a substantial difference in having the zinc oxide ceramic body 8 fired at a low temperature and an insulating layer such as a non-lead glass-based side high resistance layer 9.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the production method of the present invention, first, a mixed powder of bismuth oxide and antimony oxide is calcined. At this time, other additives can be calcined. Specifically, for example, first, a mixed powder of antimony oxide and bismuth oxide, first, a mixed powder of bismuth oxide and chromium oxide, and third, a mixed powder of boron oxide and bismuth oxide can be calcined. it can. Thereafter, these are mixed with other additives such as zinc oxide and transition element oxide to prepare a composition, and the composition is fired at a low temperature (700 to 1000 ° C.).
After cooling to room temperature, the sintered body was
Reheating treatment is performed in the range of 750 ° C.

The conditions for the reheating treatment are as follows: after the sintered body is heated in air or oxygen at a temperature of 500 ° C. or more and cooled, an accelerated life test is performed, that is, the sintered body is subjected to a high power application rate at a high temperature of 100 ° C. or more. (= Applied voltage / V _1mA ) Under long-term power application in the air, observe the change over time of leakage current due to AC resistance, gradually decrease the current,
Alternatively, the conditions showing a clear decreasing tendency were clarified and found.

The amount of conversion of the body-centered cubic crystal to bismuth oxide after the reheating treatment was measured by X-ray diffraction. A specific method for measuring the conversion is known, and is described in, for example, Japanese Patent Publication No. 22362/1993 (Cited Document 1).

In the voltage nonlinear resistor manufactured by firing at about 1200 ° C. according to the conventional method, the optimum annealing condition corresponding to long life was about 500 ° C. (FIG. 5), but in the present invention, 700 to 1000 ° C. For example, in the case of a sintered body heated and sintered at around 900 ° C., for example, around 900 ° C., as shown in FIG. I found it.

In this case, the formation (conversion) rate of the body-centered cubic bismuth oxide is about 8%.
It was also found to be 0% to 100% (see Table 2).

However, as shown in FIG. 1, as the heating temperature such as heating at 700 ° C. becomes higher, the flatness on the low current side (V _{1 mA} /
V _{10 mu A)} is slightly worse (increases), the initial leakage current value i ₀ at t = 0 is certainly increasing, aging of the subsequent current was steadily reduced. This behavior is also observed in the case of the conventional heat treatment of the voltage non-linear resistor. However, in the conventional heat treatment at 700 ° C., not only does the initial leakage current value significantly increase, but also the leakage current increases rapidly. For example, it has been confirmed that changes over time are greatly different.

The conditions for extending the life are clearly different from those of the voltage non-linear resistor fired at a low temperature and the conventional non-linear resistor, and the manufacturing process thereof is different, especially bismuth oxide and antimony oxide, and if necessary. It is presumed that the introduction of the additive calcination step and the resulting introduction of the low-temperature heat sintering step reflect the difference in the reheating conditions.

A glass material selected from the group consisting of a sintered body having a coefficient of expansion within the range of ± 20% due to clarification of the reheating temperature and determined to be sealable on the side surface of the sintered body, for example, a lead-free glass powder (See Table 1) is coated with an appropriate binder and solvent so as to have a thickness of about 20 μm or more, preferably 50 μm or more after sealing. Insulating layer).

The difference in the conditions of the reheating treatment naturally changed the selection range of the glass material for forming the side high-resistance layer simultaneously with the reheating treatment. The range of options for use of lead-free glass materials, which had been difficult to use because the working temperature was too high in the past, has been expanded.For example, zinc borosilicate, bismuth borosilicate, zinc borate glass, and alkali borosilicate glass can be used. Was.

With respect to a glass material having an expansion coefficient lower than that of the sintered body by less than 20%, an excessive tensile stress acts on the sintered body and adversely affects the sintered body. Excessive glass material causes a large tensile stress on the glass side and breaks of the glass itself. Therefore, the range of the expansion coefficient of the sintered body and the range of ± 20% was set.

In practice, the formation of these glass materials on the side surface of the sintered body is sufficiently adhered to the side surface even after heating for 30 to 60 minutes at each sealing temperature, and the cross section is observed with a microscope or the like. No defects such as cracks, peeling and chipping were found. It was confirmed that within the range of ± 20%, the difference in the expansion coefficient had no effect on the formation of the insulating layer, and did not lower the impulse withstand capability, which is an important function. The impulse withstand voltage was set to a waveform of 4 × 10 μs in accordance with the standard, was increased by 5 kA from the peak value of 20 kA, was energized at intervals of 5 minutes until flashing or breaking, and the final breaking current value was evaluated.

As described above, the conditions for extending the life (reheating treatment) of the sintered body obtained by mixing the calcined mixed powder of the specific additive with other additives and firing at a low temperature are clarified. By sealing the lead-free glass having an expansion coefficient in the range of ± 20% under the temperature condition, a glass layer can be formed on the side surface. As described above, since the heat treatment and the side layer can be simultaneously formed, the simplification of the process and the adoption of environment-friendly lead-free glass have been successfully achieved.

[0033]

The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to these examples. Examples 1 to 5 and Comparative Examples 1 and 2 First, a method for producing a low-temperature fired zinc oxide voltage non-linear resistor will be specifically described. The bulk was prepared as follows. As shown in the calcining step (FIG. 8), predetermined amounts of antimony oxide and bismuth oxide were mixed well by a dry mixer or a ball mill, and then transferred to an alumina crucible and calcined (A).
powder). After calcining at 550 ° C. for 6 hours, the ball mill was performed again and pulverized sufficiently. Chromium oxide and bismuth oxide (calcination temperature is 550 ° C for 6 hours: B powder), boron oxide and bismuth oxide (calcination temperature is 400 ° C for 6 hours: C powder)
Similarly, after calcination and a pulverizing step, these were finally mixed sufficiently with an aqueous solution of zinc oxide powder, manganese oxide, nickel oxide, cobalt oxide and aluminum nitrate nonahydrate. The formulation was based on the amounts shown in FIG. This is mixed with polyvinyl alcohol (PVA) and a dispersing agent to prepare a slurry, and a disk type spray dryer (disk rotation speed 10
000 rpm, body diameter 1.5 m, drying temperature 210 ° C.). After being formed into a size of about φ40 × t12 by a uniaxial press machine, it was baked at 900 ° C. for about 10 hours. The temperature was raised and lowered at a rate of 50 ° C./hr and performed in the air or in an oxygen stream.
Since the impulse withstand voltage measurement also has a size effect of the voltage non-linear resistor, an actual-sized voltage non-linear resistor was also manufactured and evaluated using the resistor. The size of the molded body is a long object having a size of about φ40 × t65.

The obtained fired body was coated with a paste obtained by adding a binder (ethyl cellulose) and a solvent to the five types of powdered glass shown in Table 1 in Table 1, dried at about 120 ° C., and then put again in a furnace. Heating was performed at an appropriate sealing temperature of medium 600 ° C. to 720 ° C. for about 30 to 60 minutes, and after cooling, metallic aluminum was sprayed to form electrodes.

The expansion coefficients of these glasses and sintered bodies used are summarized in Table 1. As can be seen from a comparison of these values, those having a larger size than the sintered bodies (bismuth borosilicate glass, borosilicate Alkali glass) and small ones (zinc borosilicate glass).

[0036]

[Table 1]

The basic V-I characteristic glass sealing element (heat treatment) varies slightly before and after (Table 2), the flatness of the small-current region _{(V 1mA / V 10 μ A} ) is increased by the heating. This suggests that the initial current value i0 at the time of the application life test becomes large.

[0038]

[Table 2]

These elements were placed in a heating oven for 120 minutes.
FIG. 10 shows the result of examining the change over time of a typical current when heated to 80 ° C. and applied with a voltage of 80% (voltage of _{1 mA} × 0.8). C. (conventional element conditions, glass f of comparative example 1, lead glass with filler) and 700.degree. C. (glass a zinc borosilicate glass of example 1). It can be seen from the figure that the current tends to decrease only at 700 ° C.
In the case of ° C., the rate of current increase is rather larger than in the case of no heating, which is an undesirable tendency. All of these are completely the same as a simple reheat treatment of the sintered body as a result (FIG. 1), and are also significantly different from the life characteristics of the conventional element (also compare FIG. 5).

Next, glass b, c, d, and e of Examples 2, 3, 4, and 5 having different expansion coefficients and other glass compositions in Table 1 in addition to the above examples were respectively sealed at a firing temperature of 720 ° C. ,
FIG. 11 shows the life characteristics after sealing at 650 ° C. and 600 ° C., showing a nearly flat change with time at 600 ° C. and a gradual decrease at 650 ° C. and 720 ° C. In addition, the glass g (lead-containing glass) of Comparative Example 2 is similarly governed by the sealing temperature and shows a gradual decrease in leakage current.

The elements having different sealing conditions after the life test are denoted by X
The amount of body-centered cubic crystals produced was measured by X-ray diffraction. The results are summarized in Table 2. When the amount of generation (conversion) and the time-dependent change of current are considered together, the tendency of decrease is that the amount of conversion is 8
It is clear from Table 2 and FIGS.

Next, the results of examination of the impulse withstand capability are shown in Table 3. The thickness of the glass produced this time is about 50 μm, and has a withstand value of about 40 kA, which is almost the same as that of all the glasses. The glass used this time is well adapted to the low-temperature fired element body, and the difference in expansion coefficient within this range is sufficient to fulfill its role without any problem.

[0043]

[Table 3]

However, the impulse withstand capability depends on the thickness of the glass layer. If it is 20 μm or less, the withstand capability is reduced depending on the type of the glass. May cause a drop.

Other low-temperature calcinations are, in addition to those described above, especially calcination of only a mixed powder of bismuth oxide and antimony oxide (FIG. 8).
Chromium oxide and boron oxide can be added without calcining, that is, only A powder is prepared, and B and C powders are added as raw powder). When the glass layer was prepared in the same manner as described in Examples 1 to 5 after firing at a low temperature, the life characteristics and the impulse characteristics were almost the same.

[0046] Although marked only the atmosphere as the atmosphere during reheating, the difference in the small current region flatness _{(V 1mA / V 10 μ A} ) when re-heated in oxygen occurs. This value becomes slightly smaller, indicating an improvement direction, and the initial leakage current value i ₀ tends to decrease. However, the tendency of the current gradual decrease is related only to the temperature factor and does not change in the reheating atmosphere.

Although the detailed mechanism that enables low-temperature firing is not fully understood, the fact that the heat histories of bismuth oxide when firing at low temperature and when firing at normal high temperature are greatly different is important for the reheating conditions. It means making a difference. Therefore, basically the same result can be obtained also in the case where it is manufactured by firing at a low temperature by another method.

[0048]

According to a first aspect of the present invention, there is provided a method for producing a voltage non-linear resistor comprising zinc oxide as a main component and at least bismuth oxide and antimony oxide as additives, wherein a mixed powder of bismuth oxide and antimony oxide is prepared. After calcining, heating and sintering the composition comprising the mixed powder, zinc oxide and other additives at 700 to 1000 ° C and cooling to room temperature, the sintered body is again heated to a temperature in the range of 600 to 750 ° C. By performing the reheating treatment, 80% or more of the total bismuth oxide contained in the sintered body is γ-B
Since it is a method of manufacturing a voltage non-linear resistor characterized by conversion to i ₂ O ₃ , a voltage non-linear resistor realizing a long life and a high withstand voltage can be easily and without adversely affecting the environment. Obtainable.

According to a second aspect of the present invention, at the time of the reheating treatment, a glass material having an expansion coefficient within a range of ± 20% is simultaneously baked on a side surface of the sintered body to form an insulating layer. Since the method for manufacturing a voltage non-linear resistor according to claim 1 is characterized in that the insulating layer can be easily formed with high productivity.

According to a third aspect of the present invention, the glass material to be baked on the side surface is zinc borosilicate glass, bismuth borosilicate glass, alkali borosilicate glass or zinc borate glass, and the thickness obtained after baking is at least 20 μm or more. Since the method for manufacturing a voltage non-linear resistor according to claim 1 or 2 is provided, a voltage non-linear resistor that does not adversely affect the environment can be easily obtained.

According to a fourth aspect of the present invention, there is provided a voltage non-linear resistor manufactured by the manufacturing method according to any one of the first to third aspects. And a voltage non-linear resistor realizing high withstand voltage can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing a temporal change of a current caused by applying a constant voltage to a voltage nonlinear resistor of the present invention.

FIG. 2 is a schematic view showing a form of a conventional general zinc oxide voltage nonlinear resistor.

FIG. 3 is a cross-sectional view showing a structure of a conventional general zinc oxide voltage nonlinear resistor.

FIG. 4 is a schematic diagram showing a fine structure of a part of a crystal structure of a general zinc oxide voltage nonlinear resistor.

FIG. 5 is a characteristic diagram showing annealing conditions and a change over time of a current of a conventional zinc oxide voltage non-linear resistor.

FIG. 6 is a characteristic diagram showing a relationship between annealing conditions of a conventional zinc oxide voltage non-linear resistor and the amount of formation (conversion) of a body-centered cubic crystal determined by an X-ray diffraction method.

FIG. 7 is a sectional view of an example of a voltage non-linear resistor according to the present invention.

FIG. 8 is a process diagram showing a step of partially calcining and mixing and pulverizing an additive according to the present invention.

FIG. 9 is a process diagram showing an overall method for manufacturing a low-temperature fired device according to the present invention.

FIG. 10 is a characteristic diagram showing a time-dependent change in current after sealing various glasses.

FIG. 11 is a characteristic diagram showing a change with time in current after sealing various glasses.

[Explanation of symbols]

Reference Signs List 1 sintered body, 2 side high resistance layer, 3 metal electrode, 4 spinel particles, 5 zinc oxide particles, 6 bismuth oxide, 7
Twin boundary, 8 low temperature fired ceramic body, 9 lead-free glass side high resistance layer.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tomoaki Kato 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Inside Mitsui Electric Co., Ltd. (72) Inventor Iwao Kawamata 2-3-2 Marunouchi, Chiyoda-ku, Tokyo (72) Inventor Kazuo Kawahara 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsui Electric Co., Ltd. (72) Hide Yamashita 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsushi F term (reference) in Denki Co., Ltd. 4G030 AA32 AA42 AA43 BA04 CA01 CA05 GA08 GA25 GA27 GA33 5E034 CC03 DE08 DE12 DE20

Claims (4)

[Claims] 1. A method for manufacturing a voltage non-linear resistor comprising zinc oxide as a main component and at least bismuth oxide and antimony oxide as additives, wherein a mixed powder of bismuth oxide and antimony oxide is calcined, and , Zinc oxide and other additives in a composition of 700-10
After sintering at 00 ° C. and cooling to room temperature, the sintered body is reheated again in the range of 600 ° C. to 750 ° C., whereby 80% of the total bismuth oxide contained in the sintered body is A method for producing a voltage non-linear resistor comprising converting the above into body-centered cubic γ-Bi ₂ O ₃ . 2. The method according to claim 1, wherein, during the reheating treatment, a glass material having an expansion coefficient within a range of ± 20% is simultaneously baked on the side surface of the sintered body to form an insulating layer. Item 2. The method for producing a voltage non-linear resistor according to Item 1. 3. The glass material to be baked on the side portion is zinc borosilicate glass, bismuth borosilicate glass, alkali borosilicate glass or zinc borate glass, and is characterized in that the thickness obtained after baking is at least 20 μm or more. A method for manufacturing the voltage non-linear resistor according to claim 1. 4. A voltage non-linear resistor manufactured by the manufacturing method according to claim 1. Description: