JP5306135B2 - Current-voltage nonlinear resistor and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a current-voltage nonlinear resistor excelling in nonlinear resistance characteristics, and to provide a method of manufacturing the same. <P>SOLUTION: A current-voltage nonlinear resistor 10 includes a sintered body 20 of a mixture containing zinc oxide as the main component and at least bismuth (Bi) and antimony (Sb) as accessory components. The sintered body 20, in the current-voltage nonlinear resistor 10, is configured such that the average value of the ratio (S/L) of the longest straight line length (L) to the orthogonal straight line length (S) is 0.66 or more, where the longest straight line extends over the cross section of each zinc oxide particle 21, mainly constituting a fine structure of the sintered body 20 in a predetermined cross section of the sintered body 20 and the orthogonal straight line is orthogonal to the midpoint of the longest straight line and extends over the cross section. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a current-voltage nonlinear resistor mainly composed of zinc oxide (ZnO) applied to an overvoltage protection device such as a lightning arrester or a surge absorber, and a method for manufacturing the same.

  Generally, an overvoltage protection device such as a lightning arrester or a surge absorber is installed in a power system or electronic device circuit in order to protect the power system or electronic device from an abnormal voltage. In this overvoltage protection device, a current-voltage non-linear resistor that exhibits substantially insulation characteristics at a normal voltage and exhibits a low resistance value at an overvoltage is frequently used.

  A general current-voltage nonlinear resistor includes a disk-shaped sintered body, an insulating layer provided on a side surface of the sintered body, and electrodes provided on both end surfaces. The sintered body constituting the current-voltage nonlinear resistor is made of a ceramic element mainly composed of zinc oxide (ZnO).

  Current-voltage non-linear resistors have a non-linear resistance characteristic in which the current value changes greatly due to voltage changes, life characteristics that do not easily deteriorate even when voltage is applied for a long period of time, and are destroyed when lightning surges or switching surges are applied. Therefore, an energy resistance characteristic that absorbs the energy of the surge is required.

The sintered body of the current-voltage non-linear resistor is composed mainly of zinc oxide (ZnO), and Bi ₂ O ₃ , Co ₂ O ₃ , MnO, Sb ₂ O ₃ , and NiO are added as subcomponents thereto. Is used as a raw material (for example, see Patent Document 1). The sintered body is produced by sufficiently mixing these raw materials together with water and a binder, granulating with a spray dryer or the like, molding and sintering. Then, an insulating material for preventing flashover is applied to the side surface of the sintered body, and heat treatment is performed to form an insulating layer. Moreover, the both ends of a sintered compact are grind | polished and an electrode is attached, and a current-voltage nonlinear resistor is obtained.

  In recent years, there has been a demand for miniaturization of transformers for the purpose of reducing manufacturing costs and environmental harmony. Current-voltage nonlinear resistors are used in lightning arresters because of their excellent nonlinear resistance characteristics. When the resistance value of the current-voltage non-linear resistor is improved, the number of current-voltage non-linear resistors stacked on the lightning arrester can be reduced, and the lightning arrester can be downsized.

In order to increase the resistance of a conventional current-voltage nonlinear resistor and to obtain excellent nonlinear resistance characteristics, for example, Bi ₂ O ₃ , Co ₂ O ₃ , MnO, Sb ₂ O ₃ , NiO, etc. A technique for limiting the content to a crystal phase of Bi ₂ O ₃ contained in a sintered body containing ZnO as a main component is disclosed (for example, see Patent Document 2).

Japanese Patent Publication No. 4-25681 JP 2001-307909 A

  Currently, the non-linear resistance characteristics required for current-voltage non-linear resistors are becoming increasingly severe, and there is a need for current-voltage non-linear resistors having even better non-linear resistance characteristics.

  Therefore, the present invention has been made to solve the above problems, and an object thereof is to provide a current-voltage nonlinear resistor excellent in nonlinear resistance characteristics and a method for manufacturing the same.

In order to achieve the above object, according to one aspect of the present invention, a current-voltage nonlinear resistor comprising a sintered body of a mixture containing zinc oxide as a main component and at least Bi and Sb as subcomponents. The average particle diameter (X2) of the bismuth oxide particles contained as a subcomponent in the mixture for forming the sintered body is 0.8 μm or less, and the standard deviation based on the particle size distribution of the bismuth oxide particles A value (σ2 / X2) obtained by dividing (σ2) by the average particle diameter (X2) of the bismuth oxide particles is 0.3 or less, and the microstructure of the sintered body in a predetermined cross section of the sintered body In the cross section of each zinc oxide particle that mainly constitutes, the length (L) of the longest straight line that is the longest over the cross section, and the length of the orthogonal straight line across the cross section (S) that is orthogonal at the midpoint of the longest straight line the ratio of (S / L) average value is 0.66 or more, Serial ware value obtained by averaging the cross-sectional area of the bismuth oxide particles in a given cross-section of the sintered body (X1) is at 1.15 .mu.m ² or less, and the standard deviation based on the distribution of the cross-sectional area of each of the bismuth oxide particles (.sigma.1) The sintered body is configured so that a value (σ1 / X1) obtained by dividing the cross-sectional area of each bismuth oxide particle by an average value (X1) becomes 0.95 or less. A voltage nonlinear resistor is provided.

Moreover, according to one aspect of the present invention, there is provided a current-voltage nonlinear resistor comprising a sintered body of a mixture containing zinc oxide as a main component and at least Bi, Sb, Mn, Co, and Ni as subcomponents. a manufacturing method, comprising zinc oxide as the main component than 85 mol%, and as an auxiliary component, respectively _{Bi 2 O 3, Sb 2 O} 3, Co 2 O 3, MnO, in terms of NiO, _Bi 2 O ₃ 0.3~2.5mol%, 0.2~7mol% of _Sb 2 _{O 3, 0.2~3mol%} of _Co 2 _{O 3, 0.2~6mol%} of MnO, 0.5 to the NiO A mixture containing 5 mol% and an organic solvent were put into a wet pulverizer, at least the average particle diameter (X2) of the bismuth oxide particles was 0.8 μm or less, and the standard deviation (σ2) based on the particle size distribution of the bismuth oxide particles The bismuth oxide Mixing while pulverizing the mixture so that the value (σ2 / X2) divided by the average particle diameter (X2) of the particles is 0.3 or less, a pulverization step for preparing a slurry, and spraying the slurry, A granulated powder forming step for forming a granulated powder having a predetermined particle size, a molding step for forming a molded body having a predetermined shape by applying a predetermined pressure to the granulated powder, and the molded body from 350 to 350 A first heating step of heating to a first temperature of 500 ° C., maintaining the first temperature for a predetermined time to remove the organic solvent, and a molded body from which the organic solvent has been removed is 1000 to 1200 ° C. The molded body baked, comprising a second heating step of heating to a second temperature and firing while maintaining the second temperature for a predetermined time; and a cooling step of cooling the fired molded body In the predetermined cross section of the sintered body, the microstructure of the sintered body is mainly composed. In the cross section of each zinc oxide particle, the ratio of the length (L) of the longest straight line that is the longest across the cross section to the length (S) of the orthogonal straight line that is orthogonal at the midpoint of the longest straight line and crosses the cross section The average value of (S / L) is 0.66 or more, the average value (X1) of the cross-sectional area of each bismuth oxide particle in the predetermined cross section of the sintered body is 1.15 μm ² and The value (σ1 / X1) obtained by dividing the standard deviation (σ1) based on the distribution of the cross-sectional area of each bismuth oxide particle by the average value (X1) of the cross-sectional area of each bismuth oxide particle is 0.95 or less. A method of manufacturing a current-voltage nonlinear resistor is provided.

  According to the current-voltage nonlinear resistor of the present invention, the nonlinear resistance characteristic is excellent. In addition, according to the method for manufacturing a current-voltage nonlinear resistor of the present invention, a current-voltage nonlinear resistor having excellent nonlinear resistance characteristics can be manufactured.

It is a figure which shows the cross section of the current-voltage nonlinear resistor which concerns on this invention. It is a figure for demonstrating the microstructure model in the predetermined | prescribed cross section of the sintered compact of the mixture which has zinc oxide (ZnO) as a main component and contains at least bismuth (Bi) and antimony (Sb) as subcomponents. It is a figure which shows the result of the non-linear resistance characteristic test in Sample 1 to Sample 4. It is a figure which shows the result of the non-linear resistance characteristic test in Sample 1 to Sample 4. It is a figure which shows the result of the non-linear resistance characteristic test in Sample 1 to Sample 4. It is a figure which shows the result of the non-linear resistance characteristic test in Sample 1 to Sample 4. It is a figure which shows the result of the non-linear resistance characteristic test in Sample 1 to Sample 4. It is a figure which shows the result of the nonlinear resistance characteristic test in the samples 5-11.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a cross section of a current-voltage nonlinear resistor 10 according to the present invention.

  As shown in FIG. 1, a current-voltage non-linear resistor 10 according to the present invention includes a sintered body containing zinc oxide (ZnO) as a main component and at least bismuth (Bi) and antimony (Sb) as subcomponents. A bonded body 20 is provided. The current-voltage nonlinear resistor 10 includes an insulating layer 30 that covers the side surface of the sintered body 20 and electrodes 40 formed on the upper and lower surfaces of the sintered body 20.

  The sintered body 20 has a longest straight line that is the longest over the cross section in the cross section of each zinc oxide particle that is a current-carrying component that mainly constitutes the microstructure of the sintered body 20 in a predetermined cross section of the sintered body 20. The length (L) is orthogonal at the midpoint of the longest straight line, and the average value of the ratio (S / L) of the orthogonal straight line length (S) across the cross section is configured to be 0.66 or more. Has been.

  Here, the length (L) of the longest straight line and the length (S) of the orthogonal straight line will be described.

  FIG. 2 is a diagram for explaining a microstructure model in a predetermined cross section of a sintered body 20 of a mixture containing zinc oxide (ZnO) as a main component and at least bismuth (Bi) and antimony (Sb) as subcomponents. It is.

As shown in FIG. 2, the cross section of the sintered body 20 includes zinc oxide particles 21 that are main components, and spinel-type particles 22, bismuth oxide particles 23, and pores 24 so as to surround the zinc oxide particles 21. Exists. The spinel particles 22 are mainly composed of zinc antimonate (Zn ₇ Sb ₂ O ₁₂ ). In the sintered body 20 having such a fine structure, the portion through which electricity flows is only the zinc oxide particles 21, and the other spinel type particles 22, bismuth oxide particles 23 and pores 24 are electrically insulating components and are electrically conductive. Does not contribute. Therefore, the current flows only through the zinc oxide particles 21. Further, the zinc oxide particles 21 have a certain resistance value, that is, a linear resistance characteristic, and the zinc oxide grain boundary that is an interface between the zinc oxide particles 21 has a non-linear resistance characteristic. Therefore, the current-voltage nonlinear resistor has a nonlinear resistance characteristic. Comparing the resistance of the zinc oxide particles 21 that are linear resistance and the resistance of the zinc oxide grain boundary that is non-linear resistance, the zinc oxide grain boundary has higher resistance even in the impulse current region where the current value is very high. Note that the non-linear resistance characteristic is a characteristic in which the resistance value is high when the voltage is low, and the resistance value rapidly decreases when the voltage exceeds a predetermined voltage.

  As shown in FIG. 2, in the cross section of each zinc oxide particle in the field of view, the length (L) of the longest straight line that is the longest across the cross section is orthogonal to the midpoint of the longest straight line, The length (S) is measured, and the value of S / L is determined for the cross section of each zinc oxide particle. And S / L calculated | required about the cross section of each zinc oxide particle is arithmetically averaged, and S / L as the whole averaged is obtained. The sintered body 20 is configured so that the averaged S / L value (hereinafter referred to as average S / L) is 0.66 or more.

  In the measurement of the length of the longest straight line (L) and the length of the orthogonal straight line (S), first, the inside of the sintered body 20 is cut out, and the cut out sample is mirror-polished. Subsequently, in order to make it easy to identify the particles, the mirror-polished surface of the sintered body 20 is etched with, for example, a hydrochloric acid solution to form minute irregularities on the observation surface. And it observes with a scanning electron microscope (SEM), and measures the length (L) of a longest straight line, and the length (S) of an orthogonal straight line. In the observation by SEM, zinc oxide particles, spinel particles, bismuth oxide particles, pores, and the like can be identified based on the color of the observation photograph by observing with a reflected electron image.

  In the measurement of the length of the longest straight line (L) and the length of the orthogonal straight line (S), several SEM photographs were taken for each sample with different fields of view at a magnification of 1000 times, for example, 900 to 1000 oxidations. The longest straight line length (L) and the orthogonal straight line length (S) in the cross section of the zinc particles are measured. And S / L in the cross section of each zinc oxide particle is arithmetically averaged, and average S / L is calculated | required.

  As described above, by configuring the sintered body 20 so that the average S / L of the cross section of each zinc oxide particle in the predetermined cross section of the sintered body 20 is 0.66 or more, current-voltage nonlinear resistance The energization path in the body 10 is shortened. When the energization path is shortened, the resistance value between the electrodes 40 is lowered in the high current region, and the nonlinear resistance characteristic is improved. This energization path is shortened because the fine structure becomes uniform by making the grain growth of the zinc oxide particles 21 uniform.

  Here, when the zinc oxide particles 21 undergo a uniform sintering reaction, the particle shape approaches a spherical shape, and the cross-sectional shape approaches a circle. The average S / L is an index indicating the uniformity of grain growth of the zinc oxide particles 21. Therefore, in the sintered body 20 having an average S / L of 0.66 or more, the grain growth of the zinc oxide particles 21 is made uniform, and the energization path is shortened. Therefore, in the current-voltage nonlinear resistor 10 including the sintered body 20 having an average S / L of 0.66 or more, excellent nonlinear resistance characteristics can be obtained.

Further, in the current-voltage nonlinear resistor 10 according to the present invention, a value obtained by averaging the cross-sectional areas of the bismuth oxide particles 23 in a predetermined cross-section of the sintered body 20 (hereinafter referred to as an average cross-sectional area) (X1) is 1. is configured .15Myuemu ² below, and the average divided by the cross-sectional area (X1) (σ1 / X1) is 0 the standard deviation (.sigma.1) each bismuth oxide particles 23 based on the distribution of the cross-sectional area of each bismuth oxide particles 23 .95 or less. Here, (σ1 / X1) is used as an index indicating the variation of the bismuth oxide particles 23.

  The cross-sectional area of each bismuth oxide particle 23 is cut out from the inside of the sintered body 20 as in the case of measuring the S / L in the cross section of each zinc oxide particle 21 described above, and mirror polishing is performed on the cut-out sample. Processing, etching processing, etc. are performed. For each sample, several SEM photographs are taken at different magnifications, for example, at a magnification of 1000 times, and for example, the area of 900 to 1000 bismuth oxide particles 23 is obtained by image processing. Then, the obtained area is arithmetically averaged to obtain the average cross-sectional area (X1) of each bismuth oxide particle 23. The standard deviation (σ1) is obtained based on the distribution of the cross-sectional area of each bismuth oxide particle 23 described above.

Here, the average cross-sectional area (X1) of each bismuth oxide particle 23 is configured to be 1.15 μm ² or less, and the standard deviation (σ1) based on the distribution of the cross-sectional area of each bismuth oxide particle 23 is the average of each bismuth oxide particle 23. By configuring the value (σ1 / X1) divided by the cross-sectional area (X1) to be 0.95 or less, the bismuth oxide particles 23 are uniformly dispersed in the sintered body 20. Thereby, the fine structure of the sintered body 20 is made uniform, the energization path is shortened, and excellent non-linear resistance characteristics are obtained.

  Further, the mixture for forming the sintered body 20 of the current-voltage nonlinear resistor 10 according to the present invention contains zinc oxide as a main component and at least Bi and Sb as subcomponents.

Bi, Sb is in terms of _{Bi 2 O 3, Sb 2 O} 3 , respectively, 0.3～2.5Mol% of _Bi 2 _{O 3,} are contained _Sb 2 _{O 3} so as to include 0.2～7Mol% It is preferable. In addition, it is preferable that the zinc oxide which is a main component is contained 85 mol% or more.

The reason why it is preferable to have a 0.3～2.5Mol% content of Bi in terms of _Bi 2 _{O 3} is _Bi 2 _{O 3} has an effect of promoting the grain growth of zinc oxide grains 21, This is because if the content is less than 0.3 mol%, sintering is not sufficiently promoted and a dense sintered body cannot be obtained. Moreover, when content exceeds 2.5 mol%, it is because the zinc oxide particle 21 will become large too much and resistance value will fall.

The reason why it is preferable to have a content of Sb in terms of _Sb 2 _{O 3} and 0.2～7Mol% is _Sb 2 _{O 3} is the zinc oxide grains in the sintered to form a zinc oxide and spinel grains This is because, when the content is less than 0.2 mol%, the zinc oxide particles 21 become excessively large and the resistance value decreases. Moreover, when content exceeds 7 mol%, the particle growth of a zinc oxide particle will be suppressed and sintering will not fully be accelerated | stimulated.

  It is preferable that 85 mol% or more of zinc oxide as the main component is contained. When the content of zinc oxide is smaller than 85 mol%, the ratio of the zinc oxide as the current-carrying part to the whole becomes small, and non-linearity. It is because it adversely affects

  Moreover, the component contained as a subcomponent in a mixture is not restricted only to Bi and Sb. Further, for example, manganese (Mn), cobalt (Co), nickel (Ni), or the like may be contained as a subcomponent.

In this case, Co, Mn, and Ni are converted into Co ₂ O ₃ , MnO, and NiO, respectively, Co ₂ O ₃ is 0.2 to ₃ mol%, MnO is 0.2 to 6 mol%, and NiO is 0.5. It is preferable to contain so that it may contain ~ 5 mol%. Even in this case, it is preferable that 85 mol% or more of zinc oxide as a main component is contained.

The content of Co is preferably 0.2 to ₃ mol% in terms of Co ₂ O ₃ because Co ₂ O ₃ is mainly dissolved in spinel particles to increase nonlinear resistance characteristics. This is because it is an effective component for improving, but when the content is less than 0.2 mol%, the effect of improving the non-linear resistance characteristic cannot be sufficiently obtained. Further, even when the content exceeds 3 mol%, the effect of improving the non-linear resistance characteristics cannot be sufficiently obtained.

  The content of Mn is preferably 0.2 to 6 mol% in terms of MnO because MnO is mainly effective for solid solution in spinel particles and greatly improving non-linear resistance characteristics. Although it is a component, when the content is less than 0.2 mol%, the effect of improving the nonlinear resistance characteristic cannot be sufficiently obtained. Further, even when the content exceeds 6 mol%, the effect of improving the non-linear resistance characteristics cannot be sufficiently obtained.

  The Ni content is preferably 0.5 to 5 mol% in terms of NiO, since NiO is effective mainly for solid solution in spinel particles and greatly improving non-linear resistance characteristics. Although it is a component, when the content is less than 0.5 mol%, the effect of improving this non-linear resistance characteristic cannot be obtained sufficiently. Further, even when the content exceeds 5 mol%, the effect of improving the non-linear resistance characteristics cannot be sufficiently obtained.

  Moreover, Bi contained as a subcomponent in the mixture for forming the sintered body 20 of the current-voltage nonlinear resistor 10 according to the present invention is contained as bismuth oxide particles. The average particle diameter (X2) of the bismuth oxide particles is preferably 0.8 μm or less. Further, the bismuth oxide particles are configured such that a value (σ2 / X2) obtained by dividing the standard deviation (σ2) based on the particle size distribution of the bismuth oxide particles by the average particle size (X2) of the bismuth oxide particles is 0.3 or less. It is preferred that Here, (σ2 / X2) is used as an index indicating variation of bismuth oxide particles.

  The average particle diameter of the bismuth oxide particles, which are powders, is determined from, for example, the SEM photograph obtained by observing the bottom surface of the molded body formed by pressure formation in the step of producing the sintered body 20 by SEM. Can be measured. For example, for each sample, several SEM photographs are taken at different magnifications, for example, at a magnification of 1000 times, and the area of, for example, 900 to 1000 bismuth oxide particles existing on the bottom surface of the molded body is obtained by image processing. And let the diameter of the circle | round | yen equivalent to the calculated | required area be a particle size of each bismuth oxide particle. And the particle diameter of each bismuth oxide particle is arithmetically averaged, and it is set as the average particle diameter (X2) of bismuth oxide particle. The standard deviation (σ2) is determined based on the particle size distribution of each bismuth oxide particle described above.

  The average particle diameter (X2) of the bismuth oxide particles contained in the mixture is preferably 0.8 μm or less. If the average particle diameter (X2) exceeds 0.8 μm, the sintering becomes uneven, This is because the path becomes longer and the non-linear resistance characteristics deteriorate. The average particle size of the bismuth oxide particles contained in the mixture is preferably as small as possible. However, due to production limitations when the mixture is pulverized, the lower limit of the average particle size of the bismuth oxide particles is about 0.05 μm. .

  The value (σ2 / X2) obtained by dividing the standard deviation (σ2) based on the particle size distribution of the bismuth oxide particles by the average particle size (X2) of the bismuth oxide particles is preferably 0.3 or less. This is because if X2 exceeds 0.3, the sintering becomes non-uniform, the energization path becomes long, and the non-linear resistance characteristics deteriorate.

  The insulating layer 30 that covers the side surface of the sintered body 20 is made of, for example, an inorganic insulating material such as glass that is an electrically insulating material. The insulating layer 30 is formed by, for example, applying or spraying the above-described electrical insulating material to the side surface of the sintered body 20 and performing heat treatment. In addition, it is preferable that the thickness of the insulating layer 30 is formed to be about 0.03 to 0.5 mm from the viewpoint of the insulating performance and mechanical strength.

  The electrodes 40 formed on the upper and lower surfaces of the sintered body 20 are made of, for example, a metal material such as aluminum having electrical conductivity. The electrode 40 is formed on the upper and lower surfaces of the sintered body 20 by, for example, spraying the above-described conductive material. The thickness of the electrode 40 is preferably about 0.03 to 0.4 mm from the viewpoint of the conductivity and adhesion strength of the electrode 40.

  Here, the current-voltage nonlinear resistor 10 according to the present invention has, for example, a cylindrical shape having a diameter of 20 to 150 mm and a thickness of 1 to 50 mm. The shape of the current-voltage nonlinear resistor 10 is not limited to this.

  Next, a method for manufacturing the current-voltage nonlinear resistor 10 according to the present invention will be described.

First, it comprises zinc oxide as the main component than 85 mol%, and as an auxiliary component, respectively _{Bi 2 O 3, Sb 2 O} 3, Co 2 O 3, MnO, in terms of NiO, and _Bi 2 _{O 3} 0. ₃ to 2.5 mol%, Sb ₂ O ₃ 0.2 to 7 mol%, Co ₂ O ₃ 0.2 to ₃ mol%, MnO 0.2 to 6 mol%, NiO 0.5 to 5 mol% Weigh.

  Subsequently, the weighed mixture, and pure water and an organic binder such as polyvinyl alcohol in an amount such that the content of the mixture is 35 to 60% by weight are put into a wet pulverizer, and at least the average of bismuth oxide particles The particle diameter (X2) is 0.8 μm or less, and the value (σ2 / X2) obtained by dividing the standard deviation (σ2) based on the particle size distribution of the bismuth oxide particles by the average particle diameter (X2) of the bismuth oxide particles is 0.00. The mixture is mixed while being pulverized so as to be 3 or less to prepare a slurry.

  Here, as the wet pulverization apparatus, for example, a circulation apparatus using zirconia beads for pulverization and mixing is used. The particle size of the zirconia beads, the bead filling rate in the vessel, the peripheral speed of the stirring rotor, the circulation flow rate, the mixing time, and the like can be appropriately changed.

  Subsequently, the produced slurry is sprayed and granulated by a rotating disk method or a pressure nozzle method to produce a granulated powder. Here, the particle size of the granulated powder is preferably 50 to 150 μm. The particle size at this time is measured using, for example, a particle size distribution measuring apparatus using the wet laser diffraction method described above. Here, the reason why the particle size of the granulated powder is preferably 50 to 150 μm is that it is excellent in filling property into the mold.

  The obtained granulated powder is molded into a columnar shape by, for example, a hydraulic press molding machine to produce a molded body.

  Subsequently, this molded body is heated to a temperature of 350 to 500 ° C., and maintained at this temperature for 1 to 5 hours, for example, to remove the organic solvent.

  Subsequently, the molded body is heated to a temperature of 1000 to 1200 ° C., and is fired at this temperature, for example, for 2 hours or more. In addition, baking may be performed by heating to a baking temperature after once cooling to room temperature from a temperature (350 to 500 ° C.) for removing the organic solvent, or baking from a temperature (350 to 500 ° C.) for removing the organic solvent. You may carry out by heating to temperature. In addition, the firing is performed, for example, by using a tunnel-type continuous furnace and placing the molded body in a refractory container such as alumina or mullite. Moreover, it is preferable that the heating rate to baking temperature is 50-200 degreeC / hour from a viewpoint of the temperature uniformity in a to-be-baked thing, and a baking process lead time.

  After the elapse of the maintenance time at the firing temperature (1000 to 1200 ° C.), the fired molded body is cooled. In addition, it is preferable that the cooling rate at the time of cooling is 100-200 degreeC / hour from a viewpoint of the temperature uniformity in a to-be-baked thing, and a baking process lead time. Through this cooling step, the sintered body 20 is obtained.

  The inorganic insulating material described above is applied or sprayed onto the side surface of the sintered body 20 that is a cooled formed body, and heat-treated at a temperature of 400 to 500 ° C. for 1 to 5 hours to form the insulating layer 30.

  Further, the upper and lower end surfaces of the sintered body 20 are polished, and the electrode 40 is formed on the polished surface by, for example, spraying the above-described conductive material.

  In addition, the order which performs the process of forming the insulating layer 30, and the process of forming the electrode 40 is not specifically limited, Any may be performed first.

  Thus, the current-voltage nonlinear resistor 10 is produced through the above-described steps.

  As described above, by producing the current-voltage nonlinear resistor 10, a current-voltage nonlinear resistor having excellent nonlinear resistance characteristics can be obtained.

  Next, it will be specifically described below that the current-voltage nonlinear resistor 10 according to the present invention has excellent nonlinear resistance characteristics.

(Influence of average S / L in the cross section of zinc oxide particles)
Here, in the cross section of each zinc oxide particle 21 in the predetermined cross section of the sintered body 20, the length (L) of the longest straight line that is the longest across the cross section is orthogonal to the midpoint of the longest straight line, The influence of the average S / L, which is obtained by averaging the ratio (S / L) to the length (S) of the orthogonal straight line, on the nonlinear resistance characteristic will be described.

First, zinc oxide (ZnO) was used as a main component. As subcomponents, bismuth oxide (Bi ₂ O ₃ ) is 0.6 mol%, manganese oxide (MnO), cobalt oxide (Co ₂ O ₃ ) is 1.5 mol%, antimony trioxide (Sb ₂ O ₃ ), and oxidation. Each was adjusted so that nickel (NiO) was added in an amount of 2.5 mol% and an aluminum hydroxide (Al (OH) ₃ ) aqueous solution was added in an amount of 0.005 mol% in terms of aluminum ions (Al ³⁺ ). The balance is zinc oxide.

  The mixture prepared as described above and a binder of pure water and an organic binder adjusted so that the content of the mixture was 40% by mass were put into a circulation type wet pulverizer. Four kinds of slurries are obtained by changing the particle size (3 mm, 0.5 mm, 0.3 mm) and mixing time (0.3 hours, 0.5 hours, 1.5 hours) of zirconia beads in a wet pulverizer. Got. The pump flow rate was constant at 15 L / min.

  Subsequently, each slurry was spray-granulated with a spray dryer so that the particle size was 100 μm. The obtained granulated powder was formed into a cylindrical shaped body having a diameter of 81 mm and a thickness of 30 mm by a hydraulic press molding machine.

  Subsequently, the molded body was heated to a temperature of 500 ° C. and maintained at this temperature for 1 hour to remove an organic binder as an organic solvent.

  Subsequently, after the temperature of the molded body was once cooled to room temperature, the molded body was heated to a firing temperature of 1150 ° C. and maintained at this temperature for 2 hours for firing. The heating rate until the firing temperature was reached was 100 ° C./hour.

  After the maintaining time of the firing temperature (1150 ° C.), the fired molded body was cooled. In addition, the cooling rate at the time of cooling was set to about 100 ° C./hour. Through this cooling process, a sintered body was obtained.

  In the cross section of each zinc oxide particle in a predetermined cross section of the obtained four kinds of sintered bodies, the length of the longest straight line (L) that is the longest across the cross section is orthogonal to the midpoint of the longest straight line, The length (S) of the orthogonal straight line across the cross section was measured. Then, the ratio (S / L) of the length (L) of the longest straight line in the cross section of each zinc oxide particle and the length (S) of the orthogonal straight line is obtained, and the S / L in the cross section of each zinc oxide particle is arithmetically averaged. Average S / L.

  Specifically, first, the inside of the sintered body was cut out, the cut sample was mirror-polished, and a sample for observation with a scanning electron microscope (SEM) was produced. Here, the mirror-polished surface of the sintered body was etched with a 0.5% hydrochloric acid solution in order to make it easy to identify the particles, thereby forming minute irregularities on the observation surface. In observation by SEM, zinc oxide particles, spinel-type particles, bismuth oxide layers, and pores were identified by the color of the observation photograph by observing with a reflected electron image.

  Subsequently, for each sample, SEM photographs of 10 different fields of view were taken at a magnification of 1000 times. In each photograph, the length of the longest straight line (L) that is the longest across the cross section of each zinc oxide particle cross section. And the length (S) of the orthogonal straight line across the cross-section at a midpoint of the longest straight line. Then, the ratio (S / L) between the length of the longest straight line (L) and the length of the orthogonal straight line (S) (S / L) is obtained for the cross section of each zinc oxide particle (about 1000), and the average S is obtained by arithmetically averaging them. / L was determined.

  Subsequently, a glass frit was applied to the side surface of each sintered body and heat treated at a temperature of 500 ° C. for 1 hour to form an insulating layer. Further, the upper and lower end surfaces of each sintered body were polished, and aluminum was sprayed on the polished surface to form an electrode, whereby four types of current-voltage nonlinear resistors were obtained. Here, the obtained four types of current-voltage nonlinear resistors are referred to as Sample 1 to Sample 4, respectively. 25 pieces of each sample were prepared.

  Next, the non-linear resistance characteristics of Sample 1 to Sample 4 were evaluated.

In the evaluation of non-linear resistance characteristics, the varistor voltage (V _{1 mA} ), which is a voltage when an AC current of 1 mA commercial frequency is applied, and the voltage (V _{10 kA} ) when an 8 × 20 μs impulse current flows through _{10 kA} are measured. These ratios (V _{10 kA} / V _{1 mA} ) were evaluated as non-linearity coefficients. It shows that the nonlinear resistance characteristic is excellent, so that the value of this nonlinear coefficient is small. The varistor voltage (V _{1 mA} ) was measured according to JEC0202-1994.

  FIG. 3 is a diagram showing the results of nonlinear resistance characteristic tests on Samples 1 to 4. The average S / L is shown on the horizontal axis of FIG.

As shown in FIG. 3, it was found that the non-linearity coefficient (V _{10 kA} / V _{1 mA} ) decreases as the average S / L increases. In particular, it was found that when the average S / L was 0.66 or more, the nonlinearity coefficient was already smaller than 1.5, and excellent nonlinear resistance characteristics could be obtained.

  In addition, in the specification of the lightning arrester, when a zinc oxide element having a nonlinear coefficient smaller than 1.5 is used, a lightning arrester having excellent nonlinear resistance characteristics can be obtained. Therefore, when the nonlinear coefficient is smaller than 1.5, excellent nonlinear resistance characteristics are obtained.

(Influence of standard deviation (σ1) based on average cross-sectional area (X1) of bismuth oxide particles and cross-sectional area distribution of bismuth oxide particles)
Here, the influence of the average cross-sectional area (X1) obtained by averaging the cross-sectional areas of the bismuth oxide particles 23 in the predetermined cross-section of the sintered body 20 on the non-linear resistance characteristics will be described. Further, the influence of the value (σ1 / X1) obtained by dividing the standard deviation (σ1) based on the distribution of the cross-sectional area of each bismuth oxide particle 23 by the average cross-sectional area (X1) of the bismuth oxide particle 23 on the nonlinear resistance characteristics will be described. To do.

  Here, four types of sintered bodies (sample 1 to sample 4) prepared when the influence of the above-described average S / L was described were used. Therefore, each of these four types of sintered bodies has nonlinear resistance characteristics based on the above-described average S / L.

  When measuring the average cross-sectional area (X1) of bismuth oxide particles, zinc oxide particles, spinel particles, bismuth oxide layers, and pores were identified by the same method as the method for observing the cross section of each zinc oxide particle described above.

  And about each sample, the SEM photograph of 10 different visual fields was taken by 1000 time magnification, and the area of each bismuth oxide particle 23 (about 1000 pieces) was calculated | required by the image processing using a planimeter in each photograph. And the calculated | required area was arithmetically averaged and the average cross-sectional area (X1) of each bismuth oxide particle 23 was calculated | required.

  The standard deviation (σ1) was obtained based on the distribution of the cross-sectional area of each bismuth oxide particle 23 in the analysis data obtained by the image processing described above. Further, the standard deviation (σ1) was divided by the average cross-sectional area (X1) of the bismuth oxide particles to obtain (σ1 / X1).

  Next, the non-linear resistance characteristics of Sample 1 to Sample 4 were evaluated.

  4 and 5 are diagrams showing the results of the nonlinear resistance characteristic test in Samples 1 to 4. FIG. The horizontal axis of FIG. 4 shows the average cross-sectional area (X1) of the bismuth oxide particles 23. The horizontal axis of FIG. 5 shows a value (σ1 / X1) obtained by dividing the standard deviation (σ1) based on the distribution of the cross-sectional area of each bismuth oxide particle 23 by the average cross-sectional area (X1) of the bismuth oxide particle 23. Yes.

Here, since the non-linear resistance characteristics are evaluated using the samples 1 to 4, the non-linearity coefficient (V _{10 kA} / V _{1 mA} ) has been described when explaining the influence of the above-described average S / L. It is the same as the non-linearity coefficient (V _{10 kA} / V _{1 mA} ) in Samples 1 to 4.

As shown in FIG. 4, it was found that the non-linearity coefficient (V _{10 kA} / V _{1 mA} ) decreases as the average cross-sectional area (X1) of the bismuth oxide particles 23 decreases. In particular, it was found that when the average cross-sectional area (X1) of the bismuth oxide particles 23 is 1.15 μm ² or less, the nonlinearity coefficient is already smaller than 1.5, and excellent current-voltage nonlinear characteristics can be obtained. .

Further, as shown in FIG. 5, it was found that the non-linearity coefficient (V _{10 kA} / V _{1 mA} ) decreases as (σ1 / X1) decreases. In particular, it was found that when (σ1 / X1) is 0.95 or less, the nonlinearity coefficient is already smaller than 1.5, and excellent current-voltage nonlinear characteristics can be obtained.

(Influence of average particle diameter (X2) of bismuth oxide particles contained as a subcomponent in the mixture and standard deviation (σ2) based on particle size distribution of bismuth oxide particles)
Here, the influence of the average particle diameter (X2) of bismuth oxide particles contained as a subcomponent in the mixture for forming the sintered body 20 of the current-voltage nonlinear resistor 10 on the nonlinear resistance characteristics will be described. . Further, the influence of the value (σ2 / X2) obtained by dividing the standard deviation (σ2) based on the particle size distribution of the bismuth oxide particles by the average particle size (X2) of the bismuth oxide particles on the nonlinear resistance characteristics will be described.

  The average particle diameter (X2) of the bismuth oxide particles is obtained by pressurizing and forming granulated powder composed of four types of slurries prepared when explaining the influence of the above-described average S / L. It was measured using four types of cylindrical shaped bodies having a thickness of 81 mm and a thickness of 30 mm. In addition, in a molded object, although the shape of granulated powder deform | transforms by press formation, each mixture itself contained in it does not deform | transform.

  Specifically, SEM photographs of 10 different fields of view on the bottom surface of the molded body were taken at a magnification of 1000 times, and in each photograph, the area of each bismuth oxide particle (about 1000 particles) was obtained by image processing using a planimeter. It was.

  And the diameter of the circle | round | yen equivalent to the area | region of each calculated | required each bismuth oxide particle was made into the particle size of each bismuth oxide particle. And the particle diameter of each bismuth oxide particle was arithmetically averaged, and it was set as the average particle diameter (X2) of bismuth oxide particle.

  Further, the standard deviation (σ2) was determined based on the particle size distribution of each bismuth oxide particle. Further, (σ2 / X2) was determined by dividing the standard deviation (σ2) by the average particle diameter (X2) of the bismuth oxide particles.

  Next, the non-linear resistance characteristics of Sample 1 to Sample 4 were evaluated.

  6 and 7 are diagrams showing the results of the nonlinear resistance characteristic test in Samples 1 to 4. FIG. The horizontal axis in FIG. 6 shows the average particle diameter (X2) of the bismuth oxide particles. The horizontal axis of FIG. 7 shows a value (σ2 / X2) obtained by dividing the standard deviation (σ2) based on the particle size distribution of each bismuth oxide particle by the average particle size (X2) of the bismuth oxide particle.

Here, since the non-linear resistance characteristics are evaluated using the samples 1 to 4, the non-linearity coefficient (V _{10 kA} / V _{1 mA} ) has been described when explaining the influence of the above-described average S / L. It is the same as the non-linearity coefficient (V _{10 kA} / V _{1 mA} ) in Samples 1 to 4.

As shown in FIG. 6, it was found that the non-linearity coefficient (V _{10 kA} / V _{1 mA} ) decreases as the average particle diameter (X2) of the bismuth oxide particles decreases. In particular, it was found that when the average particle diameter (X2) of the bismuth oxide particles is 0.8 μm or less, the nonlinearity coefficient is already smaller than 1.5, and excellent nonlinear resistance characteristics can be obtained.

Further, as shown in FIG. 7, it was found that the non-linearity coefficient (V _{10 kA} / V _{1 mA} ) decreases as (σ2 / X2) decreases. In particular, it was found that when (σ2 / X2) is 0.3 or less, the nonlinear coefficient is already smaller than 1.5, and excellent nonlinear resistance characteristics can be obtained.

(Effect of sintering temperature of sintered body)
Here, the influence of the firing temperature for forming the sintered body 20 of the current-voltage nonlinear resistor 10 on the nonlinear resistance characteristics will be described.

  Here, the non-linear resistance characteristics were examined by changing the firing temperature at the time of forming the sintered body 20 constituting the sample 4 among the samples prepared when explaining the influence of the above-described average S / L. The firing temperature was 7 conditions of 950, 1000, 1050, 1100, 1150, 1200, 1250 ° C.

  The molded body for forming the sintered body 20 of Sample 4 was heated to a temperature of 500 ° C., and maintained at this temperature for 1 hour to remove the organic solvent.

  Subsequently, after the temperature of the molded body was once cooled to room temperature, the molded body was heated to the above-described firing temperature, and maintained at this temperature for 2 hours for firing. The heating rate up to the firing temperature was 100 ° C./hour.

  The subsequent manufacturing method is the same as that of the current-voltage nonlinear resistor 10 manufactured when the influence of the above-described average S / L is described.

  Seven types of current-voltage nonlinear resistors 10 (sample 5 to sample 11) were obtained by the above-described manufacturing method. Three pieces of each sample were produced.

  Next, the non-linear resistance characteristics of Sample 5 to Sample 11 were evaluated. Note that the experimental conditions and experimental methods in the evaluation of the non-linear resistance characteristics were the same as the experimental conditions and experimental methods for examining the influence of the average S / L described above.

  FIG. 8 is a diagram showing the results of nonlinear resistance characteristic tests on Samples 5 to 11. The horizontal axis in FIG. 8 shows the firing temperature.

As shown in FIG. 8, when the firing temperature was 950 ° C. (sample 5), the non-linearity coefficient (V _{10 kA} / V _{1 mA} ) was larger than 1.5, indicating that the non-linear resistance characteristics were inferior. This is probably because the sintered body 20 is not densified. When the firing temperature was 1250 ° C. (sample 11), the nonlinearity coefficient (V _{10 kA} / V _{1 mA} ) was larger than 1.5, indicating that the nonlinear resistance characteristics were inferior.

On the other hand, when the firing temperature is 1000 to 1200 ° C. (sample 6 to sample 10), the nonlinearity coefficient (V _{10 kA} / V _{1 mA} ) is smaller than 1.5, and it is understood that excellent nonlinear resistance characteristics can be obtained. It was.

(Influence of the content of each component of the mixture)
Here, each component of a mixture containing zinc oxide (ZnO) as a main component and bismuth (Bi), antimony (Sb), manganese (Mn), cobalt (Co), and nickel (Ni) as subcomponents is contained. The influence of the amount on the non-linear resistance characteristic will be described.

Table 1 shows the composition components of the mixture and the nonlinearity coefficient (V _{10 kA} / V _{1 mA} ) in the current-voltage nonlinear resistors of Sample 12 to Sample 46. In Table 1, an asterisk is a symbol for indicating a sample that is outside the scope of the present invention, and the sample to which this symbol is attached is a comparative example.

  First, content of each component of a mixture containing zinc oxide (ZnO) as a main component and bismuth (Bi), antimony (Sb), manganese (Mn), cobalt (Co), and nickel (Ni) as subcomponents Were adjusted to the values of Sample 12 to Sample 46 shown in Table 1.

  The mixture prepared as described above and a binder of pure water and an organic binder adjusted so that the content of the mixture was 40% by mass were put into a circulation type wet pulverizer. In a wet pulverizer, zirconia beads having a diameter of 0.3 mm were used, pulverization and mixing were performed at a pump flow rate of 15 L / min and a mixing time of 0.5 hours.

  Here, in the wet pulverization apparatus, the average particle diameter (X2) of the bismuth oxide particles contained as subcomponents is 0.8 μm or less, and the standard deviation (σ2) based on the particle size distribution of the bismuth oxide particles is the average of the bismuth oxide particles. The bismuth oxide particles were pulverized so that the value (σ2 / X2) divided by the particle size (X2) was 0.3 or less.

  A uniformly mixed slurry was obtained by pulverization and mixing in the wet pulverizer.

  Subsequently, each slurry was spray-granulated with a spray dryer so that the particle size was 100 μm. The obtained granulated powder was formed into a cylindrical shaped body having a diameter of 81 mm and a thickness of 30 mm by a hydraulic press molding machine.

  Subsequently, the molded body was heated to a temperature of 500 ° C. and maintained at this temperature for 1 hour to remove an organic binder as an organic solvent.

  Subsequently, after the temperature of the molded body was once cooled to room temperature, the molded body was heated to a firing temperature of 1150 ° C. and maintained at this temperature for 2 hours for firing. The heating rate until the firing temperature was reached was 100 ° C./hour.

  After the maintaining time of the firing temperature (1150 ° C.), the fired molded body was cooled. In addition, the cooling rate at the time of cooling was set to about 100 ° C./hour. Through this cooling process, a sintered body was obtained.

  Subsequently, a glass frit was applied to the side surface of each sintered body and heat treated at a temperature of 500 ° C. for 1 hour to form an insulating layer. Further, the upper and lower end surfaces of each sintered body were polished, and aluminum was sprayed on the polished surface to form electrodes, to obtain 35 types of current-voltage nonlinear resistors. Here, the obtained 35 types of current-voltage nonlinear resistors are referred to as Sample 12 to Sample 46, respectively. In addition, 10 pieces of each sample were produced.

  Next, the nonlinear resistance characteristics of Sample 12 to Sample 46 were evaluated. Note that the experimental conditions and experimental methods in the evaluation of the non-linear resistance characteristics were the same as the experimental conditions and experimental methods for examining the influence of the average S / L described above.

Table 1 shows the results of the non-linear resistance characteristic test in Samples 12 to 46. In addition, the non-linearity coefficient (V _{10 kA} / V _{1 mA} ) shown in Table 1 is a value obtained by arithmetically averaging the results of 10 pieces in each sample.

As shown in Table 1, in the current-voltage nonlinear resistor according to the present invention, it was found that the nonlinearity coefficient (V _{10 kA} / V _{1 mA} ) was smaller than 1.5.

From the above results, including zinc oxide as the main component than 85 mol%, and as an auxiliary component, respectively _{Bi 2 O 3, Sb 2 O} 3, Co 2 O 3, MnO, in terms of NiO, _Bi 2 _{O 3} the 0.3~2.5mol%, 0.2~7mol% of _Sb 2 _{O 3, 0.2~3mol%} of _Co 2 _{O 3, 0.2~6mol%} of MnO, 0.5~5mol the NiO It was found that the current-voltage nonlinear resistor 10 according to the present invention including a sintered body of a mixture containing% can obtain excellent nonlinear resistance characteristics.

  Although the present invention has been specifically described above with reference to the embodiments, the present invention is not limited to these embodiments, and various modifications can be made without departing from the scope of the invention.

  DESCRIPTION OF SYMBOLS 10 ... Current-voltage nonlinear resistor, 20 ... Sintered body, 21 ... Zinc oxide particle, 22 ... Spinel type particle, 23 ... Bismuth oxide layer, 24 ... Pore, 30 ... Insulating layer, 40 ... Electrode.

Claims (3)

A current-voltage nonlinear resistor comprising a sintered body of a mixture containing zinc oxide as a main component and at least Bi and Sb as subcomponents,
The average particle size (X2) of the bismuth oxide particles contained as a subcomponent in the mixture for forming the sintered body is 0.8 μm or less, and the standard deviation (σ2) based on the particle size distribution of the bismuth oxide particles (Σ2 / X2) obtained by dividing by the average particle size (X2) of the bismuth oxide particles is 0.3 or less,
In the cross section of each zinc oxide particle that mainly constitutes the microstructure of the sintered body in a predetermined cross section of the sintered body, the longest straight line length (L) that is the longest across the cross section and the longest straight line The average value of the ratio (S / L) to the length (S) of the orthogonal straight line across the cross-section is 0.66 or more ,
A value (X1) obtained by averaging the cross-sectional areas of the bismuth oxide particles in a predetermined cross section of the sintered body is 1.15 μm ² or less, and the standard deviation (σ1) based on the cross-sectional area distribution of the bismuth oxide particles. The sintered body is configured so that a value (σ1 / X1) obtained by dividing the cross-sectional area of each bismuth oxide particle by an average value (X1) becomes 0.95 or less. Voltage nonlinear resistor. The secondary component of the mixture is Bi, Sb, Mn, Co, from Ni, respectively _{Bi 2 O 3, Sb 2 O} 3, Co 2 O 3, MnO, in terms of NiO, and _Bi 2 _{O 3} 0.3 ~2.5mol%, 0.2~7mol% of _Sb 2 _{O 3, 0.2~3mol%} of _Co 2 _{O 3,} comprises 0.5~5mol% 0.2~6mol%, the NiO and MnO, the main The current-voltage nonlinear resistor according to claim 1 , comprising 85 mol% or more of zinc oxide as a component . A method for producing a current-voltage nonlinear resistor comprising a sintered body of a mixture comprising zinc oxide as a main component and at least Bi, Sb, Mn, Co, and Ni as subcomponents,
It contains 85 mol% or more of zinc oxide as the main component, and Bi ₂ O ₃ , Sb ₂ O ₃ , Co ₂ O ₃ Bi in terms of MnO and NiO ₂ O ₃ 0.3 to 2.5 mol%, Sb ₂ O ₃ 0.2-7 mol%, Co ₂ O ₃ 0.2 to 3 mol%, MnO 0.2 to 6 mol%, NiO 0.5 to 5 mol% of the mixture and organic solvent were charged into a wet pulverizer, and at least the average particle size of bismuth oxide particles (X2 ) Is 0.8 μm or less, and the value (σ2 / X2) obtained by dividing the standard deviation (σ2) based on the particle size distribution of the bismuth oxide particles by the average particle size (X2) of the bismuth oxide particles is 0.3 or less. Mixing while pulverizing the mixture so as to produce a slurry,
Spraying the slurry to form a granulated powder having a predetermined particle diameter; and
A molding step of applying a predetermined pressure to the granulated powder to form a molded body having a predetermined shape;
Heating the molded body to a first temperature of 350 to 500 ° C., maintaining the first temperature for a predetermined time to remove the organic solvent; and
A second heating step of heating the molded body from which the organic solvent has been removed to a second temperature of 1000 to 1200 ° C. and maintaining the second temperature for a predetermined time;
A cooling step for cooling the fired molded body;
Comprising
In the cross section of each zinc oxide particle that mainly constitutes the microstructure of the sintered body in the predetermined cross section of the sintered body that is the fired molded body, the length of the longest straight line that is the longest across the cross section ( L) and the average of the ratio (S / L) of the length (S) of the orthogonal straight line across the cross section orthogonal to the midpoint of the longest straight line is 0.66 or more,
A value (X1) obtained by averaging the cross-sectional areas of the bismuth oxide particles in the predetermined cross section of the sintered body is 1.15 μm. ² The value (σ1 / X1) obtained by dividing the standard deviation (σ1) based on the distribution of the cross-sectional area of each bismuth oxide particle by the value (X1) obtained by averaging the cross-sectional areas of the bismuth oxide particles is 0.00. A method for producing a current-voltage nonlinear resistor, wherein the current-voltage nonlinear resistor is 95 or less.

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