JP2011171665A - Current-voltage nonlinear resistor, and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a current-voltage nonlinear resistor capable of reducing resistance and excelling in a nonlinear resistance characteristic, surge current withstand capability and a charge life characteristic, and to provide a method of manufacturing the same. <P>SOLUTION: This current-voltage nonlinear resistor 10 includes a sintered body of a mixture containing zinc oxide as a main constituent, wherein the mixture contains 0.2-0.8 mol% of antimony in terms of Sb<SB>2</SB>O<SB>3</SB>, 0.2-1.5 mol% of cobalt in terms of Co<SB>2</SB>O<SB>3</SB>, 0.1-1 mol% of manganese in terms of MnO, and 0.3-2 mol% of nickel in terms of NiO, and contains bismuth so that a mol% relative ratio of bismuth to antimony satisfies a relationship of 1.5≤Bi<SB>2</SB>O<SB>3</SB>/Sb<SB>2</SB>O<SB>3</SB>≤4.5 in terms of the respective oxides; the average particle size of zinc oxide particles in the sintered body 20 is ≥25 μm; and standard deviation based on a particle size distribution of zinc oxide particles in the sintered body 20 is ≤20% of the average particle size of the zinc oxide particles. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a current-voltage non-linear resistor mainly composed of zinc oxide (ZnO) applied to a surge protect device (SPD) and a low voltage system lightning arrester, and a method for manufacturing the same.

In general, an overvoltage protection device such as a lightning arrester or a surge absorber is used to protect the power system from abnormal voltage. The lightning arrester and surge absorber have a non-linear resistor that exhibits insulation characteristics under normal voltage and low resistance when an abnormal voltage is applied, and is effective in suppressing overvoltage. This current-voltage non-linear resistor has, for example, zinc oxide (ZnO) as a main component, and Bi ₂ O ₃ , Co ₂ O ₃ , MnO, Sb ₂ O ₃ , and NiO added as subcomponents thereto. A ceramic body obtained by mixing, granulating, forming and sintering a raw material (see, for example, Patent Document 1). An insulating layer made of an electrically insulating material is formed on the side surface of the sintered body in order to prevent flashover from the side surface during surge absorption.

  Also, in recent electronic devices such as personal computers, surge resistance tends to decrease with higher functionality and higher integration. Therefore, in these electronic devices, lightning surge damage is increasing, which has a great influence on power and communication networks. Under such circumstances, demand for surge absorbers of low voltage systems such as surge protect devices (SPD) is increasing year by year. Also in this low voltage system surge absorber, a current-voltage nonlinear resistor mainly composed of zinc oxide is used due to its excellent nonlinear resistance characteristics.

  Surge protection devices are required not only to induce lightning (8/20 μs) but also to absorb large currents with a long wave tail such as direct lightning (10/350 μs). Therefore, high surge withstand characteristics are required for current-voltage nonlinear resistors. In order to improve the surge withstand characteristics, it is effective to lower the resistance value per unit volume of the current-voltage nonlinear resistor. However, for example, when a current-voltage nonlinear resistor of 200 V / mm class is used for a low voltage system of 100 V class, the thickness must be reduced to about 1 to 3 mm. For this reason, the mechanical strength is lowered and the manufacture becomes difficult, and the surge withstand characteristics are lowered. Therefore, it is required to reduce the resistance of the current-voltage nonlinear resistor.

In order to reduce the resistance of the current-voltage non-linear resistor, for example, the content of subcomponents such as Bi ₂ O ₃ , TiO ₂ , Co ₂ O ₃ , MnO, NiO, TeO _{2 with} zinc oxide as the main component Has been disclosed (for example, see Patent Document 2). This current-voltage non-linear resistor has a low resistance value and an excellent surge resistance characteristic.

Further, in the current-voltage nonlinear resistor to which zinc oxide is the main component and Bi ₂ O ₃ , TiO ₂ , Sb ₂ O ₃ is added, by limiting the temperature increase rate range at a constant temperature in the firing step, A technique for obtaining a current-voltage nonlinear resistor having a low resistance value and a small variation in operation start voltage is disclosed (for example, see Patent Document 3).

  In addition, in order to obtain long-term reliability of the surge absorber, the current-voltage nonlinear resistor is required to have improved surge withstand characteristics and excellent life characteristics.

Japanese Patent Publication No. 4-25681 JP 2003-109806 A Japanese Patent No. 3251134

However, in order to reduce the resistance of the current-voltage nonlinear resistor, a component for promoting grain growth of zinc oxide particles such as TiO ₂ is added as in the conventional current-voltage nonlinear resistor described above, Or, by controlling the firing pattern, abnormal grain growth of zinc oxide particles may occur. Therefore, the crystal grain size in the sintered body varies widely, and it is difficult to obtain sufficient surge resistance characteristics. In addition, when the crystal grain size varies, the life characteristics and non-linear characteristics also deteriorate.

  Accordingly, the present invention has been made to solve the above-described problems, and it is possible to reduce the resistance, as well as a current-voltage nonlinear resistor excellent in non-linear resistance characteristics, surge withstand capability, and electric charging life characteristics, and the same. An object is to provide a manufacturing method.

In order to achieve the above object, according to one aspect of the present invention, a current-voltage comprising a sintered body of a mixture containing zinc oxide as a main component and bismuth, antimony, manganese, cobalt, and nickel as subcomponents. in the non-linear resistor, wherein the mixture, 0.2～0.8Mol% in terms of antimony _Sb 2 _{O 3, 0.2~1.5mol%} in terms of cobalt to _Co 2 _{O 3,} a manganese 0.1 to 1 mol% in terms of MnO, 0.3 to 2 mol% in terms of nickel to NiO, and bismuth in terms of mol% relative ratio of bismuth to antimony in terms of the respective oxides 1.5 ≦ Bi ₂ O ₃ / Sb ₂ O ₃ ≦ 4.5, the zinc oxide particles in the sintered body have an average particle size of 25 μm or more, and the sintered body Zinc oxide in A current-voltage nonlinear resistor is provided, wherein a standard deviation based on a particle size distribution of the particles is 20% or less of an average particle size of the zinc oxide particles.

Moreover, according to one aspect of the present invention, a current-voltage nonlinear resistor including a sintered body of a mixture containing zinc oxide as a main component and bismuth, antimony, manganese, cobalt, and nickel as subcomponents is manufactured. In the method, 0.2 to 0.8 mol% of antimony converted to Sb ₂ O ₃ , 0.2 to 1.5 mol% of cobalt converted to Co ₂ O ₃ , and 0.2 to 1.5 mol% of manganese converted to MnO 1 to 1 mol%, containing 0.3 to 2 mol% of nickel converted to NiO, and the mol% relative ratio of bismuth to antimony converted to each oxide is 1.5 ≦ Bi _{2. O 3 / Sb 2 O 3 ≦} 4.5 wherein mixtures comprising so as to satisfy the relation, and the organic solvent so that the contents of the mixture is 30 to 60% by weight was charged into a wet pulverizing device, said mixture The mixture is mixed while being pulverized so that the average particle size is 0.5 μm or less, and a pulverizing step for producing a slurry, and the slurry is sprayed to form a granulated powder having a particle size of 70 to 130 μm. A granule powder forming step, a molding step in which a predetermined pressure is applied to the granulated powder to form a molded body having a predetermined shape, and the molded body is heated to a first temperature of 350 to 500 ° C. A first heating step of removing the organic solvent while maintaining the first temperature for a period of time; and heating the molded body from which the organic solvent has been removed to a second temperature of 900 to 1300 ° C. A second heating step for firing while maintaining the temperature of 2, and a cooling step for cooling the fired molded body and cooling at a cooling rate of 25 to 100 ° C./hour when the temperature of the molded body is 750 ° C. or lower. Current-voltage non-linearity A method of manufacturing a resistance element is provided.

  According to the present invention, it is possible to provide a current-voltage non-linear resistor excellent in non-linear resistance characteristics, surge withstand capability, and electric charge life characteristics, and a method for manufacturing the same, while reducing resistance.

It is a figure which shows the cross section of the current-voltage nonlinear resistor 10 which concerns on this invention.

  Hereinafter, embodiments 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 has zinc oxide (ZnO) as a main component and bismuth (Bi), antimony (Sb), manganese (Mn), cobalt as subcomponents. A sintered body 20 of a mixture containing (Co) and nickel (Ni) is provided. Moreover, the mixture for constituting the sintered body 20 is 0.2 to 0.8 mol% in terms of antimony converted to Sb ₂ O ₃ and 0.2 to 1.5 mol in terms of cobalt converted to Co ₂ O _3. %, Manganese is 0.1 to 1 mol% in terms of MnO, nickel is in the range of 0.3 to 2 mol% in terms of NiO, and bismuth is a mol% relative ratio of antimony to bismuth. In terms of 1.5 ≦ Bi ₂ O ₃ / Sb ₂ O ₃ ≦ 4.5.

  Furthermore, the average particle diameter of the zinc oxide particles in the sintered body 20 is 25 μm or more, and the standard deviation based on the particle size distribution of the zinc oxide particles in the sintered body 20 is 20 of the average particle diameter of the zinc oxide particles. % Or less.

  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 reason why the content of cobalt is 0.2 to 1.5 mol% in terms of Co ₂ O ₃ is that Co ₂ O ₃ is mainly dissolved in spinel particles to greatly improve nonlinear resistance characteristics. This is because it is an effective component, and when the content is less than 0.2 mol%, the effect of improving this non-linear resistance characteristic cannot be sufficiently obtained. Moreover, when content exceeds 1.5 mol%, it is because the insulation component in the inside of the sintered compact 20 will increase, and energy tolerance will deteriorate.

  The reason why the content of manganese is 0.1-1 mol% in terms of MnO is that MnO is an effective component for greatly improving the non-linear resistance characteristics by mainly dissolving in spinel particles. This is because when the content is less than 0.1 mol%, the effect of improving this non-linear resistance characteristic cannot be obtained sufficiently. Moreover, when content exceeds 1 mol%, it is because the insulation component in the inside of the sintered compact 20 will increase, and thermal stability will deteriorate.

  The reason why the content of nickel is 0.3 to 2 mol% in terms of NiO is that NiO is an effective component for largely improving the non-linear resistance characteristic by solid solution mainly in spinel particles. This is because when the content is less than 0.3 mol%, the effect of improving the non-linear resistance characteristic cannot be obtained sufficiently. Moreover, when content exceeds 2 mol%, it is because the insulation component in the inside of the sintered compact 20 will increase, and energy tolerance will deteriorate.

The reason why the content of antimony is 0.2 to 0.8 mol% in terms of Sb ₂ O ₃ is that Sb ₂ O ₃ forms spinel particles with zinc oxide to form particles of zinc oxide particles during sintering. Since it is a component that has the effect of suppressing and uniforming growth and improving the non-linear resistance characteristic, when the content is less than 0.2 mol%, the non-linear resistance characteristic is improved. This is because the effect cannot be obtained sufficiently. In addition, when the content exceeds 0.8 mol%, the insulating component inside the sintered body 20 increases, the resistance is increased, and the surge withstand characteristics are deteriorated.

By converting the mol% relative ratio of bismuth to antimony into each oxide and containing bismuth so as to satisfy the relationship of 1.5 ≦ Bi ₂ O ₃ / Sb ₂ O ₃ ≦ 4.5, More bismuth having the effect of promoting grain growth of the zinc oxide particles in the bonded body 20 can be contained than antimony having the effect of suppressing grain growth. Therefore, the sinterability of the nonlinear resistor is improved, and the resistance of the current-voltage nonlinear resistor 10 can be reduced. When the mol% relative ratio of bismuth to antimony (Bi ₂ O ₃ / Sb ₂ O ₃ ) is less than 1.5, the resistance cannot be sufficiently lowered, and when it exceeds 4.5, zinc oxide Abnormal grain growth of the grains occurs, and excellent non-linear characteristics and surge resistance characteristics cannot be obtained.

  In addition, the remainder other than the above-mentioned subcomponent in a mixture is comprised with a zinc oxide (ZnO).

  Moreover, the average particle diameter of the zinc oxide particles in the sintered body 20 constituting the current-voltage nonlinear resistor 10 is sufficiently reduced by setting it to 25 μm or more. In addition, when the average particle diameter of the zinc oxide particles becomes too large, the upper limit of the average particle diameter of the zinc oxide particles may be about 40 to 50 μm because the nonlinearity deteriorates and the manufacture becomes difficult. preferable.

  Further, by making the standard deviation based on the particle size distribution of the zinc oxide particles in the sintered body 20 constituting the current-voltage nonlinear resistor 10 to be 20% or less of the average particle diameter of the zinc oxide particles, the zinc oxide particles Since the diameter is uniform, the fine structure in the sintered body 20 is homogenized. For this reason, local bias of the conductive path is eliminated, and excellent non-linear resistance characteristics, surge withstand characteristics, and electric charge life characteristics can be obtained.

  Here, the average particle diameter of the zinc oxide particles in the sintered body 20 is determined by cutting the inside of the sintered body 20, polishing the cut sample, and observing the reflected electron image with a scanning electron microscope (SEM). Is required. Specifically, by cutting out a plurality of samples, and taking several SEM photographs with different fields of view for each sample, for example, at a magnification of 1000 times, for example, measuring the particle size of 500 to 1000 zinc oxide particles The average particle diameter of the zinc oxide particles in the sintered body 20 can be determined. Further, as described above, the standard deviation is calculated based on the particle size distribution of the zinc oxide particles in the sintered body 20 obtained from the measured average particle diameter. In addition, for example, zinc oxide particles, spinel particles, bismuth oxide layers, pores, and the like can be identified by the color of an observation photograph in a reflected electron image.

  The average particle size of the mixture containing zinc oxide, bismuth, antimony, manganese, cobalt, and nickel is preferably 0.5 μm or less. By making the average particle size of the mixture 0.5 μm or less, the raw material is uniformly dispersed, and the spinel particles and other raw materials having the effect of suppressing the grain growth of the zinc oxide particles in the sintered body 20 include the entire microstructure. Uniformly distributed. Therefore, since the grain growth of the zinc oxide particles proceeds uniformly in the firing process, there is no local bias of the conduction path, and the current-voltage nonlinear resistor 10 having excellent nonlinear resistance characteristics and surge resistance can be obtained. . On the other hand, when the average particle diameter of the mixture exceeds 0.5 μm, local bias of the current path due to abnormal grain growth of the zinc oxide particles tends to occur. In addition, although the average particle diameter of a mixture is so preferable that it is small, the minimum value of the average particle diameter of a mixture will be about 0.05 micrometer by the limit on preparation at the time of grind | pulverizing a mixture.

  Here, the average particle diameter of the mixture is measured using, for example, a wet laser diffraction / scattering particle size distribution measuring apparatus. The above average particle diameter is an average particle diameter in the median diameter.

  The standard deviation based on the particle size distribution of the mixture is preferably 75% or less of the average particle size of the mixture. By setting the standard deviation based on the particle size distribution of the mixture to 75% or less of the average particle size of the mixture, the raw materials are uniformly dispersed, and the growth of zinc oxide particles in the firing process proceeds uniformly. The particle size of the zinc oxide particles is made uniform. As a result, it is possible to obtain the current-voltage nonlinear resistor 10 having excellent nonlinear resistance characteristics and surge resistance. On the other hand, when the standard deviation based on the particle size distribution of the mixture exceeds 75% of the average particle size of the mixture, the particle size of the zinc oxide particles in the sintered body 20 becomes difficult to be uniformed, and local biasing of the current path occurs. It tends to occur. Here, a standard deviation is calculated | required based on the particle size distribution of the mixture measured with the above-mentioned particle size distribution measuring apparatus.

  The insulating layer 30 covering the side surface of the sintered body 20 is made of, for example, an inorganic insulating material such as a glass frit 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. The insulating layer 30 is preferably formed to have a thickness of about 0.05 to 0.2 mm from the viewpoint of 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 material such as aluminum or silver 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 0.05 to 0.15 mm from the viewpoint of adhesion to the sintered body.

  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.

Further, in the current-voltage nonlinear resistor 10 according to the present invention, the varistor voltage (V _{1 mA} ), which is a voltage when a current of 1 mA commercial frequency is applied, can be set to 100 V / mm or less.

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

First, 0.2~0.8mol% in terms of antimony _Sb 2 _{O 3, 0.2~1.5mol%} in terms of cobalt to _Co 2 _{O 3,} in terms of manganese to MnO 0.1 to 1 mol%, it comprises 0.3～2Mol% in terms of nickel in NiO, and bismuth, mol% relative ratio of antimony bismuth, in terms of respective oxides, 1.5 ≦ _Bi 2 O ₃ / Sb ₂ O ₃ ≦ 4.5 so as to satisfy the relationship, the balance is weighed so as to be zinc oxide (ZnO), and a mixture is prepared.

  Subsequently, the prepared mixture and the organic solvent adjusted so that the content of the mixture is 30 to 60% by weight are charged into a wet pulverizer. And it mixes, grind | pulverizing a mixture so that the average particle diameter of a mixture may be 0.5 micrometer or less, and produces a slurry. As the organic solvent, for example, a mixture of water and an organic binder such as polyvinyl alcohol is used.

  Here, as the wet pulverization apparatus, for example, a circulation type apparatus using zirconia beads having a diameter of 0.05 to 0.3 mm is used. Further, the bead filling rate in the vessel in the wet pulverization apparatus can be 35 to 95%, the peripheral speed of the stirring rotor can be 500 to 1500 rpm, and the circulation flow rate can be operated at 5 to 50 L / min.

  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 70 to 130 μm. The particle size at this time is measured using the above-mentioned laser diffraction / scattering particle size distribution measuring device or the like. Here, the reason why the particle size of the granulated powder is preferably 70 to 130 μm is that moldability is good and a dense molded body can be obtained.

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

  Subsequently, the molded body is heated to a first temperature of 350 to 500 ° C., and maintained at this temperature for 1 to 3 hours, for example, to remove the organic solvent.

  Subsequently, the molded body is heated to a temperature of 900 to 1300 ° C., which is the second temperature, and is fired at this temperature, for example, for 2 hours or more. The firing is performed, for example, by using a tunnel-type continuous furnace and placing the compact in a refractory container such as alumina or mullite. Moreover, it is preferable that the heating rate from 1st temperature to 2nd 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 maintenance time of the second temperature has elapsed, the fired molded body is cooled to room temperature. In this cooling step, it is preferable that the cooling rate when the temperature of the molded body is 750 ° C. or lower is 25 to 100 ° C./hour. By setting the cooling rate at 25 to 100 ° C./hour when the temperature of the molded body is 750 ° C. or less, it is possible to obtain the current-voltage nonlinear resistor 10 having more excellent non-linear characteristics and electric charging life characteristics. . On the other hand, when the cooling rate is slower than 25 ° C./hour, the non-linear characteristic tends to be lowered, and when it is faster than 100 ° C./hour, the electric charging life characteristic tends to be lowered. Through this cooling step, the sintered body 20 is obtained.

  Here, it is preferable to heat the sintered compact 20 cooled to room temperature in the above-described cooling step at a temperature of 350 to 700 ° C., which is a third temperature, for 10 to 40 hours. By passing through this heating step, the current-voltage nonlinear resistor 10 having more excellent energy withstand characteristics can be obtained. On the other hand, when the heating temperature is lower than 350 ° C., the improvement in energy withstand characteristics cannot be obtained, and when the heating temperature exceeds 700 ° C., the charging life characteristic is deteriorated. In addition, when the heating time is shorter than 10 hours, the improvement of the energy withstand characteristics cannot be obtained, and when the heating time exceeds 40 hours, the charging life characteristics and the energy withstand characteristics are deteriorated.

  After the maintenance time of the third temperature has elapsed, the heated sintered body is cooled to room temperature. The cooling rate in this cooling process is not particularly limited.

  The insulating layer 30 is formed by applying or spraying the above-described inorganic insulator to the side surface of the sintered body 20 that has been cooled to room temperature through the above heating process, and heat-treating at a temperature of 300 to 500 ° C. for 1 to 5 hours. To do.

  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, according to the current-voltage nonlinear resistor 10 and the manufacturing method thereof according to the present invention, bismuth having an effect of promoting the grain growth of the zinc oxide particles in the sintered body 20 suppresses the grain growth. Therefore, the non-linear resistance body can be improved in sinterability and low resistance can be achieved. Furthermore, according to the current-voltage nonlinear resistor 10 and the method for manufacturing the same according to the present invention, the zinc oxide particles grow uniformly in the firing process (heating step at the second temperature). Thus, local bias of the energization path due to abnormal grain growth is eliminated, and excellent non-linear resistance characteristics, surge withstand characteristics, and electrical charging life 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 characteristics.

(Influence of the composition ratio of bismuth and antimony in the mixture)
Here, bismuth against antimony in a mixture containing zinc oxide (ZnO) as a main component and bismuth (Bi), antimony (Sb), manganese (Mn), cobalt (Co), and nickel (Ni) as subcomponents. The influence of the mol% relative ratio on the characteristics of the current-voltage nonlinear resistor will be described.

Table 1 shows the content (mol%) of each component constituting the mixture in terms of oxide in the current-voltage nonlinear resistors of Sample 1 to Sample 11, and the mol% relative ratio of the oxides of bismuth and antimony. (Bi ₂ O ₃ / Sb ₂ O ₃ ), average particle size of the mixture, varistor voltage (V _{1 mA} ), non-linearity coefficient (V _{10 kA} / V _{1 mA} ), electrical life factor (K) and limit absorption energy . In Table 1, * marks are comparative examples showing samples that are outside the scope of the present invention.

First, zinc oxide (ZnO) was used as a main component. As subcomponents, manganese oxide (MnO) and nickel oxide (NiO) are each 0.5 mol%, cobalt oxide (Co ₂ O ₃ ) is 1 mol%, and aluminum is an aluminum hydroxide (Al ₂ O ₃ ) aqueous solution. 005 mol%, and bismuth oxide (Bi ₂ O ₃ ) and antimony trioxide (Sb ₂ O ₃ ) were adjusted to the values of Sample 1 to Sample 11 shown in Table 1. The balance is zinc oxide.

  The mixture prepared as described above, and water and an organic binder adjusted so that the content of the mixture was 40% by weight were put into a circulation type wet pulverizer. In the wet pulverizer, the average particle size of the mixture is adjusted to 0.4 μm by adjusting 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, and the mixing time. Was crushed. A uniformly mixed slurry was obtained by pulverization and mixing in the wet pulverizer.

  Here, the average particle size of the mixture was measured using a wet laser diffraction / scattering particle size distribution measuring device for the mixture collected from the wet pulverizer. Moreover, this average particle diameter is an average particle diameter in a median diameter.

  Subsequently, this slurry was spray-granulated with a spray dryer so that the particle size became 80 μm. The obtained granulated powder was formed into a cylindrical shaped body having a diameter of 100 mm and a thickness of 40 mm by a hydraulic press molding machine.

  Subsequently, the compact was heated to a temperature of 500 ° C. and maintained at this temperature for 2 hours to remove an organic binder or the like as an organic solvent.

  Next, the compact was heated to a temperature of 1150 ° C. and maintained at this temperature for 3 hours and fired. The firing was performed by using a tunnel-type continuous furnace and placing the compact in a mullite refractory container. Moreover, the heating rate until it became each baking temperature of 500 to 1150 degreeC was 100 degreeC / hour.

  After the elapse of the maintenance time of the firing temperature, the fired molded body was cooled. Here, the cooling rate when the temperature of the molded body was 750 ° C. or lower was set to 100 ° C./hour. Through this cooling process, a sintered body was obtained.

  Subsequently, glass frit was applied to the side surface of the sintered body, which was a cooled molded body, and heat-treated at a temperature of 500 ° C. for 2 hours to form an insulating layer. Furthermore, the upper and lower end surfaces of the sintered body were polished, and aluminum was sprayed on the polished surface to form an electrode to obtain a current-voltage nonlinear resistor.

With respect to the obtained current-voltage nonlinear resistors of Sample 1 to Sample 11, the varistor voltage (V _{1 mA} ), the nonlinear resistance characteristics, the electric charging life characteristics, and the surge resistance were evaluated.

The varistor voltage (V _{1 mA} ) is a voltage when a current of 1 mA commercial frequency is applied, and the varistor voltage (V _{1 mA} ) in each sample was measured according to JEC0202-1994. The smaller the value of this varistor voltage (V _{1 mA} ), the lower the resistance.

In the evaluation of the non-linear resistance characteristic, in each sample, the varistor voltage (V _{1 mA} ) described above and the voltage (V _{10 kA} ) when an 8 × 20 μs impulse current was applied at 10 kA were measured, and the ratio (V _{10 kA} / V _{1 mA} ) was evaluated as a nonlinear coefficient. It shows that the nonlinear resistance characteristic is excellent, so that the value of this nonlinear coefficient is small.

In the evaluation of the charging lifetime characteristics, the varistor voltage (V _{1 mA} ) described above was applied to each sample for 3000 hours in the atmosphere and at an atmosphere of 120 ° C., and the varistor voltage (V _{1 mA} ) before and after the application. The rate of change in leakage current (IR) when was applied was measured. Then, the ratio ((IR _3000h ) / (IR _0h )) of the leakage current (IR _3000h ) after application for 3000 hours to the leakage current (IR _0h ) before application for 3000 hours was evaluated as an applied lifetime coefficient (K). When this applied life coefficient is smaller than 1, it shows that the applied life characteristic of the current-voltage nonlinear resistor is excellent.

  In the evaluation of surge resistance, a limit absorption energy resistance test was performed on each sample. In the limit absorption energy tolerance test, lightning impulse energy having a waveform of 4 × 10 μs is applied to each sample at intervals of 10 minutes until it is electrically destroyed while increasing the discharge energy amount by 20 J / cc from 500 J / cc. did. Then, the absorbed energy immediately before the destruction was defined as the limit absorption energy (J / cc). It shows that it is excellent in surge tolerance, so that this limit absorption energy (J / cc) is large.

  In each evaluation test described above, 10 pieces of each current-voltage non-linear resistor were produced, tested for 10 pieces, and evaluated using the average value.

As shown in Table 1, in Samples 1 to 5 which are current-voltage non-linear resistors according to the present invention, all the samples have a varistor voltage (V _{1 mA} ) of 100 V / mm or less, and low resistance is achieved. I understood that it was planned. Samples 1 to 5 have excellent non-linear resistance characteristics and electrical charging life characteristics, and have a higher limit absorption energy and superior surge resistance compared to samples 6 to 11. .
(Effect of average particle size of zinc oxide particles in sintered body)
Here, the influence of the standard deviation based on the average particle diameter of the zinc oxide particles in the sintered body and the particle size distribution of the zinc oxide particles in the sintered body on the characteristics of the current-voltage nonlinear resistor will be described.

Table 2 shows the zinc oxide particle size conditions, the varistor voltage (V _{1 mA} ), the nonlinearity coefficient (V _{10 kA} / V _{1 mA} ), and the chargeable life factor (in the current-voltage nonlinear resistor according to the present invention). K) and the limit absorption energy. Here, each evaluation was performed using Sample 1 to Sample 11 described above.

  For the current-voltage non-linear resistors of Sample 1 to Sample 11, the average particle size (μ) of the zinc oxide particles in the sintered body and the standard deviation (σ) based on the particle size distribution of the zinc oxide particles in the sintered body are It was measured.

  Here, the average particle diameter of the zinc oxide particles in the sintered body is obtained by cutting out the inside of the sintered body, mirror-polishing the cut out sample, and observing the reflected electron image with a scanning electron microscope (SEM). It was. Specifically, for each sample, three samples were cut out, and for each cut out sample, five SEM photographs were taken at different magnifications at a magnification of 1000 times, and the longest side that could be drawn in the cross section of the zinc oxide particles Was measured for about 500 zinc oxide particles, and the average particle size was determined. The standard deviation was calculated based on the particle size distribution of the zinc oxide particles in the sintered body obtained from the measured average particle size.

  As shown in Table 2, in samples 1 to 5 which are current-voltage nonlinear resistors according to the present invention, the average particle diameter of zinc oxide particles in the sintered body is 25 μm or more, and in the sintered body The standard deviation based on the particle size distribution of the zinc oxide particles was 20% or less of the average particle size of the zinc oxide particles. In addition, as described above, these samples 1 to 5 have low resistance, excellent non-linear resistance characteristics and electric charging lifetime characteristics, and limit absorption as compared with samples 6 to 11. It was found that the energy was high and the surge resistance was excellent.

(Influence of the average particle size of the mixture)
Here, the influence of the average particle size of the mixture for constituting the current-voltage nonlinear resistor sintered body on the characteristics of the current-voltage nonlinear resistor will be described.

  A mixture having the same composition component used for preparing the sample 2 described above, and water and an organic binder adjusted so that the content of the mixture is 40% by weight are put into a circulation type wet pulverization apparatus. And pulverized and mixed. Further, four kinds of slurries were obtained by varying the particle diameter of zirconia beads, the bead filling rate in the vessel, the peripheral speed of the stirring rotor, the circulation flow rate, and the mixing time in a wet pulverizer.

  Here, the average particle diameters of the mixtures in the four types of slurries were 0.3 μm, 0.5 μm, 0.6 μm, and 0.7 μm, respectively. The average particle size was measured using a wet laser diffraction / scattering particle size distribution measuring apparatus. Moreover, this average particle diameter is an average particle diameter in a median particle diameter.

  Then, 4 types of sintered compacts were obtained through the same process as the process of producing the sample 2 mentioned above using each slurry.

  Subsequently, an insulating layer is formed on the side surface of each sintered body through the same process as that for manufacturing the sample 2 described above, electrodes are formed on both upper and lower end surfaces of each sintered body, and four types of current-voltage are formed. A non-linear resistor was obtained. Here, the obtained four types of current-voltage nonlinear resistors are referred to as Sample 12 to Sample 15, respectively.

Next, Sample 2, Sample 12 to Sample 15 were evaluated for varistor voltage (V _{1 mA} ) and nonlinear resistance characteristics. Note that the experimental conditions and experimental methods in these evaluations were the same as the experimental conditions and experimental methods performed for the sample 2. In each evaluation test described above, 10 pieces of each current-voltage non-linear resistor were produced, tested for 10 pieces, and evaluated using the average value.

Table 3 shows the average particle size, varistor voltage (V _{1 mA} ), non-linearity coefficient (V _{10 kA} / V _{1 mA} ), and critical absorption energy of the mixture of Sample 2 and Sample 12 to Sample 15.

As shown in Table 3, it was found that the nonlinear coefficient (V _{10 kA} / V _{1 mA} ) decreased as the average particle size of the mixture decreased. Particularly, when the average particle size of the mixture is 0.5 μm or less, the resistance is reduced and the non-linearity coefficient (V _{10 kA} / V _{1 mA} ) is reduced, and excellent non-linear resistance characteristics are obtained. It has been found that a current-voltage nonlinear resistor can be obtained.

(Effect of standard deviation based on the particle size distribution of the mixture)
Here, a standard based on the particle size distribution 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. The influence of the deviation on the characteristics of the current-voltage nonlinear resistor will be described.

  A mixture having the same components used for preparing the sample 2 described above, and water and an organic binder adjusted so that the content of the mixture is 40% by weight are introduced into a circulation type wet pulverizer. , Pulverized and mixed. In the wet pulverizer, the average particle size of the mixture becomes 0.4 μm by changing 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, and the mixing time. In this way, seven types of uniformly mixed slurries having different ratios (σ / μ) of the standard deviation (σ) based on the particle size distribution of the mixture to the average particle size (μ) of the mixture were obtained.

  Here, the average particle diameter of the mixture was measured using a wet laser diffraction / scattering particle size distribution measuring apparatus. Moreover, this average particle diameter is an average particle diameter in a median particle diameter. Moreover, the standard deviation was calculated | required based on the particle size distribution of the mixture measured with the above-mentioned particle size distribution measuring apparatus.

  Subsequent steps for producing a current-voltage non-linear resistor were performed through the same steps as those for producing the sample 2 described above, using each slurry, thereby obtaining seven types of sintered bodies.

  Subsequently, through the same process as the sample 2 described above, an insulating layer is formed on the side surface of each sintered body, electrodes are formed on the upper and lower end faces of each sintered body, and seven types of current-voltage are formed. A non-linear resistor was obtained. Here, the obtained seven types of current-voltage nonlinear resistors are referred to as Sample 16 to Sample 22, respectively.

With respect to the obtained current-voltage nonlinear resistors of Sample 16 to Sample 22, the varistor voltage (V _{1 mA} ) and nonlinear resistance characteristics were evaluated. Note that the experimental conditions and experimental methods in the evaluation of the varistor voltage (V _{1 mA} ) and the non-linear resistance characteristics were the same as the experimental conditions and experimental methods performed for the sample 2 described above. In each evaluation test described above, 10 pieces of each current-voltage non-linear resistor were produced, tested for 10 pieces, and evaluated using the average value.

Table 4 shows the conditions of the mixture (average particle diameter (μ), standard deviation (σ) and (σ / μ)) of the current-voltage nonlinear resistors of Samples 16 to 22, and the varistor voltage (V _{1 mA} ) and nonlinearity coefficient (V _{10 kA} / V _{1 mA} ).

As shown in Table 4, as the ratio (σ / μ) of the standard deviation (σ) based on the particle size distribution of the mixture to the average particle size (μ) of the mixture decreases, the nonlinearity coefficient (V _{10 kA} / V _{1 mA).} ) Became smaller. In particular, in a sample in which (σ / μ) is 75% or less, the resistance is reduced, the nonlinearity coefficient (V _{10 kA} / V _{1 mA} ) is reduced, and current-voltage having excellent nonlinear resistance characteristics It was found that a non-linear resistor was obtained. This is because when the ratio (σ / μ) of the standard deviation (σ) based on the particle size distribution of the mixture to the average particle size (μ) of the mixture is 75% or less, the raw materials are uniformly dispersed in the sintered body. This is considered to be a result obtained because the particle size of the zinc oxide particles was made uniform.

(Effect of cooling rate in the cooling process after firing)
Here, the influence of the cooling rate when the temperature of the molded body is 750 ° C. or less on the characteristics of the current-voltage nonlinear resistor in the cooling step will be described.

  A cylindrical shaped body having a diameter of 100 mm and a thickness of 40 mm was produced by the same method as that for producing Sample 2 described above.

  Subsequently, the compact was heated to a temperature of 500 ° C. and maintained at this temperature for 2 hours to remove an organic binder or the like as an organic solvent.

  Next, the compact was heated to a temperature of 1150 ° C. and maintained at this temperature for 3 hours and fired. In the process of cooling the fired molded article after the calcination temperature maintenance time has elapsed, the cooling rate when the temperature of the molded article is 750 ° C. or lower is 10 ° C./hour, 25 ° C./hour, 50 ° C./hour, 100 ° C./hour. 6 types of sintered bodies were produced at 120 ° C./hour and 200 ° C./hour. Note that the cooling rate of 100 ° C./hour corresponds to the sample 2 described above.

  Subsequently, through the same process as the sample 2 described above, an insulating layer is formed on the side surface of each sintered body, electrodes are formed on the upper and lower end surfaces of each sintered body, and six types of current-voltage are formed. A non-linear resistor was obtained. Here, among the obtained six types of current-voltage nonlinear resistors, samples other than sample 2 are referred to as sample 23 to sample 27, respectively.

  Next, for the sample 2 and the sample 23 to the sample 27, the evaluation test of the non-linear resistance characteristic and the electric charging life characteristic was performed. Note that the experimental conditions and the experimental methods in the evaluation of the non-linear resistance characteristics and the charging lifetime characteristics were the same as the experimental conditions and the experimental methods performed for the sample 2 described above. In each evaluation test described above, 10 pieces of each current-voltage non-linear resistor were produced, tested for 10 pieces, and evaluated using the average value.

Table 5 shows the cooling rate when the temperature of the molded body in the process of cooling the fired molded body in the current-voltage nonlinear resistors of Sample 2 and Sample 23 to Sample 27 is 750 ° C. or less, and the nonlinearity of the mixture 3 shows a sex coefficient (V _{10 kA} / V _{1 mA} ) and an applied lifetime coefficient (K).

As shown in Table 5, it was found that when the cooling rate at 750 ° C. or lower was increased, the nonlinearity coefficient (V _{10 kA} / V _{1 mA} ) tended to decrease, but the _{electrification} life coefficient increased. In particular, it was found that excellent non-linear resistance characteristics and electrical charging life characteristics can be obtained when the cooling rate at 750 ° C. or lower is in the range of 25 to 100 ° C./hour.

(Effect of heat treatment after cooling process)
Here, the effect of the heat treatment of the sintered body formed by cooling the fired molded body in the cooling step on the characteristics of the current-voltage nonlinear resistor will be described.

  A cylindrical shaped body having a diameter of 100 mm and a thickness of 40 mm was produced by the same method as that for producing Sample 2 described above.

  Subsequently, the compact was heated to a temperature of 500 ° C. and maintained at this temperature for 2 hours to remove an organic binder or the like as an organic solvent.

  Next, the compact was heated to a temperature of 1150 ° C. and maintained at this temperature for 3 hours and fired. In the process of cooling the fired molded article after the calcination temperature maintenance time had elapsed, the temperature of the molded article was cooled to room temperature at a cooling rate of 100 ° C./hour.

  Subsequently, the cooled sintered body was heated under 10 heating conditions (heating temperature (third temperature), heating time).

  The sintered body heated under each heating condition was cooled to room temperature. And through the same process as the process of producing the sample 2 described above, an insulating layer is formed on the side surface of each sintered body, electrodes are formed on the upper and lower end faces of each sintered body, and 10 types of current-voltage non- A linear resistor was obtained. Here, the obtained ten types of current-voltage nonlinear resistors are referred to as Sample 28 to Sample 37, respectively.

  Table 6 shows the heating conditions, the applied lifetime coefficient (K) of the mixture, and the limit absorption energy in the current-voltage nonlinear resistors of Sample 2 and Samples 28 to 37. Note that Sample 2 was not subjected to heat treatment after firing, as described above.

  As shown in Table 6, when the heating time is set to a constant 25 hours, an excellent surge withstand characteristic can be obtained while maintaining an excellent electric charging life characteristic at a heating temperature of 350 to 700 ° C. all right. Moreover, when heating temperature was fixed 550 degreeC, it turned out that the outstanding surge tolerance characteristic is acquired, maintaining the electrical charging lifetime characteristic between heating time for 10 to 40 hours.

  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, 30 ... Insulating layer, 40 ... Electrode.

Claims (7)

In a current-voltage nonlinear resistor comprising a sintered body of a mixture containing zinc oxide as a main component and bismuth, antimony, manganese, cobalt and nickel as subcomponents,
Wherein said mixture, 0.2~0.8mol% in terms of antimony _Sb 2 _{O 3, 0.2~1.5mol%} in terms of cobalt to _Co 2 _{O 3,} in terms of manganese to MnO 0 0.1 to 1 mol%, containing 0.3 to 2 mol% in terms of nickel converted to NiO, and bismuth in terms of mol% relative ratio of bismuth to antimony is 1.5 ≦ Bi in terms of the respective oxides. ₂ O ₃ / Sb ₂ O ₃ ≦ 4.5 so as to satisfy the relationship,
The average particle diameter of the zinc oxide particles in the sintered body is 25 μm or more, and the standard deviation based on the particle size distribution of the zinc oxide particles in the sintered body is 20% or less of the average particle diameter of the zinc oxide particles. A current-voltage non-linear resistor characterized by being.   The current-voltage nonlinear resistor according to claim 1, wherein the mixture has an average particle size of 0.5 μm or less.   3. The current-voltage nonlinear resistor according to claim 1, wherein a standard deviation based on a particle size distribution of the mixture is 75% or less of an average particle size of the mixture. 4. The current-voltage nonlinear resistance according to claim 1, wherein a varistor voltage (V _1mA ), which is a voltage when a current of 1 mA of commercial frequency is applied, is 100 V / mm or less. 5. body. In a method for producing a current-voltage nonlinear resistor comprising a sintered body of a mixture containing zinc oxide as a main component and bismuth, antimony, manganese, cobalt and nickel as subcomponents,
Antimony converted to Sb ₂ O ₃ is 0.2 to 0.8 mol%, cobalt is converted to Co ₂ O ₃ and 0.2 to 1.5 mol%, manganese is converted to MnO and 0.1 to 1 mol%. %, Containing 0.3 to 2 mol% of nickel in terms of NiO, and bismuth in terms of mol% relative ratio of bismuth to antimony in terms of the respective oxides, 1.5 ≦ Bi ₂ O ₃ / The mixture containing Sb ₂ O ₃ ≦ 4.5, and the organic solvent is charged into a wet pulverizer so that the content of the mixture is 30 to 60% by weight, and the average particle size of the mixture Pulverizing step of mixing the mixture so as to be 0.5 μm or less and preparing a slurry,
Spraying the slurry to form a granulated powder having a particle size of 70 to 130 μm; 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 900 to 1300 ° C. and maintaining the second temperature for a predetermined time;
A cooling step of cooling the fired molded body and cooling the molded body at a cooling rate of 25 to 100 ° C / hour when the temperature of the molded body is 750 ° C or lower. Manufacturing method.   The sintered body formed by cooling the fired molded body in the cooling step is heated to a third temperature of 350 to 700 ° C., and the third temperature is maintained for 10 to 40 hours. 6. The method of manufacturing a current-voltage nonlinear resistor according to claim 5, further comprising a third heating step of heating.   The method for producing a current-voltage nonlinear resistor according to claim 5 or 6, wherein a standard deviation based on a particle size distribution of the mixture is 75% or less of an average particle diameter of the mixture.

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