JP2008162820A - Voltage nonlinear resistor, and manufacturing method of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a voltage nonlinear resistor having varistor voltage and large current flatness equal to those of the conventional product even when being fired at a low temperature of <1,200°C. <P>SOLUTION: The voltage nonlinear resistor contains zinc, bismuth, antimony, manganese, cobalt, nickel, aluminum and boron as sintered compact structural elements, wherein the content of zinc is at least 90 mol% in the total amount of the sintered compact structural elements, the total quantity of bismuth and antimony is 0.9-3 mol%, the quantity of antimony to 1 mol bismuth is 0.25-0.5 mol and the content of boron is 0.03-0.1 mol%. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a voltage non-linear resistor that can be suitably used for a lightning arrester, a surge absorber, and the like, and a manufacturing method thereof.

  Conventionally, voltage non-linear resistors with zinc as the main component used in lightning arresters, surge absorbers, etc. are effective in improving electrical characteristics, including bismuth, which is essential for the expression of voltage non-linearity in the main component, zinc. A resistor obtained by mixing materials, granulating, molding, and firing, and having a voltage non-linear resistor thus obtained and an electrode made of metal aluminum spraying and a side high resistance layer. It is used practically as an element.

  FIG. 8 shows a general l-V characteristic of a conventional voltage nonlinear resistor. In FIG. 8, as criteria for determining whether or not the voltage nonlinearity is good in the voltage nonlinear resistor, for example, a numerical value reflecting a large current characteristic is expressed as a limit voltage value (V10 kA) at the time of 10 kA energization, an operation start voltage (VnmA), and As an indicator of the small current region, a voltage V10 μA at the time of 10 μA energization is used. The above n is determined by the size of the voltage nonlinear resistor and is 1 to 3. In addition, although the measurement of AC resistance leakage current is good for said measurement, since it is inferior in terms of accuracy, in the present invention, the above-mentioned judgment standard is adopted. In addition, since the voltage nonlinear resistor obtained in the examples described later has a small diameter, the large current characteristic is discussed based on 2.5 kA in terms of area ratio.

  FIG. 9 is a schematic diagram showing a partial fine structure of a crystal structure of a conventional general voltage nonlinear resistor. In the figure, 5 is a spinel particle mainly composed of zinc and antimony, 6 is a zinc oxide particle, 7 is a bismuth oxide main component phase, and 8 is a twin boundary in the zinc oxide crystal particle. That is, the spinel particles mainly composed of zinc and antimony are present in two kinds of existence states, one surrounded by the inside of the zinc oxide particle 6 and one existing near the triple point (multiple point) of the zinc oxide particle. In some cases, a part of the bismuth oxide main phase 7 is present not only at multiple points but also at the boundary of the zinc oxide particles 6. Bismuth oxide exists mainly in the vicinity of the triple point (multiple point) of the zinc oxide particles, but the melting point of the oxide itself is around 824 ° C., but it depends on other additives and the solid solution state. Then, it is dissolved and liquefied to form so-called liquid phase sintering. For this reason, grain growth and shrinkage densification of the main component zinc oxide are greatly promoted.

  On the other hand, as reported in Non-Patent Document 1 described later, antimony oxide and zinc oxide easily react through the presence of bismuth oxide and finally become spinel 5 through a pyrochlore phase or the like. However, this particle becomes a pinning particle for the growth of zinc oxide particles, and has the effect of suppressing the growth of zinc oxide particles, contrary to bismuth oxide. A further important effect of adding antimony oxide is to control extreme abnormal grain growth in combination with the reaction promoting effect of bismuth oxide which greatly promotes grain growth, and to promote uniform growth of zinc oxide particles.

  In the conventional manufacturing method as disclosed in Non-Patent Document 1 to Patent Document 4 described later, a temperature in the vicinity of 1200 to 1300 ° C. is generally adopted for the main firing step. This is because the density of the body becomes sufficiently high, and it is necessary to obtain appropriate voltage non-linearity and a varistor voltage (usually a voltage for passing a current value of about nmA, that is, an operation start voltage referred to as a lightning arrester).

Typical formulations described in these Non-Patent Documents 1 to 4 are 0.5 mol% of bismuth oxide, 1.0 mol% of antimony oxide, 0.5 mol of manganese oxide, cobalt oxide, and nickel oxide, respectively. %, Boron oxide 0.04 mol%, aluminum nitrate 0.004 mol%, and the other specific additive, the remaining zinc oxide, which is made in a normal ceramic process at about 1200 ° C. in the atmosphere for about 2 to 6 hr It is firing. Density of the voltage nonlinear resistor obtained by applying this method, about 5.4 g / cm ^3, an average shrinkage rate of 16%, the varistor voltage is typical electrical characteristics are 220V / mm longitudinal, The average particle diameter of zinc oxide is about 10 μm.

  In the prior art, generally, a system having a slightly larger amount of antimony as compared with bismuth as in the above-described example is employed. However, for this purpose, the firing temperature has to be increased in order to grow the zinc oxide particles to an appropriate size by generating spinel particles or the like, or to densify the sintered body. Nevertheless, conventionally, a system containing a large amount of antimony has been adopted in view of the stability, reproducibility, and yield of the voltage nonlinear resistor.

  On the other hand, as shown in Non-Patent Document 2 described later, by adjusting the addition ratio and the total amount of addition of bismuth oxide and antimony oxide to zinc oxide, the density improvement and shrinkage rate of the voltage nonlinear resistor obtained by firing are adjusted. It has been clarified that the increase in density, in other words, densification, can lower the main firing temperature to 1000 ° C. or lower. From this point of view, the sintering temperature can be lowered simply from the point of densification of the sintered body, energy saving in the production of voltage non-linear resistors, stabilization of electrical characteristics by reducing defects in zinc oxide, evaporation of bismuth oxide. Can be expected to be effective in reducing the environmental impact and resulting environmental improvements, and can be an extremely useful method in the industry.

  However, these papers do not clearly describe the electrical characteristics. Although the zinc oxide sintered body blended and manufactured in this way is densified at a low temperature of 800 to 1000 ° C., the electrical characteristics as a varistor are not sufficiently grasped, and it is practically used for a lightning arrester. It is necessary to check the characteristics as shown below to see if the element characteristics are sufficient.

First, it is necessary to define the most basic varistor voltage (VnmA) for gapless arrester design. The varistor voltage of power and distribution elements currently used is generally around 200 to 250 V / mm for normal element types and around 400 V / mm for high resistance elements in consideration of their operating duties (energy tolerance). Designed with. For this reason, at least the varistor voltage needs to be in this range. Zinc oxide particle growth occurs simultaneously in the process of shrinkage and densification, and the size of the zinc oxide particles of the device is related to the varistor voltage by the following equation (1).
VnmA = k · (1 / D) (1)
Here, k is a constant, and D is the average particle diameter of the zinc oxide particles. Therefore, the larger the D, the lower the varistor voltage. If the firing is sufficiently advanced, the particle size becomes large, but at the same time, it is required to satisfy both the densification and the necessary varistor voltage.
In addition, it is necessary that the large current flatness directly related to the protection performance of the lightning arrester (the ratio of the voltage at the current value as an index to the varistor voltage, for example, see FIG. 8) is as small as possible in terms of its operation function.

  In addition, since an alternating voltage is constantly applied to the zinc oxide element, the lifetime, that is, the stability over time of the resistance leakage current is also important. Although it is a dynamic characteristic, it is also desired that the resistance leakage current or watt loss at high temperature is small so as not to cause thermal runaway due to an increase in element temperature when absorbing surge energy. There is also whether or not the withstand amount (surge energy absorption capability), which is one of the essential requirements of the lightning arrester element, has reached a practical level.

  Summarizing the above for practical functions, it is necessary to confirm at least the density, shrinkage rate, varistor voltage, flatness of large current region, lifetime, temperature dependence of watt loss, and withstand capability. There is almost no information about the current situation.

M.M. Inada, Japan Journal of Applied Physics, 17 [1], P1-10 (1978), J. et al. Kim, et al, Journal of the American Ceramic Society, 72 [8], P1390-1395 (1989), JP 2004-238257 A, JP 2001-307909 A, Japanese Patent Publication No. 5-22362, JP-A-61-59703

  In view of the above-described current state of the prior art, the present invention is sufficiently dense even when fired at a low temperature of less than 1200 ° C., and has a varistor voltage and a large current flatness equivalent to those of a conventional product fired at a high temperature of 1200 ° C. or higher. And a method for manufacturing the same.

  The present invention is a voltage nonlinear resistor containing zinc, bismuth, antimony, manganese, cobalt, nickel, aluminum, and boron as fired body constituent elements, wherein the amount of zinc in the total amount of the fired body constituent elements is at least 90. Mol%, the total amount of bismuth and antimony is 0.9 to 3 mol%, the amount of antimony per mol of bismuth is 0.25 to 0.5 mol, and the amount of boron is 0.03 to 0.1 mol %.

The present invention is also a voltage non-linear resistor comprising zinc oxide (ZnO) as a main component and containing oxides of bismuth, antimony, manganese, cobalt, nickel, aluminum, and boron, and comprises bismuth oxide (Bi ₂ O ₃ Conversion) and antimony oxide (Sb ₂ O ₃ conversion) in the range of 0.5 to 1.5 mol%, antimony oxide with respect to 1 mol of bismuth oxide is 0.25 to 0.5 mol, boron oxide The amount of addition (in terms of B ₂ O ₃ ) is 0.015 to 0.05 mol%.

  The method for producing a voltage non-linear resistor according to the present invention includes a method of firing each oxide of the fired body constituent element or a mixture of each compound that generates the oxide by heating at a firing maximum temperature of 950 to 1050 ° C. The cooling rate from the maximum temperature to 500 ° C. is at least 75 ° C./hr or more.

  According to the present invention, it is possible to obtain a voltage nonlinear resistor having electrical characteristics that can be sufficiently sintered even at a temperature of about 1000 ° C. and can be used for a lightning arrester or the like. When the firing temperature is about 1000 ° C., there are effects such as energy saving of firing, mitigation of refractory deterioration and simplification of heat-resistant use of the furnace structure, and further reduction of the total amount of additives, that is, resource saving. Thus, it can greatly contribute to the advancement of the manufacturing technology of the zinc oxide voltage nonlinear resistor.

Embodiment FIG. 1 is a perspective view of a resistor element using a voltage nonlinear resistor of the present invention, and FIG. 2 is a sectional view taken along line XX of FIG. 1 and 2, a resistor element 10 includes a voltage nonlinear resistor 1 of the present invention (hereinafter abbreviated as “resistor 1”) formed in a disc shape, and a flat plate provided on the lower surface of the resistor 1. From the metal electrode 3, the flat metal electrode 2 provided on the upper surface, and the ring-shaped side high resistance layer 4 made of an electrically insulating resin, glass, or oxide provided on the side surface of the resistor 1. It is configured. The side high resistance layer 4 functions to prevent external flash in order to obtain a large current characteristic of the resistor element 10. The resistor 1 is a voltage non-linear resistor obtained by the conditions and methods shown in the examples to be described later, and is formed into a disk shape. The metal electrodes 2 and 3 are made of metal aluminum on the upper and lower surfaces of the resistor 1, respectively. The side high resistance layer 4 is applied and baked with an electrically insulating material such as an epoxy-modified silicone resin, a paste containing an oxide such as Bi, Sb, or Si, or a paste containing glass powder, or It is formed by other methods. Hereinafter, the configuration and manufacturing method of the resistor 1 will be described.

  The resistor 1 of the present invention contains zinc, bismuth, antimony, manganese, cobalt, nickel, aluminum, and boron as fired body constituent elements. The amount of zinc in the resistor 1 is at least 90 mol% in the total amount of the fired body constituent elements, the total amount of bismuth and antimony is 0.9 to 3 mol%, and antimony with respect to 1 mol of bismuth. The amount is 0.25 to 0.5 mol, the amount of boron is 0.03 to 0.1 mol%, and the amounts of manganese, cobalt, nickel, and aluminum are all 0.001 to 9 mol. %, In particular 0.004 to 3 mol%.

  When the amount of each element described above is within the above range, the above-described object of the present invention can be achieved. However, in order to obtain the resistor 1 having a further excellent varistor voltage and large current flatness, the resistor The amount of zinc in 1 is preferably at least 93 mol%, the total amount of bismuth and antimony is preferably 0.5 to 1.5 mol%, and the amount of antimony per mol of bismuth is 0.35 to 0. 0.5 mol is preferable, the boron content is preferably 0.03 to 0.1 mol%, and the amounts of manganese, cobalt, nickel, and aluminum are each 0.005 to 2 mol%. It is preferable.

The resistor 1 containing the fired body constituting element of the present invention can be produced by firing each oxide of the fired body constituting element or a mixture of compounds that produce the oxide by heating. At that time, as a zinc compound as a raw material, ZnO, zinc oxalate, zinc hydrogencarbonate, or other zinc compounds that decompose to generate ZnO by heating during firing are used. Examples of the bismuth compound as a raw material include bismuth oxide such as Bi ₂ O ₃ , Bi ₂ O ₄ , Bi ₂ O ₅ , bismuth nitrate, bismuthyl carbonate, or other bismuth oxide that decomposes by heating during firing to produce bismuth oxide. Compounds are used. Antimony compounds as raw materials include antimony oxides such as Sb ₂ O ₃ , Sb ₂ O ₄ , Sb ₂ O ₅ , mixed aqueous solutions of antimony chloride oxide and sodium carbonate, antimony sulfide, or decomposed by heating during firing. Other antimony compounds that produce bismuth oxide are used.

As a manganese compound used as a raw material, manganese oxide such as MnO, Mn ₂ O ₃ , Mn ₃ O ₄ , MnO ₂ , Mn ₂ O ₇ , manganese oxide hydrate, manganese nitrate, manganese carbonate, manganese oxalate, or during firing Other manganese compounds that decompose by heating to produce manganese oxide are used. The cobalt compound as the raw _{material, CoO, Co 2 O 3,} Co 3 O 4 cobalt oxide, such as, cobalt carbonate, and other cobalt compounds which generate decomposed to cobalt oxide by heating at cobalt hydroxide, firing Is used. As the nickel compound used as a raw material, NiO, nickel cobalt carbonate, nickel hydroxide, nickel nitrate, or other nickel compounds that decompose to generate NiO by heating during firing are used.

The aluminum compound used as a raw material is decomposed by heating during firing of aluminum oxide such as α-alumina, γ-alumina, δ-alumina, χ-alumina, η-alumina, ρ-alumina, or alumina hydrate. Other aluminum compounds that produce aluminum oxide are used. Boron oxides such as B ₂ O ₂ , B ₂ O ₃ , and B ₄ O ₅ , or metaboric acid, orthoboric acid, tetraboric acid, or boron oxide that is decomposed by heating during firing is generated as a raw material boron compound. Other boron compounds are used.

  Next, the manufacturing method of the resistor 1 of the present invention will be described. Each of the oxides of the above-mentioned fired body constituting elements or each compound that forms the oxide by heating is weighed and mixed so that the content of the fired body constituting elements after firing is in the above range, and then the mixture to be fired Get. Next, the mixture to be fired is fired at a firing maximum temperature of 950 to 1050 ° C. The firing time may be about 2 to 6 hours as usual, but if the maximum firing temperature deviates from the above temperature range, the above-mentioned problem of the present invention is not achieved. Therefore, the firing maximum temperature is particularly preferably 960 to 1030 ° C. The cooling after the firing may be performed in the air or in an oxygen stream, but regarding the cooling rate, the cooling rate from the highest firing temperature to 500 ° C. is preferably at least 75 ° C./hr or more, particularly preferably at least 90 ° C./hr or more. . If the cooling rate from the highest firing temperature to 500 ° C. is too fast, for example, cooling to 500 ° C. is possible at 250 ° C./hr or more, but at a lower temperature, the temperature difference from room temperature decreases and it becomes difficult. . EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention in detail, this invention is not limited to the below-mentioned Example.

Examples 1 to 3 and Comparative Examples 1 to 10
The manufacturing method of the resistor 1 in the following examples and comparative examples is basically a ceramic process that is usually used. As a starting raw material, zinc oxide (ZnO), antimony oxide _{(Sb 2 O} 3), bismuth oxide _{(Bi 2 O} 3), manganese oxide _{(Mn 3 O} 4), cobalt oxide _{(Co 3 O} 4), nickel oxide ( O), each powder, boric acid _(H 3 BO ₃₎ solution, and aluminum nitrate nonahydrate _{(Al (NO} 3) using the 3 · _9H 2 O) aqueous solution, their respective amounts are shown in the table of FIG. 3 It mix | blended in the quantity ratio used as mol%. Each amount of the boric acid aqueous solution and the aluminum nitrate 9-hydrate aqueous solution is the amount of boric acid and aluminum nitrate 9-hydrate. FIG. 3 shows only the molar ratio of Sb ₂ O ₃ and Bi ₂ O ₃ (Sb / Bi), the total molar percentage of Sb ₂ O ₃ and Bi ₂ O ₃ (Sb + Bi), and the molar percentage of boric acid (B). However, Mn ₃ O ₄ is all 0.15 mol%, Co ₃ O ₄ is all 0.4 mol%, NiO is all 0.5 mol%, and aluminum nitrate nonahydrate is Comparative Example 5 and Comparative Example 8. Is 0.004 mol%, all others are 0.006 mol%, and the balance is ZnO.

Although FIG. 3 is described in terms of mol% of the starting material, the element mol% in Example 1 of the present invention can be converted, and therefore, as an example, Example 1 is shown in element mol%. In Example 1, since the molar ratio (Sb / Bi) is 0.44 and the total mol% (Sb + Bi) is 1.4 mol%, Bi ₂ O ₃ is 1 mol%, and Sb ₂ O It can be seen that ₃ is 0.4 mol%. The _Co 3 _{O 4} is 0.4 mol%, _Mn 3 _{O 4} 0.15 mol%, NiO 0.5 _mol%, H ₃ BO 3 0.06 _{mol%, Al (NO 3) 3} · 9H ₂ O is 0.006 mol%, and the balance is ZnO. Therefore, when calculating mol% of each element from these numerical values, Bi: 1.95 mol%, Sb: 0.78 mol%, Co: 1.17 mol%, Mn: 0.44 mol%, Ni: 0 .49 mol%, B: 0.06 mol%, Al; 0.006 mol%.

  Examples 1 to 3 are all included in the amount of the present invention, but in Comparative Example 1, Sb / Bi and Sb + Bi are excessive, and in Comparative Example 2, Sb / Bi is excessive. In Example 3, Sb + Bi is excessive, in Comparative Examples 4-8, Sb / Bi is excessively small, in Comparative Examples 7 and 8, the molar amount of boron is excessively large, and in Comparative Example 9, Sb + Bi is excessively small. In Comparative Example 10, the boron molar amount is excessive.

First, other starting materials except for zinc oxide are pulverized and mixed well with a wet ball mill using zirconia balls as a medium, and then a predetermined amount of zinc oxide, PVA (polyvinyl alcohol), and a dispersing agent are sufficiently mixed with a dispa mill. A slurry was prepared. Each of the slurries prepared above was granulated with a disk-type spray dryer (disk rotation speed: 7000 rpm, body diameter: 1.5 m, drying temperature: 170 ° C.) to obtain granules having an average particle diameter of about 40 μm. Next, this granule was press-molded to a size of about φ40 mm × t13 mm with a uniaxial pressure of about 400 kgf / cm ² . Each of these resistors 1 was baked in an electric furnace for about 6 hours at each baking temperature (maximum baking temperature) shown in the table of FIG. 3, and then the temperature was lowered in the atmosphere at a temperature drop rate shown in FIG. On the other hand, since the square wave resistance measurement also has a size effect of the resistor element 10, an actual size resistor 1 was also produced. A production spray dryer was separately prepared with the same composition. The size of the resistor 1 is about φ80 mm × t25 mm.

  The fired bodies (resistors 1) of Examples 1 to 3 and Comparative Examples 1 to 10 thus obtained were polished and washed as necessary, and metal aluminum was sprayed on both upper and lower surfaces thereof to form metal electrodes 2 and 3. Then, an epoxy-modified silicone was formed as a resin layer on the side surface by a spraying method to form the side high resistance layer 4, and thus a resistor element 10 having the shape and structure shown in FIGS. 1 and 2 was obtained. Various characteristics of each of the resistor elements 10 are collectively shown in FIG. The density of the resistor 1 is an apparent value obtained from its diameter and weight, and the shrinkage rate is a value of shrinkage in the disk radial direction.

  3, all of Examples 1 to 3 have a varistor voltage of 238.5 to 254.0 (V1 mA / mm, and a large current flatness of 1.587 to 1,599 (V2.5 kA / mm). On the other hand, none of Comparative Examples 1 to 10 satisfies both the high varistor voltage and the low large current flatness.

  Comparative Example 1 is a conventional blend similar to Patent Document 1 with a conventional antimony-rich (Sb / Bi = 2) blend, and is thus fired at a high temperature of 1200 ° C. Despite being fired at a temperature lower by about 220 ° C., the characteristics of the resistor element 10 obtained from Example 1 to Example 3 are higher than those of antimony, as can be seen in the comparative example of FIG. However, the compound system containing a large amount of bismuth is sufficiently sintered from the viewpoint of shrinkage and density.

From FIG. 3, it is clear that there is the following tendency.
(1) The smaller the Sb / Bi, that is, the smaller the Sb (Comparative Example 4), or the smaller the total amount of Sb + Bi, the lower the varistor voltage.
(2) As the amount of boron increases, the varistor voltage tends to increase.
From the above, it can be seen that Sb / Bi is in the preferred range of 0.25 to 0.5 and Sb + Bi of 0.5 to 1.5 mol%.

  The amount of antimony is related to the number (amount) of spinel particles that suppress the growth of zinc oxide particles, and when it decreases, the varistor voltage is lowered. Boron probably reacts with bismuth to reduce the effect of promoting grain growth of bismuth.

Examples 4-9, Comparative Examples 11-14
The table in FIG. 4 focuses on the formulation of Example 1 with excellent characteristics, and shows the VI characteristics of the resistor 1 when the firing maximum temperature (holding time is 6 hours) and the temperature lowering rate are changed. First, when the rate of temperature decrease is 75 ° C./hr, the varistor voltage is slightly high and the large current flatness is a large value at 950 ° C. or less, indicating that the firing temperature has a lower limit. When the firing temperature is increased outside the temperature range of the present invention, the varistor voltage rapidly decreases and the large current flatness increases, so the temperature is limited to 1050 ° C. or lower.

  The V-I characteristic also greatly depends on the cooling rate, and when it is slower than 50 ° C./hr, the varistor voltage is slightly low and the large current flatness is a large value. On the other hand, at 250 ° C./hr, the varistor voltage decreases again. High-speed cooling is presumed to be because an electrical barrier is not sufficiently formed at a grain boundary formed between zinc oxides.

  From these results, the firing temperature is limited to 950 ° C. with a lower limit of 950 ° C., and the temperature decrease rate is 75 ° C./hr or more and about 200 ° C./hr. Naturally, depending on the blending, there is a slight difference in the optimum firing temperature and temperature drop rate that are more preferable within the above range. Although the temperature drop rate generally depends on the furnace structure, even if the furnace cooling rate (for example, 75 ° C./hr or more) is high, the temperature of the element itself can be virtually tracked only up to about 500 ° C. Then, tailing occurs. Therefore, the electrical characteristics are particularly important in the cooling rate at the initial temperature drop, that is, the temperature range in which the molten bismuth oxide crystallizes at the time of cooling, that is, the range of 900 ° C. to 700 ° C.

  Life characteristics were then performed under accelerated test conditions. FIG. 5 shows the time-dependent change of the resistance leakage current by applying an AC voltage of 0.9 (applied voltage / V1 mA) to the resistor element 10 heated to 115 ° C. in an oven. In FIG. 5, the graph (c) is Example 1, the graph (d) is Example 2, the graph (e) is Example 3, and the graph (f) is each measurement result for Comparative Example 10, The results of a life test using Sb / Bi and boron content as parameters are shown.

  In general, it is desirable that the leakage current does not change with time or shows a slight decreasing tendency, so it is clear from the figure that Sb / Bi and boron content have a great influence on the change with time. Thus, it is indicated that the upper limit of the boron content is appropriately within a range of 0.1 mol%. In particular, when viewed from the change of current over time, both blending regions that satisfy the characteristics are limited. When the boron content is 0.1 mol% (Example 3), the current value once increases and then decreases after passing the peak. The one having a lower boron content (Example 1 and Example 2) than Example 3 is a more desirable direction with little change in general and stable. Sb / Bi is also related to the absolute value of the leakage current, and shows a tendency that a slightly larger value, that is, 0.4 is better than 0.3.

  The lower limit of the boron content is 0.03 mol%, and if it is less than this, this value is limited because humidity resistance other than the life characteristics may be affected. When each resistor 1 shown in FIG. 5 was examined using an X-ray diffractometer, the result of FIG. 6 was obtained. 6A shows X-ray diffraction for Examples 1 to 3, and FIG. 6B shows X-ray diffraction for Comparative Example 10. FIG. FIG. 6A shows that the crystal phase of bismuth oxide having excellent lifetime characteristics in Examples 1 to 3 is almost monoclinic alone. On the other hand, it can be seen from FIG. 6B that the element having the positive current change derivative of Comparative Example 10 is mainly composed of tetragonal crystals and another crystal phase.

  As pointed out heretofore, it is well known that the crystal phase of bismuth oxide is largely related to the life characteristics, but the present invention has shown that bismuth oxide having a monoclinic system is desirable. FIG. 7 shows the relationship between the watt loss and the ambient temperature in the temperature range from room temperature to around 200 ° C. of the resistor 1 in a state where an AC voltage of 0.9 (applied voltage / V1 mA) is applied. It is. In FIG. 7, graph (a) shows the measurement results for Example 1, and graph (b) shows the measurement results for Comparative Example 10. From Example 1 and Comparative Example 10, the amount of boron greatly affects the above relationship. I understand that

  When the fine structure as shown in FIG. 9, for example, of the resistor 1 is observed by means such as SEM, the number of electrically insulating portions such as spinel particles and bismuth oxide increases by several times when the amount of antimony oxide is large. For this reason, since there are few excess insulating particles, a current path is ensured, the large current flatness is improved, and at the same time, the energy resistance is expected to be improved. Therefore, in Example 1, the resistor 1 having a diameter of 68 mm and a thickness of 21 mm fired at 980 ° C. in a mass production furnace is provided with a metal electrode 2, a metal electrode 3, and a side high resistance layer 4 as shown in FIGS. 1 and 2. The resistor element 10 was obtained by applying a square wave resistance test. Although a current of 1200 A was applied 10 times at intervals of 2 minutes in 2 ms, there were no inconveniences such as penetration breakage, cracking, and external flashing, and even compared with the conventional resistor element obtained by firing at around 1200 ° C. It had incomparable characteristics. Further, as shown in FIGS. 3 and 4, the electric capacity of the element 10 is somewhat dependent on the composition of the voltage nonlinear resistor of the present invention fired at around 1000 ° C. as compared with Comparative Example 1. Although there is a large capacity. This is advantageous in the design of the lightning arrester because the leakage current due to the capacitance is reduced and the voltage distribution across the lightning arrester can be made uniform.

  The voltage nonlinear resistor of the present invention is highly likely to be used as a lightning arrester, a surge absorber, or the like.

It is a perspective view of the resistor element of embodiment of this invention. It is XX sectional drawing of FIG. It is a table | surface which shows the composition and characteristic of the Example and comparative example of this invention. It is another table | surface which shows a composition and characteristic of the Example and comparative example of this invention. It is a graph which shows the relationship of the resistance leakage current with respect to the electricity application time of the Example of 1 part of this invention, and a comparative example. It is a X-ray-diffraction pattern of a 1 part Example and comparative example of this invention. It is a graph which shows the relationship of the watt loss with respect to the ambient temperature of the Example of 1 part of this invention, and a comparative example. The general lV characteristic of the conventional voltage nonlinear resistor is shown. It is a schematic diagram which shows the one part fine structure of the crystal structure of the conventional voltage nonlinear resistor.

Explanation of symbols

10: resistor element, 1: voltage nonlinear resistor, 2: metal electrode, 3: metal electrode,
4: Side surface high resistance layer, 5: Spinel particles, 6: Zinc oxide particles, 7: Bismuth oxide,
8: Twin boundary.

Claims (4)

  A voltage non-linear resistor containing zinc, bismuth, antimony, manganese, cobalt, nickel, aluminum, and boron as fired body constituent elements, wherein the amount of zinc in the total amount of the fired body constituent elements is at least 90 mol% The total amount of bismuth and antimony is 0.9 to 3 mol%, antimony is 0.25 to 0.5 mol per mol of bismuth, and boron content is 0.03 to 0.1 mol%. A voltage non-linear resistor characterized by. In a voltage nonlinear resistor containing zinc oxide (ZnO) as a main component and containing oxides of bismuth, antimony, manganese, cobalt, nickel, aluminum, and boron, bismuth oxide (in terms of Bi ₂ O ₃ ) and antimony oxide (Sb) There total of ₂ O ₃ equivalent) in the range of 0.5 to 1.5 mol%, and antimony oxide is 0.25 to 0.5 mole with respect to bismuth oxide 1 mole, boron oxide _(B 2 _{O 3} conversion) The voltage non-linear resistor, characterized in that the amount of is 0.015-0.05 mol%.   The voltage nonlinear resistor according to claim 1 or 2, wherein the bismuth oxide crystal system contained in the voltage nonlinear resistor is contained as a monoclinic crystal system.   Each oxide of the fired body constituting element or a mixture of each compound that generates the oxide by heating is set to a maximum firing temperature of 950 to 1050 ° C., and a cooling rate from the firing maximum temperature to 500 ° C. is at least 75 ° C. 3. The method of manufacturing a voltage non-linear resistor according to claim 1, wherein the voltage non-linear resistor is not less than / hr.

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