JP2005145809A

JP2005145809A - Zinc oxide-based sintered compact, zinc oxide varistor, and lamination type zinc oxide varistor

Info

Publication number: JP2005145809A
Application number: JP2003420145A
Authority: JP
Inventors: Atsushi Iga; 篤志伊賀
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-11-15
Filing date: 2003-11-15
Publication date: 2005-06-09

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problems in firing of the conventional zinc oxide varistor that the firing generates a pyrochlore phase and the like being solid at low temperature and results in high-temperature sintering and therefore electric power consumption is heretofore high and the materials liable to evaporate at elevated temperature are heretofore wasted. <P>SOLUTION: Cr<SB>2</SB>O<SB>3</SB>-containing Bi<SB>2</SB>O<SB>3</SB>compound synthetic powder is prepared by previously mixing Cr<SB>2</SB>O<SB>3</SB>and Bi<SB>2</SB>O<SB>3</SB>so as to attain a molar ratio of 1:02 to 0.15 and heat treating the mixture. A ZnO-based sintered compact is obtained by adding at least 0.05 to 5.0 parts by weight the Bi<SB>2</SB>O<SB>3</SB>compound synthetic powder, 0.1 to 10.0 parts by weight at least one oxide selected from the group consisting of respective oxides of Sb, Ti, Sn, Zr, Nb, Ta, V, Mo, W, Si, and rare earths, and 0.5 to 7.0 parts at least one compound selected from the group consisting of respective oxides of Bi, Co, Mn, Ni, and B, and boric acid and Al salt, to 100 parts by weight ZnO and mixing the mixture, then molding the mixture and firing the molding at 700 to 980°C. An electrode and side face insulation coating are formed therefrom and the zinc oxide varistor having excellent electric characteristics is thus obtained. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

発明の詳細な説明Detailed Description of the Invention

本発明は電気回路中のサージ吸収などに用いられる酸化亜鉛系焼結体と酸化亜鉛バリスタおよび積層型酸化亜鉛バリスタに関する．The present invention relates to a zinc oxide sintered body, a zinc oxide varistor, and a laminated zinc oxide varistor used for surge absorption in an electric circuit.

従来の低温度焼結の酸化亜鉛バリスタは、酸化亜鉛粉末と添加物である酸化ビスマスと酸化アンチモンの複合合成粉末、酸化ビスマスと酸化クロムの複合合成粉末、酸化ビスマスと酸化ホウ素の複合合成粉末、酸化コバルト粉末、酸化マンガン粉末および硝酸アルミニウム（酸化アルミニウム対応分）を混合し、成形し、焼成し、冷却して焼結されることが知られている（例えば、特許文献１参照、）。
また、従来の低温度焼結の酸化亜鉛バリスタは、酸化亜鉛粉末と添加物である酸化ホウ素と酸化クロムの複合合成粉末、酸化ビスマス粉末、酸化アンチモン粉末、酸化コバルト粉末、酸化マンガン粉末、酸化ニッケル粉末および硝酸アルミニウム（酸化アルミニウム対応分）を混合し、成形し、焼成し、冷却して焼結されることも知られている（例えば、特許文献２参照、）。
また、従来の高温度焼結用の酸化亜鉛バリスタは、酸化亜鉛と添加物である酸化ビスマス、酸化アンチモン、酸化コバルト、酸化マンガン、酸化クロムを混合し、成形し、焼成し、冷却過程で粒界部分に液相の酸化クロムと酸化ビスマスの複合合成成分を形成する経過をして焼結されることが知られている（例えば、非特許文献１参照、）。Conventional low temperature sintered zinc oxide varistors are composed of zinc oxide powder and additive composite composite powder of bismuth oxide and antimony oxide, composite composite powder of bismuth oxide and chromium oxide, composite composite powder of bismuth oxide and boron oxide, It is known that cobalt oxide powder, manganese oxide powder and aluminum nitrate (corresponding to aluminum oxide) are mixed, molded, fired, cooled and sintered (for example, see Patent Document 1).
In addition, conventional low temperature sintered zinc oxide varistors are composed of composite powder of zinc oxide powder and additives boron oxide and chromium oxide, bismuth oxide powder, antimony oxide powder, cobalt oxide powder, manganese oxide powder, nickel oxide It is also known that powder and aluminum nitrate (corresponding to aluminum oxide) are mixed, molded, fired, cooled and sintered (for example, see Patent Document 2).
In addition, conventional zinc oxide varistors for high-temperature sintering are prepared by mixing zinc oxide and additives bismuth oxide, antimony oxide, cobalt oxide, manganese oxide, chromium oxide, forming, firing, and granulating in the cooling process. It is known that sintering is performed in the course of forming a composite component of chromium oxide and bismuth oxide in the liquid phase at the boundary portion (see, for example, Non-Patent Document 1).

特開平９−６７１６１号公報（第２２−２３頁） JP-A-9-67161 (pages 22-23) 特開２００２−９７０７１号公報（第７−８頁） JP 2002-97071 A (Pages 7-8) マサノリ・イナダ（ＭａｓａｎｏｒｉＩｎａｄａ）．「エフェクツ・オブ・ヒート・トリートメント・オン・クリスタル・フェイズ・マイクロストラクチャー・アンド・エレクトリカル・プロパティーズ・オン・ノンオーミック・ジンク・オキサイド・セラミックス」（ＥｆｆｅｃｔｓｏｆＨｅａｔ−ＴｒｅａｔｍｅｎｔｏｎＣｒｙｓｔａｌＰｈａｓｅｓ，ＭｉｃｒｏｓｔｒｕｃｔｕｒｅａｎｄＥｌｅｃｔｒｉｃａｌＰｒｏｐｅｒｔｉｅｓｏｆＮｏｎｏｈｍｉｃＺｉｎｃＯｘｉｄｅＣｅｒａｍｉｃｓ）．（欧文）応用物理学会誌（ＪａｐａｎｅｓｅＪｏｕｒｎａｌｏｆＡｐｐｌｉｅｄＰｈｙｓｉｃｓ）．（社）応用物理学会発行．昭和５４年８月（１９７９）．第１８巻．第８号．Ｐ．１４３９−１４４６ Masanori Inada. "Effects of Heat-Treatment on Crystal Properties and Electrical Professionals" Effects of Heat Treatment on Crystal Phase, Microstructure and Electrical Properties on Non-Ohmic Zinc Oxide Ceramics (Effects of Heat-Treatment on Crystal Properties and Electrical Professionals) of Nonohmic Zinc Oxide Ceramics). (European) Journal of Applied Physics (Japan Journal of Applied Physics). Published by Japan Society for Applied Physics. August 1979 (1979). Volume 18. No.8. P. 1439-1446

発明が解決しようとする課題Problems to be solved by the invention

従来の方法で高性能の酸化亜鉛バリスタを得るには、１１５０℃〜１３００℃の高い焼結温度を必要とした．これらの高い温度で焼成すると大気中においても酸化ビスマスなどの蒸発は活発である．また、酸化ビスマスは多くの種類の物質と反応しやすく、炉材や容器等のセラミックス材など多くの物質を容易に腐食する．すなわち、高い焼結温度は電力消費が大きいのみならず、酸化ビスマスなどの激しい飛散とそれに伴う炉材や容器の消耗をもたらすので、焼成温度の低温度化が試みられていた．又、焼成温度が高いときには、炉内の焼成物の置かれた場所により、温度、昇温速度、酸化ビスマスや酸化アンチモンの蒸気圧などに差が生じ、これらを均一に保つことが困難で、特性のバラツキを生じやすいなどの問題をもっていたので、焼成温度の低温度化が試みられてきている．In order to obtain a high-performance zinc oxide varistor by the conventional method, a high sintering temperature of 1150 ° C. to 1300 ° C. was required. Evaporation of bismuth oxide etc. is active even in the atmosphere when firing at these high temperatures. In addition, bismuth oxide easily reacts with many kinds of substances and easily corrodes many substances such as furnace materials and ceramic materials such as containers. In other words, the high sintering temperature not only consumes a large amount of power, but also causes severe scattering of bismuth oxide and concomitant consumption of furnace materials and containers, so attempts have been made to lower the firing temperature. Also, when the firing temperature is high, depending on the place where the fired product is placed in the furnace, the temperature, the rate of temperature rise, the vapor pressure of bismuth oxide and antimony oxide, etc., it is difficult to keep them uniform, Since there were problems such as the tendency of variations in characteristics, attempts have been made to lower the firing temperature.

近年添加物の量や添加方法の研究が進み、９００〜９５０℃で焼結して従来以上の高い性能をもつ酸化亜鉛バリスタが開発されてきている．すなわち、酸化クロムに対し酸化ビスマスや酸化ホウ素などを添加し、熱処理を施しておいて酸化亜鉛に他の添加物と共に加えることによって、焼成温度の低温度化が大幅に進展してきている．すなわち、酸化亜鉛粉体に酸化ビスマス、酸化アンチモンなどと共に酸化コバルト、酸化マンガン、酸化ニッケルの鉄族系酸化物を添加した混合粉体に、さらに酸化クロムに対し酸化ビスマスや酸化ホウ素などを添加し、熱処理を施して得た酸化クロム複合合成粉末を加えることによって９００℃〜９５０℃の焼成で、高いレベルの電気特性を持った焼結体が得られることがあきらかとなった．従来の組成では低い温度でパイロクロアの固相が発生し、代わりに液相の発生を妨げ、液相焼結が起きにくくなっていた．In recent years, research on the amount and method of additives has progressed, and zinc oxide varistors that have been sintered at 900 to 950 ° C. and have higher performance than before have been developed. That is, by adding bismuth oxide, boron oxide, etc. to chromium oxide, applying heat treatment and adding it together with other additives to zinc oxide, the firing temperature has been greatly lowered. In other words, bismuth oxide, boron oxide, etc. are added to chromium oxide to a mixed powder obtained by adding iron oxides of cobalt oxide, manganese oxide, nickel oxide together with bismuth oxide, antimony oxide, etc. to zinc oxide powder. It was revealed that a sintered body having a high level of electrical characteristics could be obtained by firing at 900 ° C. to 950 ° C. by adding the chromium oxide composite composite powder obtained by heat treatment. In the conventional composition, a pyrochlore solid phase was generated at a low temperature. Instead, the liquid phase was prevented and the liquid phase sintering was difficult to occur.

従来の酸化亜鉛バリスタの組成では、酸化ビスマスと種々の酸化物と接触し、低い温度で固体のパイロクロア相などを発生し、これらのパイロクロア相などの固相は高い温度になるまで存在し、高温になって初めて酸化亜鉛と反応して、酸化ビスマスを主成分とする液相を発生して、ようやく液相焼結が起きていた．かくのごとく、従来の組成で焼結しようとするとするときには、高い温度の焼結が要求された。高い温度で焼結すると、高い電力を消費するのみならず、高温で蒸発しやすい材料を浪費する。これらのことから、出来れば焼結温度を低温下したいという期待があった。In the composition of conventional zinc oxide varistors, bismuth oxide comes into contact with various oxides and generates a solid pyrochlore phase, etc. at a low temperature. Solid phases such as these pyrochlore phases exist until they reach a high temperature. Only after the reaction with zinc oxide, a liquid phase mainly composed of bismuth oxide was generated, and finally liquid phase sintering occurred. Thus, when trying to sinter with the conventional composition, high temperature sintering was required. Sintering at high temperatures not only consumes high power, but also wastes materials that tend to evaporate at high temperatures. From these things, there was an expectation that the sintering temperature would be lowered if possible.

本発明は、上記の問題を解決して、低温度焼結で粒成長を促進し、非直線抵抗特性などの電気特性および信頼性に優れた低電圧の酸化亜鉛バリスタを高歩留りで製造するための酸化亜鉛系焼結体を提供することを目的とする．The present invention solves the above problems, promotes grain growth by low-temperature sintering, and produces a low-voltage zinc oxide varistor excellent in electrical characteristics such as non-linear resistance characteristics and reliability at a high yield. The purpose is to provide a zinc oxide-based sintered body.

課題を解決するための手段Means for solving the problem

前記目的を達成するため、本発明の酸化亜鉛系焼結体は、予め酸化ビスマス１モル比に対して酸化クロム０．０２〜０．１５モル比を加え化成処理を施して酸化ビスマス系化成物を作成しておき、酸化亜鉛１００重量部に対し、上記酸化ビスマス系化成物を少なくとも０．０５〜７．０の重量部で含有する組成物を形成し、７００℃〜９８０℃で焼成してなる構成を備えたものである．In order to achieve the above object, the zinc oxide-based sintered body of the present invention is preliminarily subjected to a chemical conversion treatment by adding 0.02 to 0.15 mole ratio of chromium oxide to 1 mole ratio of bismuth oxide to form a bismuth oxide-based chemical composition. A composition containing at least 0.05 to 7.0 parts by weight of the above bismuth oxide-based chemical is formed with respect to 100 parts by weight of zinc oxide, and calcined at 700 to 980 ° C. It has the following structure.

また前記目的を達成するため、本発明の酸化亜鉛系焼結体は、予め酸化ビスマス１モル比に対して酸化クロム０．０２〜０．１５モル比および酸化ホウ素０．０２〜０．１５モル比で加え化成処理を加えて酸化ビスマス系化成物を作成しておき、酸化亜鉛１００重量部に対し、上記酸化ビスマス系化成物を少なくとも０．０５〜７．０の重量部で含有する組成物を形成し、７００℃〜９８０℃で焼成してなる構成を備えたものである．In order to achieve the above object, the zinc oxide-based sintered body of the present invention has a chromium oxide 0.02 to 0.15 molar ratio and a boron oxide 0.02 to 0.15 molar in advance with respect to 1 molar ratio of bismuth oxide. A bismuth oxide-based chemical compound is prepared by adding a chemical conversion treatment in a ratio, and the composition contains the bismuth oxide-based chemical compound in an amount of at least 0.05 to 7.0 parts by weight with respect to 100 parts by weight of zinc oxide. Is formed, and is fired at 700 ° C. to 980 ° C.

また前記目的を達成するため、本発明の酸化亜鉛系焼結体は、予め酸化ビスマス１モル比に対して酸化クロム０．０２〜０．１５モル比を加え化成処理を施して酸化ビスマス系化成物を作成しておくか、または、予め酸化ビスマス１モル比に対して酸化クロム０．０２〜０．１５モル比および酸化ホウ素０．０２〜０．１５モル比で加え化成処理を加えて酸化ビスマス系化成物を作成しておき、酸化亜鉛１００重量部に対し、上記酸化ビスマス系化成物を少なくとも０．０５〜７．０の重量部と、少なくとも酸化アンキモン、酸化チタンと酸化すずと酸化ジルコンと酸化ニオブと酸化タンタルと酸化バナジウムと酸化モリブデンと酸化タングステンと酸化珪素と酸化マクネシュームと希土類酸化物からなる群れより選ばれる少なくとも一種の酸化物０．０５〜８．０重量部とを含有して組成物を形成し、７００℃〜９８０℃で焼成してなる構成を備えたものである．In order to achieve the above object, the zinc oxide-based sintered body of the present invention is preliminarily subjected to a chemical conversion treatment by adding 0.02 to 0.15 mole ratio of chromium oxide to 1 mole ratio of bismuth oxide to form a bismuth oxide-based chemical conversion. The product is prepared or oxidized beforehand by adding a chemical conversion treatment with 0.02 to 0.15 mole ratio of chromium oxide and 0.02 to 0.15 mole ratio of boron oxide with respect to 1 mole ratio of bismuth oxide. A bismuth-based chemical is prepared, and the bismuth oxide-based chemical is at least 0.05 to 7.0 parts by weight with respect to 100 parts by weight of zinc oxide, at least ankymon oxide, titanium oxide, tin oxide, and zircon oxide. And at least one selected from the group consisting of: niobium oxide, tantalum oxide, vanadium oxide, molybdenum oxide, tungsten oxide, silicon oxide, macnesium oxide, and rare earth oxide Containing the compound from 0.05 to 8.0 parts by weight to form a composition, in which a structure formed by baking at 700 ℃ ~980 ℃.

また前記目的を達成するため、本発明の酸化亜鉛バリスタは、予め酸化ビスマス１モル比に対して酸化クロム０．０２〜０．１５モル比を加え化成処理を施して酸化ビスマス系化成物を作成しておき、酸化亜鉛１００重量部に対し、上記酸化ビスマス系化成物を少なくとも０．０５〜７．０の重量部で含有する組成物を形成し、７００℃〜９８０℃で焼成して得た酸化亜鉛系焼結体、または、予め酸化ビスマス１モル比に対して酸化クロムおよび酸化ホウ素を０．０２〜０．１５モル比および０．０２〜０．１５モル比で加え化成処理を加えて酸化ビスマス系化成物を作成しておき、酸化亜鉛１００重量部に対し、上記酸化ビスマス系化成物を少なくとも０．０５〜７．０の重量部で含有する組成物を形成し、７００℃〜９８０℃で焼成して得た酸化亜鉛系焼結体、または、予め酸化ビスマス１モル比に対して酸化クロム０．０２〜０．１５モル比を加え化成処理を施して酸化ビスマス系化成物を作成しておき、あるいは、予め酸化ビスマス１モル比に対して酸化クロムおよび酸化ホウ素を０．０２〜０．１５モル比および０．０２〜０．１５モル比で加え化成処理を加えて酸化ビスマス系化成物を作成しておき、酸化亜鉛１００重量部に対し、上記酸化ビスマス系化成物を少なくとも０．０５〜７．０の重量部で含有し、さらに、少なくとも酸化アンキモン、酸化チタンと酸化すずと酸化ジルコンと酸化ニオブと酸化タンタルと酸化バナジウムと酸化モリブデンと酸化タングステンと酸化珪素と希土類酸化物からなる群れより選ばれる少なくとも一種の酸化物０．０５〜８．０重量部を含有する組成物を形成し、７００℃〜９８０℃で焼成して得た酸化亜鉛系焼結体に電極および側面に絶縁コートが形成されてなるという構成を備えたものである．In order to achieve the above object, the zinc oxide varistor of the present invention is prepared by adding 0.02 to 0.15 mole ratio of chromium oxide to 1 mole ratio of bismuth oxide and subjecting it to a chemical conversion treatment. In addition, a composition containing at least 0.05 to 7.0 parts by weight of the above bismuth oxide-based chemical is formed with respect to 100 parts by weight of zinc oxide, and obtained by firing at 700 ° C. to 980 ° C. Zinc oxide-based sintered body, or chromium oxide and boron oxide are added in advance at a molar ratio of 0.02 to 0.15 and 0.02 to 0.15 molar ratio with respect to 1 molar ratio of bismuth oxide, and a chemical conversion treatment is added. A bismuth oxide-based chemical is prepared, and a composition containing at least 0.05 to 7.0 parts by weight of the bismuth oxide-based chemical is formed with respect to 100 parts by weight of zinc oxide. Baked at ℃ A zinc oxide-based sintered body, or a bismuth oxide-based chemical compound prepared by adding 0.02 to 0.15 mole ratio of chromium oxide to a mole ratio of bismuth oxide in advance, First, chromium oxide and boron oxide were added in a molar ratio of 0.02 to 0.15 and a molar ratio of 0.02 to 0.15 with respect to 1 molar ratio of bismuth oxide to form a bismuth oxide-based chemical composition. And 100 parts by weight of zinc oxide, the bismuth oxide-based chemical compound is contained in an amount of at least 0.05 to 7.0 parts by weight, and at least ankymon oxide, titanium oxide, tin oxide, zircon oxide, and niobium oxide. 0.05 to 8.0 weights of at least one oxide selected from the group consisting of tantalum oxide, vanadium oxide, molybdenum oxide, tungsten oxide, silicon oxide, and rare earth oxides Part forming a composition containing, at the electrodes and sides 700 ℃ ~980 zinc oxide-based sintered body obtained by firing at ° C. those with a structure that insulating coating is formed.

また前記目的を達成するため、本発明の積層型酸化亜鉛バリスタは、予め酸化ビスマス１モル比に対して酸化クロム０．０２〜０．１５モル比を加え化成処理を施して酸化ビスマス系化成物を作成しておき、酸化亜鉛１００重量部に対し、上記酸化ビスマス系化成物を少なくとも０．０５〜７．０の重量部で含有する組成物を得て、または、予め酸化ビスマス１モル比に対して酸化クロムおよび酸化ホウ素を０．０２〜０．１５モル比および０．０２〜０．１５モル比で加え化成処理を加えて酸化ビスマス系化成物を作成しておき、酸化亜鉛１００重量部に対し、上記酸化ビスマス系化成物を少なくとも０．０５〜７．０の重量部で含有する組成物を得て、または、上記２種のそれぞれの組成物に対してさらに少なくとも酸化アンキモン、酸化チタンと酸化すずと酸化ジルコンと酸化ニオブと酸化タンタルと酸化バナジウムと酸化モリブデンと酸化タングステンと酸化珪素と酸化マグネシウムと希土類酸化物からなる群れより選ばれる少なくとも一種の酸化物を含有し、酸化亜鉛１００重量部に対して上記酸化物０．０５〜８．０重量部を加えて組成物を得て、ついで得られた組成物を薄板状に成形し、得られた成形体に対して金属電極材料を交互に積層し、積層体を焼成し、得られた積層型酸化亜鉛バリスタを構成して備えたものである．In order to achieve the above object, the laminated zinc oxide varistor of the present invention is prepared by adding 0.02 to 0.15 mole ratio of chromium oxide to 1 mole ratio of bismuth oxide and subjecting it to a chemical conversion treatment. To obtain a composition containing at least 0.05 to 7.0 parts by weight of the above bismuth oxide-based chemical with respect to 100 parts by weight of zinc oxide, or in advance at a molar ratio of bismuth oxide of 1 On the other hand, chromium oxide and boron oxide are added at 0.02 to 0.15 molar ratio and 0.02 to 0.15 molar ratio, and a chemical conversion treatment is performed to prepare a bismuth oxide-based chemical, and 100 parts by weight of zinc oxide On the other hand, a composition containing at least 0.05 to 7.0 parts by weight of the bismuth oxide-based chemical is obtained, or at least an ankymon oxide and an acid are further added to each of the two types of compositions. Containing at least one oxide selected from the group consisting of titanium, tin oxide, zircon oxide, niobium oxide, tantalum oxide, vanadium oxide, molybdenum oxide, tungsten oxide, silicon oxide, magnesium oxide and rare earth oxide, and zinc oxide 100 A composition is obtained by adding 0.05 to 8.0 parts by weight of the above oxide with respect to parts by weight, and then the resulting composition is formed into a thin plate shape. Are laminated and fired, and the resulting laminated zinc oxide varistor is provided.

本発明の酸化亜鉛系焼結体は、焼結を調整するためおよび焼結後の焼結体の電気特性向上のために、主成分の酸化亜鉛の粉体に、この中に添加物として予め化成処理・粉砕をうけた酸化ビスマス系化成物粉末を含めて各種の添加物を添加し、混合し、混合物を成形し、成形体を焼成して得る．本発明はかくして得る酸化亜鉛系焼結体と酸化亜鉛系焼結体に電極および側面コートを施して得る酸化亜鉛バリスタ、および混合物を薄板状に成形し、電極材料と交互に積層し、焼結し、積層型の酸化亜鉛バリスタを得る。In order to adjust the sintering and to improve the electrical characteristics of the sintered body after sintering, the zinc oxide-based sintered body of the present invention is preliminarily added as an additive to the main component zinc oxide powder. Various additives including bismuth oxide-based chemical powders that have been subjected to chemical conversion treatment and pulverization are added and mixed, the mixture is molded, and the compact is fired. In the present invention, a zinc oxide-based sintered body thus obtained, a zinc oxide varistor obtained by applying an electrode and a side coat to the zinc oxide-based sintered body, and a mixture are formed into a thin plate shape, laminated alternately with electrode materials, and sintered. Thus, a laminated zinc oxide varistor is obtained.

かねてより酸化ビスマスを主添加物とする酸化亜鉛バリスタには重要課題があった．すなわち添加物として用いられる酸化ビスマスには、固体の段階で種々の酸化物と接触すると、固相反応しやすくなる性質がある。これらの酸化ビスマスを含む化合物には、酸化ビスマスの融点になっても固体のままで安定なものがあり、その結果、これらの温度に達しても液相焼結が困難になる。つまり、液相焼結の温度が高くなり、焼結温度が高くなる。ところが酸化ビスマスの代わりに、酸化ビスマスと少量の酸化クロムとが共存している場合、これらの酸化ビスマス相は種々の酸化物と接触しても低い温度で固体化合物を形成することがなく、これらの酸化ビスマス相は酸化亜鉛が反応して酸化ビスマスを主成分とする液相が低い温度で発生し、低い温度で液相焼結が起きることが明かとなった．かくして低温で高性能の酸化亜鉛バリスタが得られるようになった．For some time, zinc oxide varistors with bismuth oxide as the main additive have had important problems. In other words, bismuth oxide used as an additive has a property of facilitating a solid-phase reaction when it comes into contact with various oxides at a solid stage. Some of these compounds containing bismuth oxide remain solid and stable even when the melting point of bismuth oxide is reached. As a result, even when these temperatures are reached, liquid phase sintering becomes difficult. That is, the temperature of liquid phase sintering becomes high and the sintering temperature becomes high. However, when bismuth oxide and a small amount of chromium oxide coexist instead of bismuth oxide, these bismuth oxide phases do not form solid compounds at low temperatures even when they come into contact with various oxides. It was revealed that the bismuth oxide phase of bismuth oxide reacts with zinc oxide to generate a liquid phase mainly composed of bismuth oxide at a low temperature, and liquid phase sintering occurs at a low temperature. Thus, high-performance zinc oxide varistors can be obtained at low temperatures.

以下実施例を用いて本発明をさらに具体的に説明する．なお、下記の実施例において「重量」は、「ｗｔ」と表示することがある．Hereinafter, the present invention will be described more specifically with reference to examples. In the following examples, “weight” may be displayed as “wt”.

下記の実施例において、各実施例においては、比較を容易とするために、アルミニウム添加量と、コバルト、マンガンおよびニッケルの酸化物の添加量とを一定とした．当初の原料粉末および熱処理し、粉砕された後の粉末の粒径は、以下の通りである．In the following examples, the aluminum addition amount and the addition amounts of cobalt, manganese and nickel oxides were made constant in each example for easy comparison. The particle sizes of the original raw material powder and the powder after heat treatment and pulverization are as follows.

＊ＺｎＯ：０．５〜１．０μｍ
＊Ｃｏ_３Ｏ_４、ＭｎＯ_２、ＮｉＯ：１〜５μｍ
＊Ｂｉ_２Ｏ_３：１〜１０μｍ
＊Ｓｂ_２Ｏ_３：１〜５μｍ
＊ＳｎＯ_２：０．５〜５μｍ
＊Ｃｒ_２Ｏ_３：１〜５μｍ
＊Ｂ_２Ｏ_３：１〜１０μｍ
＊ＳｉＯ_２：１〜５μｍ
＊ＴｉＯ_２：１〜５μｍ
＊ＺｒＯ_２：１〜５μｍ
＊Ｎｂ_２Ｏ_５：１〜５μｍ
＊Ｔａ_２Ｏ_５：１〜５μｍ
＊Ｖ_２Ｏ_５：１〜５μｍ
＊ＭｏＯ_３：１〜５μｍ
＊ＷＯ_３：１〜５μｍ
＊希土類酸化物（Ｙ_２Ｏ_３、Ｐｒ_６Ｏ_１１）：１〜１０μｍ
＊いずれにおいても酸化ビスマスに酸化クロムと酸化ホウ素の少なくとも一種をくわえて化成化した粉末（ボールミルで６０時間粉砕後）：０．８〜２．５μｍ
＊成形用混合粉体（ボールミルで６０時間粉砕後）：平均２．７μｍ
なお、以降の実施例内において、「／」の部分は、その左右の酸化物を加えた混合物であることを示すこととする．
（実施例１）* ZnO: 0.5 to 1.0 μm
* Co ₃ O ₄ , MnO ₂ , NiO: 1 to 5 μm
* Bi ₂ O ₃ : 1 to 10 μm
* Sb ₂ O ₃ : 1 to 5 μm
* SnO ₂ : 0.5 to 5 μm
* Cr ₂ O ₃ : 1 to 5 μm
* B ₂ O ₃ : 1 to 10 μm
* SiO ₂ : 1 to 5 μm
* TiO ₂ : 1 to 5 μm
* ZrO ₂ : 1 to 5 μm
* Nb ₂ O ₅ : 1 to ₅ μm
* Ta ₂ O ₅ : 1 to ₅ μm
* V ₂ O ₅ : 1 to ₅ μm
* MoO ₃ : 1 to 5 μm
* WO ₃ : 1 to 5 μm
* Rare earth oxide (Y ₂ O ₃ , Pr ₆ O ₁₁ ): 1 to 10 μm
* In any case, powder formed by adding bismuth oxide to at least one of chromium oxide and boron oxide (after grinding for 60 hours with a ball mill): 0.8 to 2.5 μm
* Molded powder for molding (after grinding for 60 hours with a ball mill): 2.7 μm on average
In the following examples, the “/” part indicates a mixture obtained by adding the left and right oxides.
(Example 1)

Ｂｉ_２Ｏ_３粉末とＣｒ_２Ｏ_３粉末とをモル比で１：０．０５で混合し、大気雰囲気下５５０℃で５時間熱処理した後、安定化ジルコニアを粉砕メディアとするモノマロンポットを用いて微粉砕することにより、Ｂｉ_２Ｏ_３／Ｃｒ_２Ｏ_３を含有する酸化ビスマス・酸化クロム熱処理の酸化ビスマス系化成物粉末を得た．次いで、酸化亜鉛系焼結体製造用の各種配合料をＺｎＯ粉末：Ｂｉ_２Ｏ_３／Ｃｒ_２Ｏ_３酸化ビスマス系化成物粉末：Ｓｂ_２Ｏ_３粉末：Ｃｏ_３Ｏ_４粉末：ＭｎＯ_２粉末：ＮｉＯ粉末；Ａｌ（ＮＯ_３）_３・９Ｈ_２Ｏ＝１００：ｘ：１．０：０．６７２：０．４１４：０．２５１：０．００７５（重量比）となるように配合し、モノマロンポットのボールミルで湿式混合粉砕した．ただし、Ｂｉ_２Ｏ_３／Ｃｒ_２Ｏ_３酸化ビスマス系化成物粉末の量としてｘ＝０．０４、０．１、０．３、０．５、１、３、５および１０を選択した．得られた配合粉末を乾燥し、ディスク状に加圧成形した後、得られた成形体を大気中で９００℃で１０時間保持した後、室温まで降温して、酸化亜鉛系焼結体を得た．得られた焼結体は、厚さ１．２ｍｍ、直径１４ｍｍであった．次いで、得られた焼結体の一部に７００℃で１時間熱処理した（以下においては、酸化亜鉛系焼結体を熱処理したものをも、単に「酸化亜鉛系焼結体」ということがある）．Bi ₂ O ₃ powder and Cr ₂ O ₃ powder were mixed at a molar ratio of 1: 0.05, heat treated at 550 ° C. for 5 hours in an air atmosphere, and then a monomalon pot using stabilized zirconia as a grinding medium was used. By pulverizing, a bismuth oxide / chromium oxide heat-treated bismuth oxide-based chemical compound powder containing Bi ₂ O ₃ / Cr ₂ O ₃ was obtained. Subsequently, various compounding materials for producing the zinc oxide-based sintered body are obtained by using ZnO powder: Bi ₂ O ₃ / Cr ₂ O ₃ bismuth oxide-based chemical powder: Sb ₂ O ₃ powder: Co ₃ O ₄ powder: MnO ₂ powder: NiO _{_{_{powder; Al (NO 3) 3 ·}}} 9H 2 O = 100: x: 1.0: 0.672: 0.414: 0.251: 0.0075 formulated to be (weight ratio), Monomaron Wet mixed and pulverized with a pot ball mill. However, x = 0.04, 0.1, 0.3, 0.5, 1, 3, 5, and 10 were selected as the amount of Bi ₂ O ₃ / Cr ₂ O ₃ bismuth oxide-based chemical compound powder. After drying the obtained blended powder and press-molding it into a disk shape, the obtained molded body was held in the atmosphere at 900 ° C. for 10 hours, and then cooled to room temperature to obtain a zinc oxide-based sintered body. It was. The obtained sintered body had a thickness of 1.2 mm and a diameter of 14 mm. Next, a part of the obtained sintered body was heat-treated at 700 ° C. for 1 hour (in the following, a heat-treated zinc oxide-based sintered body may be simply referred to as “zinc oxide-based sintered body”). ).

図１は、本発明の酸化亜鉛系焼結体を用いて作成したディスクタイプの酸化亜鉛バリスタの概略斜面図である．前記のようにして得た酸化亜鉛系焼結体１１の両面にアルミニウムを溶射することにより、アルミニウム層（図示せず）を形成し後、形成されたアルミニウム層上にさらに銅を溶射することにより、電極１２を形成した．電極１２にリード線１３をはんだ付けした後、リード線部分以外の焼結体および電極部分を樹脂塗装することにより、本発明による酸化亜鉛バリスタを得た．このようにして得られた酸化亜鉛バリスタの電気特性を評価した．初期の電気特性として、１ｍＡの電流を流した時の両端子間の１ｍｍ厚みに対する電圧、すなわち立ち上がり電圧Ｖ１ｍＡ／ｍｍを測定し、Ｖ１ｍＡとＶ０．１ｍＡとを用いて求めた非直線抵抗指数０．１ｍＡα１ｍＡを測定した．なお、以下において、非直線抵抗指数０．１ｍＡα１ｍＡを単にα値と略称することがある．非直線抵抗指数が大きいほど、サージ吸収能力が大きくなる．さらに低電流域における非直線抵抗特性をＶ１ｍＡ／Ｖ０．０１ｍＡで評価した．Ｖ１ｍＡ／Ｖ０．０１ｍＡが１．１５以下の値をとる場合には、漏れ電流が小さく、発熱に対する注意は不要であり、バリスタ素子は安定性に優れている．FIG. 1 is a schematic slope view of a disk-type zinc oxide varistor made using the zinc oxide-based sintered body of the present invention. By spraying aluminum on both surfaces of the zinc oxide-based sintered body 11 obtained as described above, an aluminum layer (not shown) is formed, and then copper is sprayed on the formed aluminum layer. The electrode 12 was formed. After soldering the lead wire 13 to the electrode 12, the zinc oxide varistor according to the present invention was obtained by resin coating the sintered body and the electrode portion other than the lead wire portion. The electrical characteristics of the zinc oxide varistor thus obtained were evaluated. As the initial electrical characteristics, a voltage with respect to 1 mm thickness between both terminals when a current of 1 mA was passed, that is, a rising voltage V1 mA / mm, was measured, and a non-linear resistance index of 0. 1 was obtained using V1 mA and V0.1 mA. 1 mAα1 mA was measured. In the following, the non-linear resistance index 0.1 mAα1 mA may be simply abbreviated as α value. The greater the non-linear resistance index, the greater the surge absorption capacity. Furthermore, the non-linear resistance characteristics in the low current region were evaluated at V1 mA / V0.01 mA. When V1mA / V0.01mA takes a value of 1.15 or less, the leakage current is small, and attention to heat generation is unnecessary, and the varistor element is excellent in stability.

さらに、直流負荷に対するバリスタの信頼性を評価した．すなわち、バリスタに対し、８０℃の高温雰囲気中で０．７ワットの直流負荷を５００時間印加した後、冷却して、バリスタ立ち上がり電圧Ｖ１ｍＡの変化率、すなわち直流負荷変化率△Ｖ１ｍＡ／Ｖ１ｍＡを測定した．バリスタ立ち上がり電圧Ｖ１ｍＡの変化率△Ｖ１ｍＡ／Ｖ１ｍＡが小さいほど、酸化亜鉛バリスタの電気特性は安定しており、信頼性が高いことを示す．さらに、電流サージに対するバリスタの信頼性を以下のようにして、評価した．８×２０μｓｅｃ、１．５ｋＡのパルスを１０回印加した場合のバリスタ立ち上がり電圧Ｖ１ｍＡの変化率、すなわちサージ変化率△Ｖ１ｍＡ／Ｖ１ｍＡを測定した．表１は実施例１の配合を示し表２に実施例１で得られたバリスタの電気特性の評価結果を示す．Furthermore, the reliability of the varistor for DC load was evaluated. That is, a 0.7 watt DC load was applied to the varistor in a high-temperature atmosphere at 80 ° C. for 500 hours and then cooled, and the change rate of the varistor rising voltage V1 mA, that is, the DC load change rate ΔV1 mA / V1 mA was measured. did. The smaller the change rate ΔV1mA / V1mA of the varistor rising voltage V1mA, the more stable the electrical characteristics of the zinc oxide varistor and the higher the reliability. Furthermore, the reliability of the varistor against current surge was evaluated as follows. The rate of change of the varistor rising voltage V1 mA when a pulse of 8 × 20 μsec and 1.5 kA was applied 10 times, that is, the rate of change of surge ΔV1 mA / V1 mA was measured. Table 1 shows the formulation of Example 1, and Table 2 shows the evaluation results of the electrical characteristics of the varistor obtained in Example 1.

サージ変化率の値が小さいほど、酸化亜鉛バリスタの電気特性が安定しており、その信頼性が高いことを示している．いずれも変化率の絶対値が５％以下の場合に信頼性が高いことを示している．表２に示す結果から、＃１０１（比較例）では添加物酸化ビスマス系化成物粉末の量が少なく、焼結不良で特性のデータが得られず、＃１０８（比較例）の場合には焼結体がくっついて特性の測定が出来なくなって、＃１０１および＃１０８の場合にはいずれも特性が得られなかった。一方、＃１０２〜＃１０７では本実施例による配合料混合物粉体成形体は、９００℃という低い温度でも焼結することができることが明らかである．そして、この焼結体を使用して得られたバリスタは、非直線抵抗特性が良好であり、長時間の直流負荷に対しても、また電流のサージに対しても、立ち上がり電圧Ｖ１ｍＡの変化率（△Ｖ１ｍＡ／Ｖ１ｍＡ）の絶対値が５％以下であり、信頼性に優れている．また表２に示す結果から明らかなように、同一ロット内での電気特性のバラツキも小さかった．さらに、表２には示していないが、本実施例の酸化亜鉛系焼結体を用いて酸化亜鉛バリスタを作成する場合には、異なるロット間での電気特性のバラツキも、同一ロット内の電気特性のバラツキと同様に小さかった．
（実施例２）The smaller the value of the rate of change in surge, the more stable the electrical characteristics of the zinc oxide varistor and the higher its reliability. Both show high reliability when the absolute value of the rate of change is 5% or less. From the results shown in Table 2, in the case of # 101 (comparative example), the amount of additive bismuth oxide-based chemical compound powder is small, and characteristic data cannot be obtained due to poor sintering. The properties were not able to be measured due to the sticking together, and in the case of # 101 and # 108, no properties were obtained. On the other hand, in # 102 to # 107, it is clear that the compounding material mixture powder compact according to the present example can be sintered even at a low temperature of 900 ° C. The varistor obtained by using this sintered body has good non-linear resistance characteristics, and the rate of change of the rising voltage V1 mA with respect to a long-time DC load and a surge of current. The absolute value of (ΔV1mA / V1mA) is 5% or less, and the reliability is excellent. As is clear from the results shown in Table 2, there was little variation in electrical characteristics within the same lot. Furthermore, although not shown in Table 2, when a zinc oxide varistor is made using the zinc oxide-based sintered body of this example, the variation in electrical characteristics between different lots is also different from that in the same lot. It was as small as the characteristic variation.
(Example 2)

Ｂｉ_２Ｏ_３粉末とＣｒ_２Ｏ_３粉末とをモル比で１：ｘで混合し、大気雰囲気下５５０℃で５時間熱処理した後、安定化ジルコニアを粉砕メディアとするモノマロンポットを用いて微粉砕することにより、Ｂｉ_２Ｏ_３／Ｃｒ_２Ｏ_３を含有する酸化ビスマス・酸化クロム熱処理の酸化ビスマス系化成物粉末を得た．ただし、Ｂｉ_２Ｏ_３／Ｃｒ_２Ｏ_３酸化ビスマス系化成物粉末のＢｉ_２Ｏ_３粉末とＣｒ_２Ｏ_３粉末とをモル比で１：ｘとしてｘ＝０．０１、０．０３、０．０５、０．１、０．１３、および０．２０を選択した．次いで、酸化亜鉛系焼結体製造用の各種配合料をＺｎＯ粉末：Ｂｉ_２Ｏ_３／Ｃｒ_２Ｏ_３酸化ビスマス系化成物粉末：ＳｎＯ_２粉末：Ｃｏ_３Ｏ_４粉末：ＭｎＯ_２粉末：ＮｉＯ粉末：Ａｌ（ＮＯ_３）_３・９Ｈ_２Ｏ＝１００：０．３：０．８：０．６７２：０．４１４：０．２５１：０．００７５（重量比）となるように配合し、モノマロンポットのボールミルで湿式混合粉砕した．得られた配合粉末を乾燥し、ディスク状に加圧成形した後、得られた成形体を大気中で９５０℃で１０時間保持した後、室温まで降温して、酸化亜鉛系焼結体を得た．次に、実施例１と類似の方法で酸化亜鉛バリスタを得た．表３に試料の組成を、表４に電気特性の評価結果を示す．Bi ₂ O ₃ powder and Cr ₂ O ₃ powder were mixed at a molar ratio of 1: x, heat-treated at 550 ° C. for 5 hours in an air atmosphere, and then finely mixed using a monomalon pot using stabilized zirconia as a grinding medium. By pulverizing, a bismuth oxide / chromium oxide heat-treated bismuth oxide-based chemical powder containing Bi ₂ O ₃ / Cr ₂ O ₃ was obtained. _{_{_{However, Bi 2 O 3 / Cr 2}}} O 3 with _Bi 2 _{O 3} powder and _Cr 2 _{O 3} powder and the molar ratio of bismuth oxide-based chemical powder 1: x = 0.01,0.03,0 as x. 05, 0.1, 0.13, and 0.20 were selected. Subsequently, various compounding materials for producing the zinc oxide-based sintered body are made of ZnO powder: Bi ₂ O ₃ / Cr ₂ O ₃ bismuth oxide-based chemical powder: SnO ₂ powder: Co ₃ O ₄ powder: MnO ₂ powder: NiO powder. _{_{_{: Al (NO 3) 3 ·}}} 9H 2 O = 100: 0.3: 0.8: 0.672: 0.414: 0.251: 0.0075 formulated to be (weight ratio), Monomaron Wet mixed and pulverized with a pot ball mill. After drying the obtained blended powder and press-molding it into a disk shape, the obtained molded body was held in the atmosphere at 950 ° C. for 10 hours and then cooled to room temperature to obtain a zinc oxide-based sintered body. It was. Next, a zinc oxide varistor was obtained by a method similar to Example 1. Table 3 shows the composition of the sample, and Table 4 shows the evaluation results of the electrical characteristics.

表４に示す結果から、＃３０１（比較例）では添加物Ｂｉ_２Ｏ_３／Ｃｒ_２Ｏ_３酸化ビスマス複合合成粉末のＢｉ_２Ｏ_３粉末とＣｒ_２Ｏ_３粉末とをモル比で１：ｘとしてｘの量が少なく、特性のデータがバラツキが大きく、＃３０６（比較例）の場合には特性の電圧が高くなって測定が出来なくなって、＃３０１および＃３０６の場合には特性値が良好ではないということができる．一方、＃３０２〜＃３０５では本実施例による配合料混合物粉体成形体は、９５０℃という低い温度でも焼結することができることが明らかである．そして、この焼結体を使用して得られたバリスタは、非直線抵抗特性が良好であり、長時間の直流負荷に対しても、また電流のサージに対しても、立ち上がり電圧Ｖ１ｍＡの変化率（△Ｖ１ｍＡ／Ｖ１ｍＡ）の絶対値が５％以下であり、信頼性に優れている．また、表４に示す結果から明らかなように、同一ロット内での電気特性のバラツキも小さかった．さらに、表４には示していないが、本実施例の酸化亜鉛系焼結体を用いて酸化亜鉛バリスタを作成する場合には、異なるロット間での電気特性のバラツキも、同一ロット内の電気特性のバラツキと同様に小さかった．
（実施例３）From the results shown in Table 4, in the case of # 301 (comparative example), the additive Bi ₂ O ₃ / Cr ₂ O ₃ bismuth oxide composite synthetic powder Bi ₂ O ₃ powder and Cr ₂ O ₃ powder were used in a molar ratio of 1: x. As a result, the amount of x is small, the characteristic data varies widely, and in the case of # 306 (comparative example), the characteristic voltage becomes high and measurement is impossible. In the case of # 301 and # 306, the characteristic value is It can be said that it is not good. On the other hand, in # 302 to # 305, it is clear that the compounding material mixture powder compact according to the present example can be sintered even at a low temperature of 950 ° C. The varistor obtained by using this sintered body has good non-linear resistance characteristics, and the rate of change of the rising voltage V1 mA with respect to a long-time DC load and a surge of current. The absolute value of (ΔV1mA / V1mA) is 5% or less, and the reliability is excellent. As is clear from the results shown in Table 4, the variation in electrical characteristics within the same lot was also small. Furthermore, although not shown in Table 4, when a zinc oxide varistor is produced using the zinc oxide-based sintered body of the present example, the variation in electrical characteristics between different lots is also different from that in the same lot. It was as small as the characteristic variation.
(Example 3)

Ｂｉ_２Ｏ_３粉末：Ｃｒ_２Ｏ_３粉末：Ｂ_２Ｏ_３粉末＝１：ｘ：ｘ（モル比）になるように３種の粉末を混合し、大気雰囲気下６００℃で５時間熱処理し、微粉砕した後、再び同条件で熱処理し、安定化ジルコニアを粉砕メディアとするモノマロンポットのボールミルで微粉砕することにより、酸化ビスマス・酸化クロム・酸化ホウ素含有の酸化ビスマス系化成物粉末を得た．ただし、酸化ビスマス系化成物粉末の量としてｘ＝０．０１、０．０３、０．０７、０．１、０．１２、および０．２０を選択した．次いで、酸化亜鉛系焼結体製造用の各種配合料をＺｎＯ粉末：Ｂｉ_２Ｏ_３／Ｃｒ_２Ｏ_３／Ｂ_２Ｏ_３の酸化ビスマス系化成物粉末：Ｙ_２Ｏ_３粉末：Ｃｏ_３Ｏ_４粉末：ＭｎＯ_２粉末：ＮｉＯ粉末：Ａｌ（ＮＯ_３）_３・９Ｈ_２Ｏ＝１００：３．５：０．５：０．６７２：０．４１４：０．２５１：０．００７５（重量比）となるように配合し、モノマロンポットのボールミルで湿式混合粉砕した．得られた配合混合粉末を乾燥し、ディスク状に加圧成形した後、得られた成形体を大気中で９００℃で１０時間保持した後、室温まで降温して、酸化亜鉛系焼結体を得た．次いで、得られた酸化亜鉛系焼結体の一部に７００℃の熱処理を施した．次に、実施例１と類似の方法で酸化亜鉛バリスタを得て評価した．表５に試料の組成を、表６に電気特性の評価結果を示す．Bi ₂ O ₃ powder: Cr ₂ O ₃ powder: B ₂ O ₃ powder = 1: 3 types of powders were mixed so as to be x: x (molar ratio) and heat-treated at 600 ° C. for 5 hours in an air atmosphere. After pulverization, heat treatment is performed again under the same conditions, and pulverization is performed with a monomalon pot ball mill using stabilized zirconia as the pulverization medium to obtain a bismuth oxide-based chemical powder containing bismuth oxide, chromium oxide, and boron oxide. It was. However, x = 0.01, 0.03, 0.07, 0.1, 0.12, and 0.20 were selected as the amount of the bismuth oxide-based chemical powder. Next, various compounding materials for producing the zinc oxide-based sintered body were used as ZnO powder: Bi ₂ O ₃ / Cr ₂ O ₃ / B ₂ O ₃ bismuth oxide-based chemical powder: Y ₂ O ₃ powder: Co ₃ O _4. powder: MnO ₂ powder: NiO _{_{_{powder: Al (NO 3) 3 ·}}} 9H 2 O = 100: 3.5: 0.5: 0.672: 0.414: 0.251: 0.0075 (weight ratio) The mixture was mixed and pulverized with a monomalon pot ball mill. After drying the obtained blended powder and press-molding it into a disk shape, the obtained molded body was held in the atmosphere at 900 ° C. for 10 hours, and then cooled to room temperature to obtain a zinc oxide-based sintered body. Obtained. Subsequently, a heat treatment at 700 ° C. was performed on a part of the obtained zinc oxide-based sintered body. Next, a zinc oxide varistor was obtained and evaluated in the same manner as in Example 1. Table 5 shows the composition of the sample, and Table 6 shows the evaluation results of the electrical characteristics.

表６に示す結果から、＃５０１（比較例）では酸化ビスマス複合合成粉末添加物Ｂｉ_２Ｏ_３／Ｃｒ_２Ｏ_３／Ｂ_２Ｏ_３の酸化ビスマス複合合成粉末の量が少なく、特性のデータがバラツキが大きく、＃５０８（比較例）の場合には特性の電圧など電気特性のバラツキが大きく、＃５０１および＃５０８の場合には特性値が良好ではないということができる．一方、＃５０２〜＃５０７では本実施例による配合料混合物粉体成形体は、９００℃という低い温度でも焼結することができることが明らかである．そして、この焼結体を使用して得られたバリスタは、非直線抵抗特性が良好であり、長時間の直流負荷に対しても、また電流のサージに対しても、立ち上がり電圧Ｖ１ｍＡの変化率（△Ｖ１ｍＡ／Ｖ１ｍＡ）の絶対値が５％以下であり、信頼性に優れている．また、表６に示す結果から明らかなように、同一ロット内での電気特性のバラツキも小さかった．さらに、表６には示していないが、本実施例の酸化亜鉛系焼結体を用いて酸化亜鉛バリスタを作成する場合には、異なるロット間での電気特性のバラツキも、同一ロット内の電気特性のバラツキと同様に小さかった．
（実施例４）From the results shown in Table 6, in # 501 (comparative example), the amount of bismuth oxide composite synthetic powder additive Bi ₂ O ₃ / Cr ₂ O ₃ / B ₂ O ₃ is small, and the characteristic data is In the case of # 508 (comparative example), there are large variations in electrical characteristics such as the characteristic voltage. In the case of # 501 and # 508, the characteristic values are not good. On the other hand, in # 502 to # 507, it is clear that the compounded mixture powder molded body according to the present example can be sintered even at a low temperature of 900 ° C. The varistor obtained by using this sintered body has good non-linear resistance characteristics, and the rate of change of the rising voltage V1 mA with respect to a long-time DC load and a surge of current. The absolute value of (ΔV1mA / V1mA) is 5% or less, and the reliability is excellent. As is clear from the results shown in Table 6, the variation in electrical characteristics within the same lot was also small. Furthermore, although not shown in Table 6, when a zinc oxide varistor is made using the zinc oxide-based sintered body of this example, the variation in electrical characteristics between different lots is also different from that in the same lot. It was as small as the characteristic variation.
Example 4

Ｂｉ_２Ｏ_３粉末：Ｃｒ_２Ｏ_３粉末：Ｂ_２Ｏ_３粉末＝１：０．０５：０．０７（モル比）になるように３種の粉末を混合し、大気雰囲気下４００℃で５時間熱処理し、微粉砕した後、再び同条件で熱処理し、安定化ジルコニアを粉砕メディアとするモノマロンポットのボールミルで微粉砕することにより、Ｂｉ_２Ｏ_３／Ｃｒ_２Ｏ_３／Ｂ_２Ｏ_３の酸化ビスマス系化成物粉末を得た．次いで、実施例１と同様の手法により、試料を作成した．すなわち、ＺｎＯ粉末：Ｂｉ_２Ｏ_３／Ｃｒ_２Ｏ_３／Ｂ_２Ｏ_３の酸化ビスマス系化成物粉末：Ｔａ_２Ｏ_５粉末：Ｃｏ_３Ｏ_４粉末：ＭｎＯ_２粉末：ＮｉＯ粉末：Ａｌ（ＮＯ_３）_３・９Ｈ_２Ｏ粉体＝１００：４：ｘ：０．６７２：０．４１４：０．２５１：０．００７５（重量比）となるように配合し、湿式法で６０時間混合粉砕した後、乾燥し、造粒し、成形した．ただし、Ｔａ_２Ｏ_５粉末の量としてｘ＝０．０３、０．０７、０．１、０．５、１、３、６、および１０を選択した．得られた成形体を９００℃で焼成した．また焼結体の一部には、７００℃の熱処理を施した．次に、実施例１と類似の方法で酸化亜鉛バリスタを得て評価した．表７に試料の組成を、表８に電気特性の評価結果を示す．Bi ₂ O ₃ powder: Cr ₂ O ₃ powder: B ₂ O ₃ powder = 1: 0.05: 0.07 (molar ratio) 3 kinds of powders were mixed and 5 at 400 ° C. in an air atmosphere. After heat-treating for a time and finely pulverizing, heat-treating again under the same conditions, and finely pulverizing with a ball mill of a monomalon pot using stabilized zirconia as a pulverizing medium, Bi ₂ O ₃ / Cr ₂ O ₃ / B ₂ O ₃ A bismuth oxide based chemical powder was obtained. Next, a sample was prepared in the same manner as in Example 1. That is, ZnO powder: Bi ₂ O ₃ / Cr ₂ O ₃ / B ₂ O ₃ bismuth oxide-based chemical powder: Ta ₂ O ₅ powder: Co ₃ O ₄ powder: MnO ₂ powder: NiO powder: Al (NO ₃ ) ₃ · 9H ₂ O powder = 100: 4: x: 0.672 : 0.414: 0.251: 0.0075 ( formulated as a weight ratio), after 60 hours were mixed by a wet method , Dried, granulated and molded. However, x = 0.03, 0.07, 0.1, 0.5, 1, 3, 6, and 10 were selected as the amount of Ta ₂ O ₅ powder. The obtained molded body was fired at 900 ° C. A part of the sintered body was heat-treated at 700 ° C. Next, a zinc oxide varistor was obtained and evaluated in the same manner as in Example 1. Table 7 shows the composition of the sample, and Table 8 shows the evaluation results of the electrical characteristics.

表８に示す結果から、＃７０１（比較例）ではＴａ_２Ｏ_５粉末の量が少なく、特性のデータがバラツキが大きく、＃７０８（比較例）の場合には特性の電圧など電気特性のバラツキが大きく、＃７０１および＃７０８の場合には特性値が良好ではないということができる．一方、＃７０２〜＃７０７では本実施例による配合料混合物粉体成形体は、９５０℃という低い温度でも焼結することができることが明らかである．そして、この焼結体を使用して得られたバリスタは、非直線抵抗特性が良好であり、長時間の直流負荷に対しても、また電流のサージに対しても、立ち上がり電圧Ｖ１ｍＡの変化率（△Ｖ１ｍＡ／Ｖ１ｍＡ）の絶対値が５％以下であり、信頼性に優れている．また、表８に示す結果から明らかなように、同一ロット内での電気特性のバラツキも小さかった．さらに、表８には示していないが、本実施例の酸化亜鉛系焼結体を用いて酸化亜鉛バリスタを作成する場合には、異なるロット間での電気特性のバラツキも、同一ロット内の電気特性のバラツキと同様に小さかった．これら本実施例による酸化亜鉛系焼結体を用いて製造された酸化亜鉛バリスタは、非直線抵抗特性が良好であり、長時間の直流負荷に対しても、またサージに対しても、立ち上がり電圧Ｖ１ｍＡの変化率（△Ｖ１ｍＡ／Ｖ１ｍＡ）の絶対値が５％以下で、信頼性に優れていた．From the results shown in Table 8, in the case of # 701 (comparative example), the amount of Ta ₂ O ₅ powder is small and the characteristic data has a large variation. In the case of # 708 (comparative example), the variation in electrical characteristics such as the characteristic voltage. In the case of # 701 and # 708, it can be said that the characteristic value is not good. On the other hand, in # 702 to # 707, it is clear that the compounding material mixture powder compact according to this example can be sintered even at a low temperature of 950 ° C. The varistor obtained by using this sintered body has good non-linear resistance characteristics, and the rate of change of the rising voltage V1 mA with respect to a long-time DC load and a surge of current. The absolute value of (ΔV1mA / V1mA) is 5% or less, and the reliability is excellent. As is clear from the results shown in Table 8, the variation in electrical characteristics within the same lot was also small. Furthermore, although not shown in Table 8, when a zinc oxide varistor is made using the zinc oxide-based sintered body of this example, the variation in electrical characteristics between different lots is also different from that in the same lot. It was as small as the characteristic variation. The zinc oxide varistors manufactured using the zinc oxide-based sintered bodies according to these examples have good non-linear resistance characteristics, and have a rising voltage against a long-term DC load and surge. The absolute value of the change rate of V1mA (ΔV1mA / V1mA) was 5% or less, and the reliability was excellent.

発明の効果The invention's effect

以上実施例をあげて説明したように、本発明の酸化亜鉛系焼結体は、酸化亜鉛に対して添加物として少なくとも小量の酸化クロムを含有した酸化ビスマス系化成物を含有して加え、焼結することにより、低温で高性能な電気特性を可能とした。また、本発明の酸化亜鉛系焼結体は、酸化亜鉛に対して添加物として少なくとも小量の酸化クロムと少量の酸化ホウ素を含有した酸化ビスマス系化成物を含有して加え、焼結することにより、低温で高性能な電気特性を可能とした。これらの酸化ビスマス系化成物を添加することにより、昇温中に安定な固相が形成されず、低温焼結が進むことになった。本発明の酸化亜鉛系焼結体は、酸化亜鉛に、酸化アンチモンと酸化チタンと酸化すずと酸化ジルコンと酸化ニオブと酸化タンタルと酸化バナジウムと酸化モリブデンと酸化タングステンと酸化珪素と酸化マグネシウムと希土類酸化物からなる群れより選ばれる少なくとも一種の酸化物を添加し、上記酸化ビスマス系化成物が含有して加えられるときに、効果的であり、優れた酸化亜鉛バリスタに至る。As described above with reference to the examples, the zinc oxide-based sintered body of the present invention contains a bismuth oxide-based chemical compound containing at least a small amount of chromium oxide as an additive to zinc oxide, Sintering enables high-performance electrical properties at low temperatures. Further, the zinc oxide-based sintered body of the present invention contains a bismuth oxide-based chemical composition containing at least a small amount of chromium oxide and a small amount of boron oxide as an additive to zinc oxide, and is sintered. This enables high-performance electrical characteristics at low temperatures. By adding these bismuth oxide-based chemicals, a stable solid phase was not formed during the temperature rise, and low-temperature sintering proceeded. The zinc oxide sintered body of the present invention comprises zinc oxide, antimony oxide, titanium oxide, tin oxide, zircon oxide, niobium oxide, tantalum oxide, vanadium oxide, molybdenum oxide, tungsten oxide, silicon oxide, magnesium oxide, and rare earth oxidation. When at least one oxide selected from the group consisting of substances is added and the bismuth oxide based chemical compound is contained and added, it is effective and leads to an excellent zinc oxide varistor.

また、本発明の酸化亜鉛系焼結体は、低温度で焼結できるので、焼結の際の電力消費を少なくすることが可能となり、同時に焼結に用いる電気炉の炉材や容器の消耗を少なくすることができ、省エネルギーや省資源に大きく寄与することができる．さらにまた、本発明の酸化亜鉛系焼結体には、銀などの融解温度よりも低い温度でも焼結するものがあり、これらの焼結体内部に焼成の際に同時に銀電極を形成することが可能となった．その結果、銀の内部電極をもった、高性能の積層型の酸化亜鉛バリスタを製造できるようになった．なお、実施例では、主に９００℃および９５０℃の焼成のデータを示したが、さらに低温で焼結しても良特性を持った物が得られ、また添加物の種類や量を調整することにより、７００℃まで焼成温度を下げても、良特性のバリスタが得られることがあきらかとなった．In addition, since the zinc oxide-based sintered body of the present invention can be sintered at a low temperature, it is possible to reduce power consumption during sintering, and at the same time, consumption of furnace materials and containers of an electric furnace used for sintering. Can be reduced, and can greatly contribute to energy and resource saving. Furthermore, some of the zinc oxide-based sintered bodies of the present invention are sintered even at a temperature lower than the melting temperature of silver or the like, and a silver electrode is simultaneously formed inside these sintered bodies at the time of firing. Became possible. As a result, high-performance multilayer zinc oxide varistors with silver internal electrodes can be manufactured. In the examples, the firing data mainly at 900 ° C. and 950 ° C. were shown. However, even if sintered at a lower temperature, a product having good characteristics can be obtained, and the kind and amount of the additive can be adjusted. Thus, it has become clear that a good varistor can be obtained even when the firing temperature is lowered to 700 ° C.

本発明の実施例１の酸化亜鉛系焼結体を用いて作成したディスクタイプの酸化亜鉛バリスタの概略斜視図． FIG. 3 is a schematic perspective view of a disk-type zinc oxide varistor produced using the zinc oxide-based sintered body of Example 1 of the present invention.

符号の説明Explanation of symbols

図１ディスクタイプの酸化亜鉛バリスタ
１１酸化亜鉛系焼結体
１２電極
１３リード線Fig. 1 Disc type zinc oxide varistor 11 Zinc oxide sintered body 12 Electrode 13 Lead wire

Claims

予め酸化ビスマス１モル比に対して酸化クロム０．０２〜０．１５モル比を加え化成処理を施して酸化ビスマス系化成物を作成しておき、酸化亜鉛１００重量部に対し、上記酸化ビスマス系化成物を少なくとも０．０５〜７．０の重量部で含有する組成物を形成し、７００℃〜９８０℃で焼成して得た酸化亜鉛系焼結体。In advance, 0.02 to 0.15 mole ratio of chromium oxide is added to 1 mole ratio of bismuth oxide to perform chemical conversion treatment to prepare a bismuth oxide based chemical composition. A zinc oxide-based sintered body obtained by forming a composition containing at least 0.05 to 7.0 parts by weight of a chemical and firing at 700 to 980 ° C.

予め酸化ビスマス１モル比に対して酸化クロムおよび酸化ホウ素を０．０２〜０．１５モル比および０．０２〜０．１５モル比で加え化成処理を加えて酸化ビスマス系化成物を作成しておき、酸化亜鉛１００重量部に対し、上記酸化ビスマス系化成物を少なくとも０．０５〜７．０の重量部で含有する組成物を形成し、７００℃〜９８０℃で焼成して得た酸化亜鉛系焼結体。First, chromium oxide and boron oxide were added in a molar ratio of 0.02 to 0.15 and a molar ratio of 0.02 to 0.15 with respect to 1 molar ratio of bismuth oxide to form a bismuth oxide-based chemical composition. A zinc oxide obtained by forming a composition containing the bismuth oxide-based chemical compound in an amount of at least 0.05 to 7.0 parts by weight with respect to 100 parts by weight of zinc oxide and firing at 700 ° C. to 980 ° C. System sintered body.

組成物が少なくとも酸化アンキモン、酸化チタンと酸化すずと酸化ジルコンと酸化ニオブと酸化タンタルと酸化バナジウムと酸化モリブデンと酸化タングステンと酸化珪素と酸化マクネシュームと希土類酸化物からなる群れより選ばれる少なくとも一種の酸化物を含有し、酸化亜鉛１００重量部に対して上記酸化物０．０５〜８．０重量部であることを特徴とする請求項１または請求項２に記載の酸化亜鉛系焼結体．The composition is at least one oxide selected from the group consisting of at least ankymon oxide, titanium oxide, tin oxide, zircon oxide, niobium oxide, tantalum oxide, vanadium oxide, molybdenum oxide, tungsten oxide, silicon oxide, magnesium oxide, and rare earth oxide. 3. The zinc oxide-based sintered body according to claim 1, wherein the oxide is 0.05 to 8.0 parts by weight with respect to 100 parts by weight of zinc oxide.

請求項１又は請求項２又は請求項３に記載の酸化亜鉛系焼結体に電極を形成し、さらに側面に絶縁膜を形成してなる酸化亜鉛バリスタ．A zinc oxide varistor formed by forming an electrode on the zinc oxide-based sintered body according to claim 1, claim 2 or claim 3, and further forming an insulating film on a side surface.

積層型の酸化亜鉛バリスタにおいて、請求項１又は請求項２又は請求項３に記載の組成物を薄板状に成形し、得られた成形体と金属電極材料が交互に積層し、焼成して得ることを特徴とする積層型酸化亜鉛バリスタ．In a laminated zinc oxide varistor, the composition according to claim 1, claim 2 or claim 3 is formed into a thin plate shape, and the obtained compact and metal electrode material are alternately laminated and fired. A laminated zinc oxide varistor characterized by that.