Ngk Insulators, Inc.

Osamu Imai

Ritsu Sato

Masami Nakata

Kunio Ohira

Hironori Suzuki

Shoji Seike

Koichi Umemoto

Yuji Asai

Noriyasu Oguri

Junko Yoshizawa

Masaru Murase

A semiconductive glaze product is provided, which exhibits low thermal expansion coefficient without adversely affecting other glaze characteristics, and which, when applied to an insulator, attains enhanced mechanical strength of the insulator. The semiconductive glaze product contains a glaze composition and a flux. The glaze composition contains a KNaO&#x2014;MgO&#x2014;CaO&#x2014;AlO-SiObase glaze, in which the compositional proportions of KNaO, MgO, and CaO, as represented by the Seger formula, are 0.1 to 0.4, 0.2 to 0.6, and balance, respectively. The glaze composition contains a metal oxide composition including tin oxide and antimony oxide, wherein the amount of flux is 10 parts by weight or less on the basis of 100 parts by weight of the glaze composition.

Semiconductive glaze product, method for producing the glaze product, and insulator coated with the glaze product

Alumina cement mortar is used as a source material for a kneaded cement cured body for joining hardware onto an insulator body, whereby the insulator can maintain high initial and long term mechanical strength and high electrical strength over a long period of time, and the curing time for forming the cured body is shortened to reduce the cost of producing the insulator. The alumina cement mortar is formed by kneading a mixture of alumina cement particles having a specific surface area of at least 3500 cm /g, a polymer-steric-hindrance type water reducing agent, an aggregate, and water, or an alumina cement mortar is obtained by kneading a mixture of alumina cement particles having an amorphous phase on an outer peripheral surface of particles and having a specific surface area of at least 3500 cm /g, a water reducing agent, an aggregate, and water.

Joined insulator body

A process for preparing a solid material containing coal ash includes a first step of mixing coal ash with a calcium compound to obtain a mixture, a second step of molding the mixture to obtain a molded article, and a third step of subjecting the molded article obtained in the second step to a hydrothermal treatment at a temperature of at least 120.degree. C. under high pressure. In the first step, 40 to 95 parts by weight of the coal ash is mixed with 60 to 5 parts by weight of the calcium compound, and the coal ash to be used has a bulk density of at least 0.8 g/cm.sup.3, an average particle diameter of 5 to 40 .mu.m and an aluminum content of 35% by weight or less in terms of Al.sub.2 O.sub.3. By the use of a blowing agent or the like, it is also possible to obtain a porous lightweight solid. As a consequence, there can be obtained a solid containing coal ash and having a high mixing ratio of coal ash, excellent dimensional stability to water, high strength and a decreased unevenness of the strength, and this kind of solid can be used in applications such as building materials, construction materials, artificial aggregates and the like. Furthermore, a laminated solid having not only the above-mentioned characteristics but also weight reduction properties can also be obtained, and this solid can be used to form building materials such as panels, blocks, bricks and boards for accoustic use, artificial lightweight aggregates and the like.

Process for preparing solidified material containing coal ash

A piezoelectric semiconductor is a single crystal composed mainly of ZnO having properties such as electrical conductivity of 10.sup.-11 .about.10.sup.-3 1/.OMEGA..multidot.cm suitable for use as an acoustoelectric element, by adding a given amount of H.sub.2 O.sub.2 to the alkali solvent, or by using NH.sub.4 OH in the alkali solvent, or by doping the ZnO single crystal with Li or a trivalent metal. The piezoelectric semiconductor can be suitably used as a ultrasonic transducer material of acoustoelectric type and can also be used as a material for ultrasonic amplification, an surface acoustic wave filter, a piezoelectric transducer, a fluorescent material for emitting a low-velocity electron beam, etc.

Piezoelectric semiconductor

A ZnO.sub.2 voltage non-linear resistor excellent in all characteristics of life under electrical stress, current impulse withstandability, discharge voltage ratio, change rate of discharge voltage after application of current impulse and moisture absorbency contains, as additive ingredients: 0.4-1.5 mol. % bismuth oxides as Bi.sub.2 O.sub.3, 0.3-1.5 mol. % cobalt oxides as Co.sub.2 O.sub.3, 0.2-1.0 mol. % manganese oxides as MnO.sub.2, 0.5-1.5 mol. % antimony oxides as Sb.sub.2 O.sub.3, 0.1-1.5 mol. % chromium oxides as Cr.sub.2 O.sub.3, 0.4-3.0 mol. % silicon oxides as SiO.sub.2, 0.5-2.5 mol. % nickel oxides as NiO, 0.001-0.05 mol. % aluminum oxides as Al.sub.2 O.sub.3, 0.0001-0.05 mol. % boron oxides as B.sub.2 O.sub.3, 0.0001-0.05 mol. % silver oxides as Ag.sub.2 O, and 0.0005-0.1 mol. % zirconium oxides as ZrO.sub.2, which bismuth oxides contain 30 wt. % of a .gamma.-type crystalline phase. A small-sizable ZnO.sub.2 voltage non-linear resistor having a higher varistor voltage in addition to the above characteristics contains, as additive ingredients: 0.3-1.5 mol. % bismuth oxides as Bi.sub.2 O.sub.3, 0.3-1.5 mol. % cobalt oxides as Co.sub.2 O.sub.3, 0.2-1.5 mol. % manganese oxides as MnO.sub.2, 0.5-1.5 mol. % antimony oxides as Sb.sub.2 O.sub.3, 0.1-1.5 mol. % chromium oxides as Cr.sub.2 O.sub.3, 4.0-10.0 mol. % silicon oxides as SiO.sub.2, 0.5-2.5 mol. % nickel oxides as NiO, 0.001-0.05 mol. % aluminum oxides as Al.sub.2 O.sub.3, 0.0001-0.05 mol. % boron oxides as B.sub.2 O.sub.3, 0.0001-0.05 mol. % silver oxides as Ag.sub.2 O, and 0.0005-0.1 mol % zirconium oxides as ZrO.sub.2, which bismuth oxides contain 30 wt. % of a crystalline .gamma.-type phase.

Voltage non-linear resistor

A voltage non-linear resistor element mainly including ZnO, substantially free from internal defects, exhibiting an excellent current impulse withstand capability, can be manufactured by a process wherein an SiC inclusion in the starting ZnO powder is restricted to at most 10 ppm, preferably at most 0.1 ppm, by weight, whereby formation of closed pores in the element is prevented, which is otherwise caused by decomposition of considerable amount of SiC during firing. The starting ZnO powder has an average particle diameter (R) of 0.1-2.0 .mu.m, preferably 0.3-0.8 .mu.m, a particle size distribution within the range of between 0.5R and 2R, of at least 70%, preferably 80%, by weight, needle-like crystals of at most 20%, preferably at most 10%, by weight, and an SiC content as an impurity of at most 10 ppm, preferably at most 0.1 ppm, by weight.

Starting material for use in manufacturing a voltage non-linear resistor

A voltage non-linear resistor element mainly comprising ZnO, substantially free from internal defects, exhibiting an excellent current impulse withstand capability, can be manufactured by a process wherein an SiC inclusion in the starting ZnO powder is restricted to at most 10 ppm, preferably at most 0.1 ppm, by weight, whereby formation of closed pores in the element is prevented, which is otherwise caused by decomposition of considerable amount of SiC during firing. The starting ZnO powder has an average particle diameter (R) of 0.1-2.0 .mu.m, preferably 0.3-0.8 .mu.m, a particle size distribution within the range of between 0.5R and 2R, of at least 70%, preferably 80%, by weight, needle-like crystals of at most 20%, preferably at most 10%, by weight, and an SiC content as an impurity of at most 10 ppm, preferably at most 0.1 ppm, by weight.

Process for manufacturing a voltage non-linear resistor and a zinc oxide

Process for manufacturing a voltage non-linear resistor

An improved voltage non-linear resistor having a superior voltage-current characteristic property, a superior switching current impulse withstand capability, a superior lightning current impulse withstand capability, and a large discharge voltage V.sub.0.1mA of 230-330 V/mm, a small deterioration rate of the discharge voltage V.sub.0.1mA after applying a lightning current impulse, a prolonged electric life under electrical stress and an improved discharged voltage at a large current area is provided which contains zinc oxide as a main component, and desired amounts of subsidiary components of bismuth oxide, cobalt oxide, manganese oxide, antimony oxide, chromium oxide, silicon oxide, nickel oxide, aluminum oxide, boron oxide and silver oxide. The resistor has a discharge voltage of V.sub.0.1mA of 230-330 V/mm at a current density of 0.1 mA/cm.sup.2 calculated per unit thickness of the sintered resistor, a discharge voltage ration V.sub.10A /V.sub.0.1mA of 1.2-1.45 a current densities of 10 A/cm.sup.2 and 0.1 mA/cm.sup.2, a deterioration rate of discharge voltage of not more than 10% at a current density of 0.1 mA/cm.sup.2 before and after twice applying a lightning current impulse of a current density of 5 KA/cm.sup.2 (4/10 .mu.s wave form), and discharge voltage ratio V.sub.0.1mA /V.sub.1.mu.A of not more than 1.4 at current densities of 0.1 mA/cm.sup.2 and 1 .mu.A/cm.sup.2.

Voltage non-linear resistor and method of producing the same

An excellent voltage non-linear resistor for use in a gapped lightning arrestor having a composition containing 1 0.5-1.2 mole % of bismuth oxide calculated as Bi.sub.2 O.sub.3, 2 0.3-1.5 mole % of cobalt oxide calculated as Co.sub.2 O.sub.3, 3 0.2-0.8 mole % of manganese oxide calculated as MnO.sub.2, 4 0.5-1.5 mole % of antimony oxide calculated as Sb.sub.2 O.sub.3, 5 0.1-1.5 mole % of chromium oxide calculated as Cr.sub.2 O.sub.3, 6 0.6-2.0 mole % of silicon oxide calculated as SiO.sub.2, 7 0.8-2.5 mole % of nickel oxide calculated as NiO, 8 0.004-0.04 mole % of aluminum oxide calculated as Al.sub.2 O.sub.3, 0.0001-0.05 mole % of boron oxide calculated as B.sub.2 O.sub.3 , 10.circle.  0.001-0.05 mole % of silver oxide calculated as Ag.sub.2 O, and 11.circle.  the rest of zinc oxide, 12.circle.  a limited current of 250-350 V/mm at a current density of 0.1 A/cm.sup.2 calculated per unit thickness of the sintered resistor, 13.circle.  a limited current ratio of V.sub.0.1A /V.sub.0.1mA of 1.2-1.7 at current densities of 0.1 A/cm.sup.2 and 0.1 mA/cm.sup.2, and 14.circle.  a deterioration rate of limited current of not more than 3% at a current density of 0.1 A/cm.sup.2 before and after applying twice a lightning surge current (4/10 .mu.s wave form) of 5 KA/cm.sup.2 per unit surface area.

Voltage non-linear resistor for gapped lightning arrestors and method of

A voltage non-linear resistor, composed mainly of zinc oxide and contains at least bismuth oxide, antimony oxide, and silicon oxide as additives, wherein crystalline phases of bismuth oxide includes at least two kinds of .beta. and .delta. satisfying the following inequalities: ##EQU1## in which .beta. and .delta. are contents of the .beta. type crystalline phase and the .delta. type crystalline phase, respectively. A voltage non-linear resistor is also provided, wherein bismuth oxide further includes an .alpha. type crystalline phase, and .alpha., .beta. and .delta. satisfy the following inequalities: ##EQU2## in which .alpha. is a content of the .alpha. type crystalline phase. A voltage non-linear resistor is further provided, wherein the resistor contains at least .delta. type crystalline phase of bismuth oxide and an amorphous phase containing bismuth, and a content of bismuth in each of the phases satisfies the following inequalities:

Voltage non-linear type resistors

A voltage non-linear resistor having lightning discharge current withstanding capability, switching surge current withstanding capability, and voltage non-linear index .alpha., including a resistor element body consisting essentially of zinc oxide, and a side highly resistive layer composed of a zinc silicate phase consisting essentially of Zn.sub.2 SiO.sub.4 and a spinel phase consisting essentially of Zn.sub.7 Sb.sub.2 O.sub.12 arranged on a side surface of the resistor element body, can be attained, having a porosity of the resistor element body of 2% or less, zinc silicate particles existing continuously in the side highly resistive layer, and a porosity of 10% or less in a region of the side highly resistive layer within 30 .mu.m or less from the resistor element body. A method of producing the voltage non-linear resistor is also provided.

An improved voltage non-linear sintered resistor which includes zinc oxide, bismuth oxide and at least one metal oxide additive selected from the group consisting of antimony oxide, silicon oxide, and mixtures thereof. The sintered resistor includes at least two crystalline phases including .alpha. and .delta. crystalline phases of bismuth oxide and has a quantity ratio of .alpha./.delta. crystalline phases of bismuth oxide of about 0.1-0.8.

A voltage non-linear resistor having a voltage non-linear resistance element consisting mainly of zinc oxides and a high resistance layer including a zinc silicate phase consisting mainly of Zn.sub.2 SiO.sub.4 and a spinel phase consisting mainly of Zn.sub.7 Sb.sub.2 O.sub.12 has a continuous zinc silicate phase in which zinc silicate particles are arranged continuously. Therefore, in the voltage non-linear resistor according to the invention, a flashover can be preferably prevented, and thus a stable electric characteristics especially lightning discharge current withstanding capability can be obtained.

A voltage non-linear resistor excellent in varistor voltage characteristics, lightning discharge current withstanding capability and life performance against applied voltage comprises a disc-like voltage non-linear element and a thin insulating covering layer integrally provided on the side surface of said element. In the resistor according to the invention, said element comprises zinc oxides as main ingredient, 0.1-2.0% bismuth oxides, as Bi.sub.2 O.sub.3, 0.1-2.0% cobalt oxides, as CO.sub.2 O.sub.3, 0.1-2.0% manganese oxides, as MnO.sub.2, 0.1-2.0% antimony oxides, as Sb.sub.2 O.sub.3, 0.1-2.0% chromium oxides, as Cr.sub.2 O.sub.3, 0.1-2.0% nickel oxides, as NiO, 0.001-0.05% aluminum oxides, as Al.sub.2 O.sub.3, 0.005-0.1% boron oxides, as B.sub.2 O.sub.3, 0.001-0.05% silver oxides, as Ag.sub.2 O and 7-11% silicon oxides, as SiO.sub.2, and said layer comprises 45-60% silicon oxides, as SiO.sub.2, 30-50% zinc oxides, as ZnO, 1-5% bismuth oxides, as Bi.sub.2 O.sub.3 and antimony oxides for the remainder (% stands for mole %). The resistor of the invention preferably further comprises a thin glassy layer superimposed on the insulating covering layer. The resistors are advantageously adaptable to arrestors, surge absorbers used in high voltage power systems.

Growing community of inventors

Kasugai, Japan

Osamu Imai