Abstract: A beta-alumina solid electrolyte for use in a sodium-sulfur battery is composed of beta-alumina crystals having a degree of orientation toward the C axis thereof, of 0.2-0.4 and an aspect ratio of 4.0 or less. The beta-alumina solid electrolyte is composed of the beta-alumina crystals having a degree of orientation toward the C axis thereof, of 0.2-0.4 and has such a particle diameter distribution that the average particle diameter is 3 .mu.m or less, the proportion of the particles having a particle diameter of 5 .mu.m or less is 90% or more, and the maximum particle diameter is 300 .mu.m or less. A process for producing a beta-alumina solid electrolyte using an alumina source material, a magnesium source material and a sodium source material, uses a magnesium-aluminum spinel as the magnesium source material and subjects all materials to mixing, granulation, molding and firing to obtain a beta-alumina solid electrolyte without subjecting the materials to calcination.

Abstract: A beta-alumina solid electrolyte for use in a sodium-sulfur battery is composed of beta-alumina crystals having a degree of orientation toward the C axis thereof, of 0.2-0.4 and an aspect ratio of 4.0 or less. The beta-alumina solid electrolyte is composed of the beta-alumina crystals having a degree of orientation toward the C axis thereof, of 0.2-0.4 and has such a particle diameter distribution that the average particle diameter is 3 .mu.m or less, the proportion of the particles having a particle diameter of 5 .mu.m or less is 90% or more, and the maximum particle diameter is 300 .mu.m or less. A process for producing a beta-alumina solid electrolyte using an alumina source material, a magnesium source material and a sodium source material, uses a magnesium-aluminum spinel as the magnesium source material and subjects all materials to mixing, granulation, molding and firing to obtain a beta-alumina solid electrolyte without subjecting the materials to calcination.

Abstract: A zinc oxide lightning-conducting element is disclosed which includes a metal oxide sintered body mainly composed of zinc oxide, and electrodes which consist of metal vapor-deposited films provided on opposite surfaces of the sintered body in a thickness of not less than 300 .ANG. and noble metal coat films coated onto the metal vapor-deposited films. At least one kind of a metal oxide is added and mixed into the zinc oxide.

Abstract: In a lightning arrestor insulator wherein a ZnO element having voltage non-linear resistant characteristics is embedded in an insulator body and integrally fixed with a glassy bonding material, the glassy bonding material has a thermal expansion coefficient smaller than either of those of the ZnO element and the insulator body. As the glassy bonding material, a low melting PbO-B.sub.2 O.sub.3 system glass having a composition to separate, during solidification, low expanding ceramic crystals is preferably employed.

Abstract: A high voltage porcelain insulator having a glaze applied to at least a head portion of the insulator which head portion is covered by a metal fitting and a cement. The glaze essentially consists of, in terms of weight, from 64.0 to 68.0% of SiO.sub.2, from 17.5 to 19.0% of Al.sub.2 O.sub.3, from 5.0 to 6.5% of MgO, not more than 3.0% of CaO, from 2.0 to 2.8% of K.sub.2 O and Na.sub.2 O in a total amount, and from 3.0 to 9.0%, when calculated as MnO, a compound which is converted to MnO and or MnO.sub.2 after being fired at a temperature range suitable for firing porcelain.

Abstract: A porcelain electrical insulator resistant to destruction by projectiles comprises a shed and a head portion protrusively and integrally formed with the shed. The thinnest part of the shed is not less than 5 mm, and the thickness of the head portion which is to be covered with a cap or the thickness of the insulator in the vicinity of the junction portion between the head portion and the shed is not less than 2 times the minimum thickness of the shed.