Abstract: A solid electrolyte tube for sodium sulfur cells, having an outer surface of a roughness defined by an arithmetical mean deviation of the profile (R.sub.a) of not exceeding 2.0 .mu.m and a maximum height of the profile (R.sub.max) of not exceeding 15 .mu.m, is produced by leveling the outer surface of the solid electrolyte tube in a state of green body, bisque fired and calcined body, or fired body, by means of a finishing apparatus such as a centerless grinding machine, external cylindrical grinding machine, lathe, or the like. The solid electrolyte tube having a smooth and even surface can be prevented from crack formation due to local concentration of Na ion, S, sodium polysulfide and thermal stress thereon, so that it can improve durability and reliability.

Abstract: A discharge tube for a high pressure metal vapor discharge lamp is disclosed, which comprises a translucent alumina tubular body, first and second end plates of cermet having a firing shrinkage factor which is less than that of the translucent alumina tubular body, end first and second electrode support members partially embedded in inner sides of the first and second end plates, respectively. The first end plate is fitted to the first end portion of the alumina tubular body and bonded thereto through shrinkage fitting at a shrinkage fitting ratio of the tubular body to the first end plate being from 3 to 6% during a simultaneous sintering of the first end plate to the tubular body and a simultaneous bonding of the first electrode support member to the first end plate through shrinkage fitting at a shrinkage fitting ratio of the first end plate to the first electrode support member being from 4 to 16% when the alumina tubular body is fired to be translucent.

Abstract: A ceramic envelope device for a high-pressure metal-vapor discharge lamp, including a translucent ceramic tube, a pair of electrically conducting end caps closing opposite ends of the ceramic tube, and a pair of opposed discharge electrodes each of which is supported at its one end by the corresponding end cap such that the other end of the electrode protrudes from the inner surface of the corresponding end cap in a longitudinally inward direction of the ceramic tube. Each of the end caps is covered at its inner surface with an electrical insulator. The electrical insulator has a protruding portion surrounding a part of the corresponding electrode which protrudes from a radially central portion of the inner surface of the corresponding end cap. The surrounded part of the corresponding electrode is radially spaced from the protruding portion (the electrical insulator).

Abstract: Disclosed herein is a discharge tube for a high pressure metal vapor discharge lamp, which discharge tube comprises a translucent alumina tubular body, a lower end plate bonded to one end portion of the alumina tubular body which has an electrode support member inside thereof and is bonded to the alumina tubular body when the alumina tubular body is subjected to the light transmission treatment through firing, another end plate which has an electrode support member inside thereof and is bonded to the other end of the translucent alumina tubular body by means of a frit.

Abstract: A ceramic envelope device for a high-pressure metal-vapor discharge lamp, including a translucent ceramic tube, a pair of end caps closing opposite ends of the ceramic tube, and a pair of oppositely located discharge electrodes each of which is supported at a first end by the corresponding end cap such that a second end of the electrode protrudes from an inner surface of the corresponding end cap in the longitudinal direction of the ceramic tube. The end caps are electrically conductive, and completely covered at their inner surfaces with an electrical insulator.

Abstract: Barium titanate series semiconductive ceramics having a positive temperature coefficient of electric resistance are disclosed. The ceramics consist mainly of a barium titanate series compound and contain specifically limited small amounts of titanium dioxide, silicon oxide, aluminum oxide, at least one element selected from the group consisting of rare earth elements, yttrium, bismuth, antimony, niobium, tantalum and tungsten, at least one element selected from the group consisting of manganese, copper, iron and chromium, and zinc oxide. The ceramics are low in the variance of electric resistance values and have a low water absorption and hence are low in the change of electric properties due to the lapse of time.

Abstract: A ceramic is disclosed which maintains a high electric resistance over a wide temperature range and has a large temperature coefficient of resistance variation at temperatures just below the aforesaid range, the PTC ceramic consisting essentially of100 parts by weight of four ingredients includingA. 1 mol of barium titanate composition,B. 0.003 to 0.05 mol of titania,C. 0.003 to 0.05 mol of alumina, andD. 0.005 to 0.06 mol of silica;0.05 to 0.3 part by weight ofE. tantalum pentoxide and/or antimony pentoxide; and0.005 to 0.03 part by weight ofF. manganese and/or copper.