Abstract: A system of dielectric ceramic compositions suitable for various microwave applications. The system comprises a plurality of stoichiometrically-related compositions, each composition having its own particular set of dielectric properties and consisting essentially of a sintered mixture represented by the general formula:BaTi.sub.4-w M.sub.w O.sub.9 --xZn.sub.2 TiO.sub.4 --yBaO--zTa.sub.2 O.sub.5wherein M is at least one type of metal and 0.0.ltoreq.w.ltoreq.about 0.05 and wherein x, y, and z are molar fractions of respective components with values within the following respective ranges: 0.0.ltoreq.x.ltoreq.about 0.45; about 0.01.ltoreq.y.ltoreq.about 0.20; and 0.0.ltoreq.z.ltoreq.about 0.10.

Abstract: Iron is used as a dopant in barium titanate semiconductor ceramic material to increase the positive temperature coefficient of resistance thereof. By the use of about 0.010 to 0.500 weight percent silica and about 0.0075 to 0.0190 weight percent iron, room temperature resisitivity can be kept adequately low while the temperature coefficient of resistance is significantly increased.

Abstract: A PTC heating element with a honeycomb ceramic body comprising a barium titanate and semiconductor element, which provides the ceramic body with a positive temperature coefficient of resistance over the Curie point. An electrode is deposited on each end of the honeycomb body. The electrodes according to the present invention have a non-ohmic property, while the conventional electrodes have been ohmic. A high rush current and migration are advantageously decreased by the non-ohmic electrodes.

Abstract: Disclosed herein is a heating element for an air heater and the like comprising a ceramic material in the form of a honeycomb as well as the process for producing the ceramic material. The heating element is characterized by its relatively high amount of heat generation capability compared to a conventional heating element of the same size. Preferable ceramic materials for the heating element have a temperature coefficient of electrical resistance of from 5 to 20%/.degree.C., and consist essentially of from 38.7 to 47.3 molar % of BaO, from 2.5 to 11 molar % of PbO, from 49.8 to 50% of TiO.sub.2, from 0.05 to 0.3 molar % of a semiconductor forming element and from 0.002 to 0.015 part by weight of Mn.

Abstract: A semiconductor ceramic composition having positive temperature characteristics which comprises titanates of barium, lead and calcium which have 1 - 40 mole % of lead titanate and 1 - 22 mole % of calcium titanate and 38 - 98 mole % of barium titanate and 0.03 - 0.6 mole % of a semiconductor-forming component based on said titanates.