Electrical Properties of Ceramics as Influenced by Temperature

Data on dielectric strength, resistivity and power factor are presented for a high-tension porcelain, a zircon porcelain celain and an alumina porcelian. Additional data on mica and fused silica taken from the literature are included for comparison purposes. The temperature range covered in the experimental work extends from 25 to 1000 degrees centigrade. When the logarithms of the dielectric strength, resistivity or power factor are plotted against the reciprocal of the absolute temperature, two straight lines of different slopes result in each case. The intersection of these two lines define a transition temperature between the disruptive and thermal regions of electric breakdown. An interesting feature of this investigation is the discovery that the transition temperatures as determined by the dielectric strength coincide approximately with those determined by resistivity or power factor. The transition temperature gives some indication of the maximum temperature beyond which the material should not be used in practice. Considerable advantage of zircon and alumina porcelains over high tension porcelain for high temperature applications are indicated. The data are discussed in the light of existing conduction and electric breakdown theories.