Ceramic dielectrics with controlled temperature coefficients of permittivity

Electrical properties of a number of ceramics containing calcium titanate with additions of 2Bi2O3 5TiO2 and others consisting essentially of Bi2O3 2TiO2 have been measured, and a composition CaTiO3, 0.08(2Bi2O3, 5TiO2 has been prepared with a permittivity of 187, low loss (tan ¿<0.002 at 1 Mc/s) and a temperature coefficient of ¿970 parts in 106degC. The electrical properties of ceramics consisting of calcium titanate and calcium titanosilicate have also been studied and found to include a zero-temperature-coefficient composition with a permittivity of more than 80 and low loss (tan ¿<0.0005 at 1 Mc/s). Xray data for these ceramics are given, and the occurrence in them of a cubic pyrochlore-type phase of bismuth titanate is reported. This pyrochlore type of bismuth titanate may be produced with a zero temperature coefficient of permittivity. The possible use of some of these ceramics as capacitor dielectrics with controlled temperature coefficients is indicated.