Dielectric Properties of Ceramics in the System (Sr0.50Pb0.25Ca0.25)TiO3-Bi2O3·3TiO2 and Their Applications in a High-Voltage Capacitor

The dielectric behavior of (1- x )(Sr_0.5Pb_0.25Ca_0.25) TiO₃-x(Bi₂O₃·3TiO₂) was studied using x=O to 8.25 mol%. Around the point at which x equals 1.56 mol%, the following phenomena were observed: (1) At ?;22°C, the weak field permittivity increased substantially with a dc bias field, becoming more than twice the zero bias value at a field of 3 kV/mm; (2) the permittivity peak shifted markedly toward a high temperature under a dc bias field; (3) relaxation behavior was evident; and (4) there are large hysteresis loops at low temperatures and double hysteresis loops, which seem to be related to a field-enforced ferroelectric phase, in a wide temperature range. We used dielectrics with an optimized composition of x =4.30 mol% in a small, highly reliable, 15-kV high-voltage ceramic capacitor.