Perovskite solid solution in the (1-x)[0.4BiScO 3-0.6BaTiO 3]+x (K 1/2Bi 1/2)TiO 3 [BSBT-KBTx] system was synthesized using conventional sintering and hot-isostatic pressing. Dielectric properties of BSBT ceramics with different dopant levels of KBT were characterized as a function of temperature and frequency for potential use of high-temperature capacitors. The BSBT ceramics with KBT exhibited high dielectric permittivities (�� r) (>1700 at RT) and low dielectric loss over the temperature range from 100�� to 300��C, with flat temperature coefficients of permittivity (TC��s). In addition, BSBT ceramics with increasing KBT were observed to possess dielectric relaxation characteristics at temperatures (>RT) as observed in lead-based relaxors. Furthermore, high energy densities, being on the order of 4.0 J/cm 3 at 220 kV/cm was observed for the BSBT-KBT20 ceramics from the electric-field polarization behavior. �� 2009 The American Ceramic Society.