(1-x)[0.4BiScO3-0.6BaTiO3] + x (K 1/2Bi1/2)TiO3 [BSBT-KBTx] ceramics in the perovskite solid solution system were studied for potential high temperature capacitor applications. The diectric properties of BSBT-KBTx ceramics were investigated as a function temperature and frequency. The BSBT-KBTx ceramics showed high dielectric permittivity (> 1000 @RT) and low dielectric loss over the temperature range from 100 ∼ 300°C with a flat temperature coefficient (TCC). In addition, BSBT-KBTx ceramics were observed to possess a dielectric relaxation at temperatures (> 300 K). Polarization measurements as a function of electric field showed high energy storage densities with 1.8 J/cm3 at 120 kV/cm. Therefore, dielectrics in this novel ternary system appear to be promising candidates for high temperature and energy storage capacitors.