We report synthesis, structure and dielectric properties of double perovskite-type Ba3-xKxCaNb2O9-delta (x = 0.5, 0.75, 1, 1.25) (KBCN). Powder X-ray diffraction (XRD) confirmed the formation of double perovskite-type structure and lattice constant decreases with increasing Kin KBCN. AC impedance study showed a single semicircle over the investigated temperatures and frequencies in dry H-2, H-2 + 3% H2O, 3% H2O + N-2, while two semicircles were observed at low temperatures in air, which could be attributed to bulk and grain-boundary contributions. Unlike un-doped BCN, KBCN exhibits negligible grain-boundary and electrode effects to the total electrical properties and is consistent with perovskite-type K-doped BaZrO3. The bulk dielectric constant and dielectric loss were found to increase with increasing K content in KBCN and also found to change with sintering temperature. Among the samples investigated, Ba1.75K1.25CaNb2O9-delta sintered at 1100 degrees C showed the highest dielectric constant of 65 at 10(6) Hz and dielectric loss of 0.14 at 400 degrees C in air. Isothermal dielectric constant and electrical conductivity at 1 MHz were found to be independent at elevated temperatures, while vary at low-frequency and low temperatures. Below 700 degrees C, dielectric constant and dielectric loss decreases with increasing frequency, whereas an opposite trend was observed for the electrical conductivity. (C) 2011 Elsevier Ltd. All rights reserved.