A new group of complex oxide materials were synthesized by the conventional solid state method. These compounds have the general formula Ba2-xSrxSmTaO6 (x = 0, 0.5, 1.0, 1.5 or 2) and complex perovskite structures. The compounds belonging to this Ba2-xSrxSmTaO6 group exhibited a regular transition from the ideal cubic structure to a pseudocubic structure as the strontium content is increased. Pure Ba2SmTaO6 gave an ideal cubic perovskite crystal structure of A(2)(BB')O-6 type, while pure Sr2SmTaO6 was found to have a pseudocubic structure. The unit cell dimensions of these compounds varied from 8.4687 to 8.3232 Angstrom as the amount of Sr (x) in Ba2-xSrxSmTaO6 increased from 0 to 2. The theoretical density of these samples also decreased from 7.6756 to 6.9401 gm/cm(3) as the value of x is changed from 0 to 2. All these powders could be sintered to more than 90% theoretical density at 1650 degreesC in 4 h. These compounds were found to be thermally stable and did not show any phase change. They had dielectric constants in the range 14-18 and the loss factor values were about 2 x 10(-3) at a frequency of 10(7) Hz. These Ba2-xSrxSmTaO6 ceramics gave moderate values of dielectric constant and loss factor, in the range suitable for use as substrates for superconductors. (C) 2003 Elsevier B.V. All rights reserved.