Preparation and properties of Ba 2− xSr xSmTaO 6 ( x=0–2): a group of new perovskite materials

Abstract

A new group of complex oxide materials were synthesized by the conventional solid state method. These compounds have the general formula Ba 2− x Sr x SmTaO 6 ( x=0, 0.5, 1.0, 1.5 or 2) and complex perovskite structures. The compounds belonging to this Ba 2− x Sr x SmTaO 6 group exhibited a regular transition from the ideal cubic structure to a pseudocubic structure as the strontium content is increased. Pure Ba 2SmTaO 6 gave an ideal cubic perovskite crystal structure of A 2(BB′)O 6 type, while pure Sr 2SmTaO 6 was found to have a pseudocubic structure. The unit cell dimensions of these compounds varied from 8.4687 to 8.3232 Å as the amount of Sr ( x) in Ba 2− x Sr x SmTaO 6 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 °C 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 2×10 −3 at a frequency of 10 7 Hz. These Ba 2− x Sr x SmTaO 6 ceramics gave moderate values of dielectric constant and loss factor, in the range suitable for use as substrates for superconductors.