Changes in ordered structure and dielectric properties with the A-site andB-site cation ratios of complex perovskites (Sr1-xBax)(Sr0.33+yTa0.67-y)O3-delta

Complex perovskites with large-sized B'-site cations, (Sr1-xBax) (Sr0.33+yT a0.67-y)O3-delta (0 less than or equal to x less than or equal to 1, 0 less than or equal to y less than or equal to 0.17), were fabricated to examine the transformation behavior between the (1. 1) and (1:2) order types and d ielectric property change with A-site cation substitution. The (1:2) type o rder was found to appear in a limited Ba-rich composition range. Structural strain induced by size difference between the A-site and large-sized B'-si te cations might be responsible for the occurrence of the (1.1) type order in perovskite compounds substituted with move than 50% Sr2+ on the A-site s ublattice. Low epsilon(r) and positive temperature coefficient of epsilon(r ) observed for the (1:2) ordered samples were explained by the restricted i on movement in the (1:2) type order array. (C) 1999 Elsevier Science Limite d. All rights reserved.