Relationships between Sr substitution for Ba and dielectric characteristics in Sm2BaZnO5 ceramics

The effects of Sr substitution for Ba in Sm2(Ba1−xSrx)ZnO5 solid solutions on the crystal structure and microwave dielectric properties were investigated in this study. The ϵr values of Sm2(Ba1−xSrx)ZnO5 are slightly increased with increasing x in the range 0⩽x⩽0.1, and the Q·f values are extremely decreased from 35 505 to 8522 GHz. The variations in the Q·f values may depend on the differences in the crystal structure because a single phase of Sm2(Ba1−xSrx)ZnO5 with tetragonal structure was produced for x⩾0.1 compositions instead of an orthorhombic structure. The highest Q·f value in Sm2(Ba1−xSrx)ZnO5 with a tetragonal structure was 19 283 GHz at x=1. The increase in the Q·f values of samples with x⩾0.1 were attributed to the grain growth induced by the Sr substitution for Ba. In the sample at x=1 many microcracks were observed. In order to remove these cracks, Co was substituted for Zn in Sm2SrZnO5, which improved the Q·f values.