Effect of Sr substitution for Ba on microwave dielectric properties of Sm2(Ba1−xSrx)(Cu0.5Zn0.5)O5 ceramics

The influence of Sr substitution for Ba on the microwave dielectric properties and crystal structure of the Sm2(Ba1−xSrx)(Cu0.5Zn0.5)O5 ceramics was studied. However, it was found that the limit of the solid solution was approximately x = 0.4 from the XRPD patterns. In the single phase region, the sintering temperature dependence of the microwave dielectric properties of the solid solutions was investigated. The dielectric constants of the solid solutions were approximately 18 in the sintering temperature range of 1150–1250° C, whereas the Qf values of the solid solutions strongly depended on the composition x. The Qf values of the solid solution decreased with an increase in composition x; the differences in the Qf values were attributed to the morphological changes in the samples which arose from the Sr substitution for Ba. However, the Qf value of approximately 65,000 GHz was obtained at x = 0 in the sintering temperatures ranging from 1150 to 1250° C. The temperature coefficient of resonant frequency (τf) of the solid solutions varied from negative to positive values, ranging from −6 to 7 ppm/°C with the Sr substitution for Ba; a near zero τf value was obtained at x = 0.05; a small amount of Sr substitution for Ba was substantially effective in improving the τf values of the solid solutions.