Substitution of CaO by BaO to improve the microwave dielectric properties of CaO–Li2O–Sm2O3–TiO2 ceramics

Sintered CaO–Li2O3–Sm2O3–TiO2(16:9:12:63) composition (CLST) at 1325°C shows microwave dielectric properties: εr=104.1, Q∗f value=4320 GHz, and τf=13.2 ppm/°C. When BaO is used to substitute CaO in the CLST composition to form CaO–BaO–Li2O–Sm2O3–TiO2=16−x:x:9:12:63 (x=2 and 4 for CBLST2 and CBLST4), the sintered CBLST2 and CBLST4 ceramics show coexistence of two phases, the perovskite CaO–Li2O3–Sm2O3–TiO2 (CLST) phase and BaSm2Ti4O12 (BST). As the BaO content increases from 0 to 4 mol%, the dielectric constant of CBLST ceramics decreases from 104.1 to 94.5, the Q∗f value increases from 4320 to 6740, and the τf value changes from 13.2 to 3.24 ppm/°C.