Microwave dielectric properties and microstructures of xBa0.33Sr0.67TiO3-(1-x)Ba4Sm9.33Ti18O54 ceramics with near-zero temperature coefficient

The phase composition, microstructures, sintering behavior, and microwave dielectric properties of Ba0.33Sr0.67TiO3-Ba4Sm9.33Ti18O54 ceramics prepared via conventional solid-state route were systematically investigated as a function of the Ba0.33Sr0.67TiO3 molar fraction and sintering temperature. All the sintered ceramics only exhibited a single orthorhombic tungsten bronze structure BaSm2Ti4O12 phase. And all samples sintered at 1400 degrees C showed fully dense and homogeneous microstructures. The variation of bulk density and dielectric properties are related with the Ba(Zn1/3Nb2/3)O-3 molar fraction, but not with a same trend. As Ba ions in A1 sites are substituted by Sr ions, Qxf values enhanced dramatically. The optimum microwave dielectric properties with an epsilon(r) value of 80.13, a Qxf value of 11386GHz (at 3.5GHz), and a (f) value of -0.34ppm/degrees C were obtained for 0.03Ba(0.33)Sr(0.67)TiO(3)-0.97Ba(4)Sm(9.33)Ti(18)O(54) ceramics sintered at 1400 degrees C for 4h.