Effects of adding B2O3 on microwave dielectric properties of 0.9625MgTiO3-0.0375(Ca0.5Sr0.5)TiO3 composite ceramics

A series of 0.9625MgTiO(3)-0.0375(Ca0.5Sr0.5)TiO(3)composite ceramics added with different amounts of B2O3(1-5 wt%) were prepared via the solid state sintering method using the pre-synthesized raw MgTiO(3)and (Ca0.5Sr0.5)TiO(3)powders by molten-salt reaction. The sintering temperature of 0.9625MgTiO(3)-0.0375(Ca0.5Sr0.5)TiO(3)composite ceramics can be reduced from 1275 degrees C to 1175 degrees C due to the liquid phase sintering effect of B2O3. When the adding amount of B(2)O(3)was more than 2 wt%, a new phase MgTi(2)O(5)could be detected by X-ray diffraction, which would substantially degrade the dielectric properties of the obtained ceramics. Resultantly, the quality factor (Q center dot f) and dielectric constant (epsilon(r)) of the samples increase first and decrease later with increasing addition amount of B2O3. In addition, the temperature coefficient of resonant frequency (tau(f)) progressively increases with increasing content of B2O3. By sintering at 1175 degrees C for 4 hours, the obtained 0.9625MgTiO(3)-0.0375Ca(0.5)Sr(0.5)TiO(3)composite ceramics with 2 wt% B(2)O(3)possess the optimal microwave dielectric properties of epsilon(r) = 18.9,Q center dot f = 57 000 GHz and tau(f) = -1.2 ppm/degrees C.