Dielectric Properties of (Ba, Sr, Ca)TiO3 Ceramics for Tunable Microwave Devices

(Ba_0.9-xSr_xCa_0.1)TiO₃ (x=0.25~0.5) and (Ba_0.6-ySr_0.4Ca_y)TiO₃ (y=0.05~0.2) ceramics were fabricated by the mixed-oxide method. All BSCT specimens owned dense and homogeneous structure without the second phase. By comparing the properties of (Ba_0.9-xSr_xCa_0.1)TiO₃ and (Ba_0.6-ySr_0.4Ca_y)TiO₃, we found that the influence of Ba/Sr ratio on Curie temperature is greater than that of Ba/Ca ratio. The increasing of Ca content could decrease the dielectric loss and dielectric constants, but it would decrease the tunability as well. (Ba_0.55Sr_0.4Ca_0.05)TiO₃ and (Ba_0.5Sr_0.4Ca_0.1)TiO₃ are expected to be the candidate materials for microwave tunable devices, whose tunability, dielectric constant and loss were 24.1%, 4300, 0.28% and 16.5%, 3200, 0.096% respectively.