Microwave dielectric properties of Ca0.8Sr0.2TiO3-Li0.5Sm0.5TiO3 ceramics with near-zero temperature coefficient of resonant frequency

The structural evolution and microwave dielectric properties of (1 - x)Ca0.8Sr0.2TiO3 (x = 0-1.0) solid solutions were investigated. Most samples exhibit the single orthorhombic perovskite structure and a homogeneous microstructure with high density except for the composition with x = 0.5 which included a small amount of the TiO2 phase. Increasing Li0.5Sm0.5TiO3 content results in a structual change in symmetry around x = 0.8. A-site ordering structures were observed in compositions with x >= 0.80. The dielectric constant (epsilon(x)) decreased with increasing x. The quality factor (Q x f) decreased first up to x = 0.5 with increasing x. then increased again up to x = 0.82, and then decreased as x increased to x = 1.0. The temperature coefficient of the resonant frequency (tau(f)) decreased from high positive values to negative values with increasing x. A near zero tau(f) was achieved at x = 0.81. Optimized microwave dielectric properties were estimated to be epsilon(r) = 95. Q x f = 3303 GHz, and tau(f) = -1.8/degrees C at x = 0.81.