Structure, chemical bond, and microwave dielectric properties of (Sr1−xCax)2(Ti1−xSnx)O4 ceramics

Dense (Sr 1 − x Ca x ) 2 (Ti 1 − x Sn x )O 4 ( x  = 0.0, 0.05, 0.10, 0.15) ceramics were synthesized by a standard solid-state reaction method. The formation of solid-solution with an I 4/ mmm space group was revealed from the X-ray diffraction patterns and Rietveld refinement results. The variation of the microwave dielectric properties was systematically analyzed using the dielectric polarizability and complex chemical bond theory. The dielectric constant ( ε r ) was mainly determined by the ionic polarizability per unit volume. Qf value was closely associated with the increasing amount of Sr 3 Ti 2 O 7 secondary phase and the declined lattice energy. Meanwhile, the variation of Qf value was further analyzed by extrapolating the intrinsic dielectric loss from the infrared reflectivity spectra. τ f value was successfully adjusted toward zero, which could be explained by the enhanced bond energy. The optimal microwave dielectric properties were achieved at x  = 0.10, with ε r  = 33.6, Qf  = 73,150 GHz, and τ f  = 115 ppm/°C.