Processing and microwave dielectric properties of Sr₅Ta₄TiO₁₇ ceramics

Sr₅Ta₄TiO₁₇ ceramics was processed via solid state mixed oxide sintering route. X-ray diffraction revealed single phase formation of Sr₅Ta₄TiO₁₇ ceramics that crystallized into an orthorhombic crystal structure with a space group Pnnm with lattice parameters of a = 5.681 Å, b = 32.542 Å and c = 3.968 Å, refined by the least squares method. The unit cell density (ρ_th) was 6.71 g/cm³. The microstructure consisted of plate-like grains and the average size was increased from 2 μm to 5 μm with an increase in sintering temperature from 1450 °C to 1575 °C. Optimum microwave dielectric properties, i.e. є_r ~ 66,Q_uf_o ~ 8500 GHz and τ_f ~ 180 ppm/°C, were achieved for Sr₅TaTiO₁₇ ceramics sintered at 1550 °C for 4 h.