Influence of Nd doping on microwave dielectric properties of SrTiO₃ ceramics

Sr_1−xNd_xTiO₃ (x = 0.08–0.14) ceramics were prepared by conventional solid-state methods. The analysis of crystal structure suggested Sr_1−xNd_xTiO₃ ceramics appeared to form tetragonal perovskite structure. The relationship between charge compensation mechanism, microstructure feature and microwave dielectric properties were investigated. Trivalent Nd³⁺ substituting Sr²⁺ could effectively decrease oxygen vacancies. This reduction and relative density were critical to improve Q × f values of Sr_1−xNd_xTiO₃ ceramics. For ε_r values, incorporation of Nd could restrain the rattling of Ti⁴⁺ cations and led to the reduction of dielectric constant. The τ_f values were strongly influenced by tilting of oxygen octahedral. The τ_f values decreased from 883 to 650 ppm/°C with x increasing from 0.08 to 0.14. A better microwave dielectric property was achieved for composition Sr_0.92Nd_0.08TiO₃ at 1460 °C: ε_r = 160, Q × f = 6602 GHz, τ_f = 883 ppm/°C.