Microwave Dielectric Properties and Thermally Stimulated Depolarization Currents of (1 − x )MgTiO 3 – x Ca 0.8 Sr 0.2 TiO 3 Ceramics

(1 −  x )MgTiO 3 – x Ca 0.8 Sr 0.2 TiO 3 (0.04 ≤  x  ≤ 0.2, MT ‐ CST ) composite ceramics were prepared by the conventional solid‐state reaction process. The phase composition, microwave dielectric properties, and microwave dielectric loss mechanisms were studied. Ca 0.8 Sr 0.2 TiO 3 was employed as a τ f compensator for MgTiO 3 , and they coexisted well without forming any secondary phases. Interestingly, significant dielectric relaxations associated with oxygen vacancy defects were observed in all the MT ‐ CST ceramics through the dielectric‐temperature spectra. Thermally simulated depolarization current was therefore conducted to obtain the defects associated with extrinsic dielectric loss mechanisms. The concentrations of both defect dipole [ ( Ti Ti ′ ) − ( V O ∙ ∙ ) ] and in‐grain oxygen vacancies ( V O ∙ ∙ ) increased with the increasing x , which could induce microwave dielectric loss consequently. It demonstrated that the behaviors of Q  ×  f were basically influenced by phase composition and defects here. Temperature‐stable ceramics can be achieved at x  = 0.06, where the microwave dielectric properties were ε r  = 21.19, Q  ×  f  = 110 900 GHz ( f  = 9.295 GHz), and τ f  = −0.9 ppm/°C, respectively.