Effect of Ce ³⁺ doping on phase and microwave dielectric properties of 0.94MgTiO ₃ −0.06(Ca _0.8 Sr _0.2 )TiO ₃ ceramics

Abstract In this study, 0.94Mg _{(1‐3 x /2)} Ce _x TiO ₃ −0.06(Ca _0.8 Sr _0.2 )TiO ₃ (MCe _x T−CST, 0≤ x ≤0.01) composite ceramics were prepared at a low temperature of 1175°C by using the 50‐nm‐sized powders. The effects of Ce ³⁺ doping on crystalline phase, microstructure, and microwave dielectric properties of MCe _x T−CST were studied. A main ilmenite (Mg,Ce)TiO ₃ phase and a minor perovskite (Ca _0.8 Sr _0.2 )TiO ₃ phase coexist well with the appearance of impurity MgTi ₂ O ₅ phase in MCe _x T−CST. The dielectric properties of MCe _x T−CST are affected by the molecular polarizability, the impurity phase, and the Ce ³⁺ doping. The replacement of Mg ²⁺ by high valence Ce ³⁺ could effectively inhibit the formation of oxygen vacancy, resulting in the enhancement of Q×f . When x = 0.005, MCe _x T−CST exhibits microwave dielectric properties with a moderate ε _r of 21.5, a high Q×f of 67 000 GHz, and a near‐zero τ _f of −0.74 ppm/°C. The results reveal that the Ce ³⁺ substitution is a prospective approach to optimize the microwave dielectric properties of MgTiO ₃ ‐based ceramics.