Doping Effects of Ta on Conductivity and Microwave Dielectric Loss of MgTiO ₃ Ceramics

Abstract

Two kinds of solid solution systems of Ta‐doped MgTiO 3 were identified by X‐ray diffraction, which can be represented by the formulae MgTi 1− x (Mg 1/3 Ta 2/3 ) x O 3 (0≤ x <0.5) and MgTi 1− x Ta x O 3 (0≤ x <0.05). The conductivity and microwave dielectric loss for the two solid solution systems were examined by AC impedance and microwave resonator measurements, respectively. In the system MgTi 1− x (Mg 1/3 Ta 2/3 ) x O 3 , the mechanism for the solid solution formation is the isovalent substitution of for Ti 4+ . In the system MgTi 1− x Ta x O 3 , the doping mechanism is the aliovalent substitution of Ta 5+ for Ti 4+ , where for a small amount Ta doping, the oxygen vacancies formed during the high‐temperature preparation are filled by an extra oxygen introduced from Ta 2 O 5 and further Ta doping leads to an increase in the contents of and electrons, which was consistent with conductivity measurements. In both systems, the Q × f values improved, e.g., ∼17% for the isovalent substitution at x =0.08 and ∼10% for the aliovalent substitution at x =0.02. The filling oxygen vacancy and the substitution of Ta/Mg for Ti may contribute to the improvement of Q × f values for both systems.