Annealing Effects on Conductivity and Microwave Dielectric Loss of MgTiO3 Ceramics

Abstract

MgTiO3 ceramics were annealed in various atmospheres of air, O2 and N2 at a low temperature of 800 °C and the influences of annealing on the conductivity and microwave dielectric loss were investigated. The conductivity variation with the annealing atmosphere is consistent with the defect equilibrium 2OO×↔2VO•• + O2↑+ 2e', indicating n-type conductance for MgTiO3. Annealing in air/O2 is favorable for eliminating oxygen vacancies and electron defects and thus decreases the conductivity. The N2-annealing increases the contents of oxygen vacancies and electron defects as well as the conductivity. Annealing in air/O2/N2 reduced the microwave dielectric loss irrespective of the contrary effects of air/O2-annealing and N2-annealing on the defects and conductivity, suggesting the frozen defects associated with the oxygen loss during the high-temperature sintering and the low-temperature N2-annealing have negligible effects on microwave dielectric loss. Other factors, such as the release of thermally induced strain, may be responsible for the reduction of microwave dielectric loss due to the low-temperature annealing in air/O2/N2.