Annealing Effects on Conductivity and Microwave Dielectric Loss of MgTiO3 Ceramics

MgTiO3 ceramics were annealed in various atmospheres of air, O-2 and N-2 at a low temperature of 800 degrees 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 2O(O)(x) <-> 2V(O)(center dot center dot) + O-2 up arrow + 2e', indicating n-type conductance for MgTiO3. Annealing in air/O-2 is favorable for eliminating oxygen vacancies and electron defects and thus decreases the conductivity. The N-2-annealing increases the contents of oxygen vacancies and electron defects as well as the conductivity. Annealing in air/O-2/N-2 reduced the microwave dielectric loss irrespective of the contrary effects of air/O-2-annealing and N-2-annealing on the defects and conductivity, suggesting the frozen defects associated with the oxygen loss during the high-temperature sintering and the low-temperature N-2-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/O-2/N-2. (C) 2011 The Japan Society of Applied PhysicsPhysics, AppliedSCI(E)EI0ARTICLE6null5