Influence of thermal treatments on the low frequency conductivity and microwave dielectric loss of CaTiO3 ceramics

We prepared CaTiO3 by solid state reactions as a model for Ti-based microwave dielectric ceramics to investigate the influence of thermal treatment on conductivity and microwave dielectric loss. The intrinsic defect concentrations of CaTiO3 may be modified by air-quenching, air-annealing and thermal treatment in various atmospheres such as O-2. Ar and air. CaTiO3 has p-type conductance implying that calcium vacancy V-Ca(x) may be the dominant defect. The variation in defect concentration influences the low frequency conductivity but not the microwave dielectric loss. The V-Ca(x), concentration in the air-quenched sample was found to be lower than that in the air-annealed one. However, the former showed similar to 8% deterioration and the latter showed a 14% improvement in the Q x f value. The data, therefore, suggests that other factors such as thermally induced strain rather than intrinsic defects may influence the microwave dielectric loss. (C) 2010 Elsevier B.V. All rights reserved.