Conductivity and Dielectric Loss of Tungsten-Bronze-Type BaNd₂Ti₄O₁₂ Microwave Ceramics

Abstract

Tungsten-bronze type titanate BaNd2Ti4O12 ceramics were synthesized by solid state reactions. The conductivity and microwave dielectric loss of the samples that were thermally treated under various conditions and Ta-doped were investigated by electrochemical impedance measurement and microwave dielectric resonator measurement. The variation in conductivity with annealing atmospheres of air, O2, and N2 was consistent with the defect equilibriums 2O × O ↔2V •• O +O2↑+2eʹ and Ti × Ti +eʹ↔TiʹTi, suggesting n-type conductance for BaNd2Ti4O12. Thermal treatment in air/O2 was found to favor the elimination of the native defects V × O, TiʹTi and weakly bound electrons thus decreasing the conductivity. Thermal treatment in a N2 atmosphere, which had a low oxygen partial pressure, increased the defect content and the conductivity. Thermal treatment in air/O2/N2 did not clearly affect the microwave dielectric loss, suggesting that native [Article] www.whxb.pku.edu.cn