The temperature and frequency dependent dielectric and conductivity properties were measured on as-sintered as well as oxygen annealed KNbO3 ceramics. The results showed that in addition to phase transition peaks, well defined relaxation peaks were observed in the temperature range 450–700 K. These peaks could be suppressed by annealing the samples in the oxygen atmosphere. The dc conductivity and maximum dielectric constant values decreases after oxygen annealing. Activation energy, calculated from dielectric relaxation and conductivity data on the samples, suggested that both the processes were due to doubly charged oxygen vacancies formed during sintering process. Dielectric relaxation was attributed to the hopping of oxygen vacancies in the six equivalent sites in perovskite structure. The dielectric and conductivity behaviours were influenced by the density of the samples. The results were explained on the basis of defect concentration and their dynamics.

Role of Oxygen Vacancies on Relaxation and Conduction Behavior of KNbO3 Ceramic. G.Singh, V.S.Tiwari, P.K.Gupta: Journal of Applied Physics, 2010, 107[6], 064103