Thermal depoling and relaxation property of (Na,K)NbO3 system

(Na,K)NbO3 ceramics was synthesized by an ordinal solid state reaction method. Thermally stimulated depolarization current (TSDC) pattern of the poled ceramics was measured. Electrically poled Na0.5K0.5NbO3 ceramics generated anomalous large discharge current at around 370 °C during the heating step due to the thermal relaxation of oxygen vacancy. The oxygen vacancy piled up around electrodes and formed the electrically inhomogeneous structure in the ceramics. In addition, the anomalous current of K-riched ceramics was larger than that of Na-riched one. This result suggested that the equilibrium composition of NaNbO3–KNbO3 system was near to Na-riched composition against Na0.5K0.5NbO3.