Thermal Depolarization Measurement for Na0.5K0.5NbO3 Piezoceramics

The thermal depolarization of Na0.5K0.5NbO3 ceramics was investigated by thermally stimulated depolarization current (TSDC) measurement in a short circuit and under a 0.5 V induced bias. The large current anomaly of the relaxation of oxygen vacancies was observed at approximately 370 °C, as well as sharp pyrocurrent peaks at T O–T (209 °C) and T C (417 °C) in a short circuit when the ceramics were poled under 3 kV/cm at 150 °C. The temperature of the start of broad current flow (325 °C) was close to the bending point temperature of the Arrhenius plot of the bias-induced TSDC pattern (313 °C). The temperature corresponded to the temperature at which k p began to decrease. The degradation of the piezoelectric property of the poled Na0.5K0.5NbO3 ceramics closely correlated to the thermal relaxation of oxygen vacancies.