Defect control for low leakage current in K0.5Na0.5NbO3 single crystals

Leakage current properties of K0.5Na0.5NbO3 (KNN) single crystals grown by a flux method have been investigated to establish a guiding principle of defect control for high-performance lead-free piezoelectric devices. The substitution of Mn at the Nb site and the following annealing under moderate oxidation condition was effective for suppressing leakage current of KNN crystals. Electron spin resonance measurements demonstrate that oxidation of Mn during annealing plays an essential role in low leakage current in the KNN system. Mn-doped KNN crystals exhibited a low leakage current density (∼10−8A∕cm2) and relatively large remanent polarization of 40μC∕cm2 at 25°C.