Optical, piezoelectric, leakage current and polarization fatigue studies of NBT-KNN ceramics near MPB

ABSTRACTLead-free (1-x)Na0.5Bi0.5TiO3-xK0.5Na0.5NbO3/(1-x)NBT-xKNN solid solutions (x = 0.05, 0.06, 0.07, 0.08) near morphotropic phase boundary (MPB) were investigated for their optical, piezoelectric, polarization fatigue and leakage current properties. Optical band gap of all the ceramics was found to be ∼3 eV. The x = 0.07 composition exhibited large piezoelectric and electromechanical coupling coefficient, small leakage current density of ∼1.04 × 10−6 A/cm2 at 40 kV/cm. The bipolar fatigue behavior carried out by the remnant polarization vs. number of cycles (up to 109). These findings confirmed the existence of MPB in x = 0.07 composition and its potentiality for memory and actuator applications.