Dielectric/piezoelectric properties and temperature dependence of domain structure evolution in lead free (K0.5Na0.5)NbO3 single crystal

(K0.5Na0.5)NbO3 (KNN) single crystals were grown using a high temperature flux method. The dielectric permittivity was measured as a function of temperature for [001]-oriented KNN single crystals. The ferroelectric phase transition temperatures, including the rhombohedral-orthorhombic TR-0, orthorhombic-tetragonal T0-T and tetragonal-cubic T-C were found to be located at - 149 degrees C, 205 degrees C and 393 degrees C, respectively. The domain structure evolution with an increasing temperature in [001]-oriented KNN single crystal was observed using polarized light microscopy (PLM), where three distinguished changes of the domain structures were found to occur at - 150 degrees C, 213 degrees C and 400 degrees C, corresponding to the three phase transition temperatures. (C) 2009 Elsevier Ltd. All rights reserved.