Temperature dependence of dielectric and electromechanical properties of (K,Na)(Nb,Ta)O₃ single crystal and corresponding domain structure evolution

Domain structures and their evolution with temperature in the [001] _C oriented (K,Na)(Nb,Ta)O₃ (KNNT) single crystal have been studied before and after poling by polarizing light microscopy. The results indicate that the KNNT crystal is difficult to be completely poled by the room temperature poling process. The domain structure is rather stable in the orthorhombic phase, but exhibits substantial changes near the phase transition temperatures T_O-T and T_C. Narrower stripe domains are formed during both the orthorhombic-tetragonal and tetragonal-cubic phase transition processes, no intermediate phases were found during the phase transitions. The temperature dependence of the dielectric and piezoelectric properties were measured, and the influence of domain structures on the dielectric and electromechanical properties were quantified.