Temperature evolution of domains in potassium niobate single crystals

Abstract

The behavior of domain walls in KNbO3 single crystals with temperature variation from room temperature to 300 °C has been investigated in situ by a heating visualization system. It has been observed that domain walls show active behavior in a small temperature range from the phase transition temperature of 225 °C, the range being about 10 °C in the orthorhombic phase and 15 °C in the tetragonal phase. The 90° domain walls are generated randomly and extend themselves rapidly within the crystal in high density. The 60° domain walls, which are only observed in orthorhombic phase, do not appear randomly but are formed along the boundary of intersecting 90° domain walls. The results suggest that the 90° domain walls are most likely caused by microdefects within the crystal, and that dislocations at the junction of intersecting 90° domain walls supply nucleation sites for the 60° domain walls. © 1996 American Institute of Physics.