Domain Boundary and Domain Switching in a Ceramic Rare‐Earth Orthoniobate LaNbO 4

By using TEM and X‐ray diffraction, the domain structure in ceramic LaNbO 4 has been studied. It has been found that the domains have two different orientations, separated by a boundary with_irrational Miller indexes between (20) I / (402) II and (20) I /(602) II lattice planes, which is in good agreement with the boundary indexes calculated from elasticity theory and spontaneous strain tensor. The orientation relationship between the domains has been determined as a rotation of 95.6° about the [010] axis. A model for domain boundary configuration, a diffuse boundary with a transition zone, has been proposed according to TEM diffraction patterns and HRTEM images. Based on this domain boundary model, a domain switching mechanism is suggested, and the corresponding driving force for domain switching is considered.