High-resolution electron microscopyin situobservation of a transformation interface between tetragonal and orthorhombic phases in YBa₂Cu₃O_7−x

Abstract The phase transformation between the tetragonal and orthorhombic phases in YBa2Cu3O7−x has been observed by in situ high-resolution electron microscopy and the structure of a transformation interface between the two phases has been determined directly from an analysis of the lattice fringes. It has been shown that the interface is fully coherent and broad over 50 nm, and that the lattice cells undergo a continual transition from the tetragonal phase to the orthorhombic phase. This observation is in good agreement with a model proposed by Malis and Gleiter for the ferroelectric-para-electric transformation in BaTiO3.