Evolution of low-temperature phases in a low-temperature structural transition of a La cuprate

The microstructure produced by a low-temperature structural phase transition in (Formula presented) has been examined by transmission electron microscopy with the help of imaging plates. The low-temperature transition was found to be proceeded not only by the growth of the (Formula presented)/low-temperature-tetragonal phases nucleated along the twin boundary but also by the nucleation and growth of the phases in the interior of the low-temperature-orthorhombic domain. In addition, because the map of the octahedron tilt as an order parameter is not identical to that of the spontaneous strain accompanied by the transition, the microstructure below the transition is understood to be a very complex mixture of the low-temperature phases.