TEMPERATURE DEPENDENCE OF THE MICROSTRUCTURE IN YBa2Cu3Oy: TRANSMISSION ELECTRON MICROSCOPY STUDY

A transmission electron microscopy study has confirmed some new features of thermal variations of the microstructure in the high-Tc superconducting compound YBa2Cu3Oy. The changes of domain structures and the nucleation process of the tetragonal phase with the increase of temperature are demonstrated by series of images taken under in-situ heating observations. At temperature near 250°C, two new sets of planar defects have been observed along the directions of a and b-axes, respectively. It has been identified that a continuous structural phase transition, from orthorhombic to tetragonal phase, occurs at about 480 °C. The structural properties of the tetragonal phase have been studied at 700°C.