Abstract
The high Tc superconductor YBa2Cu3Oy (YBCO) is an oxygen non-stoichiometric compound and its oxygen content y changes from 6.0 to 7.0 under various conditions (temperature and oxygen partial pressure). At around room temperature, the crystal structure of YBCO is tetragonal in 6.0<y<6.4 and orthorhombic in 6.4<y<7.0. The relation between oxygen content and ortho-tetra transition at y>6.6 has been unknown because of the restriction of experimental methods. In this experiments, using the newly developed TG-DTA making it possible to measure under high pressures, we have investigated oxygen non-stoichiometry of YBCO under high oxygen pressure (>1atm). In results, we obtained new knowledge of the dependence of O-T transition temperature on oxygen content y (>6.6).
