Defect chemistry of YBa 2Cu 3O x: Strong evidence for the presence of Cu +

Abstract

The defect chemistry of the new high-Tc superconducting compound YBa 2Cu 3O x was studied using precision data for the dependence of x on temperature and partial oxygen pressure. In a thermodynamic analysis it is shown that the data cannot be explained satisfactorily if the simultaneous presence of Cu 2+ and Cu 3+ only is assumed for x = 6.5 − 7. A good description is obtained, however, if the presence of Cu + is taken into account for the full stoichiometry range of x = 6 −7.