Thermodynamic desorption of oxygen in high Tc superconducting oxides

Abstract

We measure as a function of temperature and composition the equilibrium pressure of desorbed oxygen from superconducting oxides MBa2 Cu 3 O6+x (M=Eu, Y). Using the Lacher model we determine the enthalphy of formation of the excess oxygen x (-0.7 eV/atom) as well as the repulsive O-O interaction energy (0.11eV). We also observe that there is a spontaneous reabsorption of the oxygen above about 600° C with formation of more stable oxides