Thermochemistry and High Temperature Thermodynamic Properties of Rare Earth-Alkaline Earth-Copper Oxide Superconductors

Abstract

ABSTRACTEnthalpies of formation of the perovskite-related oxides, La1.85 Sr0.15CuO4, YBa2Cu3Oy, with y = 6.93, 6.69, and 6.47 have been determined at 298.15 K by perchloric acid solution calorimetry. Enthalpies of formation and free energies of reactions with H2 O(g) and CO2 (g) have been evaluated. The partial molar enthalpy of solution of oxygen in YBa2 Cu3Oy has been determined and compared with values derived from measurements or the equilibrium partial vapor pressures of oxygen. The significance of the defect state thermochemistry in conductivity is identified.