Oxygen Content and Phase Diagram of the High-Tc Superconductor Ba2ErCu3Oy

Abstract

The oxygen content of Ba₂ErCu₃O _y was determined by both thermogravimetric measurement and iodometric titration analysis. Four distinct regions were found in the diagram of log P O₂ -1/T plots. These regions were proposed to correspond to: the first orthorhombic phase (O_I), the second orthorhombic phase (O_II), the tetragonal phase (T) and the coexistence of two phases. The partial molar enthalpy of oxygen, ΔH̄O₂ , was obtained as -194±6 kJ/mol for the O_I phase, -166±4 kJ/mol for the O_II phase and -142+4 kJ/mol for the T phase. A pseudobinary phase diagram was proposed based on the log P O₂ -1/T plots, quenching investigation and high-temperature X-ray diffraction analysis.