Preparation of Y-Ba-Cu-O high-transition-temperature superconductors using BaO sub 2 and BaCO sub 3

The preparation of superconducting YBa sub(2)Cu sub(3)O sub(7-x) in static air and flowing He atmosphere from BaCO sub(3) and BaO sub(2) mixed with Y sub(2)O sub(3) and CuO has been studied. In static air BaO sub(2) reacted at slightly lower temperature than BaCO sub(3) and different mechanisms were observed for the formation reactions. Using BaO sub(2), the orthorhombic phase is readily formed, while high temperatures or prolonged heating times are needed to obtain the orthorhombic phase with BaCO sub(3). In flowing helium atmosphere, both starting materials led to products which contained metallic Cu and binary oxide compounds, with no ternary oxides being detected.