High temperature chemistry of oxide superconductors

A knowledge of the high temperature chemistry involved in the formation of the high-Tc superconductors is necessary in order to prepare materials with desired properties. The authors studied the liquidus relations in the YO1.5BaO-CuO system and have performed initial experiments to understand equilibrium conditions in the Tl-Ca-Ba-Cu-O system. This paper reviews the liquid forming reactions that pertain to the processing of Yba2Cu3O7-α generates a liquid phase that promotes deleterious grain growth of the superconducting phase. The authors show that very small deviations in stoichiometry can have a large effect on microstructure through the generation of such liquids