Growth and Characterization of High T sub c Superconducting Oxide Crystals

Our understanding of structural and chemical factors crucial to the appearence of high temperature superconductivity has been furthered by the availability of large, high quality single crystals. Typical of complex substances, these materials do not melt congruently. Thus, approaches such as flux growth are necessary for their preparation. Crystals of Ba sub 2 YCu sub 3 O sub 7 with surface areas approaching 1 cm sup 2 are obtained from CuO-rich melts. The oxygen content of these crystals can be varied, changing the behavior from insulating in Ba sub 2 YCu sub 3 O sub 6 to superconducting at 60K in Ba sub 2 YCu sub 2 O sub 6.6 to superconducting above 90K in Ba sub 2 YCu sub 3 O sub 7. Also impurity atoms can be deliberately induced to perturb systematically the superconducting behavior, thus giving further clues to the nature of high temperature superconductivity. The new Bi-Sr-Ca-Cu-O superconductors have also been grown from CuO-rich melts. In Addition, alkali chloride melts have proven to serve as suitable fluxes for crystal growth in this system. Such melts offer all of the advantages of high temperature solution growth including control of solute composition and concentration and of growth parameters such as soak time and temperature. This talk will emphasize recent progress in crystal growth of high T sub c superconducting of fundamental properties and structural systematics of this fascinating class of materials.