STRUCTURAL-CHANGES OF MULTIPHASE BISMUTH-OXIDE SUPERCONDUCTOR THIN-FILMS AT HIGH-TEMPERATURES

Structural changes during heat treatment have been studied for multiph ase bismuth-oxide thin film superconductor in terms of desorption of o xygen. Desorption of oxygen by heating has made the low Tc 2212 phase thermally unstable. About 90% of the 2212 phase has melted at 800 degr ees C. In the course of cooling, the high Tc, oxygen stoichiometric 22 23 phase has recrystallized from the melted 2212 phase. After heat tre atment, the thin film has been composed mostly of the 2223 phase with a Tc onset and a Tc endpoint of 107 and 83 K, respectively. (C) 1995 A merican Institute of Physics.