Directional Solidification and Superconductive Transition of Bi2Sr2 CaCu2O8+δ

By laser heated pedestal growth method,Bi;Sr;CaCu;O;as-grown fibers with differentmorphologies were solidified in non-equilibriumcondition at the rates of 0.1～14mm/min.At lowrates,a(Sr;Ca;)CuO;phase with long andstraight strips in shape and a white Cu-rich phasehaving a morphology of globular shape were found.With the increase of solidification rates,the phase(Sr;Ca;)CuO;becomes thinner and the Cu-richphase becomes smaller and dispersive.When thesolidification rates were last.another unstablephase(Sr;Ca;)Cu;O;occurred.In fact,the tran-sition of the semiconductive as-grown fiber to thesuperconductor is a peritectoid reaction influencedby the annealing temperature and time.