Crystalline Structures and Superconducting Properties of Rapidly Quenched BiSrCaCu2Ox Ceramics
Phase changes and superconducting properties of rapidly quenched BiSrCaCu2Ox ceramics have been studied. The rapidly quenched sample consists of an amorphous state which begins to crystallize around 510°C. The crystal system was found to be tetragonal with a=5.39Å and c=24.5Å. By annealing above 7OO°C, a tetragonal system with a=5.41Å and c=30.8Å was produced. The former crystal was a semiconductor and the latter was a superconductor with Tc=75K. A superconducting phase with Tc=105K was observed in a sample annealed at 840°C. The superconducting volume ratio in the samples had a maximum at 803–840°C. The decrease of the volume ratio at the higher temperatures is considered to result from a decomposition of the superconducting phase (75K) into a nonsuperconducting phase.
KeywordsDifferential Thermal Analysis Amorphous State Superconducting Phase Tetragonal System Temperature Dependence Resistance
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