Superconducting and Transport Properties of B-Y-Cu-O Compounds –Orthorhombic and Tetragonal Phases

Abstract

The superconducting properties and crystal structures of the Ba-Y-Cu-O compounds have been studied. Annealing and quenching experiments have been carried out to study the phase transformation between the high temperature tetragonal phase (oxygen deficient) and low temperature orthorhombic phase (oxygen rich). The former phase is semiconductor-like down to 4.2 K, whereas the latter is metallic and superconducting with T c as high as 94 K. The conspicuous difference in the transport and superconducting properties between the two phases has been attributed to the loss or formation of oxygen and Cu atom chain in the crystal structure.