Preparation of an Almost Single Phase Superconductor in the Nd-Ce-Sr-Cu-O System

A superconducting oxide with the composition (Nd0.60Ce0.175Sr0.225)2CuO4-δ was obtained as an almost single phase. This superconducting phase has a tetragonal unit cell with lattice parameters a=3.8575 Å and c=12.507 Å. The crystal structure of this phase is different from both the Nd2CuO4 type structure and the K2NiF4 type structure. Magnetic susceptibility measurement shows that (Nd, Ce, Sr)2CuO4-δ is a bulk superconductor. The superconductivity of samples annealed at a high oxygen pressure was investigated. The onset critical temperature was insensitive to high oxygen pressure.