Synthesis and Superconductivity of La_2-xBi_xCuO₄

Abstract

La_2-xBi_xCuO_4+z (0<x<0.2) was prepared under oxygen pressures between 1bar and 0.5kbar. The solid solution La_2-xBi_xCuO_4+z showed superconductivity only after being annealed under high oxygen pressure. For La₂CuO_4+z the superconducting transition temperature, Tc, was almost independent of z at around 40K, while the Tc of Bi-doped samples showed a strong dependence. The superconductive volume fraction was considersbly increased by the Bi doping. The known phase separation into nearly stoichiometric La₂CuO₄ and superconducting La₂CuO_4+z seems to be suppressed by the Bi-for-La substitution.