Plasma oxidation of the high T c superconducting perovskites

Abstract

A near room‐temperature plasma oxidation process is shown to restore superconductivity and metalliclike behavior in oxygen deficient La_2−x Sr_x CuO_4−y and YBa₂Cu₃O_7−x compounds. In the YBa₂Cu₃O_7−x compound the conversion from an oxygen deficient n‐type tetragonal to the p‐type orthorhombic phase with a concomitant factor of 5×10⁵ increase in room‐temperature conductivity is also accomplished. This process is of technological importance because oxygen can be restored in these materials at temperatures compatible with device processing. Of scientific interest, the process allows us to carefully control the oxidation state and thereby systematically study the 90 and 55 K superconducting transitions in YBa₂Cu₃O_7−x.