PLASMA OXIDATION AND 3d METAL DOPING OF HIGH-T//c SUPERCONDUCTORS.

Oxygen intercalation in ceramic superconductors is accomplished near room temperature (T less than 80 degree C) with the plasma technique. Previously, temperatures of at least 500 degree C were required. Technologically, this technique allows oxygen uptake at temperatures compatible with device processing. Scientifically, the oxygen state of the bulk material can be precisely controlled as the sole variable; no disorder from elevated temperatures or ion damage ( less than 5 mw/cm**3) occurs. The oxygen deficient insulating semiconductors YBa//2Cu//3O//7// minus //y and La//2CuO//4// minus //y become bulk superconductors after plasma oxidation as shown both by the Meissner effect and the tetragonal to orthorhombic structural transition. Plasma oxidation of the pure T//c equals 55 K phase Y/Ba//2Cu//3O//6//. //6 reveals that no T//c between 55 K and 90 K (as measured magnetically and resistively) can be produced by oxygen uptake alone. Doping of La//1//. //8//5Sr//0//. //1//5Cu//1// minus //xM//xO//4// minus //y where M equals Ni, Zn and 0 less than x less than 0. 3 has been performed. Structural, magnetic and superconducting properties show that with increased x, the Jahn-Teller distortion is relaxed, the magnetic moment from the Ni is greater than that induced on the Cu by the Zn but T//c falls faster with Zn than Ni doping.