Oxygen Plasma Effects on Zero Resistance Behavior of Yb,Er-doped YBCO (123) Based Superconductors

Abstract

Rare-earth doped YBa2Cu3O7-delta samples were synthesized starting from the corresponding oxides Y2O3, Yb2O3, Er2O3, CuO as well as Ba(OH)(2) by heating to 950 degrees C under air. The doping concentrations were adjusted to 15% Yb, 7% Er and 20% Yb, 15% Er, respectively, with respect to the yttrium content. The orthogonal phased (123) YBCO ceramics were exposed to an oxygen plasma for 140 and 380 min. Zero resistance temperature (T-c,T-0) was determined by measuring the resistivity-temperature dependence using a classical four point measurement approach. Under optimal conditions with respect to the material composition and the oxygen treatment an unusual high zero resistance temperature of 97.5 K (T-c,T-onset approximate to 101 K) was achieved. This represents an increase of T-c,T-0 by 7.5 K. The oxygen treatment could not be monitored by IR spectroscopy, X-ray fluorescence spectroscopy, and X-ray powder diffraction. The results showed good reproducibility.