Effect of Solution Composition on Superconducting Properties of YBCO Derived From TFA-MOD Process

Abstract

The crystallization process of trifluoroacetate-metal-organic deposition derived YBa2Cu3O7-y (YBCO) crystals has been investigated to understand the influence of the starting solution composition on the crystal growth process. The starting solutions with molar ratios of Y: Ba: Cu = 1.0: 2.0: 3.0 (stoichiometry) and 1.0:1.5:3.0 (Ba-deficient) were examined. The highest Ic values were achieved at 100 min holding time of the conversion step for 0.8- μm-thick YBCO films, which were independent of the starting solutions. The degradation of Ic performance was observed only in the films prepared from the stoichiometric solution with longer holding time than 100 min. The longer holding times for disappearing of the X-ray diffraction peak of BaF2 derived from the stoichiometric solution is required compared to that from the Ba-deficient solution. On the other hand, the epitaxial growth rate measured from cross-sectional scanning electron microscopic observation for the YBCO films showed no difference between each other. X-ray diffraction analysis on the YBCO films fabricated from stoichiometric starting solution suggested that BaCuO2 and/or Y2O3 phases formed during the solid-state reaction process. The degradation of Ic performance might be caused by the formation of BaCuO2 phases.