PHASE-CONTROL OF Y2BACUO5 IN HIGH-TC SUPERCONDUCTING YBA2CU3O7 CERAMICS PREPARED BY RAPID SOLIDIFICATION PROCESSING

It has recently been reported that Y2BaCuO5 (2-1-1 phase) plays an important role in improving critical current density in bulk superconducting YBa2Cu3O7 (1-2-3). We have found that it is possible to incorporate a controlled amount of 2-1-1 in 1-2-3 by post-annealing a precursor prepared by rapid solidification. The phase volume ratio [2-1-1/(1-2-3 + 2-1-1)] can be controlled in the range of 10% to 100% by post-annealing between 900 and 1020-degrees-C. Also, CuO precipitates ranging in size from approximately 2-mu-m to 20-mu-m were observed in the 1-2-3 phase and a mixture of BaO and CuO was found around these CuO precipitates by SEM and EDX. Samples made by this process show T(c)(rho = 0) of 91.5 K and a sharp superconducting transition, DELTA-T(c) = 0.4 K.