EFFECT OF GD2BACUO5 CONTENT ON THE MACRO-DEFECT STRUCTURE OF MELT-PROCESSED GDBA2CU3OY SUPERCONDUCTOR

Applications of REBa2Cu3Oy superconducting material demand materials w ith minimized macro-structural defects like cracks, voids and pores. S uch defects affect the current density values attainable and also prec lude shaping the material into useful components. In order to study an d minimize the above defects, we have melt processed GdBa2Cu3Oy with s ystematically increasing amounts of Gd2BaCuO5 (211) as reinforcement. It is observed that practically all the shrinkage associated with melt processing occurs at the melting stage and not at the texturing stage . The variation of shrinkage as well as the size of pores residual in the samples with the increasing 211 content can be correlated to the s ize of the 211 particles in the pro-peritectic liquid at 1100 degrees C. Macro-cracks, parallel to the intrinsic micro-cracks between the 12 3 platelets, are observed in all the domains. The number and nature of these cracks are independent of the 211 content. The origin of these cracks is discussed.