Melt processing and microstructural analysis of GdBa(2)Cu(3)Oy with varying amounts of Gd2BaCuO5 phase

Bulk samples of GdBa2Cu3Oy (Gd-123) with varying amount of Gd2BaCuO5 (Gd-21 1) phase are melt processed. The processing conditions and the resulting ma cro and microstructures were discussed. The T-c of the material is found to be sensitive to the processing atmosphere, and the percentage of 211 in th e precursor powder. Pure Gd-123 samples behaved differently as compared to the compositions with excess 211 phase. The amount of porosity and the aver age size of pores in the samples decreases with the increasing amount of Gd -211 in the precursor powder. The densification of the melt textured materi al is ascribed to the densification process of the precursors prior to the texturing stage. Irrespective of the Gd-211 content macro-cracks within dom ains were observed in parallel to the intrinsic micro-cracks. At the meltin g stage refinement of the Gd-211 particles originating from the decompositi on of Gd-123 was observed with the increasing amounts of external Gd-211 in the liquid. The quantitative analysis of the microstructural features, i.e ., the residual Gd-211, platelet width, domain sizes of the resulting melt textured materials were presented. Addition of Ag resulted in mild refining of 211 particles. (C) 1999 Kluwer Academic Publishers.