Textured BI-Sr-Ca-Cu-O rods processed by laser floating zone from solid state or melted precursors

Two different methods were used to prepare the precursor materials to grow superconducting textured rods using the laser floating zone (LFZ) technique: melt and solid state processing. Samples with nominal compositions of Bi2Sr2Ca-Cu2O8 (2212), Bi2Sr2Ca2Cu3O10 (2223) and Bi2Sr2Ca3Cu4O12 (2234) were prepared and textured. As grown and annealed textured rods were characterised with respect to microstructure and superconducting properties. Elemental composition and phase distribution gradients occur along the rod radius, leading to the preferential crystallization of Bi-free cuprates at the periphery and to a Bi-enriched core. The excess of Ca and Cu with respect to the stoichiometric 2212 superconducting matrix in the 2223 and 2234 samples induces strong changes in the sample microstructure. During the annealing, some 2223 crystals develop from boundary between the Bi-free cuprates and the superconducting matrix. No significant dependence of the superconducting properties on the rod-processing route is observed, the main differences are associated with radial inhomogeneities in the samples. (C) 2004 Elsevier B.V. All rights reserved.