Influence of epitaxial growth on superconducting properties of LFZ Bi-Sr-Ca-Cu-O fibres .1. Crystal nucleation and growth

Laser floating zone (LFZ) of superconducting fibres is a controlled growth technique where axially aligned structures are developed. The process is applied to the Bi-Sr-Ca-Cu-O ceramic system where Sr0.3Ca0.7CuO2 (1/1) crystallizes as primary phase with a dendritic morphology, followed by the crystallization of the superconducting phases Bi2Sr2CaCu2O8 (2212) and Bi4Sr4CaCu3O14 (4413) in the interdendritic spacing. The most favourable orientation for 1/1 dendrites shows the b-axis parallel to the pulling direction. The epitaxial orientation between the superconducting (S) phases that nucleate on the surfaces of the primary cuprate (1/1) is determined as (100)(S)[010](S) parallel to(001)(1/1)[010](1/1). The superconducting phases 2212 and 4413 have the b-axis aligned to the pulling direction and the a-and c-axis rotated pi/2 with respect to the homologous axes of the 1/1 crystals. (C) 1997 Elsevier Science B.V.