INFLUENCE OF EPITAXIAL-GROWTH ON SUPERCONDUCTING PROPERTIES OF LFZ BI-SR-CA-CU-O FIBERS .1. CRYSTAL NUCLEATION AND GROWTH

Laser floating zone (LFZ) of superconducting fibres is a controlled gr owth technique where axially aligned structures are developed. The pro cess is applied to the Bi-Sr-Ca-Cu-O ceramic system where Sr0.3Ca0.7Cu O2 (1/1) crystallizes as primary phase with a dendritic morphology, fo llowed by the crystallization of the superconducting phases Bi2Sr2CaCu 2O8 (2212) and Bi4Sr4CaCu3O14 (4413) in the interdendritic spacing. Th e most favourable orientation for 1/1 dendrites shows the b-axis paral lel to the pulling direction. The epitaxial orientation between the su perconducting (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 al igned 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.