Precursor powder influence on melt processing of high critical current BSCCO rods

摘要

The influence of the starting powder characteristics on the phase formation, microstructure and J_c (77 K) of Bi-2212 monoliths fabricated by the LFZ method has been analysed. Attractive transport critical current values (ca 90 A in ≈1.8 mm diameter rods) have been measured on samples obtained from practically any of the precursors studied, that is prereacted 2212, mixtures of 2201 and sub-micrometre sized CaCuO_2 or, alternatively, a mixture of the corresponding commercial oxides and carbonates. The latter method reduces significantly the processing procedure related to the use of chemically derived starting precursors or to the attainment of the 2212 phase in the precursor at a high purity level. The selection of particular precursor mixtures affects the final textured superconductor properties only to a limited extent. These appear to be related to the influence of the precursors on both, the melting and solidification processes, associated in turn with their modification of the reaction pathway towards 2212 formation.