Partial Melt Processing of High-Tc Bulk Bi-2212 Starting from different Precursor Powders

摘要

In the present work, Bi_2Sr_2CaCu_2O_x (Bi-2212) commercial and homemade precursor powders were investigated. Precursors with different nominal compositions were pressed and melt-processed into silver molds, being then heated at 890-920°C, under 1 atm O2. The bulk samples were then slowly cooled and further annealed at 850°C with a subsequent annealing step at 700°C. The properties of the fully processed samples depended strongly on the maximum processing temperature as well as on the precursor powder employed. Fully processed samples exhibited Ic = 84-146 A and Jc = 800-1400 A/cm~2, at 77 K. The Bi-2212 stoichiometric nominal composition provided the best results. The correlation between the final microstructure and the properties is not clear.