Improvement of the microstructure of melt-processed Sm-based superconductors

We report on the effect of the atmosphere during the decomposition of the p recursors of Sm-Ba-Cu-O bulk superconductors. It was found that the formati on of voids was greatly suppressed by two methods, melting in an oxygen gas atmosphere or in vacuum. For both methods, the atmosphere during crystalli zation was switched to an Ar gas flowing one. The samples prepared by these methods exhibited high superconducting transition temperatures with sharp transition widths. However, the zero-field critical current density was low er than that of the reference sample, which was prepared by decomposing the precursor in an Ar gas flowing atmosphere. (C) 2001 Elsevier Science B.V. All rights reserved.