Comparison of the effects of platinum and CeO$_2$ on the properties of single grain, Sm-Ba-Cu-O bulk superconductors

Abstract

SmBa$_2$Cu$3$O${7−δ}$ (Sm-123) is a light-rare-earth barium-cuprate (LRE-BCO) high-temperature superconductor (HTS) with significant potential for high field industrial applications. We report the fabrication of large, single grain bulk [Sm–Ba–Cu–O (SmBCO)] superconductors containing 1 wt% CeO$_2$ and 0.1 wt% Pt using a top-seeded melt growth process. The performance of the SmBCO bulk superconductors containing the different dopants was evaluated based on an analysis of their superconducting properties, including critical transition temperature, $T_c$ and critical current density, $J_c$ , and on sample microstructure. We find that both CeO$_2$ and Pt dopants refine the size of Sm$_2$BaCuO$_5$ (Sm-211) particles trapped in the Sm-123 superconducting phase matrix, which act as effective flux pinning centres, although the addition of CeO$_2$ results in broadly improved superconducting performance of the fully processed bulk single grain. However, 1 wt% CeO$_2$ is significantly cheaper than 0.1 wt% Pt, which has clear economic benefits for use in medium to large scale production processes for these technologically important materials. Finally, the use of CeO$_2$ results generally in the formation of finer Sm-211 particles and to the generation of fewer macro-cracks and Sm-211 free regions in the sample microstructure.