Properties of GdBCO bulk superconductors melt-processed in air using a Mg-dopedNd–Ba–Cu–O generic seed crystal

Abstract

A Mg-doped Nd–Ba–Cu–O (NdBCO) generic seed crystal has been developed recently forthe fabrication of any type of rare earth (RE) based (RE)-Ba–Cu–O single grain bulksuperconductor. The new generic seed significantly simplifies the top seeded melt growth(TSMG) process for light RE based (Nd, Sm, Gd or mixed rare earth elements) bulksuperconductors in particular. In this paper we report that single domain, bulk GdBCOsamples have been fabricated successfully in air using the new seed in a cold seedingprocess. In this study, precursor powders were enriched with different amounts ofBaO2 to investigate the extent of substitution of Gd for Ba in theGd1+xBa2−xCu3O7−δ (Gd-123) solid solution phase. The particle size of theGd2BaCuO5 (Gd-211) phase inclusions in the Gd-123 phase matrix and the spatial variation ofTc andΔTc alongthe a/b and c-axes of single grains fabricated with varying amounts of externally addedBaO2 have been investigatedas a function of BaO2 content. Jc valuesas high as 7.2 × 104 A cm−2 at 77 K and 0 T have been observed in large GdBCO grains processed under air.