Effect of different nanoscale RE2BaCuO5 additions on the formation of compositional fluctuation in Sm–Ba–Cu–O superconducting bulk materials

Abstract

This study presents the effect of different nanoscale RE211 additions—Y2BaCuO5 (nmY211), Sm2BaCuO5 (nmSm211), and Nd4Ba2Cu2O10 (nmNd422)—on the nano-scale compositional fluctuation and associated pinning mechanism of the melt-textured growth (MTG) Sm–Ba–Cu–O [SmBCO, of which the composition is Sm123 (Sm1Ba2Cu3Oy) + 25 wt% Sm211 (Sm2BaCuO5)] superconducting bulk materials. The superconductivity and microstructure results indicated that in samples with the addition of these nano-sized particles, nanoscale compositional fluctuations form during the peritectic transformation of melt-growth process, which cause Tc variation on a nanoscale and result in the formation of δTc pinning centers at high magnetic field. The compositional fluctuation regions (δTc pinning centers) are altered by the difference in peritectic temperature, the solubility in the liquid phase, and the ion radius. The direct current transport R-T properties elucidate the change of flux pinning behavior. In addition, the different influence on microstructure and superconductivity between the two methods: mixing rare-earth elements in nanoscale RE211 or in the homogeneous mixed precursor powders [e.g., (Nd, Eu, Gd)–Ba–Cu–O (NEG)] is also discussed.