Remarkable peak effect in Jc(H, T) of Y–Ba–Cu–O bulk by using infiltration growth (IG) method

This study presented the superior superconductivity of Y–Ba–Cu–O (YBCO) bulk materials grown by using modified infiltration growth (IG) method with a small Sm–Ba–Cu–O crystal as seed. Compare to the bulks grown by melt-textured growth (MTG) method, IG bulk is denser and with finer second phase (Y2Ba1Cu1O5, Y211). In addition, remarkable peak effect was observed of the IG YBCO bulk material. Peak effect in Jc(H, T) is an distinctive property of RE–Ba–Cu–O (RE = rare earth element, e.g. Sm, Nd) superconductors. However, it is found that peak effect is unusual in Y–Ba–Cu–O material. In this study, magnetism measurements also show peak effect in Jc(H, T), especially at low temperatures. At 50 K, the peak position of Jc(H, T) was about 5 Tesla. Jc value of peak, Jc(peak, 50 K), is comparable to that of self-field, Jc(0, 50 K). On the other hand, it is noted that this effect is spatial-dependent, i.e. it only can be found in particular part of bulk. To interpret the mechanism of peak effect and the spatial-dependence, different microstructure analysis, which includes scanning electron microscopy (SEM), energy disperse spectroscopy (EDS) and X-ray absorption spectrum (XAS) were used. The results indicated that the composition is inhomogeneous throughout the bulk. Diffusion of Sm from seed to YBCO bulk was observed, which is believed to occur during high temperature, and thus changed the superconductivity. The inhomogeneity of microstructure was correlated to the spatial-dependent of peak effect. Finally, this study also demonstrates a possible way to introduce peak effect in YBCO materials and thus enhance the applications in high field regions.