Semiempirical equation of the levitation-force density for (Sm123)1–x(Yb211)x superconducting samples



After the preparation of Sm123 and Yb211 by melt-powder-melt growth and solid-state-reaction, respectively, the nominal compositions of (Sm123)1–x (Yb211)x for x = 0.00, 0.05, 0.10, 0.15, 0.20 and 0.25 were prepared to examine experimentally and theoretically the effect of x in the composition on the levitation-force density. Although the amount of Yb211 increased on increasing the content x, the levitation-force density increased because the Yb211 phase structure decomposed into Yb123 and liquid phase. Owing to the fact that Yb123 welded the Sm123 grains under a slow-cooling regime, the increasing of the interaction between Sm123 grains gave rise to high potential barriers of the flux pinning and resulted in increasing of the levitation-force density with the content x. The results of the obtained general functions of the levitation-force density for all samples are in good agreement with the experimental data. This new formulation of the levitation-force density is very useful for material optimization to other researchers. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)