An investigation on the critical current density of the melt-textured YBCOwith Sm211 addition

Sm2BaCuO5 (Sm211) addition shows an improved critical current performance a nd the peak effect in the critical current density J(c) vs. applied field H curve at 77.3 K. The post-annealing at 950 degrees C reduces the critical current density and eliminates the peak effect. The followed oxygenation ca nnot recover them completely, but it seems that a weak peak appears again a fter oxygenating at 450 degrees C for 120 h. The peak behavior of J(c) may be connected with the formation and disappearance of the spatial inhomogene ous (Y,Sm)123 matrix, in which a local low-T-c (Y,Sm)(Ba,Sm)(2)Cu3Oy phase forms owing to the substitution of Sm for Ba sites, especially in Sm-rich r egions. (C) 1999 Elsevier Science B.V. All rights reserved.