Effect of a cerium/tin doping mixture on the texturing process and on the superconducting properties of top seeded melt textured YBaCuO

The influence of a cerium/tin doping mixture on top seeded melt textured pe llets of YBa2Cu3O7-delta/Y2BaCuO5 (Y123/Y211) was investigated and compared with cerium doping. The thermal cycle of the texturing process has been ad apted to this new composition, considering the variations of the decomposit ion temperature and of the melt viscosity. Growth rates of YBCO crystals ap pear to be quadrupled by the presence of tin. We manage to grow domains of diameter 30 mm from a SmBa2Cu3O6+delta seed. SEM observations have shown no modification of the Y2BaCuO5 inclusions either in size or in morphology co mpared to Y211 particules in cerium doped YBCO. However, EDS analyses have revealed the existence of submicron particles containing Y, Ba, Cu, Sn, Ce and O distributed in the matrix. Superconducting properties are greatly imp roved by the addition of a moderate amount of tin to the cerium doped YBCO. The critical temperature is shifted toward 92 K with a transition width of 0.5 K. Critical current densities at 77 K reach values as high as 9 x 10(4 ) A/cm(2) in self field, 5 x 10(4) A/cm(2) under 1 Tesla and still 2.5 x 10 (4) A/cm(2) under 2 T, which are among the best results ever obtained for t op seeded doped YBCO. (C) 2000 Kluwer Academic Publishers.