Journal of Materials Science, Vol.35, No.21, 5407-5413, 2000
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 pellets of YBa2Cu3O7-delta/Y2BaCuO5 (Y123/Y211) was investigated and compared with cerium doping. The thermal cycle of the texturing process has been adapted to this new composition, considering the variations of the decomposition temperature and of the melt viscosity. Growth rates of YBCO crystals appear 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 compared 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 improved 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 top seeded doped YBCO.