Optimization of the texture formation and characterization of large size top-seeded-melt-grown YBCO pellets

The thermal texture cycle for the top seeding of Ce doped YBCO pellets has been studied and optimised. Several quenches have proved the importance of a presintering step to have a homogeneous distribution of the Y2BaCuO5 part icles in the melt. The temperature window, in which a heterogeneous nucleat ed grain can grow, without being hindered by homogeneous nucleated grains, has been determined. By adjusting the process rate to the crystal growth ra te in this window, large well textured single domains of YBa2Cu3O7-delta ha ve been obtained, with a high degree of reproducibility. Microstructure and texture homogeneity, as well as superconducting properties have been inves tigated as a function of the position in the bulk pellet. The results have shown the high quality of the textured sample, and its high homogeneity. (C ) 1999 Elsevier Science B.V. All rights reserved.