Biaxially textured YBCO coated tape prepared using dynamic magnetic grain alignment

Abstract

A new magnetic grain alignment technique has been applied to produce biaxially aligned YBCO coated tapes. A biaxially aligned dispersion of orthorhombic Y2Ba4Cu7O15 (Y-247) powder was settled on untextured silver substrates. The Y-247 tapes were then melt processed to achieve high critical current YBa2Cu3O7 (Y-123) tapes with CuO as a secondary phase. The biaxial alignment is preserved after the densification process and a clear enhancement of Jc relative to identically prepared untextured or uniaxially textured samples is obtained. Critical current densities of up to 5000 A cm-2 at 77 K in self-field and 1500 A cm-2 in 0.5 T magnetic field at 65 K were obtained in films from 20 to 40 µm thick. Problems were experienced in achieving fully densified thick films while retaining biaxial texture. The initial grain size distribution was found to have a major influence on the final microstructure. Provided significant improvements in Jc can be obtained this method offers an alternative to coated tape processes based on epitaxial growth which has the advantage that it does not require textured substrates. The biaxial alignment technique described here intrinsically acts on the bulk material rather than at surfaces. This offers the possibility of texturing without thickness limitations.