Influence of nickel substrate grain structure on YBa2Cu3O7−x supercurrent connectivity in deformation-textured coated conductors

Abstract

Coupled magneto-optical imaging and local misorientation angle mapping have been used to demonstrate the percolative nature of supercurrent flow in YBa2Cu3O7−x(YBCO) coated conductors grown on deformation-textured Ni substrates. Barriers to current flow occur at many YBCO grain boundaries (GBs) which have propagated through the buffer layers from the underlying Ni substrate, and all Ni GBs with misorientation angles >4° initiate percolative current flow. This type of current barrier is characteristic of the conductor form and has been found to exist in samples with Jc(0 T,77 K) values >2 MA/cm2. Sharpening of the local substrate texture or improving in low-angle GB properties should lead to higher Jc values.