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

Coupled magneto-optical imaging and local misorientation angle mapping have been used to demonstrate the percolative nature of supercurrent flow in YB a2Cu3O7-x(YBCO) coated conductors grown on deformation-textured Ni substrat es. Barriers to current flow occur at many YBCO grain boundaries (GBs) whic h have propagated through the buffer layers from the underlying Ni substrat e, and all Ni GBs with misorientation angles >4 degrees initiate percolativ e current flow. This type of current barrier is characteristic of the condu ctor form and has been found to exist in samples with J(c)(0 T,77 K) values >2 MA/cm(2). Sharpening of the local substrate texture or improving in low -angle GB properties should lead to higher J(c) values. (C) 2000 American I nstitute of Physics. [S0003-6951(00)00341-7].