Abstract
Grain boundaries (GBs) in high-temperature superconductors suppress the critical current density (Jc) dramatically [1-3]. The Jc drops exponentially when GB-misorientation exceeds 4� [3]. To reduce the number of high-angle GBs, fabrication of biaxially-textured, superconducting wires via epitaxial growth on cube-textured metals has been widely investigated [4-6]. Such wires have exhibited very high-Jc in applied magnetic fields despite having a majority of GBs with total misorientations greater than 4�. Here we show that GB networks in these wires have numerous GBs with out-of-plane misorientations > 4� and few boundaries having in-plane misorientations > 4�. The high performance can be explained if the Jc is determined primarily by in-plane misorientations. This supposition was confirmed by in-field transport measurements on artificially fabricated bicrystals of superconductors having only out-of-plane misorientations. Atomic resolution imaging of bicrystals with out-of-plane misorientations show that superconducting ab-planes are continuous across such GBs in contrast to GBs with in-plane misorientations.