Correlation between YBa2Cu3O7 nuclei density and the grain orientation of the CeO2 buffered Ni–W template of the second-generation superconducting wire

Abstract

The prime goal of the second-generation superconducting wire technology is to grow high-quality epitaxial layers of YBa2Cu3O7 (YBCO) superconductor using high-rate deposition on low-cost, kilometer-long substrates. We analyze the influence of Ni–W RABiTS™ substrate grain misalignment on nucleation of epitaxial YBCO during metal-organic ex situ processing. Electron backscatter diffraction orientation maps are correlated with YBCO nuclei density obtained from scanning-electron microscopy. A critical Ni–W grain tilt misorientation angle of 8.5° was identified above which the YBCO nuclei density was observed to be extremely low, approaching zero. A proposed model explains the reduction in nuclei density as being due to the absence of (001) substrate terraces wide enough to accommodate the critical size for YBCO nuclei. This study emphasizes the strong effect of the out-of-plane tilt of substrate grains on superconducting properties of YBCO layers produced by metal-organic deposition.