Chemical solution-based epitaxial oxide films on biaxially textured Ni-W substrates with improved out-of-plane texture for YBCO-coated conductors

Epitaxial films of rare-earth (RE) niobates (where the rare earth includes La, Ce, and Nd) and lanthanum tantalate with pyrochlore structures were grown directly on biaxially textured nickel-3 at.% tungsten (Ni-W) substrates using a chemical solution deposition (CSD) process. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) analysis revealed the surface morphology of the films to be smooth and homogeneous. Detailed X-ray diffraction analysis showed that the films of pyrochlore RE niobate and La-tantalate are highly textured with cube-on-cube epitaxy. The overall texture quality of the films was investigated by measuring the full-width half-maximum (FWHM) of the (004) and (222) rocking curves. We observed a sharper texture for both lanthanum niobate (La ₃NbO ₇) and lanthanum tantalate (La ₃TaO ₇) films compared to the underlying Ni-W substrate, though they have a larger lattice misfit with the Ni-W substrates. These results were comparable to the texture improvement observed in vacuum-deposited Y ₂O ₃ seed layers. Texture improvement in the seed layer is the key towards obtaining YBCO films with a higher critical current density. Hence, solution-deposited La ₃NbO ₇ and La ₃TaO ₇ films can be used as a seed layer towards developing all metalorganic-deposited (MOD) buffer/YBCO architectures.