Pulsed laser deposition of YBCO with yttrium oxide buffer layers

Textured metallic substrate based HTS coated conductors with the YBCO/CeO₂/YSZ/CeO₂/Ni architecture have already been shown to exhibit high current densities. The CeO₂ seed layer can effectively minimize the formation of NiO during the initial deposition on Ni and the CeO₂ cap layer provides good lattice matching to the subsequent YBCO layer. However, there are reports of cracks developing in the CeO₂ seed layer after a thicker growth due to a lattice mismatch with Ni, which can lead to poor performance of the YBCO conductor. The present work explores an alternate approach by using yttrium oxide not only as the seed layer but also as the cap layer in place of CeO₂. In the literature, yttrium oxide films grown on nickel by electron beam evaporation processes were found to be dense and crack-free with good epitaxy. This is likely the first report of using Y₂O₃ as a seed as well as a cap layer within the YBCO coated conductor architecture on specimens being fabricated in a single chamber. Pulsed laser deposition was used to perform deposition of all layers. Preliminary experiments resulted in specimens with current densities of more than 1 MA/cm² at 77K in self field. Characterization of samples was accomplished using x-ray diffraction, both resistive and ac susceptibility derived T_c, and J_c transport measurements.