Flux-pinning characteristics as a function of density of columnar defects comprised of self-assembled nanodots and nanorods in epitaxial YBa2Cu3O7−δ films for coated conductor applications

Pure YBa2Cu3O7−δ (YBCO) and YBCO films with extended columnar defects comprised of self-assembled columns of nanodots and nanorods of BaZrO3 (BZO), CaZrO3 (CZO) and 8 mol.% Y2O3 stabilized ZrO2 (YSZ) were prepared by pulsed laser deposition on RABiTS templates of configuration CeO2/YSZ/Y2O3/Ni–W. Effects on increasing the size and density of columnar defects by varying the total volume fraction BZO, CZO or YSZ incorporations within the YBCO film are reported. BZO volume fraction was varied between 0% and 8%, CZO between 0% and 2% and YSZ 0–2%. The critical transition temperature (Tc) was found to linearly decrease with increase in vol.% of BZO, CZO and YSZ, with the steepest decline for CZO additions. Nevertheless, YBCO films with these columnar defects exhibit significantly reduced Jc dependence on applied field. At 77 K, best properties are obtained for 1–2 vol.% BZO incorporation in the form of columns of self-assembled nanodots and nanorods in fields of 0.1–1.5 T.