Formation of Self-Assembled, Double-Perovskite, Ba_2YNbO_6 Nanocolumns and Their Contribution to Flux-Pinning and J_c in Nb-Doped YBa_2Cu_3O_(7-δ) Films

摘要

Ba_2RENbO_6 (RE = rare earth elements including Y) compounds are considered new additives for superior flux-pinning in YBa_2Cu_3O_(7-δ)(YBCO) films due to their excellent chemical inertness to and large lattice mismatches with YBCO. Simultaneous laser ablation of a YBCO target and a Nb metal foil attached to the surface of the target resulted in epitaxial growth of YBCO films having columnar defects comprised of self-aligned Ba_2YNbO_6 (BYNO) nanorods parallel to the c-axis of the film. Compared to pure YBCO, YBCO+BYNO films exhibited no T_c reduction as well as superior J_c performance with higher self- and in-field J_c by a factor of 1.5-7 and also exhibited a strong J_c peak for H ‖ c indicative of strong c-axis correlated flux-pinning.