Tuning the microstructure and vortex pinning properties of YBCO-based superconducting nanocomposite films by controlling the target rotation speed

摘要

We report the controlled incorporation of perovskite, BaSnO3 (BSO), and double-perovskite, YBa2NbO6 (YBNO), nanocolumnar structures into a YBa2Cu3O7−δ (YBCO) film matrix by controlling the target rotation speed. A surface modified target approach has been employed to deposit YBCO+BSO and YBCO+YBNO nanocomposite films using a laser ablation technique. The effect of target rotation speed on the microstructure and subsequently on the superconducting properties has been studied in detail. The density of BSO and YBNO nanocolumnar structures is found to depend on the target rotation speed, which subsequently affects the vortex pinning properties of the superconducting films in the absence and presence of applied magnetic fields. Three rotation speeds, 3, 2 and 1 s/rot., have been attempted in this study. Compared to pure YBCO, the YBCO+BSO and YBCO+YBNO nanocomposite films exhibit superior in-field critical current density (JC) and also exhibit a strong JC peak for H ∥ c-axis, indicating strong c-axis pinning. The irreversibility line has also been found to improve significantly in the nanocomposite films. For both the target combinations (YBCO+BSO and YBCO+YBNO), the target rotation speed of 2 s/rot. has been found to give the optimum superconducting properties.