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An elastic strain model has been applied in an effort to understand the effect of the lattice strain on the diameter of the BaZrO 3 (BZO) nanorods self-assembled into aligned arrays along the c-axis in BZO-doped epitaxial YBa 2 Cu 3 O 7−δ (YBCO) thin films. The calculated elastic energy of the strained BZO/YBCO composite lattice suggests that the diameter of the nanorods is approximately independent of the doping concentration of BZO as long as the density of the nanorods is sufficiently large. An experimental confirmation was carried out using transmission electron microscopy on YBCO thin films with BZO doping varying from 2% to 6% volume concentration. The diameter of the BZO nanorods was indeed found to be approximately constant in the range of 5.2-5.9 nm. The increase of the doping concentration therefore simply leads to an increase of the nanorod density, which links directly to the matching field of the effective pinning and is consistent with the transport J c results measured for these samples.

In YBa2Cu3O7−δ (YBCO) thick films, the superconducting critical current density (Jc) decreases with increasing film thickness (t). The mechanisms responsible for this Jc–t behavior remain unclear. To probe the correlation between the film microstructure and Jc-thickness behavior, we have deposited YBCO thick films up to 3.0μm in thickness on flat and surface-miscut (100) SrTiO3 substrates with 5°, 10°, and 15° vicinal angles. The microstructures of the YBCO films were found to evolve differently on flat and miscut substrates, resulting in different Jc–t behaviors. Surprisingly the small miscut angles of 5°–10° were favorable to obtain higher Jc and smaller Jc reduction at larger film thickness.

The orientation phase diagram of self-assembled BaZrO 3 (BZO) nanostructures in c-oriented YBa 2 Cu 3 O 7 d -(YBCO) films on flat and vicinal SrTiO 3 substrates was studied experimentally with different dopant concentrations and vicinal angles and theoretically using a micromechanical model based on the theory of elasticity. The organized BZO nanostructure configuration was found to be tunable, between c-axis to ab-plane alignment, by the dopant concentration in the YBCO film matrix strained via lattice mismatched substrates. The correlation between the local strain caused by the BZO doping and the global strain on the matrix provides a unique approach for controllable growth of dopant nanostructure landscapes. In particular, a mixed phase of the c-axis-aligned nanorods and the ab-plane-aligned planar nanostructures can be obtained, leading to a three-dimensional pinning landscape with single impurity doping and much improved J c in almost all directions of applied magnetic field.

The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.