Atomic and electronic structures of BaHfO3-doped TFA-MOD-derived YBa2Cu3O7-delta thin films

作者：Molina Luna Leopoldo^*; Duerrschnabel Michael; Turner Stuart; Erbe Manuela; Martinez Gerardo T; Van Aert Sandra; Holzapfel Bernhard; Van Tendeloo Gustaaf

来源：Superconductor Science and Technology, 2015, 28(11): 115009.

DOI：10.1088/0953-2048/28/11/115009

• nanocomposites
• strain
• superconductors
• diffusion
• scanning transmission electron microscopy
• electron energy-loss spectroscopy
• electronic structure

Tailoring the properties of oxide-based nanocomposites is of great importance for a wide range of materials relevant for energy technology. YBa2Cu3O7-delta (YBCO) superconducting thin films containing nanosized BaHfO3 (BHO) particles yield a significant improvement of the magnetic flux pinning properties and a reduced anisotropy of the critical current density. These films were prepared by chemical solution deposition (CSD) on (100) SrTiO3 (STO) substrates yielding critical current densities up to 3.6 MA cm(-2) at 77 K and self-field. Transport in-field J(c) measurements demonstrated a high pinning force maximum of around 6 GN/m(3) for a sample annealed at T - 760 degrees C that has a doping of 12 mol% of BHO. This sample was investigated by scanning transmission electron microscopy (STEM) in combination with electron energy-loss spectroscopy (EELS) yielding strain and spectral maps. Spherical BHO nanoparticles of 15 nm in size were found in the matrix, whereas the particles at the interface were flat. A 2 nm diffusion layer containing Ti was found at the YBCO (BHO)/STO interface. Local lattice deformation mapping at the atomic scale revealed crystal defects induced by the presence of both sorts of BHO nanoparticles, which can act as pinning centers for magnetic flux lines. Two types of local lattice defects were identified and imaged: (i) misfit edge dislocations and (ii) Ba-Cu-Cu-Ba stacking faults (Y-248 intergrowths). The local electronic structure and charge transfer were probed by high energy resolution monochromated electron energy-loss spectroscopy. This technique made it possible to distinguish superconducting from non-superconducting areas in nanocomposite samples with atomic resolution in real space, allowing the identification of local pinning sites on the order of the coherence length of YBCO (similar to 1.5 nm) and the determination of 0.25 nm dislocation cores.

• 出版日期2015-11