The effect of lattice strain on the diameter of BaZrO3 nanorods in epitaxial YBa2Cu3O7−δ films

An elastic strain model has been applied in an effort to understand the effect of the lattice strain on the diameter of the BaZrO3 (BZO) nanorods self-assembled into aligned arrays along the c-axis in BZO-doped epitaxial YBa2Cu3O7−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 Jc results measured for these samples.