Anisotropic strain of BaZrO₃, BaCeO₃and Y₂O₃nanoinclusions in a YBa₂Cu₃O_{7 −<i>x</i>}epitaxial film matrix and its relation to the oxygen content of the superconductor

Abstract

Accurate x-ray diffraction studies of epitaxial (001) YBa2Cu3O7 − x films with inclusions of BaZrO3, BaCeO3 and Y2O3 phases have been performed. They revealed that all these inclusions are compressed along their c-axis and expanded in the ab-plane. The tetragonal distortion observed increases in the row Y2O3–BaCeO3–BaZrO3. It is suggested that an unusually large decrease of YBCO c-axis lattice parameter during the post-deposition oxygenation step is the cause of the anisotropic strain. The experimental observations on reduced and reoxygenated samples support this suggestion. The reversible character of nano-inclusions' strain appearing due to change of YBa2Cu3O7 − x oxygen content is demonstrated.