Cation nonstoichiometry and its contribution to the nanostructured inhomogeneity of tetra and ortho modifications of YBa2Cu3O7 − δ oxide

Abstract

The cation composition and structure of YBa2Cu3O7 − δ (YBCO, the 123 phase) oxide samples synthesized at 990°C in air and annealed in oxygen at 450°C are studied via elemental analysis in a transmission electron microscope and high-resolution electron microscopy. The occurrence of cation nonstoichiometry and nanostructured inhomogeneity of the 123 phase in tetragonal and orthorhombic (superconducting) structures is confirmed. The nanostructured inhomogeneity of the 123 phase is attributed to the presence of nanocrystallites (2–5 nm) of oxides with different cation compositions belonging to the Y n Ba m Cu m + n O y series.