Nanostructural inhomogeneity of YBa2Cu3O7−δ

• Results of high resolution electron microscope studies of YBa2Cu3O7−δ are reported.
• Nm-sized structural inhomogeneity has been revealed.
• We relate nanostructural inhomogeneity with local cation nonstoichiometry.
• Influence of nanoinhomogeneity on the properties of YBa2Cu3O7−δ is discussed.

Analytical and high resolution electron microscopic studies of YBa2Cu3O7−δ samples with the tetragonal and orthorhombic structure have revealed a deviation of cation composition from the stoichiometric ratio Y:Ba:Cu = 1:2:3 (1 2 3) and a structural inhomogeneity on a scale of a few nm. Nanostructural inhomogeneity has been related with local cation nonstoichiometry in the form of coherently intergrown nanodomains of oxides of the homologous series YnBamCum+nOy having cation composition different from the 123 ratio.