Analytical and structural transmission electron microscopy study of normal- superconductor interfaces in melt-textured Nd1+xBa2-xCu3Oy

The microstructure and cation stoichiometry associated with normal - superc onductor Nd4-2xBa2+2xCu2-xO10-2x - Nd(1+x)Ba(2-x)Cu(3)Oy intel faces in mel t-textured Nd1+xBa2-xCu3Oy submitted to various oxygen pressures, has been investigated by transmission electron microscopy using high resolution latt ice imaging and energy dispersive xray analysis. The interfaces processed a t 1 bar and 90 bar oxygen pressure display a variety of misfit accommodatio n mechanisms and appear, as a general trend, structurally sharp. Plots of t he Ba:Nd ratio across the interfaces show a fairly constant ratio (typicall y similar to1.85) in the matrix up to close to the interface, whereas in th e precipitate there appeared to be a gradual increase in the Ba:Nd ratio to ward the interface over about 0.1-0.5 I-lm The reported dependence of the i nterface pinning efficiency on the oxygenation might be due to a local Nd e nrichment (a few percent) of the matrix near the interface (< 20 nm) with t he precipitate, and/or a strain relaxation of the matrix very close to the interface (< 20 nm).