Interlayer structure in YBCO-coated conductors prepared by chemical solution deposition.

The functionality of YBa₂Cu₃O_7-δ (YBCO)-coated conductor technology depends on the reliability and microstructural properties of a given tape or wire architecture. Particularly, the interface to the metal tape is of interest since it determines the adhesion, mechanical stability of the film and thermal contact of the film to the substrate. A trifluoroacetate (TFA)--metal organic deposition (MOD) prepared YBCO film deposited on a chemical solution-derived buffer layer architecture based on CeO₂=La₂Zr₂O₇ and grown on a flexible Ni5 at.%W substrate with a f{100}(001) biaxial texture was investigated. The YBCO film had a thickness was 440 nm and a j_c of 1.02 MA cm._-2 was determined at 77 K and zero external field. We present a sub-nanoscale analysis of a fully processed solution-derived YBCO-coated conductor by aberration-corrected scanning transmission electron microscopy (STEM) combined with electron energy-loss spectroscopy (EELS). For the first time, structural and chemical analysis of the valence has been carried out on the sub-nm scale. Intermixing of Ni, La, Ce, O and Ba takes place at these interfaces and gives rise to nanometer-sized interlayers which are a by-product of the sequential annealing process. Two distinct interfacial regions were analyzed in detail: (i) the YBCO=CeO₂=La₂Zr₂O₇ region (10 nm interlayer) and (ii) the La₂Zr₂O₇=Ni_-5 at.%W substrate interface region (20 nm NiO). This is of particular significance for the functionality of these YBCO-coated conductor architectures grown by chemical solution deposition. [ABSTRACT FROM AUTHOR]