Reel-to-reel x-ray diffraction and Raman microscopy analysis of differentially heat-treated Y–BaF₂–Cu precursor films on metre-length RABiTS

Abstract

Reel-to-reel x-ray diffraction (XRD) and Raman micro-spectroscopy are being evaluated as potential diagnostic tools for on-line feedback in the manufacturing of long-length coated conductors. To facilitate this evaluation, a procedure based on differentially heat-treated Y–BaF2–Cu precursors exposed to time-synchronized phase composition gradients has been developed. Two time-gradient-processed Y Ba2Cu3O7−x (YBCO) tapes of different thicknesses were fabricated using this procedure. The two techniques (used in combination) provided detailed phase and microstructure information as a function of temperature and heat treatment time and identified the same optimum processing time domain windows. More importantly, these deduced optimum times were found to be in close agreement with transport Jc measurements on replicate tapes. In addition, Raman data provided unambiguous identification of key intermediate phases such as BaF2, CuO, Y2Cu2O5, and barium cuprates. Using these results, a hypothetical Y–BaF2–Cu to YBCO reaction mechanism is proposed.