Scanning Raman Spectroscopy for Reel-to-Reel Characterization of Second-Generation High Temperature Superconductors

We have implemented fast Raman spectroscopy as a characterization method to predict, evaluate and characterize a variety of features of interest for Second Generation High-Temperature Superconductors (2G-HTS), including defect and composition characterization, as well as correlation with critical current density (Jc) over a wide extent of magnetic fields (0-14T) and temperatures (4.2-77K). A major factor for the successful implementation of this technique is the optimization of the scanning parameters that includes a large number of variables to reach the best spatial and spectral resolution needed to obtain detailed sample information. We first demonstrate the capability of implementation of scanning Raman to scan pristine and defective areas about 80 mm2 on short samples utilizing a motorized XY motion stage. These scanning Raman results have been complemented with linear scans by two-dimensional x-ray diffraction (2D-XRD) in order to validate and cross-compare the results and the sensitivity of the technique. Next, the effectiveness of polarized Raman for evaluating the biaxial texture has been investigated in this work. Additionally, Raman features have been correlated not only to superconducting properties of the tapes acquired by vibrating-sample magnetization (VSM) but also with composition non-stoichiometry and nanorod dopant level of REBCO (rear earth = Gd, Y) thin films obtained by wavelength-dispersive x-ray spectroscopy (WDS) and induced coupled plasma (ICP) methods. Finally, the findings from these studies have been used to design a reel-to-reel system for in-line quality control of long-length coated conductors.