Structural studies of Nd1.85Ce0.15CuO4 + Ag superconducting system

摘要

We have studied for the first time the effect of Ag addition (0-15 wt%) to the superconducting system, Nd1.85Ce0.15CuO4, on its crystal structure and local structural features, using synchrotron X-ray diffraction (SXRD) and Raman spectroscopy, respectively. SXRD and subsequent Rietveld refinement studies on powders of Nd1.85Ce0.15CuO4 + Ag system indicate a small but significant change in lattice parameter upon Ag addition, showing evidence for possible incorporation of Ag to the extent of similar to 1 wt%. Raman spectroscopic studies indicate that the parent structure of Nd1.85Ce0.15CuO4 remains unaffected with no major local structural changes on doping with silver. However, all Raman modes show minor phonon hardening upon Ag addition, which is consistent with the unit cell volume reduction as is observed in XRD. A systematic bleaching out of the apical oxygen defect mode was also observed with increased Ag addition. Polarized Raman measurements helped to identify the asymmetric nature of the B-1g Raman mode. X-ray diffraction studies on pellets of Nd1.85Ce0.15CuO4 + Ag system further indicate a randomization of preferred orientation upon Ag addition. The superconductivity of the Nd1.85Ce0.15CuO4 + Ag system has been well characterized for all the compositions studied.