Characterization of Mn-doped electrospun LiNbO3 nanofibers by Raman spectroscopy

Mn-doped lithium niobate necklace-like nanofibers were synthesized by the electrospinning method. The morphology, microstructure and crystal structure of as-spun and annealed composite nanofibers were characterized by thermogravimetric analysis, scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and Raman spectroscopy. Ab initio simulations were performed within the density functional theory (DFT) framework as implemented in the Vienna ab initio simulation package (VASP), within the projector-augmented-wave (PAW) scheme. Lattice-dynamic calculations of the phonon modes were performed at the zone center (Γ point) of the BZ and the dynamical matrix was calculated using the direct method, implemented in the PHONON code. By comparing experimental Raman spectra of pure and Mn-doped LiNbO3, and the results of the calculations, we were able to probe Mn ion incorporation into the LiNbO3 lattice and show that Mn substitutes Li sites.