Raman-IR Spectroscopic Structural Analysis of Rare-Earth (RE3+) Doped Fluorotellurite Glasses at Different Laser Wavelengths

A structural analysis of Rare-Earth (RE3+) doped fluoro-tellurite glasses (85TeO(2)-10PbF(2)-2.5AlF(3)-2.5REF3 - in mol%) has been carried out by Raman spectroscopy, at 633, 785 and 1064 nm laser power excitation (RE3+= Pr3+, Nd3+, Sm3+, Eu3+, Gd3+, Tb3+, Dy3+, Ho3+, Er3+, Tm3+ and YB3+). ATR-FTIR, MGM, SEM-EDX, and XRD have been used as secondary techniques complementing the vibrational results. In an endeavor to have a better understanding of the structural transformations and the behavior of the TeO2 glass framework and de-polymerization, detailed analyses and discussions of the forming compounds TeO2, PbF2, and AlF3 (TPA) are presented with relevant reference to the literature. A Gaussian fitting of the bands is performed in all the TPA measurements, where the band position, FWHM, and intensity were analyzed in order to compare with the forming compounds and establish how the addition of the RE3+, lead, and aluminum fluoride influences the structural evolution of the TPA glasses. The SEM-EDS allowed the elemental composition to be obtained, the results of which present a low error with respect to the theoretical values of the stoichiometry. Further, the XRD results confirm the amorphous nature of the glass. MGM measurements show random magnetic domains, thus supporting the XRD results. The Raman analyses, carried out with different laser wavelengths, allowed the determination of the Raman bands of the glass, thus avoiding the luminescence activity of the RE3+ and over-estimation resulting from luminescence. We have been able to carefully assign the Te-O-Te intra-chain bridges such as the TeO4, TeO3 and TeO3+1 structures embedded in the glass systems, as well as the Boson bands.