Effects of Sm3+/Yb3+ co-doping and temperature on the Raman, IR spectra and structure of [TeO2-GeO2-K2O-Sm2O3/Yb2O3] glasses

Effects of Sm3+/Yb3+ co-doping on Raman scattering, IR absorption, temperature dependence of the Raman spectra up to 210 oC and the structure of two glass systems of the composition (80TeO2-10GeO2-8K2O-2Sm2O3/Yb2O3) is discussed. It was found that the addition of Yb3+ to the glass very strongly enhances the intensities of the antistokes' Raman bands at 155, 375, 557 and 828 cm-1 and quenches both the intensities of the stokes' vibration modes of the TeO4 units in the range of 120-770 cm-1 and the intensities of the OH- stretching vibration modes in the range of 2600-3300 cm-1. Sm2O3/Yb2O3 rare earth co-doping has a great influence on removing and/or changing the nature of the OH- groups. The appearance and splitting of the stretching vibration modes of the OH- groups at lower frequencies (2770, 2970 cm-1) for the Sm+3 singly doped glass sample, compared to the band at ∼3200 cm-1 for the Sm3+/Yb3+ co-doped glass sample, suggested that the OH- groups are more strongly bonded and incorporated with the glass matrix for the singly doped glass. Heating the sample up continuously weakens the hydrogen bonding of the OH- groups to the glass matrix leading to creation of NBO and breakdown of the connectivity of the OH- groups to the TeO4, TeO3+1 and TeO3 structural units. Raman bands at 286, 477, 666 and 769 cm-1 were assigned to its respective vibrations of Te2O7, TeO4-4 species, the (Te-O-Te)bending vibrations of the TeO4 triagonal bipyramids (tbps), the axial symmetric stretching vibration modes (Teax-O)s with bridging oxygen BO atoms and to the (Te-O)nbo non-bridging stretching vibration modes of the TeO3+1 and/or TeO3 pyramids