Étude du système TeO2TeF4. Caractérisation structure et thermique

Highly Transparent Fluorotellurite Glass-Ceramics: Structural Investigations and Luminescence Properties

“…The thermal behavior of the as-quenched samples was studied by Differential Scanning Calorimetry (DSC) performed using TA instrument AQ100 equipment from 300 up to 723 K and using a heating rate of 10 K.min -1 . 19 29 Under such fast sample spinning, the coherence transfer is expected to be driven by isotropic 19 F-{ 125 Te} J-couplings and the best-efficiency was achieved using excitation and reconversion delays of 133 µs. 19 F { 91 Zr}-dephased MAS spectra were recorded using a 19 F spin-echo sequence with a 91 Zr Phase-Modulated Low-Alpha/Low-Amplitude (PM-LA) pulse applied in the middle of the echo period, such that 19 F dephasing occurs due to 19 F-91 Zr isotropic J-couplings and second-order dipolar-quadrupolar effects.…”

“…19 29 Under such fast sample spinning, the coherence transfer is expected to be driven by isotropic 19 F-{ 125 Te} J-couplings and the best-efficiency was achieved using excitation and reconversion delays of 133 µs. 19 F { 91 Zr}-dephased MAS spectra were recorded using a 19 F spin-echo sequence with a 91 Zr Phase-Modulated Low-Alpha/Low-Amplitude (PM-LA) pulse applied in the middle of the echo period, such that 19 F dephasing occurs due to 19 F-91 Zr isotropic J-couplings and second-order dipolar-quadrupolar effects. 30 Sample spinning rate of 50 kHz and dephasing time of 2.2 ms were used.…”

“…The good stability of the parent glass and the corresponding glass-ceramics excludes the presence of Te-F bonds, as already observed for oxyflurotellurite crystals. 19 The band at around 450 cm -1 can be assigned to symmetric stretching vibrations of Te-O-Te (Zr) or O-Te(Zr)-O(F) bridges. The bands at 680 cm -1 , 790 cm -1 and 860 cm -1 are attributed to the stretching mode of trigonal bipyramid TeO 4 units, to the stretching vibrations of trigonal pyramidal TeO 3 and TeO 3+1 units with non-bridging oxygens (NBO) and asymmetric vibrations of Te-O-Zr (Te) bondings respectively.…”

“…[24][25][26][27][28] The resulting 65TeO 2 -35ZrF 4 glass-ceramics are highly transparent due to the presence of nanocrystals even when stabilizing two different crystalline phases i.e the unreported antiglass and the cubic ZrTe 3 O 8 phases while maintaining very low hydroxyls groups content due to the presence of fluorine in the composition. These glass-ceramics have been investigated in details by means of X-ray diffraction, 19 F, 91 Zr and 125 Te NMR, Raman spectroscopy, scanning and transmission electron microscopies. Since there is limited number of reports on the tellurite based glass-ceramics containing oxyfluoride nanocrystals doped with rare-earth ions, the luminescence of Tm 3+ -doped glass-ceramics has also been studied in both the visible and near-infrared ranges.…”

New vanadium(IV) and titanium(IV) oxyfluorotellurates(IV): V2Te2O7F2and TiTeO3F2

“…For both syntheses, the single crystals grow in a more or less molten and out-of-equilibrium multicomponent M-Te-O-F medium likely to contain Te resulting from the redox reaction 4Ti 3+ + Te 4+ ! 4Ti 4+ + Te 0 , but also Te IV oxyfluorides with a very low melting point, as shown in a previous study of the Te IV -O-F phase diagram (Ider et al, 1995). Therefore, the phase composition is only attested by the initial mixture composition and the crystal structure determination.…”