Verres thioarsénate et thiogermanate dopés à l'argent et/ou au mercure : Transport, structure et sensibilité ionique

The aim of the thesis is to study the physicochemical properties of the silver halide doped chalcogenide glasses for the possibility to use them as chemical sensors for quantitative analysis of Hg²⁺ ions. First, the macroscopic properties of AgY-As₂S₃ (Y = Br, I), HgS-GeS₂, AgI-HgS-As₂S₃ and AgI-HgS-GeS₂ glassy systems such as the densities and the characteristic temperatures (Tg and Tc) were measured and analyzed according to the glass compositions. Second, the transport properties were studied using complex impedance and dc conductivity. Measurements show that the silver halide doped chalcogenide glasses exhibit two drastically different ion transport regimes above the percolation threshold at xc ≈ 30 ppm : (i) critical percolation, and (ii) modifier-controlled regimes. Third, to unveil the composition/structure/property relationships, various structural studies were carried out. Raman spectroscopy, high-energy X-ray diffraction, neutron diffraction and small-angle neutron scattering experiments, together with RMC/DFT and AMID modelling were employed. Finally, the last part was a preliminary study of the characteristics of new chemical sensors. It was devoted to study the relationship between the membranes' composition and sensitivity but also detection limits.Le but de ce travail de thèse consiste à étudier les propriétés physico-chimiques des verres chalcogénures afin de pouvoir les utiliser comme membranes de capteurs chimiques destinés pour le dosage des ions Hg²⁺. Dans un premier temps, les propriétés macroscopiques des systèmes vitreux AgY-As₂S₃ (Y = Br, I), HgS-GeS₂, AgI-HgS-As₂S₃ et AgI-HgS-GeS₂, telles que les densités et les températures caractéristiques (Tg et Tc) ont été mesurées et analysées selon les compositions des verres. Puis, dans un second temps, les propriétés de transport ont été étudiés à l'aide de la spectroscopie d'impédance complexe d'une part, ou d'autre part, par des mesures de la résistivité. Ces dernières montrent que les verres de chalcogénures dopés à l'halogénure d'argent présentent deux différents régimes de transports au-dessus du seuil de percolation xc ≈ 30 ppm : (i) domaine de percolation critique, et (ii) domaine contrôlé par modificateur. Vient ensuite la troisième partie, elle consiste à déchiffrer les relations composition/structure/propriété grâce à plusieurs études structurales. Des mesures par spectroscopie Raman, par diffraction de neutrons et de rayons X haute énergie, par diffusion des neutrons sous petits angles (SANS), ainsi que des modélisations RMC/DFT et AMID ont été réalisées. Enfin, la dernière partie de ce travail était une étude préliminaire des caractéristiques des nouveaux capteurs chimiques. Il a été consacré à l'étude des relations entre la composition et la sensibilité des membranes ainsi qu'aux limites de détection qui les définissent

The key role of yttrium oxide on devitrification resilience of barium gallo-germanate glasses: Physicochemical properties and crystallization study

Two barium gallo-germanate glass series were elaborated to investigate the effect of the yttrium introduction on the glass physicochemical properties and crystallization behavior. One to twenty mol% of YO3/2 were either added into the glass matrix or substituted for gallium oxide. The glass structure was studied by Raman spectroscopy and the thermal, optical, thermo-mechanical and physical properties are examined. The introduction of yttrium ions in both glass series increases the glass transition temperature, crystallization temperature, softening temperature, coefficient of linear thermal expansion and density. Through differential scanning calorimetry and X-ray diffraction analyses, it was found that competition occurs between the gallo-germanate zeolite-type phase and the yttrium-containing phase. From 13 mol% of YO3/2, the yttrium introduction impedes the formation of surface crystallization in these glasses.Fabrication 3D de composants optiques intégrés à bas cout par laser femtoseconde pour des applications IRCentre for functional and surface-functionalized glasse

Chemically-invariant percolation in silver thioarsenate glasses and two ion-transport regimes over 5 orders of magnitude in Ag content

International audienceIonic conductivity σi measurements of AgY−As2S3 (Y = Br, I) glasses, covering 13 orders of magnitude in σi(x) over 5 orders of magnitude in silver content x, confirm two drastically different ion transport regimes in silver halide thioarsenate glasses. As expected, the ionic conductivity in the critical percolation domain, 20 ppm 7-10 at.% Ag, and the difference in σi(x) between AgI- and Ag2S-As2S3 glasses approaches 4 orders of magnitude. Random distribution of silver in the critical percolation domain, shown by DFT modeling of neutron and high-energy x-ray diffraction data, is a key of the observed conductivity invariance. When silver cation leaves the residence site and travels throughout the glass network, characterized by the average Ag-Ag separation distance of 12 Å or more, the memory of its original chemical form (sulfide or halide) vanishes rapidly with increasing the mean square displacement. A non-random silver distribution in the modifier controlled region implying formation of preferential conduction pathways via direct contacts of edge- and corner-sharing silver chalcogenide or chalcohalide polyhedra rules out this possibility. Chemically-invariant ionic conductivity seems to be a common feature of any disordered system with random distribution of mobile ions having similar size of charge carriers

Direct Ultrafast Laser Writing and characterization of photo-induced structures in gallo-germanate glasses

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Optical and structural characterization of femtosecond laser written micro-structures in germanate glass

Abstract We report on direct femtosecond laser writing in zinc barium gallo-germanate glasses. A combination of spectroscopic techniques allows to progress in the understanding of the mechanisms taking place depending on the energy. In the first regime (type I, isotropic local index change) up to 0.5 µJ, the main occurrence is the generation of charge traps inspected by luminescence, together with separation of charges detected by polarized second harmonic generation measurements. At higher pulse energies notably at the threshold corresponding to 0.8 µJ or in the second regime (type II modifications corresponding to nanograting formation energy domain), the main occurrence is a chemical change and re-organization of the network evidenced by the appearance of molecular O2 seen in the Raman spectra. In addition, the polarization dependence of the second harmonic generation in type II indicates that the organization of nanogratings may be perturbed by the laser-imprinted electric field

Formation of nanogratings driven by ultrafast laser irradiation in mid -IR heavy oxide glasses

This work demonstrates for the first time the formation of nanogratings inside Barium Gallo-Germanate glasses using femtosecond laser direct writing. These heavy oxide glasses, with a characterized transparency window up to 6 µm, along with the polarization sensitive birefringent nanostructures induced by femtosecond laser, offer an excellent platform for the development of mid-Infrared photonic applications. The fabricated glasses, containing both rare earth (Gd, Y) and transition metals (Zn, Ta), are directly compared to amorphous GeO 2 and commercial alumino-germanate (Corning-9754) glasses commonly used in this field. The nanogratings processing window in each glass was investigated by varying laser parameters (pulse duration, energy, repetition rate), and electron microscopy imaging directly evidenced the porous nanostructures. Among the results, a strong form birefringence in 8% ZnO-BGG glass, e.g., up to-0.029±0.001 was reported. Finally, birefringent embedded Fresnel GRIN plates were directly written in a BGG glass, to demonstrate the functionalization potential of these materials

Effect of potassium or yttrium introduction in Yb3+-doped germano-gallate glasses on the structural, luminescence properties and fiber processing

International audienceHere we report on the effect of potassium or yttrium on the luminescence spectroscopic properties of Yb 3+-doped germano-gallate glasses as well as the ability to shape them into optical fibers with the objective of using such glasses to produce near-infrared optical gain medium. Two ytterbium-doped germano-gallate glass systems, (100-x) (28Ga 2 O 3-37GeO 2-23BaO-12K 2 O)-xYb 2 O 3 (x = 0, 0.5 and 3 mol.%) and 29.6Ga 2 O 3-39.1GeO 2-24.3BaO-7 (yY 2 O 3-zYb 2 O 3) (y = 6.5, 4, 0 and z = 0.5, 3, 7 mol% respectively) have been prepared and the systematic investigation of their thermal, structural, optical and spectroscopic properties have been carried out. The increase in ytterbium oxide content leads to an increase of the glass transition temperature, crystallization temperature and the density of the glasses, as well as induces a red-shift of the cutoff wavelength. Raman spectroscopy analysis shows that both ytterbium oxide addition and potassium substitution by yttrium modify the 3D interconnected germano-gallate glass network. Lifetime diminishes with the increase of Yb 3+ concentration but remains higher in the yttrium-containing glasses. We demonstrate that the production of crystal-free light guiding fibers via the preform-to-fiber approach becomes possible only in the yttrium-containing glass system. Cutback optical attenuation measurements of the produced fibers show minimum losses of 3.3 dB/m at 1310 nm

Photosensitivity of barium germano-gallate glasses under femtosecond laser direct writing for Mid-IR applications

Barium germano-gallate glasses are attractive glass hosts for photonic applications in the mid-infrared region up to 6 µm. In this work, we investigate the photosensitivity of such glasses under femtosecond laser, with an emphasize on the formation of refractive index changes. Six glasses with varying compositions (including addition of K, Na, Y, and La) were studied. We observed several transformation regimes in the pulse energyrepetition rate landscape: Type I (isotropic refractive index change) and a spatial broadening regime with a phase shift Δφ > 2π rad at 550 nm. This translates into refractive index changes Δn > 10-2 and is comparable to values obtained in most chalcogenide glasses. The effect of glass composition on Δφ appears correlated to the number of non-bridging oxygen presented in the glass and is brought to evidence by monitoring the Cations/GaO3/2 ratio. This provides a way to design a range of germano-gallate glasses suitable to imprinting high refractive index contrast.Fabrication 3D de composants optiques intégrés à bas cout par laser femtoseconde pour des applications I

Unexpected role of metal halides in a chalcogenide glass network

International audienceChalcogenide glasses containing light alkali and Group 11 (Cu, Ag) halides MY (Y = Cl, Br, I) exhibit high ionic conductivity while their heavy alkali counterparts show promising properties for optical applications. The structural role of metal halides in chalcogenide glass networks remains either essentially unknown (alkali halides) or controversial (CuY, AgY). In addition, possible structural changes as a function of MY content have not been reported. Using pulsed neutron diffraction, high-energy X-ray scattering, Raman spectroscopy and FPMD modeling, we show unexpected role of silver halides as unconventional modifiers taking two contrasting glass compositions: (AgI)0.1(As2S3)0.9 (critical percolation domain) and (AgBr)0.5(As2S3)0.5 (modifier-controlled region) as an example. The latter alloy seems to be a promising precursor for thermoelectric applications. The deep insight into the glass structure on the short- and intermediate-range scale, including an enhanced chemical disorder, enables a rational design of these functional materials