Phosphate structure and lithium environments in lithium phosphorus oxynitride amorphous thin films

Lithium ion-conducting glasses attract wide interest for electrochemical applications like efficient energy storage devices. This work presents a structural study on involved bonding units, based on X-ray photoelectron spectroscopy and infrared spectroscopy, of lithium phosphorus oxide and oxynitride amorphous thin films prepared by RF magnetron sputtering. A thorough consideration of the mid- and far-infrared spectral regions demonstrated structural changes at the phosphate units and the lithium ion environments triggered by nitrogen incorporation and post-deposition thermal treatment. It was found that films prepared by sputtering in pure nitrogen atmosphere have about 75 % of their nitrogen atoms in sites doubly coordinated with phosphorus (P–N=P), and the rest in triply coordinated sites. It was shown also that nitrogen incorporation favors the stability of lithium ions, while annealing enhances ionic conductivity of the oxynitride films

Aging process of photosensitive chalcogenide films deposited by electron beam deposition

International audienceChalcogenide films attract broad interest due to their use as optical components like narrow band-pass filters, omnidirectional reflectors cladding, all-optical signal processing devices or optochemical sensors. Ge15Sb20S65 and As30Se50Te20 chalcogenide amorphous films were deposited by electron beam deposition (EBD) using their corresponding bulk glasses as targets. The structure of both bulk and thin film has been studied by far-IR and Raman spectroscopy. This study investigated an ordinary aging behavior of the chalcogenide films by exposing them to natural light under atmospheric conditions for a period of six months. Both films were found to be photosensitive as manifested by the shift of their optical band-gap to shorter or longer wavelength depending on chemical composition. Aging was found to induce also morphological changes, most notably the likely growth of arsenic trioxide micro-crystals on the surface of As30Se50Te20 films. Such effects were discussed in terms of photo-oxidation and photo-hydrolysis phenomena, the extent of which was found to be relatively limited for Ge25Sb10S65 films. The larger stability of the latter films against crystal growth at the surface was associated with the ability of germanium to bond to diffusing oxygen atoms in germanium-oxysulfide tetrahedral arrangements

Structural characterizations of As-Se-Te glasses

International audienceThe atomic structure of chalcogenide glasses As3Se7−xTex (0 ≤ x ≤ 3) and As2Se3−xTex (0 ≤ x ≤ 2.5) has been investigated by different methods. Short-range order has been studied by Wide-Angle X-ray Scattering (WAXS). 77Se NMR as well as Raman and infrared measurements were also performed on the different compositions. We show that the progressive introduction of tellurium in As3Se7−xTex or As2Se3−xTex induces breaking of Se-Se bonds and the formation of AsSe3−xTex pyramidal units. Experimental data also reveal the absence of Te-Te bonds even in the tellurium richest composition which let suppose a homogeneous repartition of tellurium atoms in the glassy network

Modification of silicophosphate glass composition, structure, and properties via crucible material and melting conditions

Abstract Ceramic crucibles are known to corrode in contact with glass melts. Here, we investigate the effect of alumina and fused silica crucibles on the composition, structure, and properties of silicophosphate glasses. Glasses in the system 0.3 Na2O‐0.6 P2O5‐0.1 SiO2 were melted in platinum, alumina, or fused silica crucibles at 900°C or 1200°C for 0.5‐12 hours. Al2O3 and SiO2 were found to leach from the crucibles into the glass melt and alter the glass composition: Al2O3 content increased with melting temperature and time, resulting in up to 10 mol% Al2O3; SiO2 from fused silica crucibles was also introduced into the glass, resulting in a 25% higher SiO2 content compared to the nominal composition. Glass density, transition temperature, thermal expansion, and mechanical properties were strongly affected by these compositional changes. Based on vibrational spectroscopy, this is explained by increasing numbers of P–O–Al or P–O–Si bonds, resulting in a depolymerization of the phosphate network, and ionic cross‐linking by high field strength aluminum or silicon ions. With increasing alumina content, P–O–Si bonds were replaced by P–O–Al bonds. 31P and 27Al MAS NMR spectra revealed that aluminum is present in sixfold coordination exclusively and fully bonded to phosphate species, connecting phosphate groups by P–O–Al–O–P bonds

Er3+-Al2O3 nanoparticles doping of borosilicate glass

Novel borosilicate glasses were developed by adding in the glass batch Er3+–Al2O3 nanoparticles synthetized by using a soft chemical method. A similar nanoparticle doping with modified chemical vapour deposition (MCVD) process was developed to increase the efficiency of the amplifying silica fibre in comparison to using MCVD and solution doping. It was shown that with the melt quench technique, a Er3+–Al2O3 nanoparticle doping neither leads to an increase in the Er3+ luminescence properties nor allows one to control the rare-earth chemical environment in a borosilicate glass. The site of Er3+ in the Er3+–Al2O3 nanoparticle containing glass seems to be similar as in glasses with the same composition prepared using standard raw materials. We suspect the Er3+ ions to diffuse from the nanoparticles into the glass matrix. There was no clear evidence of the presence of Al2O3 nanoparticles in the glasses after melting