Vibrational modes and structure of (AgI)x (GeS1.5)100−x chalcohalide glasses (original) (raw)
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Novel chalcohalide glasses from the Ge–S–AgI system and some physicochemical features
Journal of Materials Science, 2007
Novel bulk glassy samples of the pseudoternary chalcohalide Ge–S–AgI system have been prepared. Glasses have been obtained by monotemperature synthesis in evacuated ampoules and standard melt-quenching technique. The glass-forming region in the system determined by X-ray diffraction is situated in the S-rich region on the Ge–S side (S/Ge = 1.2, 1.5, 2 and 3) with AgI content up to 20 mol.%. Some physicochemical properties of the amorphous materials and their compositional dependence have been investigated. In addition, the theoretical average coordination number (Z), the total constraints per atom (Nco), the radial (Na) and axial (Nb) strength of the bonds have been calculated and related to the experimental results.
IR-SPECTRAL INVESTIGATIONS OF CHALCOHALIDE GLASSES FROM THE Ge-S-AgI SYSTEM
Novel bulk chalcohalide glasses from the Ge-S-AgI system are already prepared by a conventional melt-quenching technique. The structure of the investigated amorphous materials is studied by FTIR spectroscopy. The basic structural units and formations that constitute the glassy structure as corner and/or edge-shared GeS 4/2 tetrahedra, S 3-Ge-Ge-S 3 , etc. are detected. The results are found to be in a good agreement with those previously reported about similar pseudoternary amorphous materials. It is important to note that some bands in the IR spectra related to free silver cations are detected, which contribute to ionic conductivity of the materials. The last is of special interest in order to be realized practical applications of studied Ge-S-AgI samples as a coating, for example, in thin solid state batteries or sensitive layer in various sensor systems for detecting of different gaseous and liquid analytes.
Optical properties and structural correlations of GeAsSe chalcogenide glasses
Journal of Materials Science: Materials in Electronics, 2007
Ge x As y Se 100-x-y (33 £ x £ 39 and 12 £ y £16) glasses were prepared, and their structure and optical properties were studied by Raman and UV-Vis-IR spectroscopic techniques. Ge-tetrahedrons [GeSe 4 ] dominated in the structural units, and 'defect' bonds, such as Ge-Ge, Ge-As and As-As bonds, also occurred in the glasses. A structural model for calculation of the optical band gap energy (E g) of Ge-As-Se glasses was proposed, and the calculated values are consistent with experimental results. Increasing germanium and decreasing selenium content can reduce both the mean bond energies and optical band gap energies, enhancing the photo-sensitivity of the glasses.
Structural investigation of chalcogenide and chalcohalide glasses using Raman spectroscopy
Journal of Non-Crystalline Solids, 1999
HV-and HH-polarized Raman spectra of the chalcogenide glasses Ge 30 As 10 Se 60Àx Te x (25 T x T 35) and the chalcohalide glasses Ge 30 As 10 Se 30 Te 30Ày I y (0 T y T 30), Ge 30 As 10 Se 35 Te 25Àz I z (0 T z T 20) were investigated. For the chalcogenide glasses, the main structural units include [AsSe 3Àx Te x ] mixed pyramidal units, [GeSe 4Àx Te x ] mixed tetrahedral units, and Ge±Te±Ge chains. The substitution of iodine for tellurium in the chalcohalide glasses results in the formation of Ge±I, As±I, and Se±I bonds which break up the three-dimensional network. The main structural units for the chalcohalide glasses are [AsSe x Te y I z ] mixed pyramidal units where x y z 3, [GeSe x Te y I z ] mixed tetrahedral units where x y z 4, and GeSe 3a2 I mixed tetrahedral units. The symmetry properties of these structural units has been determined through the dependence of the depolarization ratio on the frequency shift. Ó
Journal of Molecular Structure, 2011
Chalcogenide glass thin films (Ge 2 S 3 ) x (As 2 S 3 ) 1Àx , with x = 0.3, 0.5, 0.7, and 0.9, were prepared by flash thermal evaporation of glass powders on c-Si substrate. We have investigated their structural properties for different average coordination numbers Z = 2.52, 2.6, 2.68 and 2.78. Structural changes were monitored by Raman scattering with two different excitation lines, k = 1064 nm and k = 514.5 nm. Recorded spectra confirmed that structural changes of the samples are connected with the change of average coordination number. Shift between spectra recorded with two different excitation lines is observed. The shift was discussed in terms of structural ordering at the threshold Z and its connection with the band-tail states.
Journal of Optoelectronics and Advanced Materials, 2001
The influence of time exposure, when exposed to above band gap light (3,52 eV) and annealing, on Gal 0 Ge 25 S 65 glasses has been studied through their effects on the structure and optical properties. To evaluate the photostructural change infrared and Raman spectra for bulk Ga 1 0 Ge 25 S 65 glasses have been measured before and after exposure. The Raman spectra are interpreted in terms of models in which the Ge atoms are fourfold coordinated and the S atoms are two fold coordinated. The observed changes in the spectral region of (S-S) stretching vibration (470-490 cm-') is a direct evidence for the occurrence of important structural changes in local bonding configuration caused by optical irradiation. It is shown that the dominant photostrucural changes are chain formation tendency of the chalcogenide atoms under the laser irradiation rather than rings.
Optical and Vibrational Spectra of CsCl-Enriched GeS2-Ga2S3 Glasses
Nanoscale Research Letters, 2016
Optical and FTIR spectroscopy was employed to study the properties of 80GeS 2-20Ga 2 S 3-CsCl chalcohalide glasses with CsCl additives in a temperature range of 77-293 K. It is shown that CsCl content results in the shift of fundamental absorption edge in the visible region. Vibrational bands in FTIR spectra of (80GeS 2-20Ga 2 S 3) 100 − х (СsCl) x (x = 5, 10, and 15) are identified near 2500 cm −1 , 3700 cm −1 , , around 1580 cm −1 , and a feature at 1100 cm −1. Low energy shifts of vibrational frequencies in glasses with a higher amount of CsCl can be caused by possible thermal expansion of the lattice and nanovoid agglomeration formed by CsCl additives in the inner structure of the Ge-GaS glass.