Band limits and the vibrational spectra of tetrahedral glasses

Galeener, F. L.

doi:10.1103/physrevb.19.4292

Cited by 727 publications

(375 citation statements)

References 13 publications

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“…SiO 2 glass with 99.99% purity in the form of a wire having a diameter of 80 µm was prepared by FHP Engineering Limited and used as the sample. The X-ray diffraction pattern and Raman spectrum of this sample agreed with those reported in previous studies 3,10,12,21,22,24,25,36,37 at ambient conditions. It was cut and polished to a thickness of about 50 µm and then put in a rhenium gasket for diamond-anvil experiments.…”

Section: Methodssupporting

confidence: 90%

“…200-500 cm − 1 , denoted as W 1 , is considered to be mainly associated with vibrational motions of six-membered rings 10,24 . On the other hand, two sharp bands at around 500 and 650 cm − 1 , denoted as D 1 and D 2 , are the defect bands and assigned to the breathing modes of four-and three-membered rings, respectively 25 .…”

Section: Resultsmentioning

confidence: 99%

“…The peaks with an asterisk may be due to the fluorescence of diamond anvils. The W 1 band at 200-500 cm − 1 is considered to be associated with Si-O-Si bending motion 24 . Because SiO 2 glass mainly consists of six-membered rings at ambient pressure, the W 1 band is considered to mainly reflect the behaviour of six-membered rings.…”

Section: Resultsmentioning

confidence: 99%

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Helium penetrates into silica glass and reduces its compressibility

2011

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SiO 2 glass has a network structure with a significant amount of interstitial voids. Gas solubilities in silicates are expected to become small under high pressure due to compaction of voids. Here we show anomalous behaviour of SiO 2 glass in helium. Volume measurements clarify that SiO 2 glass is much less compressible than normal when compressed in helium, and the volume in helium at 10 GPa is close to the normal volume at 2 GPa. X-ray diffraction and Raman scattering measurements suggest that voids are prevented from contracting when compressed in helium because helium penetrates into them. The estimated helium solubility is very high and is between 1.0 and 2.3 mol per mole of SiO 2 glass at 10 GPa, which shows marked contrast with previous models. These results may have implications for discussions of the Earth's evolution as well as interpretations of various high-pressure experiments, and also lead to the creation of new materials.

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Section: Methodssupporting

confidence: 90%

Section: Resultsmentioning

confidence: 99%

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Helium penetrates into silica glass and reduces its compressibility

2011

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“…10 With the increasing intertetrahedral angle, one peak for the borate glass splits into three peaks, one at lower wave number, another at higher wave number, and one remaining at the same wave number. 28 For the SABS-35 glass, the peaks at 1354, 1382, and 1394 cm −1 can be assigned to the splitted 1380 cm −1 peak identified for the B-O − vibration. 17 The peaks at 1466, 1510, and 1514 cm −1 can be assigned to localized stretching vibration of B -O − bonds.…”

Section: B Glass Structural Unit Local Orderingmentioning

confidence: 99%

Network structure and thermal stability study of high temperature seal glass

Mahapatra

2008

Journal of Applied Physics

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Articles you may be interested inSynthesis and structural studies of multi-component strontium zinc silicate glass-ceramics AIP Conf. Proc. 1512, 568 (2013) High temperature seal glass has stringent requirement on glass thermal stability, which is dictated by glass network structures. In this study, a SrO-La 2 O 3 -Al 2 O 3 -B 2 O 3 -SiO 2 based glass system was studied using nuclear magnetic resonance, Raman spectroscopy, and x-ray diffraction for solid oxide cell application purpose. Glass structural unit neighboring environment and local ordering were evaluated. Glass network connectivity as well as silicon and boron glass former coordination were calculated for different B 2 O 3 : SiO 2 ratios. Thermal stability of the borosilicate glasses was studied after thermal treatment at 850°C. The study shows that high B 2 O 3 content induces BO 4 and SiO 4 structural unit ordering, increases glass localized inhomogeneity, decreases glass network connectivity, and causes devitrification. Glass modifiers interact with either silicon-or boron-containing structural units and form different devitrified phases at different B 2 O 3 : SiO 2 ratios. B 2 O 3 -free glass shows the best thermal stability among the studied compositions, remaining stable after thermal treatment for 200 h at 850°C.

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“…Spectral features at 440, 490, 606, 800, 1050, and 1160 cm −1 correspond to silica Raman modes 1 , D 1 , D 2 , 3 , 4 ͑LO͒, and 4 ͑TO͒, respectively. 18 The peak at 945 cm −1 , ascribable to Si-F stretching mode, 11 is an evidence of fluorine in ϵSi-F sites. The relative intensity is consistent with a F concentration of the order of 10 4 ppm, 11 in agreement with the value estimated from the refractive index compared with data from a͒ Electronic…”

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High-energy shift of the Urbach ultraviolet absorption from attenuated dynamical disorder in fluorine modified sol-gel silica

Палеари

Meinardi

Lauria

et al. 2007

Applied Physics Letters

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Fluorine modified amorphous silica has been synthetized via sol-gel route and studied through analysis of the temperature dependence of the Urbach absorption tail in the vacuum-ultraviolet region. The modified glass has a steep absorption edge above 8 eV, with the absorption coefficient ␣ ϰ exp͓E / E U ͑T͔͒ showing Urbach energy values E U ͑T͒ ranging between 50 and 66 meV. The comparison of E U ͑T͒ with pure silica data indicates a structural softening caused by the reduction of dynamical disorder, and suggests that the F-modified sol-gel synthesis is an appropriate route for achieving high energy shifts of the absorption edge. © 2007 American Institute of Physics. ͓DOI: 10.1063/1.2794429͔ Several technological areas are looking for new material compositions and synthetic routes for the production of optical materials with transmission window extending into the vacuum ultraviolet ͑vuv͒ region and with improved radiation hardness and thermal stability. 1,2 In specific applications such as photomasks for lithography at 157 nm and materials for vuv sources, silicalike structural features are unique in assuring low thermal expansion coefficient and good workability. 3 For these reasons, modifications of silica optical properties through specific synthesis or doping processes are currently being investigated to extend its operational window into the vuv. Fluorine modified silica-based materials are promising candidates for these applications, since the silica absorption edge shifts toward high energy after fluorine doping. [4][5][6][7][8] The structural origin of this effect was analyzed in F-modified glasses from chemical vapor deposition ͑CVD͒ methods, identifying different roles of fluorine, mainly in the modification of the mean bond energy and the structural disorder of the amorphous matrix. 5,[9][10][11] In this scenario, fabrication of F-modified silica from sol-gel synthesis 12 should, in principle, be an interesting target because of the relatively lowcost and sustainable features of the process, and for the expected improvement in radiation hardness with respect to other types of silica. 13,14 However, only few studies on F-doped sol-gel silica have been reported regarding preforms for low-index optical fibers, 15 and no vuv data have been published on fluorinated silica from sol-gel synthesis. In fact, sol-gel silica usually contains a large number of OH groups that are responsible for a broad absorption band at 8 eV, 16 which is strongly detrimental for vuv applications. In the present work, we disclose a method for the fabrication of optical grade bulk samples of F-doped dry silica by means of a modified sol-gel method. Our results show that the achievable reduction of dynamical disorder and -OH content opens the way to the utilization of sol-gel materials in vuv applications.Bulk samples, about 0.5 mm thick, of fluorine-modified silica were prepared by the sol-gel technique, cogelling tetraethoxysilane and trimethoxyfluorosilane, with concentration ratio 1:9. After gelation and drying, the xerogel samp...

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Band limits and the vibrational spectra of tetrahedral glasses

Cited by 727 publications

References 13 publications

Helium penetrates into silica glass and reduces its compressibility

Helium penetrates into silica glass and reduces its compressibility

Network structure and thermal stability study of high temperature seal glass

High-energy shift of the Urbach ultraviolet absorption from attenuated dynamical disorder in fluorine modified sol-gel silica

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