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Minoru Tomozawa - One of the best experts on this subject based on the ideXlab platform.
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Fictive Temperature and Fictive pressure measurement of silica glasses using FTIR method: For thick samples and samples containing Si–H
Journal of Non-Crystalline Solids, 2012Co-Authors: Minoru TomozawaAbstract:Abstract A simple IR method using the silica structural band at ~ 2260 cm − 1 was previously developed to determine the Fictive Temperature of silica and high silica glasses. The method has been used to determine the Fictive Temperature of silica glasses with an unknown thermal history as well as for the study of their relaxation kinetics. In the present study, a similar technique using the silica structural band at ~ 2660 cm − 1 was explored. It was found that the use of the 2660 cm − 1 band is advantageous over the use of the 2260 cm − 1 band in some applications. One advantage is for silica glasses containing Si–H bonding, as Si–H gives absorbance close to the silica structural band at ~ 2260 cm − 1 , but not at ~ 2660 cm − 1 . The other advantage is that thicker samples can be used since the absorbance per unit thickness is less at ~ 2660 cm − 1 . The use of a thicker sample can be advantageous because the influence of surface structural relaxation effects is reduced. It was also shown that the method of Fictive Temperature measurement can be extended to determine the Fictive pressure of silica glasses treated under various high pressures at a constant Temperature.
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Fictive Temperature of fracture surface of a silica glass
Journal of Non-crystalline Solids, 2010Co-Authors: Minoru Tomozawa, C.y. Li, T.m. GrossAbstract:Abstract Fictive Temperatures of the fracture surface of a silica glass with high OH content were measured using FT-IR reflection method. The fracture surface exhibited a clearly higher Fictive Temperature than the original Fictive Temperature of the glass. The thickness of the fracture surface layer with higher Fictive Temperature was approximately 0.05 µm ± 0.02 µm and the highest Fictive Temperature of the fracture surface was estimated to be 70–80 °C above the glass transition Temperature. The present results indicate that fracture of silica glass, considered to be one of the most brittle materials, is accompanied by inelastic deformation.
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A glass with high crack initiation load: Role of Fictive Temperature-independent mechanical properties
Journal of Non-Crystalline Solids, 2009Co-Authors: Timothy Michael Gross, Minoru Tomozawa, A. KoikeAbstract:Abstract The crack initiation load of a series of calcium aluminosilicate glasses and selected commercial glasses were evaluated using Vickers indentation. The results showed that a calcium aluminosilicate glass containing 80 mol% SiO 2 , 10 mol% Al 2 O 3 and 10 mol% CaO exhibited a high crack initiation load comparable to that of the less-brittle glass (LB glass) developed by Asahi Glass Co., Ltd. It has previously been determined that glasses experience a Fictive Temperature increase by indentation. The indented region of a glass, therefore, acquires, in general, different mechanical properties, such as hardness and elastic moduli, from the original, unindented glass. The extent of these mechanical property changes depends upon the glass composition and a certain glass composition with Fictive Temperature-independent mechanical properties can have the deformed region with matching mechanical properties to those of the undeformed region of the glass. It was found that the calcium aluminosilicate glass having no Fictive Temperature dependence on elastic moduli gave the highest crack initiation load. However, this composition did not coincide with Fictive Temperature-independence of hardness or density.
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Fictive Temperature-independent density and minimum indentation size effect in calcium aluminosilicate glass
Journal of Applied Physics, 2008Co-Authors: Timothy Michael Gross, Minoru TomozawaAbstract:Using the calcium aluminosilicate system a glass was developed that exhibits Fictive Temperature-independent density by creating an intermediate glass between normal and anomalous glasses. Normal glass, such as soda-lime silicate glass, exhibits decreasing density with increasing Fictive Temperature while anomalous glass, such as silica glass, exhibits increasing density with increasing Fictive Temperature. This intermediate glass composition was found to exhibit the minimum indentation size effect during indentation hardness testing. It appears that the indentation size effect is correlated with a deformation-induced Fictive Temperature increase, which is accompanied by a density change and hardness change in the vicinity of the indentation. It is suggested from these observations that indentation size effect originates from the energy required to create interfaces and defects such as shear bands, subsurface cracks, and point defects near the indenter-specimen boundary, which accompany the volume change.
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Indentation-induced microhardness changes in glasses: Possible Fictive Temperature increase caused by plastic deformation
Journal of Non-Crystalline Solids, 2008Co-Authors: Timothy Michael Gross, Minoru TomozawaAbstract:The microhardness around a large indentation was measured for different types of glasses. In soda-lime silicate glass, a typical normal glass, the region in the immediate vicinity of the indentation was found to exhibit a lower hardness than the region far removed from the indentation. In silica glass, a typical anomalous glass, the region in the immediate vicinity of a large indentation was found to exhibit a higher hardness than the region far removed from the indentation. Asahi less brittle glass, an intermediate glass between normal and anomalous glasses, was found to exhibit little change in hardness in the vicinity of the large indentation. These findings can be explained by a deformation-induced Fictive Temperature increase leading to a lower hardness for soda-lime silicate glass and a higher hardness for silica glass.
Matthieu Lancry - One of the best experts on this subject based on the ideXlab platform.
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EPR reversible signature of self-trapped holes in Fictive Temperature-treated silica glass
Journal of Applied Physics, 2018Co-Authors: Matthieu Lancry, Nadège Ollier, Christian Herrero, B. H. Babu, Bertrand PoumellecAbstract:Post-mortem electron paramagnetic resonance spectroscopy experiments have been carried out between room Temperature and 20 K to examine the radiation-induced defects in Fictive Temperature (Tf) treated Heraeus F300 silica (0.1 ppm OH, 1500 ppm Cl2). In particular, we focus our attention on Self-Trapped Hole (STH) centers detected in 1000 °C, 1100 °C, and 1200 °C Tf treated samples irradiated at room Temperature by gamma rays at 6 kGy. By repeating annealing cycles between 77 and 300 K on the same samples, we observed that the EPR signal attributed to STH decreases as the Temperature increases but in a reversible manner. We evidenced a deviation from the Curie law for T > 70 K and suggested an interpretation based on the decrease in the “strain-assisted TH” population by reversible excitation of the trapped hole to a delocalized state with an activation energy of 7.8 meV. This also means that the precursors of hole trapping sites (a local strain atomic configuration) remain stable until 300 K at least.
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Temperature reversible Self-Trapped Holes in Fictive Temperature-treated silica
Advanced Photonics 2018 (BGPP IPR NP NOMA Sensors Networks SPPCom SOF), 2018Co-Authors: Matthieu Lancry, Nadège Ollier, Christian Herrero, Bertrand PoumellecAbstract:Post-mortem EPR spectroscopy has been carried out to examine the radiation-induced Self-Trapped Hole (STH) in Fictive Temperature (Tf) treated Heraeus F300 silica. By repeating isochronal annealing cycles between 77 and 300 K, we observed that STH decreases with T but in a reversible manner. We evidenced a deviation from the Curie law for T > 70 K and suggest an interpretation based on the decrease of a “strain-assisted Trapped Holes” population by a reversible excitation of the trapped hole to a delocalized state with activation energy of 7.8 meV.
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Radiation hardening of sol gel-derived silica fiber preforms through Fictive Temperature reduction
Journal Optical Society of America Applied Optics, 2016Co-Authors: B. Hari Babu, Matthieu Lancry, Nadège Ollier, Mohamed Bouazaoui, Hicham El Hamzaoui, Poumellec BertrandAbstract:The impact of Fictive Temperature (T f ) on the evolution of point defects and optical attenuation in non-doped and Er3-doped sol-gel silica glasses was studied and compared to Suprasil F300 and Infrasil 301 glasses before and after γ-irradiation. To this aim, sol-gel optical fiber preforms have been fabricated by the densification of erbium salt-soaked nanoporous silica xerogels through the polymeric sol-gel technique. These γ-irradiated fiber preforms have been characterized by FTIR, UV-vis-NIR absorption spectroscopy, electron paramagnetic resonance, and photoluminescence measurements. We showed that a decrease in the glass Fictive Temperature leads to a decrease in the glass disorder and strained bonds. This mainly results in a lower defect generation rate and thus less radiation-induced attenuation in the UV–vis range. Furthermore, it was found that γ-radiation “hardness” is higher in Er3+-doped sol-gel silica compared to un-doped sol-gel silica and standard synthetic silica glasses. The present work demonstrates an effective strategy to improve the radiation resistance of optical fiber preforms and glasses through glass Fictive Temperature reduction
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Low Loss Multimode Optical Fibers via Fictive Temperature Reduction by Means of Outer-Cladding Na Doping
Journal of Lightwave Technology, 2016Co-Authors: Matthieu Lancry, Bertrand Poumellec, Cedric GonnetAbstract:The reduction of the intrinsic Rayleigh scattering of the optical fibers by slightly altering the outer-cladding composition via the introduction of alkali is the goal of this paper. In this view, multimode fibers with Al- and Na-doped outer-cladding were fabricated via the PCVD process. In optimal conditions (typ. 10-80 ppm Na), we obtained a reduction of 0.06 dB/km at 850 nm for 50/125 multimode fibers corresponding to an attenuation decrease from 2.21 dB/km down to 2.15 dB/km. This is attributed to Rayleigh scattering reduction due to a Fictive Temperature lowering. In addition, the minor amounts of Na incorporated in the outer-cladding results in much lower NBOHC defects related absorption at 650 nm.
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The dependence of Raman defect bands in silica glasses on densification revisited
Journal of Materials Science, 2016Co-Authors: Manon Heili, Bertrand Poumellec, Cedric Gonnet, Ekaterina Burov, Charles Losq, Daniel R. Neuville, Matthieu LancryAbstract:This paper focuses on the densification signature measured by Raman spectroscopy in silica-based glasses. We have studied a pure silica glass and a 25GeO_2–75SiO_2 binary glass fabricated by plasma chemical vapor deposition (PCVD), using the Fictive Temperature T _ f as a variable parameter ranging from 950 to 1400 °C. Macroscopic density measurements highlighted two opposite behaviors: the higher the Fictive Temperature, the lower the density of the GeO_2–SiO_2 glass, in contrast to what is observed in the pure silica glass. Yet, Raman spectra of both these glasses showed similar trends: the intensities of the two defect bands, D_1 and D_2, increase with increasing Fictive Temperature. Therefore, the D_1 and D_2 bands cannot be used as a reliable signature of densification in binary glasses.
Bertrand Poumellec - One of the best experts on this subject based on the ideXlab platform.
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EPR reversible signature of self-trapped holes in Fictive Temperature-treated silica glass
Journal of Applied Physics, 2018Co-Authors: Matthieu Lancry, Nadège Ollier, Christian Herrero, B. H. Babu, Bertrand PoumellecAbstract:Post-mortem electron paramagnetic resonance spectroscopy experiments have been carried out between room Temperature and 20 K to examine the radiation-induced defects in Fictive Temperature (Tf) treated Heraeus F300 silica (0.1 ppm OH, 1500 ppm Cl2). In particular, we focus our attention on Self-Trapped Hole (STH) centers detected in 1000 °C, 1100 °C, and 1200 °C Tf treated samples irradiated at room Temperature by gamma rays at 6 kGy. By repeating annealing cycles between 77 and 300 K on the same samples, we observed that the EPR signal attributed to STH decreases as the Temperature increases but in a reversible manner. We evidenced a deviation from the Curie law for T > 70 K and suggested an interpretation based on the decrease in the “strain-assisted TH” population by reversible excitation of the trapped hole to a delocalized state with an activation energy of 7.8 meV. This also means that the precursors of hole trapping sites (a local strain atomic configuration) remain stable until 300 K at least.
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Temperature reversible Self-Trapped Holes in Fictive Temperature-treated silica
Advanced Photonics 2018 (BGPP IPR NP NOMA Sensors Networks SPPCom SOF), 2018Co-Authors: Matthieu Lancry, Nadège Ollier, Christian Herrero, Bertrand PoumellecAbstract:Post-mortem EPR spectroscopy has been carried out to examine the radiation-induced Self-Trapped Hole (STH) in Fictive Temperature (Tf) treated Heraeus F300 silica. By repeating isochronal annealing cycles between 77 and 300 K, we observed that STH decreases with T but in a reversible manner. We evidenced a deviation from the Curie law for T > 70 K and suggest an interpretation based on the decrease of a “strain-assisted Trapped Holes” population by a reversible excitation of the trapped hole to a delocalized state with activation energy of 7.8 meV.
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Low Loss Multimode Optical Fibers via Fictive Temperature Reduction by Means of Outer-Cladding Na Doping
Journal of Lightwave Technology, 2016Co-Authors: Matthieu Lancry, Bertrand Poumellec, Cedric GonnetAbstract:The reduction of the intrinsic Rayleigh scattering of the optical fibers by slightly altering the outer-cladding composition via the introduction of alkali is the goal of this paper. In this view, multimode fibers with Al- and Na-doped outer-cladding were fabricated via the PCVD process. In optimal conditions (typ. 10-80 ppm Na), we obtained a reduction of 0.06 dB/km at 850 nm for 50/125 multimode fibers corresponding to an attenuation decrease from 2.21 dB/km down to 2.15 dB/km. This is attributed to Rayleigh scattering reduction due to a Fictive Temperature lowering. In addition, the minor amounts of Na incorporated in the outer-cladding results in much lower NBOHC defects related absorption at 650 nm.
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The dependence of Raman defect bands in silica glasses on densification revisited
Journal of Materials Science, 2016Co-Authors: Manon Heili, Bertrand Poumellec, Cedric Gonnet, Ekaterina Burov, Charles Losq, Daniel R. Neuville, Matthieu LancryAbstract:This paper focuses on the densification signature measured by Raman spectroscopy in silica-based glasses. We have studied a pure silica glass and a 25GeO_2–75SiO_2 binary glass fabricated by plasma chemical vapor deposition (PCVD), using the Fictive Temperature T _ f as a variable parameter ranging from 950 to 1400 °C. Macroscopic density measurements highlighted two opposite behaviors: the higher the Fictive Temperature, the lower the density of the GeO_2–SiO_2 glass, in contrast to what is observed in the pure silica glass. Yet, Raman spectra of both these glasses showed similar trends: the intensities of the two defect bands, D_1 and D_2, increase with increasing Fictive Temperature. Therefore, the D_1 and D_2 bands cannot be used as a reliable signature of densification in binary glasses.
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Improving optical fiber preform radiation resistance through Fictive Temperature reduction
Photonics and Fiber Technology 2016 (ACOFT BGPP NP), 2016Co-Authors: Matthieu Lancry, Babu Hari Babu, Nadège Ollier, Hicham El-hamzaoui, Mohamed Bouazaoui, Bertrand PoumellecAbstract:The impact of Fictive Temperature on point defects and optical attenuation were studied in Er-doped Solgel preforms and Suprasil F300, before and after γ-irradiation. We report that lower Fictive Temperature leads to mcuh higher radiation resistance.
M Tomozawa - One of the best experts on this subject based on the ideXlab platform.
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Radial distribution of the Fictive Temperature in pure silica optical fibers by micro-Raman spectroscopy
Journal of Applied Physics, 2008Co-Authors: C. Martinet, V. Martinez, C. Coussa, B. Champagnon, M TomozawaAbstract:Micro-Raman spectra are performed at different radial positions in order to determine the Fictive Temperature distribution in pure silica optical fibers. As-received and annealed optical fibers are compared and Raman results reveal a large decrease in the Fictive Temperature after annealing. The Fictive Temperature gradient between the core and the edge of the optical fiber can be eliminated after annealing and the spectroscopic decoupling between stress and the Fictive Temperature variation is discussed. The micro-Raman is a good probe in determining the spatial distribution of the Fictive Temperature in the micrometer length scale.
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sub critical crack growth rate of soda lime silicate glass and less brittle glass as a function of Fictive Temperature
Journal of Non-crystalline Solids, 2007Co-Authors: M Tomozawa, A. Koike, Setsuro ItoAbstract:Abstract Sub-critical crack growth rates of soda-lime-silicate glass and less brittle glass with different Fictive Temperatures were compared using the DCDC method under both dry and humid atmospheres in order to investigate the origin of the unique mechanical features of the less brittle glass developed by Ito and his collaborators. In both dry and humid atmospheres, the crack velocity of the soda-lime-silicate glass was slower than that of the less brittle glass. For both glasses, the glass sample with higher Fictive Temperature showed a slower crack growth rate under both dry and humid atmospheres. These observations can be explained by the tendency for the plastic flow at the crack tip; the soda-lime-silicate glass is expected to show easier plastic flow under tension than the less brittle glass, and also the samples with higher Fictive Temperatures are expected to show easier plastic flow, leading to greater fracture toughness, KIC, and slower crack growth rate.
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Fictive Temperature measurement of single mode optical fiber core and cladding
Journal of Lightwave Technology, 2001Co-Authors: M Tomozawa, S Dubois, G OrcelAbstract:The Fictive Temperatures of single-mode optical-fiber core, along with its inner and outer cladding, were measured using an infrared (IR) reflection method on the fiber cross-sectional surface. To allow for usage of a larger IR beam size than the diameter of the fiber core, the cross-sectional area of the fiber was increased by slicing the fiber at an oblique angle, along approximately 3/spl deg/ off the fiber axis direction. The magnitude of the Fictive Temperature was estimated from the IR peak wavenumber-Fictive Temperature relation obtained for bulk glasses with the same compositions. The observed Fictive Temperature was in the range of 1150/spl sim/1300/spl deg/C for the core, 1450/spl sim/1550/spl deg/C for the inner cladding, and 1620/spl sim/1660/spl deg/C for the outer cladding and exhibited good correlation with the fiber cooling rate.
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surface Fictive Temperature of annealed and rate cooled soda lime glasses
Journal of Non-crystalline Solids, 1999Co-Authors: M Tomozawa, Yong-keun LeeAbstract:Abstract The structural uniformity of thin (∼0.55 mm) annealed soda–lime glass samples was investigated using an IR reflection method. The surface layer of annealed soda–lime glasses was found to have an IR reflection structural band with a lower peak wave number than the bulk while no residual stress was observed in the specimens. On the other hand, the IR structural band of specimens that were air-quenched from the glass transition Temperature was the same both for the surface and the bulk, indicating a uniform structure. This finding can be attributed to a lower surface Fictive Temperature of the annealed glasses produced during the slow cooling due to the surface of the glass having a faster structural relaxation than that of the bulk. The surface Fictive Temperature of rate-cooled specimens was also lower than the bulk Fictive Temperature; the slower cooled sample having a thicker surface layer with a lower Fictive Temperature.
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determination of Fictive Temperature of soda lime silicate glass
Journal of the American Ceramic Society, 1995Co-Authors: Anand Agarwal, M TomozawaAbstract:Peak positions of silica structural bands, both in infrared absorption and reflection modes, were used earlier to measure the Fictive Temperature of silica glass. In the present study, the method was applied to determine the Fictive Temperatures of a soda-lime silicate glass. For the silicate glass, the IR absorption spectra produced a broad structural band which made the precise determination of peak position difficult, and only the IR reflection band was used. Equilibrium peak positions of ∼1056 cm−1 IR band, due to Si-O stretching, were found to be directly correlated with the Fictive Temperature of the soda-lime silicate glass. The soda-lime glass exhibited an opposite dependence of the IR band position on the glass Fictive Temperature as compared to silica glass.
Akira J Ikushima - One of the best experts on this subject based on the ideXlab platform.
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Fluorine-doping concentration and Fictive Temperature dependence of self-trapped holes in SiO2 glasses
Journal of Applied Physics, 2005Co-Authors: R. P. Wang, K. Saito, N. Tai, Akira J IkushimaAbstract:Fictive Temperature (Tf) and fluorine (F)-doping concentration dependences of self-trapped holes (STHs) in silica glasses created by UV irradiation at low Temperatures have been studied by the electron-paramagnetic-resonance method. It was found that the yield of STH decreases with decreasing Tf and increasing F-doping concentration. In combination with infrared spectra measurements, the correlation among Tf, F-doping concentration, Si–O bond length, and Si–O–Si bond angle was elucidated. We conclude that the change in both Tf and F doping can modify the network of SiO2 glass, leading to the suppression of the formation of STHs.
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effects of Fictive Temperature and halogen doping on the boson peak in silica glass
Physical Review B, 2005Co-Authors: N Shimodaira, Noriyuki Hiramitsu, Kazuya Saito, S. Matsushita, Akira J IkushimaAbstract:We have investigated the effect of structural disorder on the boson peak in the Raman scattering of silica glass. The structural disorder was controlled in two ways: Fictive Temperature $({T}_{f})$ and concentration of doped halogen element (F or Cl). As results, it has been simply demonstrated from nonreduced Raman spectra that (1) the peak position and full width at half maximum of the boson peak linearly increase with increasing ${T}_{f}$ irrespective of the halogen concentrations, and in contrast, (2) the intensity is rather strongly dependent on the halogen concentrations than ${T}_{f}$. Since the result in (1) is much similar to the dependence on ${T}_{f}$ and fluorine concentration for the IR absorption around $2260\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$, it has been concluded that the boson peak in silica glass is microscopically related to the average magnitude and distribution of $\mathrm{Si}\ensuremath{-}\mathrm{O}\ensuremath{-}\mathrm{Si}$ bond angles in glass network. The intensity enhancement in (2) has suggested two possibilities about the contribution of the doped halogen element to the boson peak: One is a direct contribution of F or Cl atoms due to diffusive motions falling within the range of the boson peak. The other is an indirect contribution introduced by the termination of $\mathrm{Si}\ensuremath{-}\mathrm{O}\ensuremath{-}\mathrm{Si}$ bridges to some sort of vibrational motions, which may be related to the boson peak.
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Specific Volume of Fluorine-Doped Silica Glass with Various Fictive Temperatures
Japanese Journal of Applied Physics, 2004Co-Authors: Hiroshi Kakiuchida, Kazuya Saito, Akira J IkushimaAbstract:The specific volume of silica glass was measured as a function of Fictive Temperature and the concentration of fluorine dopant up to 1550°C and 7.2 mol%, respectively. It was found that the relationship between volume and Fictive Temperature is strongly influenced by the fluorine dopant. The rate of change in volume to change in Fictive Temperature, which is negative for pure silica glass, increases linearly with increasing fluorine concentration and then becomes positive at the concentration higher than 3.3 mol%. On the other hand, the relationship between Fictive Temperature and spatially averaged structure, observed by infrared absorption and Raman spectra, is negligibly affected by the dopant. Such a difference between behaviors in the density and in the vibrational spectra indicates the possibility that with varying Fictive Temperature, a structural change in the local volume around the doped fluorine is much larger than the average structural change over the whole volume in the bulk.
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Rayleigh Scattering in Fluorine-Doped Silica Glass
Japanese Journal of Applied Physics, 2003Co-Authors: Hiroshi Kakiuchida, Kazuya Saito, Akira J IkushimaAbstract:The Rayleigh scatterings of fluorine-doped silica glasses as a function of Fictive Temperature were examined. The scattered intensity of pure silica glass increases proportionally to Fictive Temperature, implying that density fluctuation increases proportionally to Fictive Temperature. While the Rayleigh scattering caused by concentration fluctuation increases with increasing fluorine concentration, the scattering due to the density fluctuation does not seem to depend significantly on fluorine concentration.
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Fictive-Temperature dependence of structural relaxation in silica glass
Journal of Applied Physics, 2003Co-Authors: Hiroshi Kakiuchida, Kazuya Saito, Akira J IkushimaAbstract:To clarify the factors that determine the structural relaxations in silica glass, the influence of Fictive Temperature on the relaxation process was investigated. It was found that the relaxations at different heat-treatment Temperatures are enhanced with a rise in the Fictive Temperature. The structural relaxation is not simply the Maxwell process that is determined only by the heat-treatment Temperature. Since the density of silica glass increases with a rise in the Fictive Temperature, the mechanism of the aforementioned enhancement cannot be understood by the free volume theory, which has often been utilized for explaining structural relaxations in many glass formers. The present results reveal the significance of the Fictive Temperature in understanding the structural relaxation phenomenon in silica glass.