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1.
The Raman spectra of binary high-silica glasses have been studied. The main peaks at 808 cm?1 and 710 cm?1 in vitreous B2O3 and vitreous P2O5, respectively, are greatly reduced in binary high-silica glass, whereas a peak at 425 cm?1 due to GeOGe vibration and a peak at 1320 cm?1 due to P = O vibration remain strong, increasing in intensity with decreasing SiO2 concentration. In the stimulated Raman spectra of a P2O5-SiO2 glass fiber pumped by a mode-locked and Q-switched Nd:YAG laser at 1.064 μm, strong Stokes emissions due to the P = O vibration have been observed at 1.24 μm and 1.48 μm. In the spectra for a GeO2-SiO2 glass fiber, four narrow-width Stokes emissions due to the GeOGe vibration have been observed at 1.115, 1.172, 1.235 and 1.305 μm. 相似文献
2.
New compouning techniques were devised to prepare high-purity Ge28Sb12Se60 (TI 1173)and Ge33As12Se55 TI 20). The methods were based on the combination of the reactant purification and compounding steps. The goal of the program was to establish the absorption limit for the glasses and to lower the absorption at 10.6 μm. At the present purity level, the GeSbSe glass is found to have an absorption level of about 0.01 cm?1 at 10.6 μm while the absorption level for the GeAsSe glass is 0.05 cm?1. Underlying causes for the limits are discussed along with the possibilities for improvement. 相似文献
3.
The refractive index frequency dependence in the 1–11 μm range for AsSe, GeSe and AsGeSe glassforming systems and for three- and four-component systems obtained by substitution of antimony, bismuth, tin, lead, sulphur and tellurium for arsenic, germanium and selenium, being their periodic system counterparts, is investigated. A comparison of optical constants of chalcogenide glasses with those for other optical materials by means of constructing of an Abbe-type diagram in n2.0 ? v2.0 coordinates is considered. The possibility of chalcogenide glass refraction calculation by means of additive formulas is discussed. It is shown that critical points on the property-composition curves coincide with structural region boundaries in all of the investigated systems. These data are considered as further experimental support for the polymer nature of chalcogenide glasses. 相似文献
4.
In order to better understand the distribution of tetrahedra in multicomponent tetrahedral network structures of melts and glasses, we have investigated the Raman spectra of binary SiO2GeO2 glasses. We compare the Raman spectral features of the end-member glasses and discuss their vibrational origins. The mixing of GeO2 and SiO2 melts results in a continuous random network structure of TO4 tetrahedra (T Si, Ge) in the glass. Raman bands corresponding to the asymmetric stretch (vas) of oxygen in GeOGe, SiOSi and SiOGe bonds are observed in the glasses having intermediate compositions along the SiO2GeO2 join. The presence of three distinct vas (TOT) bands in the spectrum of a glass having Si/Ge one reveals that a considerable degree of SiGe disorder exists in the glass. The presence of a single symmetric oxygen stretching band in the spectra of binary SiO2GeO2 glasses indicates that the symmetric stretch modes (vs) of oxygen in SiOSi, SiOGe and GeOGe bonds are strongly coupled. An observed decrease in the halfwidth of the vs (TOT) band in the spectra of SiO2GeO2 glasses with increasing concentration of GeO2 may be attributed to a decrease in the average TOT bond angle and a predominance of six-membered ring structures. Results of the present study support the assignment of the bands in the 900–1200 cm?1 region of the alumino-silicate glasses, spectra to the vas(AlOSi) and vas(SiOSi) modes. In contrast to the alumino-silicate glasses, however, the SiO2GeO2 glasses have a much higher degree of disorder of the network-forming cations. 相似文献
5.
Se, As and Ge self-diffusion were investigated in three different glasses of the chalcogenide system SeGeAs by means of the radioactive tracers 75Se, 73As and 71Ge. All D values (Se between 200 and 290°C, As between 240 and 290°C and Ge between 280 and 295°C) lay between 10?14 and 5 × 10?16 cm2 s?1. The diffusion profiles were analyzed using a chemical micro-etching technique. Roles of glass structure and possible diffusion mechanism are discussed. 相似文献
6.
The dc and ac conductivities of glasses of the system GeSbSe (with the general formula GexSb10Se90?x have been studied. The dc conductivity results indicate a maximum in the glass transition temperature and activation energy and a minimum in conductivity for the composition Ge25Sb10Se65. These results have been explained on the basis of the prevalent structural arrangement wherein structural units of GeSe2 and Sb2Se3 are dispersed among excess Se or Ge. Based on this picture, a model has been developed which accounts for the observed dependence of conductivity on composition at any temperature. The ac results have been utilized to find the hopping conductivity as a function of composition; the characteristics of lone pair amorphous semiconductors seem to account for the observed features. 相似文献
7.
Electrical conduction in various inorganic glasses was studied as a function of hydrostatic pressure up to 2000 atm and phenomenologically classified into electronic, ionic and mixed types. In electronically conducting glasses such as AsSe chalcogenide glasses and Fe2O3P2O5 glass, the conduction is enhanced by application of pressure. On the other hand in ionically conducting glass such as Na2OB2O3 glass, the conduction is suppressed through the concept of an activation volume. The compatibility of electronic and ionic conduction processes in glasses such as Ag-doped AsSe glasses and Bi2O3B2O3 glass, which have more complex conduction processes, was discussed from these aspects. 相似文献
8.
The introduction of Ag in SiAsTe glasses permits the incorporation of Se, otherwise volatile and/or degradable as a constituent in Si-containing chalcogenide glasses. SiAsAgTeSe glasses exhibit much higher softening ranges and glass transition temperatures than encountered in known chalgogenide systems. A glass Si35As15Ag10Te20Se20 had the viscosity log ν = 13 at about 500°C, as compared to 370°C for the base glass Si35As25Te40, the viscosity of log ν = 9.8 at about 560°C, as compared to 442°C for the base glass. Phase separation occurs in the system SiAsAgTeSe and becomes manifest in two glass transitions indicated by changes in the slopes of the expansion curves and breaks in the softening point-composition relations. The existence and behavior SiAsAgTeSe glasses suggests the possible development of higher Tg i.r. transparencies and higher Tg semiconductor glasses than described so far. 相似文献
9.
When CuAsSe glasses are irradiated, they exhibit higher concentrations of darkening than AsSe glasses. Since darkening depends on the composition, the darkening centers in CuAsSe glasses to be of the same kind as those in AsSe glasses, i.e. arsenic clusters. Concerning the kinetics of erasing, it was found that the activation energy and the rate constant of erasing in CuAsSe are almost equal to those in AsSe glasses, but for the kinetics of darkening, it was found that the activation energy of darkening is equal to that of AsSe but α0, which is proportional to the number of latent darkening centers, and the darkening rate constant k1 are about twice as high as the corresponding constants of AsSe glasses. This may be the reason for the greater darkening in CuAsSe glasses. The high value of α0 was attributed to the generation of more AsAs bonds on the addition of Cu to the AsSe glass network. The high value of k1 was attributed to the increase in efficiency of photo-decomposition because of the many impurity levels in the band gap and also because of the narrow optical energy gap in the CuAsSe glasses. 相似文献
10.
Koichi Shimakawa 《Journal of Non》1981,43(2):229-244
It is found that the optical gap EAB for amorphous A-B alloys can be determined by the energy gap EA for element A and EAB for the element B in the equation EAB(Y) = YEA + (1?Y) EB where Y is the volume fraction of element A. Calculations based on a random bond network agree with experiments for SiGe, SbSe, and AsTe films (class A). Calculations based on a chemically ordered bond network which tends to form microscopic molecular species gree with experimental results for the AsSe, AsS, GeTe and Sb2Se3As2Se3 systems (class B). In contrast to the above systems, agreement with experiment is not obtained for the TeSe, As2Te3As2Se3 and GeTe2GeSe2 systems which contain atoms of both Te and Se (class C). The classification into three types (classes A, B and C) is consistent with the calculation based on effective medium percolation theory which interprets the compositional dependence of the conductivity of chalcogenide glasses. 相似文献
11.
We have used differential scanning calorimetry (DSC) to examine the thermally induced transformations of bulk and thin-film amorphous alloys within a large portion of the GeSeTe system. Most chalcogen-rich compositions showed a discontinuous increase of heat capacity when heated through the glass transition temperature TG. The Ge-rich compositions, which could only be prepared as sputtered amorphous films, were invariably characterized by an irreversible exothermic crystallization process on heating, beginning at the crystallization temperature TX. Values of Tg and TX have been tabulated for all alloys investigated and the compositional dependence of Tg has been examined in the light of recent models for viscous flow in glass-forming chalcogenide systems. In addition, a region of liquid immiscibility has been observed in the vicinity of Ge20Se40Te40 in which a GeSe2-rich liquid phase segregates from a tellurium-rich liquid phase. The existence and limits of this immiscibility region have been rationalized on the basis of ionic perturbations to the covalent bonding. The segregation of a GeSe2-rich liquid increases the concentration of GeSe bonds which are the strongest and most ionic of the six angle-bond types which can occur in this system. 相似文献
12.
《Journal of Non》1986,83(3):272-281
The optical properties near the fundamental absorption edge has been studied for a series of SixSe1−x glasses using photoacoustic spectroscopy. The compositional dependence of the bandgap EO, derived from these measurements, is presented and contrasted with the GeSe and the SiS systems. This data is qualitatively explained with a model which accounts for differing numbers of homopolar and heteropolar and heteropolar bonds as the composition is varied. Additional support for this interpretation is found in the compositional behavior of the glass transitions of these alloys. 相似文献
13.
The results of the measurement of transverse and longitudinal sound velocities on eigth glass compositions of the GeSbSe system are reported and their elastic moduli evaluated. While the velocities, elastic moduli and Debye temperature show variation with composition for GexSb10Se90?x glasses, they are essentially constant for the glasses with stoichiometric compositions. The dependence of bulk modulus on mean atomic volume has been analysed. Both the mean atomic volume and the type of bonding are found to be effective in determining the composition dependence of bulk modulus. 相似文献
14.
The glass transition temperatures were measured in the systems AsS, As0.5P0.5S, PSe, AsSe and PAsSe. Heat capacities of the glasses in the selenium systems were obtained by differential scanning calorimetry. As shown by the residual entropies departures from ideality are high in the chalcogen glasses. The results are discussed in terms of the structure of glasses in these systems. The thermodynamic data of glasses and liquids in these systems indicate a balance of intra- and intermolecular saturation of bonds. The amount of polymerization increases with increasing average molecular weight in the glass and with increasing temperature in some of the investigated liquids. 相似文献
15.
De Neufville prepared homogeneous glasses ranging in composition from pure GeO2 to GeO by quenching bulk samples from the melt and by vapor deposition. For compositions in the range of 10–20 mol % excess Ge dissolved in GeO2, he found that phase separation into amorphous Ge rich and amorphous GeO2 phases occurred. The results reported here on a 7.5 mol % excess Ge composition using differential scanning calorimetry have shown that a two-step phase separation mechanism is operative. A homogeneous GeGeO2 glass phase separates at 450°C into amorphous GeO2 and amorphous GeO. The GeO phase separates at 570°C into crystalline Ge and amorphous GeO2. The heat measured at 570°C is equal to the sum of the heats of phase separation of GeO and crystallization of Ge. The amorphous GeO2 crystallizes at 670°C with a heat of crystallization of 4.65 kcal/mol (± 0.5). Additional support for a two-step phase separation mechanism is provided by kinetic arguments based on the viscosity dependence on composition and on the structure of the amorphous GeO phase and its stability relative to the homogeneous GeGeO2 glass. 相似文献
16.
X-ray diffraction studies of glasses in the following ternary systems have been made: Na2OMgOSiO2, Na2OZnOSiO2, Na2OCaOSiO2 and Na2OBaOSiO2. The following heavy atom substitutions have been used: Ag for Na and Ge for Si. The changes in the electron radial distribution curves resulting from AgNa replacement can be explained as amplifications of relatively well-defined NaSi distances, which are nearly the same in all the glasses investigated. The GeSi substitution causes changes which can be explained on the basis of isostructural GeSi substitutions. 相似文献
17.
《Journal of Non》1986,79(3):285-294
The structure of Na2OGeO2 melts in the temperature range from 1100 to 1150°C has been investigated with the high temperature X-ray diffraction technique. Comparing the radial distribution functions obtained for the melts with those for the corresponding glasses, the first peak due to the GeO interatomic distance is invariant upon melting, although it becomes broader due to thermal vibration. The second peak for the GeGe interatomic distance for melts shifts toward the large distance, which is explained by broadening of the GeOGe bond angle, not by the thermal expansion of the GeOGe bond. The composition dependences of GeO distances and coordination numbers of the Ge4+ ion of the melts are found to be almost the same as the corresponding glasses, indicating that even in melts at such high temperatures 6-fold coordinated Ge4+ ions are present and their content changes with the Na2O content as in the case of the corresponding glasses. 相似文献
18.
Robert B. Greegor Farrel W. Lytle Donald R. Sandstrom Joe Wong Peter Schultz 《Journal of Non》1983,55(1):27-43
The coordination and nearest-neighbor bond distances of Ti in a series of TiO2SiO2 glasses have been quantitatively determined using a combination of XANES and EXAFS measurements about the Ti K-edge at 4966 eV. The glasses covering the range 0.012 to 14.7 wt% TiO2 were prepared by flame hydrolysis of predetermined mixtures of SiCl4 and TiCl4 vapors. At TiO2 concentrations below ~0.05 wt%, Ti is found in a rutile-like octahedral coordination. With increased TiO2 content in the glass, a two-site model applies, in which Ti is found predominately in a fourfold site. About ~9 wt% TiO2, t6he sixfold/fourfold ratio increases appreciably and eventually at ~15 wt% TiO2, crystalline TiO2 segregates out as a second phase. The average TiOSi bond angle in these glasses was estimated to be ~159 ° which is slightly larger than the most probable value of 152 degrees for SiOSi in vitreous SiO2. Within the accuracy of the edge shift measurements all Ti in the glass is in 4+ valence. Finally, various physical properties such as density, optical transparency and thermal expansion are correlated in light of the new structural data for this interesting binary silicate glass system. 相似文献
19.
The formation of glass in the GeSiS system was investigated. After synthesis of material with the general formula Ge1?xSixSy, where x was chosen to be 0.05, 0.1, 0.2, 0.3 and y was in the range 1.28–3.6, cylindrical samples were prepared and used for the characterization of glass by means of DTA. It was found that the substitution of germanium with silicon does not lead to any expressive change of the glass transition temperature, crystallization and the onset of melting. 相似文献
20.
《Journal of Non》2007,353(32-40):2959-2974
A summary is given of the partial structure factors that have been measured for liquids and glasses in the Ge–Se binary system by using diffraction methods. Information is presented on the pair correlation functions describing the atomic species and use is made of the Bhatia–Thornton formalism to separate those pair correlation functions describing the system topology from those that describe the chemical ordering. The information made available by the measured Bhatia–Thornton partial structure factors on the thermodynamic properties of Ge–Se mixtures is briefly summarized. The properties of the network structures formed in liquid and glassy Ge–Se compounds are investigated as a function of composition, temperature and pressure. For GeSe2 at ambient pressure it is shown that the so-called first sharp diffraction peak, which appears in the measured diffraction patterns at a small scattering wavevector value of ≈1 Å−1 and which is associated primarily with Ge–Ge correlations, does account for discernable features of the observed intermediate range order in both the liquid and glassy phase. The first sharp diffraction peak in the measured Ge–Ge partial structure factor for both phases is described by comparable parameters suggesting communality in the underlying intermediate range order which survives the glass transition. Homopolar bonds are found to be a feature in the structure of liquid GeSe and both liquid and glassy GeSe2 with Ge–Ge and Se–Se distances in the ranges 2.33(3)–2.42(2) and 2.30(2)–2.34(2) Å, respectively. 相似文献