Bulk and impurity infrared absorption in 0.5 As2Se30.5 GeSe2 glass

A study of infrared absorption in the 250–4000 cm^?1 region has been carried out for 0.5 As₂Se₃0.5 GeSe₂ glasses quantitatively doped with oxide impurity. The frequencies of the intrinsic 2- and 3-phonon absorption bands at 490 and 690 cm^?1 correspond well to those predicted from combinations of the high frequency bands in the first order IR and Raman spectra of As₂Se₃ and GeSe₂ glasses.Glasses doped with As₂O₃ exhibit the same oxide impurity absorptionbands as those doped with GeO₂. Unlike As₂Se₃ glass, at impurity concentrations up to 1000 ppm As₂O₃, 0.5 As₂Se₃0.5 GeSe₂ glass exhibits only one major oxide impurity species, characterized by absorption bands at 780 and 1260 cm^?1 and due to oxygen bonded to network Ge. The observation of a much weaker network AsO vibration band at 670 cm^?1 confirms that oxygen bonds preferentially to Ge in this glass. The same minor oxide species appears to determine excess IR absorption at the CO₂ laser wavelength of 10.6 μm in both As₂Se₃ and 0.5 As₂Se₃ 0.5 GeSe₂ glasses. The frequencies and intensities of absorption bands due to hydrogen impurities are also quite comparable for these two materials.     

Vibrational spectra of vapor-deposited binary phosphosilicate glasses

Room temperature infrared transmission spectra in the range 4000-250 cm^?1 of binary phosphosilicate glass (PSG) films deposited by reacting argon- or nitrogen-diluted PH₃SiH₄O₂ mixtures on heated silicon substrates at 300–400° C have been obtained across the whole composition range. In all the as-deposited binary films, an absorption at ≈1300 cm^?1 characteristics of the P=O vibration was found to persist, together with a couple of broad absorptions in the regions 1200-900 cm^?1 and 500 cm^?1. Using a differential infrared technique the broad feature in the higher frequency region has been resolved into two well-defined bands at ≈1100 and 970 cm^?1. A detailed analysis shows that the intensity variation of the differential band at ≈1100 cm^?1 conforms well, at least to 50 mol% P₂O₅, to a simple structural model that yields an analytic distribution of POSi linkages as a function of composition by assuming chemical mixing in the vapor-deposited P₂O₅SiO₂ system. Furthermore, the system may be written as (P=O)₂ O₃SiO₂ in order to emphasize the similarity of its coordination scheme with that of the B₂O₃SiO₂ system studied earlier. The nature of these CVD films has also been elucidated by thermal and water treatments.     

Raman study of the structure of glasses along the join SiO2GeO2

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 SiO₂GeO₂ 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 (v_as) of oxygen in GeOGe, SiOSi and SiOGe bonds are observed in the glasses having intermediate compositions along the SiO₂GeO₂ join. The presence of three distinct v_as (TOT) bands in the spectrum of a glass having Si/Ge one reveals that a considerable degree of SiGe disorder exists in the glass. The presence of a single symmetric oxygen stretching band in the spectra of binary SiO₂GeO₂ glasses indicates that the symmetric stretch modes (v_s) of oxygen in SiOSi, SiOGe and GeOGe bonds are strongly coupled. An observed decrease in the halfwidth of the v_s (TOT) band in the spectra of SiO₂GeO₂ glasses with increasing concentration of GeO₂ may be attributed to a decrease in the average TOT 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 v_as(AlOSi) and v_as(SiOSi) modes. In contrast to the alumino-silicate glasses, however, the SiO₂GeO₂ glasses have a much higher degree of disorder of the network-forming cations.     

Infrared absorption of some high-purity chalcogenide glasses

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 GeSbSe glass is found to have an absorption level of about 0.01 cm^?1 at 10.6 μm while the absorption level for the GeAsSe glass is 0.05 cm^?1. Underlying causes for the limits are discussed along with the possibilities for improvement.     

Anomalous physical properties and Raman spectra of glassy B2O3BaTiO3Na2O materials

Anomalous physical properties (refractive index and density) of B₂O₃BaTiO₃Na₂O ternay glasses are determined and discussed on the basis of the structure present in the glasses and evidenced by vibrational Raman spectroscopy.These glasses behave in a manner analogous to the alkali B₂O₃X₂O binary glasses for molar ratio R = basic oxide/B₂O₃ up to 0.3, with oxygen binding by means of bridging bonds while boron coordination changes from the trigonal to tetrahedral type. The phenomenon is indicated by a progressive weakening of the 806 cm^?1 peak (attributable to a breathing vibration of the boroxol unit) and by a concomitant strengthening of the ～775 cm^?1 peak (attributable to a vibrational mode of boroxol units, or derived units, containing at least one 4-coordinate boron atom). For higher R values the Raman spectra bring to light the progressive demolition of the structural units responsible for the 775 cm^?1 Raman peak, which gives rise (the transformation is complete for R ～ 1) to two new main structural units, orthoborate [BTi₄O₁₀]^?1 (peak at 845 cm^?1) and metaborate BO₂^? (peak at 715 cm^?1).     

Relationship between density,viscosity and structure of GeO2 melts at low and high pressures

A correlative study of the viscosity, density and structure of GeO₂ melts has been carried out at low and high pressures. It is observed that under isothermal (1425°C) conditions the viscosity decreases from 6.0 × 10³ poise at 1 bar to 1.2 × 10³ poise at 9.5 kbar. The maximum variation in the density of quenched GeO₂ glasses is from 3.62 ± 0.02 g cm^?3 for glass formed from a liquid quenched at 1 atm and 1425°C to 3.95 ± 0.04 g cm^?3 for glass formed from a liquid quenched at 18 kbar and 1700°C.The similarity of the Raman spectra of GeO₂ melt quenched at 1 atm (1425°C) and at 18 kbar (1700°C) implies that the scattering units in GeO₂ glasses quenched at low and high pressures are the same. The intensity of the Rayleigh tail, however, decreases in glasses quenched at successively higher pressures, the structure apparently becoming more ordered with increasing pressure. The Raman spectra of the GeO₂ polymorphs with quartz and rutile structures, crystallized at 1150°C and at 4 and 6 kbar, respectively, are distinct because of the difference in Ge coordination, resulting in a large difference in the frequency and intensity of the GeO symmetric stretching mode in the two polymorphs. A comparison of the Raman spectra of GeO₂ glasses with those of crystalline GeO₂ polymorphs shows that the local ordering in GeO₂ glass is similar to that of hexagonal GeO₂ in which Ge is tetrahedrally coordinated.The decrease in the viscosity of GeO₂ melt with increasing pressure cannot be attributed to a pressure-induced coordination change [1]. More likely, there is a systematic change in the nature of the GeO bond with increasing pressure. The increase in the degree of local ordering in GeO₂ melts quenched at high pressures does explain the progressive increase in melt density.     

Raman spectrum of vitreous As2S3

The spontaneous Stokes and anti-Stokes Raman spectrum of vitreous As₂S₃ is reported. The spectrum was recorded with both HeNe and Ar ion laser excitation lines in the transmission and reflection modes respectively. Spectra were recorded at various temperatures between 20°K and 465°K, the softening temperature of As₂S₃ glass. It is shown conclusively that the quasicontinous scattering observed at low wave number shifts (< 100 cm⁻¹) is real in agreement with the theory of Shuker and Gammon and not an arbitrary background as previously reported. An approximate density of vibrational states is deduced from the polarized Raman spectra.     

Raman spectroscopic study of scandium in sodium silicate glasses

Glasses in the Na₂OSiO₂Sc₂O₃ system have been studied by Raman and difference Raman spectroscopy. Addition of Sc₂O₃ to sodium silicate glasses results in new vibrational bands at 1025 cm^?1 and 360 cm^?1. The high frequency band is interpreted to be due to Sc⁺³ quasi-complexes formed by Sc⁺³ ions coordinated by SiO₄^?4 tetrahedra having non-bridging oxygens. The discrete character of the scandium-produced bands implies incipient separation of Sc⁺³-enriched silicate structures from purely silicate structures.     

Formation and optical properties of (R2O or R′O)Nb2O5Ga2O3 glasses

Glass-forming tendencies of melts in the systems (alkali oxide or alkaline earth oxide)-Nb₂O₅Ga₂O₃ were examined by an ordinary crucible-melting technique. The glass-forming tendency increased with increasing radius of alkali or alkaline earth ion in the respective groups. Clear glasses were obtained on a practically useful scale in the systems (K₂O or Cs₂O)Nb₂O₅Ga₂O₃ and (SrO or BaO)Nb₂O₅Ga₂O₃. The infrared absorption spectra indicated that the Ga³⁺ ions in the glasses are tetrahedrally coordinated with oxygen ions. The glasses showed high optical transmissions from the ultraviolet region of 0.3 μm in wavelength to the infrared region of 7 μm, except for a region near 3 μm. The absorption near 3 μm, which is attributed to OH vibration, could be eliminated by replacing part of the carbonate in the raw materials with a fluoride and melting the mixture of raw materials in a dry N₂ gas atmosphere. The glass-forming tendencies of the melts and the optical transmissions of the glasses were discussed in terms of the glass structure.     

Raman and infrared spectra on silica gel evolving toward glass

Infrared and Raman spectra of gels obtained from specially prepared solutions of Si(OC₂H₅)₄ (TEOS) which have been thermally treated in the 40–800°C temperature range, are reported and discussed with reference to the spectra of fused quartz.The results show that the gel to glass transformation is an hydrolytic polycondensation process, which takes plase gradually and is practically completed in the samples treated at 800°C.Particularly revealing is the behaviour of the bands due to OH (associated and/or unassociated H-bonded) stretching modes, including those of water, which are weakened by increasing temperature; the behaviour of the band due to the SiOH stretching mode; the behaviour of the network bands, some of which become more intense with increasing temperature, due to asymmetric and symmetric stretching and the bending SiOSi modes.In the Raman spectra of gels heated at different temperatures two peaks also appear at ≈600 and ≈490 cm^?1, which are also present in the Raman spectrum of fused quartz, they are related to network defects of the glass structure, for which no definite interpretation has yet been given in the literature.     

Infrared spectra and structure of superionic conducting glasses in the system AgIAg2OMoO3

Thin blown films of glasses with the mole ratio Ag₂O/MoO₃ = 1 in the system AgIAg₂OMoO₃ (or the pseudobinary system AgIAg₂MoO₄) show three absorption bands in the range 4000-200 cm^?1; 875 cm^?1 (w), 780 cm^?1 (s), and 320 cm^?1 (m, b), which are characteristic of tetrahedral MoO₄^2? ions. The glasses with the ratio Ag₂O/MoO₃ < 1 have two additional bands at 600 cm^?1 (w) and 450 cm^?1 (vw), which are characteristic of condensed ions of MoO₄ tetrahedra, probably Mo₂ O₇^2? ions. These glasses are thus composed of Ag⁺, I^?, MoO₄^2?, and probably Mo₂O₇^2? ions, and classified as “ionic” glasses containing one type of cations. The presence of partial covalency in the Ag⁺… ^?OMo link and the influence of ion exchange of Ag⁺ with K⁺ on IR spectra are discussed. The molar volume of the glasses with the ratio Ag₂O/MoO₃ = 1 is primarily determined by a fairly dense packing of the constituent anions, I^? and MoO₄^2?.     

Raman spectra and structure of sodium aluminogermanate glasses

Polarized Raman spectra of x NaAlO₂·(100 ? x) GeO₂ glasses (x = 0, 5, 10, 15, 20, 25, 33, 42, and 50) are presented. Analyses of the Raman data indicate that the aluminogermanate glasses have three-dimensional network structures consisting of interconnected AlO₄ and GeO₄ tetrahedra; Na⁺ ions are present in cavities and charge balance the Al³⁺ ions. Systematic changes are observed in the frequencies, intensities and polarization characteristics of spectral bands with variations in the NaAlO₂ content of these glasses. The antisymmetric stretching mode [ν_as (TOT), where T = Al, Ge] in the high-frequency region of the spectra (800–1000 cm^?1) appears as a doublet consisting of well-defined bands in the spectra of glasses along the entire join. Both components of the high-frequency doublet shift to a lower frequency with increasing NaAlO₂ content, indicating that the ν_as (GeO₄) and ν_as(AlO₄) stretching modes are coupled. The variations in the TO force constants and TOT bond angles with change in composition most likely cause the bands to shift. The frequencies of the Raman bands of sodium aluminogermanate glasses are compared with those of the corresponding bands in isostructural sodium gallogermanate glasses. On the basis of this comparison, the origin and delocalization of the vibrational modes producing characteristic Raman bands in the spectra of these glasses are discussed. The changes observed in the Raman spectra of aluminogermanate glasses with variation in NaAlO₂ content are analogous to those observed in the spectra of glasses along the NaAlO₂SiO₂ join.     

X-ray diffraction study of Na2OGeO2 melts

The structure of Na₂OGeO₂ 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 GeO interatomic distance is invariant upon melting, although it becomes broader due to thermal vibration. The second peak for the GeGe interatomic distance for melts shifts toward the large distance, which is explained by broadening of the GeOGe bond angle, not by the thermal expansion of the GeOGe bond. The composition dependences of GeO 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.     

Structure and properties of MoO3-containing zinc borophosphate glasses

ZnO–B₂O₃–P₂O₅ glasses doped with MoO₃ were investigated in the series (100?x)[0.5ZnO–0.1B₂O₃–0.4P₂O₅]–xMoO₃, where bulk glasses were obtained by slow cooling in air within the compositional region of 0 ? x ? 60 mol% MoO₃. The incorporation of MoO₃ into the parent zinc borophosphate glass results in a weakening of bond strength in the structural network, which induces a decrease in chemical durability and glass transition temperature. Raman spectra reflect the incorporation of molybdate groups into the glass network of the studied glasses by the presence of the polarized vibrational band at ≈976 cm^?1 ascribed to the MO_x symmetric stretching vibrations and the depolarized band at ≈878 cm^?1 ascribed to the Mo–O–Mo stretching vibration. The incorporation of molybdate units into the glass network results in the depolymerization of phosphate chains and the formation of P–O–Mo bonds, as reflected in Raman and ³¹P NMR spectra. According to the ¹¹B MAS NMR spectra, tetrahedral B(OP)_4?x(OMo)_x units are formed in the glasses, whereas only a small amount of BO₄ units is converted to BO₃ units in the MoO₃-rich glasses.     

Ionic conductivity of Li2OB2O3 thin films

The ionic conductivity of evaporated Li₂OB₂O₃ thin films has been studied. These thin films were found to show a considerably high ionic conductivity of 1 × 10^?7 Ω^?1 cm^?1 at room temperature. The conductivity increases with increasing Li content and exhibits a maximum value near 3Li₂O·B₂O₃. The structure of these films was determined using infrared absorption and laser Raman scattering spectroscopy. Using the results, the correlation between structure and conductivity is also discussed.     

Some features of EPR and optical spectra of vanadium in aluminophosphate glasses

The EPR and optical spectra of vanadium in glasses of ternary Al₂O₃P₂O₅SiO₂ and Al₂O₃P₂O₅B₂O₃ systems have been measured. The results were compared with earlier data for vanadium in binary phosphate, aluminophosphate and silicaphosphate glasses and with results of de-Biasi for V⁴⁺ in crystalline powder α-crystobalite AlPO₄. The superpositions of two hyperfine spectra (ASB-I and ASB-II) were found for many glasses of ternary systems. Both spectra can be attributed to VO²⁺ ions. The intensity ratio of the ASB-II spectrum to ASB-I depends on glass composition but is great (> 7) for all the glasses. Only the ASB-II spectrum was observed in glasses with low concentration of Al₂O₃. The spectral parameters of ASB-II spectrum are g_| = 1.916–1.921; g_⊥ 1.980–1.988; A_| = (188?190) × 10^?4cm^?1 and A_⊥ = (74–77) × 10^?4cm^?1. Three intense bands at 370, 455 and 700 ans 720 nm observed in these glasses can be attributed to V³⁺ ions. The excellent agreement of the parameters of the EPR spectrum of V⁴⁺ ions in crystalline α-crystobalite AIPO₄ and ASB-II spectra in the glasses under study suggest the identical electron structure of the paramagnetic species. This species is believed to be characterized by optical bands at 680 and 790 nm which have been observed by de Biasi. The orbital mixing coefficients indicate strong tetragonal distortion of vanadyl complexes responsible for the ASB-II spectrum. It is assumed that VO²⁺ ions responsible for this spectrum act as modifiers fitting into the relatively small holes of the three-dimensional networks of phosphate glasses containing no cations of large radii. The microscopic basicity of oxygens in such holes must be about 0.48.     

Structural interpretations for some Raman lines from vitreous silica

An interpretation based on non-random structural features is advanced for the 490 and 604 cm^?1 Raman lines from vitreous silica. The sharp, polarized 490 cm^?1 line is considered to arise from a small concentration of planar rings involving three $\text{SiO}{}_{\mathrm{<mtext>4</mtext><mtext>2</mtext>}}$ tetrahedra. The somewhat broader line at 604 cm^?1 is thought to be associated with rings of various sizes, both planar and puckered, that are connected to the rest of the structure by elongated SiO bonds. Changes in the concentration and/or Raman scattering cross-section of these ring structures produced by changes in fictive temperature, neutron irradiation, high elastic tensile and compressive stresses, annealing, and by changes in the SiOH content are thought to produce the intensity variations observed in these two Raman lines.     

Vibrational spectra and structure of chloro-fluorozirconate glasses

A series of barium chloro-fluorozirconate glasses have been prepared. Their IR absorption, IR reflectivity and Raman spectra have been measured down to 33 cm^?1. The glass transition and crystallization temperatures have also been measured. The high frequency IR absorption and Raman modes of the chloro-fluorozirconate glasses have been assigned as in fluorozirconate glasses. The IR reflection spectra of chloride-containing glasses differed from the fluorozirconates in that one band was clearly related to Cl atom motions. The structure of the glasses probably consists of zig-zag chains of ZrCl₂F₄ mixed halide octahedra plus a pure fluoride matrix whose structure is similar to that of a ZrF₄BaF₂ glass with the same composition.     

Raman spectroscopic investigation of the structure of silicate glasses (II). Soda-alkaline earth-alumina ternary and quaternary glasses

Raman spectra of some ternary and quaternary glasses in the system Na₂OCaOMgOAl₂O₃SiO₂ are presented. The spectra are interpreted in terms of the structural alteration of the glass as the composition is altered from the binary end members to more complicated glasses. Addition of CaO and MgO to soda-silica glasses act only to increase the disorder of the network slightly. Addition of Al₂O₃ greatly modifies the network. In some soda-lime-aluminosiliscate compositions an estimate can be made of the amount of aluminum in four- and six-fold coordination. It is shown that the amounts of four- and sixfold coordinated aluminum depend on the glass composition.     

Observation of chemical reaction and liquid structure of SGe by Raman spectroscopy

The measurements of the Raman spectra on liquid Ge_XS_1?X (0≤X≤0.1) were carried out. The A₁ mode of $\text{GeS}{}_{\mathrm{<mtext>4</mtext><mtext>2</mtext>}}$ (ca. 340 cm^?1) was observed in the liquids. The comparison with the spectra of liquid S suggests that Ge reacts on the polymeric species. During the chemical reaction of solid Ge and liquid S below ca. 500°C, the L.T.GeS₂ crystal growth was observed. The spectral features of the L.T.GeS₂ surprisingly resemble those of GeS glasses. The glass forming region was extended to X = 0.03 by careful rapid quenching. The overall compositional dependence of the Raman spectra of Ge_XS_1?X (0.03≤×≤0.341) was analysed in comparison with the spectra of the L.T. and the H.T. crystal and can be explained by the model that with increase of X(>ca. 0.2) the H.T. GeS₂-like spectra emerge abruptly from the L.T.GeS₂-like spectra in lower X. Standing on the model, the glassy structures in this system are discussed.