Showing papers in "Journal of Non-crystalline Solids in 1995"

AB initio molecular dynamics for liquid metals

Abstract: In recent years, ab initio molecular dynamics (MD) techniques have made a profound impact on the investigation of the structure of the electronic and dynamic properties of liquid and amorphous materials In this paper, recent developments in this field are reviewed and it is shown that the exact calculation of the electronic groundstate at each MD timestep is feasible using modern iterative matrix diagonalization algorithms Together with the use of ultrasoft pseudopotentials, ab initio MD simulations can be extended to open-shell transition metals with a high density of states at the Fermi-level The technique is applied to a number of interesting cases: (a) liquid simple metals (Li, Na, Al, Ge), (b) liquid transition metals (Cu, V), and (c) the transition from a liquid metal to an amorphous semiconductor by the rapid quenching of Ge

The short-range structure of zinc polyphosphate glass

Abstract: 31 P magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy and Raman spectroscopy have been used to examine the polyhedral arrangements in x ZnO · (1 − x )P 2 O 5 (0.50 ≤ x ≤ 0.71) glasses. The depolymerization of P metaphosphate chains by the addition of ZnO is quantitatively described by the increase in the concentration of Q 1 -phosphate sites, determined from the 31 P MAS-NMR spectra. When x > 0.60, the NMR and Raman spectra exhibit peaks due to Q 0 and Q 2 tetrahedra, indicating that structures disproportionate in glass melts near the pyrophosphate composition. The splitting of the Raman peak due to the Q 1 terminal oxygen stretching mode indicates that a variety of P-O-Zn bonds participate in the polyphosphate glass structure. The complex mixture of P and Zn polyhedra contributes to the glass-forming tendency of the high ZnO (> 60 mol%) compositions.

Chalcogenide glasses: a review of their preparation, properties and applications

Abstract: The author provides an update of: glass preparation in bulk, fibre and film form; optical and thermal properties, and potential applications of chalcogenide glasses.

Covalent bond approach to the glass-transition temperature of chalcogenide glasses

Abstract: Good correlation between the glass-transition temperature, T g , and the overall mean bond energy, 〈 E 〉, of a covalent network of a glass was found for 186 binary and ternary chalcogenide glasses. This correlation satisfies the Arrhenius relation for viscosity where the apparent activation energy of viscosity, E μ , is empirically related to the overall mean bond energy. The chemical bond arrangement is probably the main factor influencing T g in chalcogenide glasses.

Correlation between structure and thermal conductivity of organic aerogels

Abstract: Organic aerogels are derived from the sol-gel polymerization of resorcinol with formaldehyde. While these materials are usually produced as monoliths, this paper describes a new method for the production of organic aerogel microsphere powders. Supercritical drying provides highly porous aerogels which have an open-cell structure consisting of interconnected solid particles with typical diameters of 10 nm. The structure is controlled by the sol-gel polymerization conditions. This paper addresses the correlation between structure and thermal conductivity of these novel materials. Thermal conductivity measurements have been performed on both monoliths and powders using a hot-wire device. The measurements under variation of gas pressure as well as spectral infrared transmission measurements allow the determination of the solid, gaseous and radiative thermal conductivity as a function of density and catalyst concentration. The results show that the thermal conductivity components are clearly correlated with the aerogel structure: porosity and connectivity between the particles determine the solid conductivity, while the pore size influences the gaseous conductivity and radiative transport depends on the mass specific infrared absorption of the building units.

A simple IR spectroscopic method for determining fictive temperature of silica glasses

Abstract: Infrared spectroscopy was used to determine fictive temperature of silica glasses. Positions of both the fundamental structural band at ∼ 1122 cm−1 monitored in infrared (IR) reflection mode and an overtone of this band at ∼ 2260 cm−1 monitored in IR transmission mode were found to be directly correlated with the glass fictive temperature. At any particular fictive temperature, the equilibrium structural band positions were found to be independent of the impurity content, such as hydroxyl, in different types of silica glass. From band shifts, the average SiOSi bond angle was computed to decrease by about 1.3° when the fictive temperature increased from 950 to 1400°C. Using this method, fictive temperatures of various as-received silica glasses were determined.

Hydrophobic silica aerogels

Abstract: Hydrophobic silica aerogels were produced by the -Si(Me)3 (trimethylsilyl substituent: TMS) modification of alcogels followed by CO2 supercritical drying. The structure of trimethylsilyl modified silica aerogel (TMSA) was the silica matrix produced by hydrolysis and condensation of only tetramethoxysilane (TMOS). TMS was modified on the surface of the silica matrix. TMSA was extremely moisture-resistant. The density, size, and transparency of TMSA samples were maintained after the moisture-resistance test. The moisture-resistance of trimethylsilyl modified silica aerogels (TMSAs) was superior to that of conventional aerogels supercritically dried by the ethanol method. Another feature of TMSA was the small shrinkage during supercritical drying. The shrinkage ratio of TMSA was less than 3% by comparison with about 5% for conventional aerogels. TMSA had the same transparency as conventional aerogels, with a transmittance of 90% at a thickness of 1 cm. The existence of TMS was observed using infrared, 13C nuclear magnetic resonance (NMR) and 29Si NMR.

Luminescence quenching by OH groups in highly Er-doped phosphate glasses

Abstract: Highly (up to 4 mol% Er2O3) Er-doped phosphate bulk glasses have been prepared by common glass-melting techniques. Afterwards, a heat treatment was performed on the as-melted samples. The photoluminescence lifetime of Er ions for the 4I132–4I152 transition increases substantially, typically from 3 ms up to 7 ms for a sample doped with 2 mol% Er2O3, due to the heat treatment. The increase of the lifetime is ascribed to a decrease in concentration of hydroxyl groups incorporated in the glass, which is confirmed by IR absorption spectroscopic measurements. The photoluminescence peak intensity also increases because of drying by a factor of 3 to 7 depending on glass composition. Based on electric dipole-dipole interaction theory, the luminescence concentration quenching mechanism by hydroxyl groups is modelled. The model predicts that more than half of the hydroxyl groups in the glass is coupled to Er ions. The influence of the glass structure and role of Al3+ on the Er3+ luminescence is studied by infrared spectroscopy.

Amorphous silica studied by high energy X-ray diffraction

Abstract: The use of hard X-rays (60–300 keV) for diffraction studies of disordered materials has several advantages: higher resolution in direct space, smaller correction terms, removal of truncation effects, the possibility for operating in extreme environments and for direct comparison between X-ray and neutron data. A feasibility study of amorphous silica has been performed at 95 keV, using a wiggler synchrotron beam-line at HASYLAB and a cylindrical sample, 3 mm in diameter. The range of Q between 0.8 and 32 A−1 was covered. A thorough discussion of the experimental challenges is given. The resulting systematic error intrinsic to the scattering process (not including errors in the form-factors) is found to be of the order of 0.2%. The data have been analyzed in terms of a model of the short-range order. The OSiO bond angle distribution is found to be nearly Gaussian, centered around 109.3(3)° with a rms value of 4.2(3)°. For the SiOSi bond angle, several types of distribution V(α) = V1(α) sin(α) were investigated. Best fits were obtained for rather broad distributions with V having its maximum at 147° and V1 at 180°.

Water diffusion into silica glass: Structural changes in silica glass and their effect on water solubility and diffusivity☆

Abstract: Infrared spectroscopy was used to measure structural changes, water surface concentrations and effective hydroxyl diffusion coefficients in silica glass during isothermal hydration heat-treatments at temperatures from 80 to 1150°C in 0.467 atm of water vapor. The observed glass structural changes were determined to be identical to relaxation during annealing, and it was found that infrared spectrometry may be used to measure glass fictive temperatures. Minute amounts of water had a pronounced accelerating effect on structural relaxation, and relaxation, in turn, affected the water content of the glass in three ways: (1) slow relaxation at low temperatures hindered the glass-water reaction or caused a slow increase of the reaction equilibrium constant; (2) expansion of the glass during water entry allowed an increase of the molecular water solubility; and (3) healing of the glass during bulk relaxation caused a decrease of the hydroxyl solubility. These processes occurred at different rates causing a peculiar increase and then decrease with time of both the surface hydroxyl concentration in thick specimens and total hydroxyl uptake in thin specimens. This observation was used to demonstrate that hydroxyl solubility measurements taken below 850°C by other researchers are not true equilibrium solubilities. Additionally, the kink at 550°C in the Arrhenius plot of Deff,OH as observed by Wakabayashi and Tomozawa in 1989 was found to be a time-dependent phenomenon which is explained in terms of slow glass-water reaction during relaxation. Diffusion of water into silica glass is therefore suggested to be bounded by two extremes: a high-temperature (> 850°C)/long-time extreme where relaxation and reaction are faster than diffusion and water diffuses according to the Doremus model and a low-temperature/short-time extreme in which relaxation and reaction are slower than diffusion and water penetration is limited only by the diffusion coefficient of molecular water in the glass.

Shrinkage during drying of silica gel

Abstract: A model is provided for predicting gel shrinkage during drying by combining the empirical observations that: (1) the bulk modulus of a gel increases with density, ρ, according to K p = K 0 ( ρ ρ y ) m (2.5 ≤ m ≤ 4) ; and (2) the variation in pore radius, r, is approximately proportional to pore volume (contrary to the dependence, r α ρ −1 3 , conventionally assumed). No allowance is made for viscoelastic relaxation, so the model applies only for drying from an inert solvent. The model may be used to guide processing efforts to yield either aerogel-like materials with high porosity or xerogels with high density and small pore size for adsorbents, membranes, etc. The extent of shrinkage is governed by two dimensionless parameters, P and m. The quantity P = As γ cos (θ)mρ y K 0 (where As is specific surface area, γ is surface tension, and θ is the contact angle) represents the relative magnitudes of capillary pressure and gel stiffness, and m describes the variation of stiffness with density. For P values less than 1, the shrinkage upon drying is less than 10%, and is reversible. For shrinkages greater than ⋍ 50%, the density increase is irreversible, and is proportional to P 1/(m - 1). Predicted shrinkage is compared with experimental results for silica gels dried from different surface tension pore fluids (2

NMR investigation of the structure of some bioactive and related glasses

Abstract: A magic angle spinning nuclear magnetic resonance (MAS-NMR) investigation of the environments of 29 Si, 31 P and 23 Na, in glasses from the Na 2 OCaOSiO 2 (6 wt% P 2 O 5 ) system, has shown that the distribution of non-bridging oxygens can be described by a binary distribution of Q 2 and Q 3 silicon species. The changes in the chemical shifts of these two species with composition are interpreted as resulting from the preferential association of Na + with Q 3 and Ca 2+ with Q 2 . It is suggested that it is this partitioning that determines bioactivity by controlling the dissolution, hydrolysis and condensation reactions which occur at the interface between the glass and the physiological environment.

Optical properties of transparent glass-ceramics in K2ONb2O5TeO2 glasses

Abstract: Transparent glass-ceramics consisting of a cubic crystalline phase with crystallites having diameters between 20 and 40 nm in the composition of 15K2O15Nb2O570TeO2 (mol%) have been fabricated. A phase with cubic structure is formed by post-heat-treatment at around 390°C for 1 h and transforms into a stable phase at temperatures above 450°C. The glass-ceramics consisting of a stable crystalline phase are opaque. The transparency of glass-ceramics is attributed to a small particle size (average radius: 10–20 nm) of the cubic crystalline phase. The optical and dielectric properties for the transparent glass-ceramics obtained by heat-treatment at 425°C for 1 h are: refractive index, n = 2.11 ± 0.02; relative permittivity (1 kHz, 300 K), ϵr = 44 ± 1 and third-order non-linear optical susceptibility, χ(3) = 3.3 × 10−13esu. These values are larger than those for the original base glass, i.e. n = 2.02 ± 0.02, ϵr = 28 ± 1 and χ(3) = 0.9 × 10−13esu. Second-harmonic generation is clearly observed in transparent glass-ceramics. These transparent glass-ceramics have a potential as a new type of non-linear optical material.

Silica aerogel captures cosmic dust intact

Abstract: The mesostructure of silica aerogel resembles strings of pearls, ranging in size from 10 to 100 A. This fine mesostructure transmits nearly 90% of incident light in the visible, while providing sufficiently gentle dissipation of the kinetic energy of hypervelocity cosmic dust particles to permit their intact capture. In 1987, silica aerogel was introduced as a capture medium to take advantage of its low density, fine mesostructure and, most importantly, its transparency, allowing optical location of captured micron sized particles. Without this feature, locating such captured particles in an opaque medium, e.g., polymer foams, is nearly impossible. The capture of hypervelocity particles has been extensively simulated in the laboratory. At the time of this symposium, more than 2.4 m2 of 20 mg/ml silica aerogel will have been flown on Space Shuttle (STS-47, STS-57, STS-60, STS-64 and STS-68). Demonstration of capturing hypervelocity particles ushers in a new, simple avenue to science in capturing intact cosmic dust from space. Since our introduction of aerogel for intact capture of cosmic dust, many useful features unique to aerogel have been identified.

Pr3+-doped GeGaS glasses for 1.3 μm optical fiber amplifiers☆

Abstract: The synthesis and optical properties of Pr-doped GeGaS glasses are reported. The radiative properties associated with the important 1G4 → 3H5 transition of Pr3+ at 1.3 μm have been determined by absorption and fluorescence measurements coupled with Judd-Ofelt analysis. As compared with ZBLAN glass, Pr-doped GeGaS glasses have a longer fluorescence lifetime and a larger stimulated emission cross-section, which are favorable for an efficient fiber amplifier. The concentration quenching of Pr3+ in these glasses has also been studied by fluorescence lifetime measurements.

Silica aerogel films at ambient pressure

Abstract: Silica films with refractive indices in the range of 1.006 – 1.036 (equivalent porosity 98.5–91%) have been prepared at ambient pressure by a process wherein organo-siloxane polymers are deposited on a silicon substrate by conventional dip-coating at 25°C and 0.85 bar (atmospheric pressure in Albuquerque) and heating to 450°C. The film thicknesses (from scanning electron microscopy) vary from 0.1 to 3.5 μm, depending upon the dip-coating rate (0.05 – 1.9 cm/s) and concentration of the sol. The process was optimized by varying the dilution, aging, organic modification, heat treatment and dip-coating conditions, allowing control of film porosity in the range ∼ 30–99%. Imaging ellipsometry has been used to study the evolution of film porosity and thickness in situ. It is observed that the high porosity in these films is mainly attributable to dilation or ‘springback’ of the film during the final stage of drying.

Preparation of low-density xerogels at ambient pressure

Abstract: For successful large-scale commercialization of aerogel technology to occur, aerogel costs must be dramatically reduced. Using a previously developed model for predicting gel shrinkage during drying, a number of approaches for producing aerogels under ambient pressure conditions are presented. The extent of drying shrinkage is governed by two parameters, the dimensionless group, P = Asγ cos(θ)mρ0/K0, which represents the relative magnitudes of capillary pressure and gel stiffness, and the parameter, m, which describes the stiffness variation with density. For P less than 1, the density increase upon drying is less than 10%. Necessary steps to produce aerogels which are commercially viable include: (1) the use of low-cost precursors such as sodium silicate; (2) the production of aerogel granules to greatly reduce diffusion and heat transfer-related process timescales; (3) development of a continuous aerogel process technology which employs a minimum of solvents (number and volume), does not require expensive high-pressure supercritical or surface modification techniques, which has short process times at each step and which is built upon existing unit operations. If possible, structural relaxation after the drying critical point should be enabled to yield lower density materials for a given P value.

New organic aerogels based upon a phenolic-furfural reaction☆

Abstract: The aqueous polycondensation of (1) resorcinol with formaldehyde and (2) melamine with formaldehyde are two proven synthetic routes for the formation of organic aerogels. A new type of organic aerogel based upon a phenolic-furfural (PF) reaction was recently discovered. This solgel polymerization has a major advantage over past approaches since it can be conducted in alcohol (e.g., 1-propanol), thereby eliminating the need for a solvent exchange step prior to supercritical drying from carbon dioxide. The resultant aerogels are dark brown in color and can be converted to a carbonized version upon pyrolysis in an inert atmosphere. Brunauer-Emmett-Teller (BET) surface areas of 350–600 m2/g have been measured, and transmission electron microscopy reveals an interconnected structure of irregularly shaped particles or platelets with ∼ 10 nm dimensions. Thermal conductivities as low as 0.015 W/m K have been recorded for PF aerogels under ambient conditions. Chemistry and structure-property relationships of these new materials are described.

Thin aerogel films for optical, thermal, acoustic and electronic applications

Abstract: Aerogels are a special class of continuously porous solid materials which are characterized by nanometer size particles and pores. Typically, aerogels are made using sol-gel chemistry to form a solvent filled, high porosity gel that is dried by removing the solvent without collapsing the tenuous solid phase. As bulk materials, aerogels are known to have many exceptional, and even some unique physical properties. Aerogels provide the highest thermal insulation and lowest dielectric constant of any other material known. However, some important applications require the aerogels in the form of thin films or sheets. For example, electronic applications require micrometer thin aerogel films bonded to a substrate, and others require thicker films, either on a substrate or as free standing sheets. Special methods are required to make aerogel thin films or sheets. In this paper, the authors discuss the special conditions needed to fabricate thin aerogel films and they describe methods to make films and thin sheets. They also give some specific applications for which aerogel films are being developed.

Compression of aerogels

Abstract: When an aerogel is pressurized in a mercury porosimeter, the network is compressed, but no mercury enters the pores. Therefore, porosimetry cannot be used to measure the pore size distribution in an aerogel, but it does provide a measure of the bulk modulus of the network. For silica aerogels, the network is linearly elastic under small strains, then exhibits yield followed by densification and plastic hardening. In the plastic regime it is found that the bulk modulus has a power-law dependence on density with an exponent of ≈ 3.2. For the same gels, the linear elastic modulus (before compression) also obeys a power law, but the exponent is ⋍ 3.6, as found by several other groups. If a gel is compressed to a pressure, P1, that exceeds the yield stress, then returned to ambient pressure, the plastic deformation is irreversible; if that gel is then compressed to pressure P2 > P1, it behaves elastically up to ⋍ P1, then yields and follows the same power-law curve. Thus the location of the yield point of a previously compressed material indicates the maximum pressure to which the sample had been subjected; in particular, the compression curve can be used to estimate the capillary pressure exerted on a xerogel during drying.

Optical properties of fluoride glasses: a review

Abstract: Current research activities on optical properties of fluoride glasses are reviewed; emphasis is given to the refractive-index dispersion and multiphonon absorption. The dependence of optical properties of fluoride glasses on their chemical composition has been summarized and interpreted under consideration of fluoride glasses as ionic substances in nature. The methods for calculating optical properties of fluoride glasses have been reviewed and a new calculation system for refractive-index dispersion and multiphonon absorption of fluoride glasses is proposed.

Glass ceramics: new compositions and uses

Abstract: Glass ceramics, materials prepared by the controlled crystallisation of glasses, have a variety of established uses dependent on their uniform reproducible fine-grain microstructures, absence of porosity and wide-ranging properties which can be tailored by changes in composition and heat treatment. Moreover, during manufacture complex shapes may be produced using standard glass-forming techniques prior to crystallisation and dimensional changes are small. In recent years, new compositions, processing methods and applications have begun to emerge. Among the recent developments considered are new phosphate-based compositions, the use of sol—gel processing, glass ceramic matrix composites, glass ceramics in microelectronics packaging, glass ceramics bonded to metals and as joining media, high-strength and high-toughness materials and machineable compositions.

Deformation of aerogels during characterization

Abstract: Aerogels have such low moduli that they can exhibit large strains under very small loads, and this leads to errors in measurements of porosity and pore size. The use of porosimetry, thermoporometry and nitrogen sorption on aerogels is examined and it is shown that all of these techniques underestimate the pore volume and pore size of typical aerogels. Even at the highest pressures there may be no intrusion of mercury at all, so porosimetry serves only to measure the bulk modulus of the aerogel network, not its pore size distribution; an analysis of the conditions for intrusion as a function of modulus and pore size of the gel is presented. Direct experimental observation of a silica aerogel indicates that its volume shrinks by ⋍ 50% as liquid nitrogen condenses in its pores. Consequently, it is likely that the quantity of macropores in aerogels has been seriously overestimated in the past.

Acoustic properties and potential applications of silica aerogels

Abstract: Acoustic properties of cylindrical silica aerogels in both ultrasonic and audible range are presented. Velocity measurements for low ultrasonic frequencies show that the low-density aerogels can exhibit unexpected attenuation for well-defined frequency bands. Measurements of the acoustical impedance of samples in the audible range show that the results depend dramatically on the geometry and/or the boundary conditions imposed to the samples. The ‘attenuation’ bands in which the samples present an unexpected high attenuation are related to the aerogel density. These particular results are discussed in two ways; first for application purposes and second in terms of a possible theoretical explanation. Neither the classical theory of propagation in a homogeneous material nor the Biot theory for porous materials can explain the results.

Ionic conductivities and structure of lithium phosphorus oxynitride glasses

Abstract: Lithium phosphorus oxynitride glasses with different lithium contents have been prepared by melting base glasses at high temperature in a flowing ammonia atmosphere for 16–72 h. The melt was then furnace-cooled to room temperature to avoid bubble formation in the sample. The structure of the lithium phosphorus oxynitride glasses was probed by X-ray photoelectron spectroscopy and high performance liquid chromatography. The results of ac impedance measurements show that nitrogen incorporation into the glass structure increases the ionic conductivity. The highest conductivity was found in Li0.99PO2.55N0.30 glass with σ ∼ 3.0 × 10−7 S cm−1 at 25°C and Ea = 0.60 eV.

Relationship between optical transparency and nanostructural features of silica aerogels

Abstract: Silica aerogels are considered to be of great promise for use in transparent thermal insulation systems in solar architecture. The optical transparency of these highly porous materials is influenced by the reaction parameters upon preparation and the precursor used. Previously it was shown that the specific extinction due to bulk scattering decreases both with increasing macroscopic density and increasing pH-value of the sol-gel starting solution. Recently, it was also found that within the measurement accuracy the light scattering intensity of the aerogel bulk equals the extrapolated small-angle X-ray scattering intensity towards scattering angle zero if both types of measurement are performed with respect to an absolute scale. In the meantime, ultra small-angle X-ray scattering measurements have been performed in order to close the gap in momentum space between light and conventional small-angle X-ray scattering. As a result it can be stated that the nearly isotropic (Rayleigh) scattering is caused by the same nanostructural inhomogeneities of the aerogel network which lead to the characteristic small-angle scattering pattern. As a consequence, the amount of isotropically scattered light and thus the optical extinction can be directly related to a quantity called the correlation volume. For a variety of silica aerogels, it is shown how the latter depends on the nanostructural features of the gel network, such as average particle size, interparticle arrangement, pore diameter and an ordering parameter, which accounts for concentration effects.

Monolithic silica aerogel insulation doped with TiO2 powder and ceramic fibers

Abstract: The thermal conductivities of silica aerogels doped with TiO2 powder and ceramic fibers were investigated by varying the gas pressure and the temperature. Doped SiO2 aerogel with a density of 260 kg m−3 has a thermal conductivity of 0.038 W m−1 K−1 at 800 K in air.

Transport properties of gas in silica aerogel

Abstract: The motion of gas molecules in silica aerogel is restricted by the solid silica matrix. As a result, the mean free path, velocity distribution function, diffusivity, viscosity and thermal conductivity are changed. In this work, relations for these quantities are derived for a gas in silica aerogel using an approach similar to that used for a gas in free space. Results for the mean free path predict that, for p ≥ 10 bar, the mean free path of the gas molecules in aerogel will be almost the same as in free space. However, as the pressure is reduced, the mean free path reaches a constant finite value instead of increasing as in free space. The thermal conductivity of a gas in aerogel starts to decrease at p = 10 bar and is almost negligible at 0.01 bar, while the thermal conductivity of a gas between parallel walls 1 cm apart starts to decrease at p = 10 −4 bar and is almost negligible at p = 10 −7 bar. The predicted thermal conductivity of a gas in aerogel is in good agreement with experimental results.

Modelling the silica glass structure by the Rietveld method

Abstract: To refine amorphous structures like crystalline ones is impossible. This statement needs now some reconsideration in the case of silica glass. Starting with a microstrained crystalline model deriving from the α-carnegieite structure, atomic coordinates refinements by the Rietveld method prove to be possible. The credibility of the study is supported by the simultaneous fit of neutron and X-ray diffraction data. The agreement R χ factors are the best ever obtained with a small-size model built exclusively from [SiO 4 ] tetrahedra linked by corners. However it is concluded that ‘best’ remains insufficient.

Vibrational properties of SiO and SiH in amorphous SiOx:H films (0 ≤ x ≤ 2.0) prepared by plasma-enhanced chemical vapor deposition☆

Abstract: The stretching and bending absorptions arising from SiO and SiH bonds in amorphous SiOx:H films, prepared by rf glow discharge decomposition of a SiH4O2 mixture at 300°C, have been investigated by infrared absorption measurements as a function of the O content, x. Changes in the profiles of the SiH stretching absorption as a function of x were examined on the basis of a random-bonding model. A charge-transfer model is employed to derive the oscillator strength of the SiH stretching absorption and the peak frequencies of the SiH and SiO stretching absorption, for the Si(Si4−nOn)(n = 1−4) and HSi(Si3−nOn)(n = 0−3) bonding configurations. The absorption over the range 500–900 cm−1, related to the SiH and SiO bending motions, can be decomposed into five components around 650, 780, 800, 840 and 880 cm−1. It is found that the intensities of the 780, 840 and 880 cm−1 bands are closely correlated with those of the SiH stretching absorptions at 2115, 2200 and 2260 cm−1, respectively. The origins of these absorption bands along with the 650 and 800 cm−1 bands are discussed.