Oxide impurity absorptions in Ge-Se-Te glass fibres

Oxide impurity absorptions in Ge-Se-Te glass fibres and the cause of the absorption loss around 943 cm^–1, the frequency of the CO² laser, have been investigated. The oxygen in the glass bounds preferentially to germanium and causes the absorptions due to Ge-O bond vibrations at 765 cm^–1 (band I) and 1230cm^–1 (band II). The excess absorptions due to these bands were determined as 0.228cm^–1/P.p.m. wt O₂ for band-I and 0.006cm^–1 /p.p.m. wt O₂ for band II. The loss of the fibre at 943cm^–1 increased with the oxygen content. It was, however, revealed from the deconvolution of the IR spectra into the independent absorption components that the absorption tails of band I and band II did not affect the loss at 943 cm^–1. The content of the impurities except oxygen analysed by a mass spectroscopy was too low to affect the loss at 943 cm^–1.     

Effect of Oxygen Impurity on the Optical Transmission of As2Se3.4Glass

As₂Se_3.4glass samples with controlled oxygen content in the range (1.4–7.9) × 10^–2wt % were used to assess the effect of oxygen impurity on the IR absorption spectrum of the glass. The spectral dependence of the extinction coefficient for oxygen impurity was determined in the range 600–1400 cm^–1. It was shown that the presence of 10^–5wt % O gives rise to additional losses comparable to the intrinsic losses in the CO₂lasing range.     

Optical absorption spectra studies for amorphous Cu2O-Bi2O3 glass system

Infrared absorption spectra were measured in the spectral range 4000–200 cm^–1 for the Cu₂O-Bi₂O₃ glass system. Strong bands were observed around 436–477, 600–632, 700–715, 810–875, 975–1000, 1550–1610 and 3225–3510 cm^–1 which are due to harmonics of the Bi-O-Bi stretching vibration, Cu-O stretching vibrations, O-Bi-O stretching vibrations, O-Bi-O bending vibrations, Bi-O stretching vibrations, free H₂O normal-mode bending vibrations and free H₂O molecules or OH^– ions, respectively. Quantitative justification of these absorption bands shows that the values of the experimental wave number for most recorded absorption bands agree well with the theoretical ones.The optical absorption spectra were recorded for the same glass system in the spectral range 300–700 Nm. These records show that the absorption edge has a tail extending towards lower energies. The edge shifts towards lower energies with increasing Cu₂O content. This shift is mostly related to the structural rearrangement and the relative concentrations of the glass basic units. By increasing the Cu₂O content, the optical energy gap decreases, while the width of the localized states increases.     

Effect of Electron Irradiation on the 77-K Band Gap of Rutile

The diffuse reflectance spectrum of powder TiO₂ (rutile) is measured from 0.36 to 0.9 m at 77 K before and after electron irradiation. The 77-K band gap of rutile is determined to be 3.0–3.02 eV. Irradiation with 30-keV electrons to a fluence of 10¹⁷ cm^–2 has no effect on the band gap of rutile. Reflectance data attest to the presence of two absorption bands near the intrinsic edge. The strength of these absorptions correlates with the radiation hardness of rutile.     

Effect of neutron irradiation on the high-frequency IR spectra of quartz glass

We have studied the effect of neutron irradiation in a nuclear reactor on the high-frequency IR absorption spectra of quartz glasses. Three groups of bands were identified in the range 1400–2300 cm^?1 (at 1610, 1910, and 2270 cm^?1), and one group, in the range 2870–2970 cm^?1. The effects of neutron dose, ambient atmosphere, and sample geometry on these bands have been assessed. The results have been correlated with the irradiation-induced changes in the fundamental modes of the glass network and the luminescent and structural properties of the glasses. Mechanisms have been proposed for the radiation-induced changes in the spectral characteristics of some of the absorption bands. We assume activation of some combined frequencies at v > 1400 cm^?1 and local vibrations in the impurity region of the spectrum. High neutron doses produce marked changes in the IR spectrum, which seem to be associated with structural changes in the glass. The likely mechanism of such changes is discussed.     

IR study of Pb-Sr titanate borosilicate glasses

The infrared spectra (IR) of various glass compositions in the glass system, [(Pb _x Sr_1−x )O·TiO₂]-[2SiO₂·B₂O₃]-[BaO·K₂O]-[La₂O₃], were recorded over a continuous spectral range (400–4000 cm⁻¹) to study their structure systematically. IR spectrum of each glass composition shows a number of absorption bands. These bands are strongly influenced by the increasing substitution of SrO for PbO. Various bands shift with composition. Absorption peaks occur due to the vibrational mode of the borate network in these glasses. The vibrational modes of the borate network are seen to be mainly due to the asymmetric stretching relaxation of the B-O bond of trigonal BO₃ units. More splitting is observed in strontium-rich composition.     

A study on interfacial mechanisms and structure of poly(ethylene-co-methacrylic acid)/copper with reflection–absorption infrared spectroscopy

The interfacial mechanism and structure of poly(ethylene-co-methacrylic acid)/copper were investigated using reflection-absorption infrared spectroscopy (RAIR). Based on IR spectrum of EMAA/copper, a strong absorption peak appearing at approximate 1,600 cm⁻¹ is attributed to the asymmetric stretching vibration of COO^― (υCOO_as^―) and a relatively weak absorption band at 1,375 cm⁻¹ is assigned to the symmetric stretching vibration of COO^― (υCOO_s^―). Therefore, it can be determined that copper interacts with EMAA through a strong ionic interaction and carboxylate structure is formed in the interfacial regions. And, according to the band intensities of carboxylate stretching modes and different sensitivities of RAIR to perpendicular and parallel transition moments, it can be concluded that EMAA is absorbed onto a copper substrate with a configuration in which the twofold axis of the C_2υ point group for carboxylate group inclines certain degree from the normal to the surface. In addition, the interfacial carboxylate structure of EMAA/copper is confirmed to be a monodentate one through calculating the difference (Δυ)between the asymmetric carboxylate stretch (υCOO_as^―) and the symmetric stretch (υCOO_s^―).     

Infrared spectra and composition dependence investigations of the vitreous V2O5/P2O5 system

A series of glasses in the V₂O₅-P₂O₅ system was prepared and their compositions analysed. The glass densities and molar volumes were determined. The results obtained revealed three compositional regions. In addition, the infrared absorption spectra of these glasses were measured at room temperature in the frequency range 1600–200 cm^–1. The compositional dependence of the bands present, attributed to a given band and mode of vibration, was investigated. However, the infrared data confirmed the results obtained from the density and molar volume measurements.     

Raman microscopy study of basic aluminum sulfate

The tridecameric aluminum polymer [AlO₄Al₁₂(OH)₂₄(H₂O)₁₂]⁷⁺ was prepared by forced hydrolysis of Al³⁺ up to an OH/Al molar ratio of 2.2. Upon addition of sulfate the tridecamer crystallised as the monoclinic basic aluminum sulfate Na_0.1[AlO₄Al₁₂(OH)₁₂(H₂O)₁₂](SO₄)_3.55. These crystals have been studied using FT-Raman microscopy and compared to the basic aluminum nitrate, Na₂SO₄·xH₂O and Al₂(SO₄)₃·xH₂O. The Raman spectrum of basic aluminum sulfate is dominated by two broad bands which are assigned to the ₁ and ₃ bands at 981 and 1051 cm^{– 1} of the sulfate group in the Al₁₃ sulfate structure. Furthermore the band at 724 cm^{– 1} is assigned to an Al–O mode of the polymerised Al–O–Al bonds in the Al₁₃ Keggin structure. The sharp band at 1066 cm_{– 1} and the minor band at 1384 cm^{– 1} are interpreted to be due to a small amount of nitrate impurity on a different position in the structure than the nitrate present in the Al₁₃ nitrate crystal structure, based on the shift in band position of both the ₁ symmetric stretching and ₃ asymmetric stretching modes.     

Piezo-spectroscopic behavior of the emission bands of α-alumina in the 13900–14250 cm<Superscript>− 1</Superscript> spectral range

The emission spectrum of -alumina in the spectral range between 13900 and 14250 cm^–1 is characterized by several bands which are much weaker than the two intense and sharp R1 and R2 bands appearing at 14400 and 14430 cm^–1, respectively; these latter are known as Ruby lines and they are the emission bands used in the Ruby laser. Furthermore these bands shift in frequency with stress (Piezo-Spectroscopic effect). In this paper, for the first time, the stress-dependent peak frequency of the weaker bands in the 13900–14250 cm^–1 range is calibrated, and the results are presented as Piezo-Spectroscopic coefficients. The calibration is performed by reporting the frequency shift of each investigated band as function of varying stresses. The stresses, residual in nature, are obtained by fabricating composite materials where -alumina is mixed in various amounts with (i) Ceria-Stabilized Tetragonal Zirconia Polycrystals (Ce-TZP) and (ii) silicon carbide, SiC. The composite materials are prepared at high temperature (1500°–1800°C); due to the difference in thermal expansion, upon cooling to room temperature -alumina develops compressive and tensile stresses, when mixed with Ce-TZP and SiC, respectively. The stress values necessary for the calibration are obtained from the frequency shift of the R2 band, using its well-established Piezo-Spectroscopic coefficient (7.6 cm^–1/GPa). Then the newly obtained Piezo-Spectroscopic coefficients of the bands in the 13900–14250 cm^–1 range are tested to retrieve the stresses in two sets of composites; finally the stress values are compared with those obtained in the same samples from the frequency shift of the R2 band. The comparison shows a very good agreement, thus providing evidence that the bands in the 13900–14250 cm^–1 range can be used to monitor stresses in -alumina-based materials.     

Infrared spectra of silicon nanowires

Infrared (IR) spectra of the silicon nanowires (SiNWs) with oxide layer are analyzed by introducing the disorder-induced mechanical coupling between the optically active oxygen asymmetric stretch (AS) and inactive oxygen asymmetric stretch (I-AS) modes in terms of the transverse-optic (TO) and longitudinal-optic (LO) vibrational modes. The shapes of the IR spectra are similar to that of the reported SiO₂, indicating that the SiNWs possess an oxide layer outside. The TO frequencies of coupled AS and I-AS are experimentally observed as peak at approximately 1085 cm^− 1 and its shoulder of 1200 cm^− 1, respectively. The other TO absorption peaks of ∼ 468 cm^− 1, ∼ 480 cm^− 1, and ∼ 808 cm^− 1 are also observed. Furthermore, the intensity of the AS-mode TO band centered at ∼ 1085 cm^− 1 decreases while those of silicon lattice absorption peaks are enhanced with the crystalline quality increased.     

Cation distribution and infrared properties of NixMn1 ? xFe2O4 ferrites

The spinel ferrite system Ni _x Mn_{1 – x} Fe₂O₄, with x = 0, 0.1, 0.25, 0.5, 0.75 and 1, is prepared by the standard double sintering ceramic method. X-ray diffraction and IR spectroscopy are used to analyze the relationship between infrared properties and content of the nickel ions. With nickel ion substitution addition, the lattice parameter, X-ray density, cation distribution, inversion parameter and radius of octahedral and tetrahedral sites are calculated. The IR spectra obtained at room temperature in the frequency range 350–1000 cm^–1, show four absorption bands. The high frequency band (₁) and low frequency band (₂) are assigned to the tetrahedral and octahedral complexes, respectively. The relationship between bands and nickel content was also investigated and found that the absorption bands linearly increase with the increasing content of nickel ions, which is correlated to the cation distribution calculated by Bertaut method.     

Infrared and Raman spectra of new molybdenum and tungsten oxyfluoride glasses

The infrared (400–1200 cm^–1) and Raman (200–1150 cm^–1) spectra are reported for the new AO₃-BaF₂-RF glasses where A is molybdenum or tungsten and RF is the alkali fluoride LiF, NaF and mixed LiF-NaF respectively. The observed absorption bands of each glass series were assigned to their vibrational modes. This study has shown that structural units formed in these glasses include [MoO₄] and [WO₄] tetrahedra, [MoO₆], [WO₆], [MoF₆] and [WF₆] octahedra groups.     

An infrared study of the structure of GeO2-CeO2 thin films

The infrared spectra of amorphous thin films consisting of GeO₂ co-evaporated with CeO₂ are presented and interpreted in relation to the spectrum of the pure amorphous GeO₂ film. The lower frequency side of the broad absorption band within this spectrum peaking at 730 cm^–1 is believed to be due to defect centres similar to the O ₁ ^– and O ₃ ⁺ centres found in a-SiO₂. Absorption at higher frequencies within this band is due to the O stretch vibrations of the Ge-O-Ge linkage. After considering the vibrations of the O ₁ ^– and O ₃ ⁺ centres in detail, it is shown that the band at 495 cm^–1 cannot be due to either of these centres and must therefore by caused by some other reactive defect centres. The variation of the position of the 730 cm^–1 peak within the series of spectra is noted and probable explanations are offered. The optical absorption edge of a-GeO₂ thin film is compared with that of a-SiO and a possible explanation of the basic differences is proposed.     

Infrared absorption in thick film resistors

Infrared absorption in polymer and glass-based thick film resistors has been measured between 400 and 1500 cm^–1. Sample structures are discussed on the basis of X-ray, Fourier transform-infrared and resistance-temperature data. It is shown that in polymer-based thick film resistors, the particulate phase is mostly responsible for the infrared absorption between 400 and 900 cm^–1, whereas the infrared absorption at higher wave numbers is related to the continuous phase. In glass-based thick film resistors, absorption is mostly determined by the highly doped glass. The results indicate that thick film resistors can be used as an absorbent coating in the 400–1500 cm^–1 region by suitable selection of the continuous and particulate phases.     

FTIR investigation of structural modifications during low-temperature ageing of polycarbonate

Conformational changes are sought during low-temperature ageing of solution-cast films of BPA-polycarbonate, by observing the conformationally sensitive IR aromatic breathing band at 1600 cm^–1. Preliminary results using the carbonyl band at 1775 cm^–1 had shown some indication of ageing-induced changes in the distribution of conformations. The present results obtained on the 1600 cm^–1 band show no indication whatever of conformational rearrangements. This result, at variance with observations of conformational rearrangements accompanying sub-T _g annealing, lends support to the concept that sub-T _g annealing and low temperature ageing are two distinct processes.     

Infrared and Structural Properties of Y1?xNdxBa2Cu3O7?δ (0 ≤ x ≤ 1)

Infrared and structural properties of Y_1–x Nd _x Ba₂Cu₃O_7– (0 x 1) were investigated using infrared absorption spectroscopy and X-ray powder diffraction. The unit cell parameters of the samples were defined using X-ray diffraction data. The resistance measurements showed that the samples revealed superconductivity in the temperature range of 80–100 K. It was observed that by the substitution of Nd to Y in YBa₂Cu₃O_{7 –} IR band at 573 cm^–1 that is assigned as Cu–O axial antisymmetric stretching mode shifts to 533 cm^–1 while the band at 620 cm^–1 that is due to Cu–O symmetric stretching mode in YBa₂Cu₃O_7– shifts to 588 cm^–1.     

Raman microscopy study of basic aluminum sulfate Part II Raman microscopy at 77 K

The tridecameric aluminum polymer [AlO₄Al₁₂(OH)₂₄(H₂O)₁₂]⁷⁺ was prepared by forced hydrolysis of Al³⁺ up to an OH/Al molar ratio of 2.2. Upon addition of sulfate the tridecamer crystallised as the monoclinic basic aluminum sulfate Na_0.1[AlO₄Al₁₂(OH)₂₄(H₂O)₁₂](SO₄)_3.55. These crystals have been studied using Raman microscopy at 300 and 77 K and compared to Na₂SO₄·xH₂O and Al₂(SO₄)₃·xH₂O. The Raman spectrum of basic aluminum sulfate is dominated by two broad bands, which are assigned to the ₂ and ₄SO₄ ^2– triplets at 446, 459 and 496 cm^–1 and 572, 614 and 630 cm^–1. The ₁ is observed as a single band at 990 cm^–1, partly overlapped by the ₃ triplet at 979, 1009 and 1053 cm^–1 of the sulfate group in the Al₁₃ sulfate structure. Furthermore the band at 726 cm^–1 is assigned to an Al–O mode of the polymerised Al–O–Al bonds in the Al₁₃ Keggin structure. For the first time the OH-stretching region of the basic aluminum sulfate has been reported. The 77 K spectrum shows the presence of 3 crystal water bands at 3035, 3138 and 3256 cm^–1 accompanied by 3 Al–H₂O bands at 3354, 3418 and 3498 cm^–1 and 4 Al-OH bands at 3533, 3584, 3671 and 3697 cm^–1.     

Study of Mechanical Activation of Diopside in a CO2 Atmosphere

Interaction of natural diopside CaMgSi₂O₆ with CO₂ during mechanical activation in a CO₂ atmosphere has been studied. It has been shown that, depending on the kind of mechanical activator used, two types of CO₂ sorption by diopside are possible. If grinding is not accompanied by crystal structure disordering, the sorption of CO₂ on the diopside surface is similar to the sorption on metal oxides in the form of undistorted CO₃ ^2– groups, resulting in a nonsplit absorption band at 1430 cm^–1 in the infrared spectrum. If the mechanical activation of diopside leads to amorphization of the sample, it absorbs CO₂ in the form of distorted carbonate groups, which results in the appearance of a double carbonate band with maxima at 1433 and 1522 cm^–1 in the infrared spectrum of the ground sample. This band is similar to the one corresponding to CO₃ ^2– groups in the infrared spectra of carbonate-containing silicate glass. The carbonate content in the diopside sample reaches about 15% CO2 (or 35% CaCO₃) after mechanical activation in an AL-1000 activator in the CO₂ atmosphere for 580 min. X-ray diffraction, infrared spectroscopic data, carbonate content, and BET surface area measurements indicate that CO₂ molecules are likely to penetrate the structurally disordered diopside sample by a tribosorption mechanism. The results on the relaxation of the activated diopside sample during heating are presented.     

Redox behaviour of copper mordenite zeolite

Fourier transform-infrared photoacoustic spectroscopy (FT-IR/PAS) and X-ray diffraction (XRD) techniques have been used to study the reduction of copper (II) oxide supported on mordenite zeolite, through the adsorption of carbon monoxide and hydrogen gases at 723 K. It was found that bands due to the bridged hydroxyl groups (3614–3630 cm^–1) and the Al-OH groups (3780–3787cm^–1) show significant changes upon carbon monoxide and hydrogen adsorption whereas the Si-OH band did not change after the adsorption. Two further bands were detected at 2156 and 2297 cm^–1, assigned to carbon monoxide adsorbed on Cu⁺ species and on the copper-aluminate species, respectively. XRD patterns have demonstrated the proposed interaction between Cu²⁺ with aluminium mordenite, to form aluminate, whereas FT-IR spectra have established an interaction between carbon monoxide molecules and the aluminate species.