Structural role and coordination environment of Fe in Fe2O3–PbO–SiO2–Na2O composite glasses (original) (raw)
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J. Non-Crystalline Solids 353 pp. 2717-2733 (2007)
The effect of the composition and casting temperature on the structural role of Fe in a series of binary (Fe 2 O 3 -PbO and Fe 2 O 3 -Na 2 O) and ternary (Fe 2 O 3 -PbO-SiO 2 ) glass and glass ceramic materials is studied by means of X-ray fluorescence (XRF) mapping, X-ray absorption fine structure (XAFS) and Mö ssbauer spectroscopies. According to the Mö ssbauer results the majority of Fe exists in the Fe +3 state. The XRF maps reveal that Fe-rich islands evolve into the vitreous matrix of ternary samples that contain more than 40 wt% Fe 2 O 3 . In these samples the XAFS results disclose that 40-43 at.% of the Fe atoms belong to the Fe-rich microcrystalline islands formed by Fe x O y oxides. Furthermore, the structural role of Fe +3 in the ternary glasses is found to depend on the Fe 2 O 3 content. Finally in the binary Fe 2 O 3 -PbO systems the majority of Fe +3 is octahedrally coordinated in the Fe 2 O 3 and/or PbFe 12 O 19 crystalline phases.
Effect of Fe 2O 3 concentration on the structure of the SiO 2–Na 2O–Al 2O 3–B 2O 3 glass system
Spectrochimica Acta Part A-molecular and Biomolecular Spectroscopy, 2011
The structural properties of the glass matrix 40SiO 2 ·30Na 2 O·1Al 2 O 3 ·(29 − x)B 2 O 3 ·xFe 2 O 3 (mol%), 0.0 ≤ x ≤ 29.0 were studied by X-ray diffraction (XRD), differential thermal analysis (DTA) and Raman and infrared spectroscopy (FT-IR). XRD demonstrated Fe 3 O 4 crystal formation for Fe 2 O 3 concentrations of 29.0 mol%. DTA showed that glass transition and crystallization temperatures changed as a function of Fe 2 O 3 concentration and that these alterations were related to structural change in the glass system. Interesting aspects of Raman and FT-IR spectra were found, and this gives information about of the structure changes in Si-O-Si units of these glasses as a function of Fe 2 O 3 concentration.
Studies of glass structure in the TeO2 Fe2O3 system
Materials Research Bulletin, 1979
Some structure characteristics of glasses in the TeO 2-Fe~O 3 system have been studied by means of Moessbauer and IR spectroscopy and positron annihilation.Discussion is been made about the character of the che -mica1 bonds and structuring of the glasses on the basis of the experimental data obtained. 735 736 V. KOZHUKHAROV, et al. Vol. 14,
Modification of the Fe-environment in Fe 2O 3 glass/glass ceramic systems containing Pb, Na and Si
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2006
The effect of composition and casting temperature on the microstructure and the oxidation state of Fe in a series of glass/glass ceramic materials that contain Fe2O3, PbO, Na2O and SiO2 is studied by means of X-ray fluorescence mapping (XRF), micro- (μ-) and conventional X-ray absorption fine structure (XAFS) and 75Fe Mössbauer spectroscopies. The Mössbauer results reveal that the majority of
Infrared spectra of FeO?PbO?PO glasses
Vibrational Spectroscopy, 2005
The structure of three Fe 2 O 3-PbO-P 2 O 5 glass groups has been investigated using IR spectroscopy. The intensity and frequency of the IR bands have been measured to follow the changes in the structural groups in the glass matrix. The spectral analyses revealed that the short-range order of the glassy matrix is strongly affected by the addition of PbO and/or Fe 2 O 3 to P 2 O 5 glass. The changes observed in IR spectra of PbO-P 2 O 5 glasses are related to the dual role of lead ions as a glass former and modifier. The results revealed that there are critical concentrations of Fe 2 O 3 at which iron ions change their local structure. The critical composition depends strongly on the content of both PbO and P 2 O 5 in glass. The fraction of P-O-P linkages is constant for O/P > 3, i.e. above the critical concentration of Fe 2 O 3 .
Journal of Non-Crystalline Solids, 2015
Sodium-alkaline earth-silicate glasses, of nominal molar composition 16Na 2 O-10RO-74SiO 2 (R = Ca, (Ca,Mg) and Mg) doped with 0.5 wt% of Fe 2 O 3 , were studied by UV-Visible-NIR absorption spectroscopy and electron paramagnetic resonance (EPR) at X-and Q-band to understand the structural control of Fe 3+ optical absorption properties as a function of iron redox and glass composition. By comparing with a set of [4] Fe 3+ , [5] Fe 3+ and [6] Fe 3+ crystalline references, optical absorption spectra indicate the presence of 5-fold Fe 3+ in addition to a majority of tetrahedral Fe 3+. The combination of Q-and X-band EPR data shows Fe 3+ partition among isolated, distributed sites and Ferich clusters, providing unique insight into the distortion of isolated Fe 3+ sites. It demonstrates also the peculiar character of the residual Fe 3+ sites that exist in reduced glasses. Changing Ca to Mg increases the amount of tetrahedral Fe 3+ sites and decreases their distortion. The presence of Mg also reduces the amount of isolated rhombic Fe 3+ sites and promotes the formation of clusters. These clusters confirm the non-homogeneous structure of silicate glasses, as well as the preference of Fe 3+ for a more calcic than magnesian environment in sodic (Ca,Mg) glasses.
Preparation and structural characterization of some Fe2O3-B2O3-ZnO glasses and glass ceramics
Journal of Physics Conference Series, 2009
X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy have been employed to investigate the (Fe 2 O 3) x •(B 2 O 3) (60-x) •(ZnO) 40 samples, with 0 ≤ x ≤ 20 mol%. The samples have been prepared by melting at 1100 °C for 10 minutes followed by rapid cooling at room temperature. The structure of samples was analyzed by means of XRD. XRD pattern show that the sample without iron ions and the samples contained 3 and 5 mol% were glasses. For samples contain 10, 15 and 20 mol% Fe 2 O 3 it obtains glass ceramics. These glass ceramics contains a unique crystalline phase, zinc ferrite (ZnFe 2 O 4), embedded in an amorphous matrix. FTIR spectroscopy data suggest that for the glass samples the iron ions play the network modifier role. These data show that the glass network consists of BO 3 and BO 4 structural units. For glass ceramics samples FTIR spectra show characteristic bands of ZnFe 2 O 4 .
Influence of iron ions on the structural properties of some inorganic glasses
Journal of Radioanalytical and Nuclear Chemistry Articles, 1987
The effects of iron on the structural properties of Zn-borosilicate glass and Pb-metaphosphate glass were studied using X-ray diffraction,57Fe Mössbauer spectroscopy and IR spectroscopy. Zn-borosilicate glass was prepared with varying amounts of Fe2O3 (up to 30% wt.). It was found that the chemical form of added iron (-FeOOH, -Fe2O3 or Fe3O4) affects the Fe3+/Fe2+ ratio, as well as the distribution of iron ions at different coordination sites. At high concentration of iron the crystallization of zinc ferrite in the glass matrix takes place. X-ray diffraction and57Fe Mössbauer spectroscopy showed that the amount of zinc ferrite in Zn-borosilicate glass decreases with the following order of addition: -FeOOH-Fe2O3Fe3O4. In Pb-metaphosphate glass doped with high concentration of -Fe2O3, the crystallization of Fe3(PO4)2 is pronounced. The assignments of IR band positions and the corresponding interpretation are given. The importance of this study for the technology of vitrification of high-level radioactive wastes is emphasized.
Structure of NaFeSiO4, NaFeSi2O6, and NaFeSi3O8 glasses and glass-ceramics
American Mineralogist
The crystallization of iron-containing sodium silicate phases holds particular importance, both in the management of high-level nuclear wastes and in geosciences. Here, we study three as-quenched glasses and their heat-treated chemical analogs, NaFeSiO4, NaFeSi2O6, and NaFeSi3O8 (with nominal stoichiometries from feldspathoid, pyroxene, and feldspar mineral groups, i.e., Si/Fe = 1, 2, and 3, respectively) using various techniques. Phase analyses revealed that as-quenched NaFeSiO4 could not accommodate all Fe in the glass phase (some Fe crystallizes as Fe3O4), whereas as-quenched NaFeSi2O6 and NaFeSi3O8 form amorphous glasses. NaFeSi2O6 glass is the only composition that crystallizes into its respective isochemical crystalline polymorph, i.e., aegirine, upon isothermal heat-treatment. As revealed by Mössbauer spectroscopy, iron is predominantly present as fourfold-coordinated Fe3+ in all glasses, though it is present as sixfold-coordinated Fe3+ in the aegirine crystals (NaFeSi2O6), a...
Structure–property relationships in multicomponent oxide glasses
Comptes Rendus Chimie, 2002
Cations play a complex structural role in oxide glasses, as they occur in different kinds of environments, which allow them to exert a contrasted influence on physical and chemical properties of these glasses. The combination of structural information given by a wide range of spectroscopic methods and by radiation scattering, combined with numerical modelling, has given insight on the structural organisation around these cations. Among these characteristic properties are unusually low-coordination numbers, such as 5-fold coordination, and the presence of extended ordered domains, in which cation polyhedra are edge-or corner-sharing. This review presents evidence for a structural control of several physical and chemical properties in oxide multicomponent glasses. The use of zinc as a stabilising glass component arises from its network-forming position, which implies the presence of low-charge cations in its surrounding and as a consequence decreases the concentration of modifier components. The compositional dependence of glass coloration by transition elements has been investigated thoroughly through the example of nickel in silicate and borate glasses. The wide range of coloration observed may be explained by the existence of three kinds of environments, with nickel occurring in 4-, 5-, and 6-coordination. The relationships of these sites with the medium-range organisation of the glasses have been understood by a combined use of EXAFS spectroscopy and neutron scattering with isotopic substitution. The two other examples that are presented to illustrate structureproperty relationships concern the physical solubility of gazes in glasses and the alteration processes of glasses used as analogues of nuclear waste matrices. In this last example, the use of structural probes as zirconium illustrates the influence of the alteration solution on the process of glass corrosion and further development of a gel at the glass-solution interface. A comparison with the evolution of the surrounding of iron shows that the two major processes, hydrolysis/condensation and dissolution/precipitation, depend on the element considered. To cite this article: G.