Elaboration and Structural Investigation of Iron (III) Phosphate Glasses (original) (raw)
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Chemical durability and structure of zinc–iron phosphate glasses
Journal of Non-Crystalline Solids, 2001
The chemical durability of zinc±iron phosphate glasses with the general composition 40 À xZnO±xFe 2 O 3 ±60P 2 O 5 has been measured. The chemical durability and density of these glasses increase with increasing Fe 2 O 3 content. Glasses containing more than 30 mol% Fe 2 O 3 had an excellent chemical durability. The dissolution rate (DR), calculated from the weight loss in distilled water at 90°C for up to 32 days, was $10 À9 g=cm 2 = min which is 100 times lower than that of window glass and 300 times lower than that of a barium ferro, aluminoborate glass. The structure and valence states of the iron ions in these glasses were investigated using M ossbauer spectroscopy, X-ray diraction, infrared spectroscopy and dierential thermal analysis. X-ray diraction indicates that the local structure of the zinc±iron phosphate is related to the short range structures of crystalline Zn 2 P 2 O 7 , Fe 3 P 2 O 7 2 and FePO 3 3. Both Fe(II) and Fe(III) ions are present in all of these glasses. The presence of an Fe±O±P related band in the infrared (IR) spectra of the glasses containing more than 30 mol% Fe 2 O 3 is consistent with their excellent chemical durability.
Optical and structural investigations on iron-containing phosphate glasses
Journal of Materials Science, 2011
The article reports the preparation and complex characterization of iron-containing phosphate glasses considered to be ecological materials, as they contain non-toxic compounds related to environment. The oxide system Li2O–MgO–(CaO)–Al2O3–P2O5–(FeO/Fe2O3) was investigated in respect to its structural changes caused by MgO replacement with CaO and by the iron addition. UV–vis–NIR (ultraviolet–visible–near infrared) spectroscopy as well as thermo-gravimetric (TG) measurements, differential thermo-analysis (DTA), X-ray diffraction (XRD) analysis, electronic paramagnetic resonance (EPR), and Mossbauer (nuclear gamma resonance) spectroscopy have been used to investigate redox states and coordination symmetry of iron, together with vitreous network changes during the heat treatment up to 1000 °C. UV–vis–NIR transmission spectroscopy revealed no structural modifications when MgO was substituted by CaO, but noteworthy absorption bands attributed to Fe2+/Fe3+ species. TG analysis made in the 20–1000 °C range shows low weight loss accompanied by several thermal effects, as evidenced by DTA. XRD patterns for the glass samples heat treated at about 700 °C revealed the presence of different phosphate crystalline phases containing Mg, Al, and Fe ions. EPR spectroscopy revealed the presence of paramagnetic Fe3+ ions and the change of the first coordination symmetry, when the samples are heated below the vitreous transition temperature. Mossbauer spectroscopy has evidenced two paramagnetic species, Fe2+ and Fe3+, both in octahedral coordination symmetry and a clustering process supported by only Fe3+ ions.
Journal of Non-Crystalline Solids, 2002
The local environment around iron ions in iron phosphate glasses of starting batch composition 40Fe 2 O 3 -60P 2 O 5 (mol%) melted at varying temperatures or under different melting atmospheres has been investigated using Fe-57 M€ o ossbauer and X-ray absorption fine structure (XAFS) spectroscopies. M€ o ossbauer spectra indicate that all of the glasses contain both Fe(II) and Fe(III) ions. The quadrupole splitting distribution fits of M€ o ossbauer spectra show that Fe(II) ions occupy a single site whereas Fe(III) ions occupy two distinct sites in these glasses. When melted at higher temperatures or in reducing atmospheres, the Fe(II) fraction in the glass increases at the expense of Fe(III) ions at only one of the two sites they occupy. The pre-edge feature in the XAFS data suggests that the overall disorder in the nearneighbor environment of iron ions decreases with increasing Fe(II) fraction. The XAFS results also show that the average iron-oxygen coordination is in the 4-5 range indicating that iron ions have mixed tetrahedral-octahedral coordination. Ó
Iron phosphate glasses: Bulk properties and atomic scale structure
Journal of Nuclear Materials
Bulk properties such as glass transition temperature, density and thermal expansion of iron phosphate glass compositions, with replacement of Cs by Ba, are investigated as a surrogate for the transmutation of 137 Cs to 137 Ba, relevant to the immobilisation of Cs in glass. These studies are required to establish the appropriate incorporation rate of 137 Cs in iron phosphate glass. Density and glass transition temperature increases with the addition of BaO indicating the shrinkage and reticulation of the iron phosphate glass network. The average thermal expansion coefficient reduces from 19.8 Â 10 À6 K À1 to 13.4 Â 10 À6 K À1 , when 25 wt. % of Cs 2 O was replaced by 25 wt. % of BaO in caesium loaded iron phosphate glass. In addition to the above bulk properties, the role of Ba as a network modifier in the structure of iron phosphate glass is examined using various spectroscopic techniques. The Fe II content and average coordination number of iron in the glass network was estimated using M€ ossbauer spectroscopy. The Fe II content in the un-doped iron phosphate glass and barium doped iron phosphate glasses was 20, 21 and 22 ± 1% respectively and the average Fe coordination varied from 5.3 ± 0.2 to 5.7 ± 0.2 with increasing Ba content. The atomic scale structure was further probed by Fe K-edge X-ray absorption spectroscopy. The average coordination number provided by extended X-ray absorption fine structure spectroscopy and Xray absorption near edge structure was in good agreement with that given by the M€ ossbauer data.
Obtaining and characterization of calcium/magnesium/iron lithium phosphate glasses
2010
The paper reports a study on lithium phosphate glasses, containing calcium or magnesium and ferric/ferrous oxides. Iron oxides provide high chemical stability against water and enhance the glass capacity to embed different chemical compounds. The wet synthesis method provides an enhanced homogeneity of the glass batch and improves the optical quality of the glass samples. FTIR and Raman spectroscopy revealed the network former role of P2O5 as well as the modifier/former role of iron. The vibration mode shifted at 1250 cm -1 is attributed to the iron that enters into the phosphate network, forming Fe-O-P bonds instead of P-O-P bonds.
The structural dual role of Fe2O3 in some lead-phosphate glasses
Vibrational Spectroscopy, 2008
The FT-IR study of iron concentration effect on the xFe2O3·(1−x)[2P2O5PbO] glass system with 0≤x≤50mol% has revealed the dual role of Fe2O3 both as network modifier and former. The addition of iron oxide leads to more PO bond breakage and the formation of the P–O–Fe bonds. We concluded that at high content of Fe2O3 it acts in the structure of glasses
The glass formation and crystallization studies on iron phosphate–silicate glasses
Journal of Thermal Analysis and Calorimetry
The assessment of impact of incorporation of various amount of Fe 2 O 3 at the expense of MgO and CaO on the glassy phase formation and thermal stability exhibited in P 2 O 5-SiO 2-K 2 O-MgO-CaO-Fe 2 O 3 system was carried out. The characteristic temperatures for iron phosphate-silicate glasses and glass-crystalline materials were designated from associated DSC curves. Selected samples were subjected to the process of induced crystallization, and products combined with particular exothermic effects were identified. Combination of DSC, XRD and SEM-EDS methods enabled to collect invaluable data concerning the course of crystallization of not only iron phosphate-silicate glasses subjected to the process of induced crystallization, but also glass-crystalline materials obtained directly through melt-quenched technique. The amount of particular crystalline products associated with selected devitrificates was determined via Rietveld technique. Results of the conducted study indicated that Fe 2 O 3 addition conduces to the decrease in crystallization temperatures and thermal stability which was reflected in calculated values of DT and K W parameters. Concomitantly, glass with 20 mol% iron (III) oxide addition exhibited significantly improved, distinctive thermal stability among the materials in the analyzed series. The connection of crystalline phases with gradual alterations in polymerization degree of glass matrix was also established. The performed study is a contribution to the knowledge of iron phosphate glasses family and associated glass-crystalline materials. Keywords Glass-forming ability Á Crystallization process Á Fe 2 O 3 Á Iron phosphate-silicate glasses & Justyna Kuczek
Iron valence and coordination in phosphate glasses as studied by optical spectroscopy
Journal of Non-Crystalline Solids, 1998
Optical spectroscopy was employed to study iron phosphate glasses of the general composition xFe2O3(100−x)P2O5 (14≤x≤47 mol%). Cation vibrational properties showed that iron is predominantly present as iron(II) in glasses of lower total iron content and as iron(III) in glasses of higher total iron content. In glasses containing 40 and 47 mol% Fe2O3 some of iron(III) ions changed from octahedral to
Redox effects on the structure and properties of Na-Mo-Fe-phosphate glasses
Journal of Non-Crystalline Solids, 2021
Na-Mo-Fe-phosphate glasses were prepared with reducing and oxidizing raw materials and the effects of the different Fe 2+ /Fe 3+ and Mo 5+ /Mo 6+ ratios on glass structure and properties were determined. Mössbauer spectroscopy confirms significantly greater concentrations of Fe 2+ ions in the reduced glasses and distorted Fe 3+ O 4 sites preferred over the Fe 3+ O 6 sites in the oxidized glasses. Raman spectroscopy reveals the presence of isolated Mo 6+ O 6 sites in the oxidized glasses, and highly distorted Mo 5+ O 5 sites in reduced Mo-rich glasses. The presence of specific Fe-and Mo-polyhedra is correlated with the average phosphate anion length, as characterized by high-pressure liquid chromatography. Generally, for the similar compositions, oxidized glasses have greater molar volumes than the reduced glasses, associated with the formation of isolated Mo 6+ O 6 octahedra and the absence of highly crosslinked Mo 5+ OPO 4 units. T g increases with increasing Fe 3+ fractions in the Fe-rich glasses, whereas for the Mo-rich glasses, T g increases with greater Mo 5+ fractions.