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  • 1
    Electronic Resource
    Electronic Resource
    High pressure X-ray diffraction study of ilvaite CaFe 2 2+ Fe3+[Si2O7/O/(OH)] (1993)
    Springer
    Physics and chemistry of minerals 20 (1993), S. 402-406 
    Details
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract An in situ high pressure X-ray diffraction study on synthetic pure ilvaite powder has been performed using a diamond anvil cell. A phase transition from monoclinic to orthorhombic (Pbnm) has been observed at 2.25 Gpa, which can be described as a λ-transition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00203109
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Crystallographic phase transition and valence fluctuation in synthetic mn-bearing ilvaite CaFe2+ 2-x Mn2+ xFe3+ [Si2O7/O/(OH)] (1992)
    Springer
    Physics and chemistry of minerals 18 (1992), S. 491-496 
    Details
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract The dependence of the electronic and the crystallographic structure on temperature of synthetic Mnbearing ilvaites CaFe2+ 2-xMn2+ xFe3+ [Si2O7/O/OH] with 0≤x≤0.19 has been investigated. The change of the electronic structure was studied by 57Fe Mössbauer spectroscopy. The spectra show an increasing valence fluctuation rate between Fe2+ and Fe3+ in the double chain of edge-sharing octahedra with increasing temperature resulting in a mixed valent state of iron. The valence fluctuation rate is distinctly increased by the Mnsubstitution. The temperature of the crystallographic phase transition T x as studied by a high temperature Guinier method is distinctly lowered by the Mn-substitution (x = 0.0, T x=390K; x = 0.12, T x =370K; x = 0.19, T x=295K). The reasons for this behaviour are discussed in terms of Fe2 +, Fe3 + cation order-disorder, electronic relaxation rate, and relaxation of the lattice. In the monoclinic phase there is electron hopping between Fe2 +, Fe3 + pairs whereas in the orthorhombic phase there is extended electron delocalization via a narrow, d-band mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00205263
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  • 3
    Electronic Resource
    Electronic Resource
    Synthesis and characterization of Mn-bearing ilvaite CaFe 2−x 2+ MnxFe3+ [Si2O7/O/(OH)] (1989)
    Springer
    Mineralogy and petrology 40 (1989), S. 101-109 
    Details
    ISSN: 1438-1168
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Zusammenfassung Mn-haltiger Ilvait CaFe 2−x 2+ Mnx Fe3+ [Si2O7/O/(OH)] wurde unter hydrothermalen Bedingungen bei Drucken von 2 und 3 kbar, Temperaturen zwischen 300 und 400°C und bei Sauerstoff Fugazitäten, die durch Festkörperpuffer (Fe2O3/Fe3O4 und Ni/NiO) kontrolliert wurden, hergestellt. Röntgenbeugungsuntersuchungen zeigen, daß mit steigendem Mn-Einbau der monokline Winkelβ kleiner wird, und daß bei x = 0.19 ein Phasenübergang von der monoklinen zur orthorhombischen Struktur erfolgt. Die Fe-Verteilung wurde mit Mössbauer-Spektroskopie bestimmt.
    Notes: Summary Synthesis of Mn-bearing ilvaites, CaFe 2−x 2+ MnxFe3+ [Si2O7/O/(OH)], with 0 ≤ x ≤0.19, have been performed under hydrothermal conditions at 2 and 3 kbars, T = 300 -400°C and at oxygen fugacities defined by the Fe2O3/Fe3O4 - and the Ni/NiO -buffer. As shown by X-ray diffraction, the substitution of Fe2+ by Mn2+ decreases the monoclinic angleβ and causes a phase transition from monoclinic to orthorhombic at x = 0.19. The Fe-distribution has been determined by Mössbauer spectroscopy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01164320
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  • 4
    Electronic Resource
    Electronic Resource
    Synthesis and characterization of themixed valent iron silicate ilvaite, CaFe3[Si2O7/O/(OH)] (1987)
    Springer
    Mineralogy and petrology 37 (1987), S. 97-108 
    Details
    ISSN: 1438-1168
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Zusammenfassung Das gemischt valente Eisensilikat Ilvait CaFe 2 2 +Fe3+ [Si2O7/0/(OH)] wurde unter hydrothermalen Bedingungen bei Temperaturen zwischen 300 und 500 °C, Drucken zwischen 1,5 und 4,0 Kbar und bei Sauerstoff-Fugazitäten, die durch Festkörperpuffer (Fe3O4/Fe2O3, Fe/Fe3O4 and Ni/NiO) kontrolliert wurden, hergestellt. Diese Ilvaite sind alle monoklin mit den Zellparameters a0=13,0065 (9) Å, b0 = 8,8073 (7) Å, c0 = 5,8580 (4) Å und β = 90,332 (6)°. Die Qualität der Proben wurde mit Mössbauer Spektroskopie überprüft. Rasterelektronenmikroskopische Aufnahmen zeigten idiomorphe Kristalle mit einer Größe bis 30 μ.
    Notes: Summary The mixed valent iron silicate ilvaite CaFe 2 2 +Fe3+ [Si2O7/O/(OH)] has been synthesized under hydrothermal conditions at temperatures between 300 and 500°C, pressures between 1.5 and 4 Kbars and oxygen fugacities controlled by the solid state buffers Fe3O4/Fe2O3, Fe/Fe3O4 and Ni/NiO. All these ilvaites are monoclinic (P21/a with cell parameters a0 = 13.0065 (9) Å, b0 = 8.8073 (7) Å, c0 = 5.8580 (4) Å, and β = 90.332 (6)°. The quality of the samples has been checked by Mössbauer spectroscopy. Scanning electron microscopic pictures show small euhedral crystals with a size up to 30 μ.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01164185
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