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An in situ neutron diffraction study of cation disordering in synthetic qandilite Mg2TiO4 at high temperatures

  • Hugh St. C. O’Neill , Simon A. T. Redfern EMAIL logo , Sue Kesson and Simine Short
Published/Copyright: March 31, 2015
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American Mineralogist
From the journal American Mineralogist Volume 88 Issue 5-6

Abstract

Temperature-dependent cation order-disorder has been studied in many 2+ - 3+ oxide spinels but 4+ - 2+ spinels have been found to be either completely normal or completely inverse when examined at room temperature. Here we report the temperature dependence of the cation distribution in the 4-2 spinel synthetic qandilite (Mg2TiO4) from in situ time-of-flight neutron powder diffraction experiments to 1416 °C. At room temperature, Mg2TiO4 is confirmed to have completely inverse cation distribution, with Ti atoms occupying half the octahedrally coordinated cation sites. Cation disordering becomes observable above about 900 °C, with 4% of the Ti occupying the tetrahedral site by 1416 °C. The rate of reordering on cooling is fast, such that high-temperature disorder is not preserved on cooling to room temperature. The thermodynamics of the change in cation distribution with temperature can be described by an enthalpy of Mg-Ti disorder of -46.1 ± 0.4 kJ/mol.

Received: 2002-6-7
Accepted: 2002-12-2
Published Online: 2015-3-31
Published in Print: 2003-5-1

© 2015 by Walter de Gruyter Berlin/Boston

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https://doi.org/10.2138/am-2003-5-615

Articles in the same Issue

  1. TEM study of mullite growth after muscovite breakdown
  2. The reduction of aqueous Au3+ by sulfide minerals and green rust phases
  3. Manganoan kinoshitalite in Mn-rich marble and skarn from Virginia
  4. Expandability of anchizonal illite and chlorite: Significance for crystallinity development in the transition from diagenesis to metamorphism
  5. X-ray absorption spectroscopy of silicates for in situ, sub-micrometer mineral identification
  6. Radiation damage in zircon
  7. Neutron and temperature-resolved synchrotron X-ray powder diffraction study of akaganéite
  8. Li-rich zincostaurolite and its decompression-related breakdown products in a diaspore-bearing metabauxite from East Samos (Greece): An EMP and SIMS study
  9. Olivine from planetary basalts: Chemical signatures that indicate planetary parentage and those that record igneous setting and process
  10. Observations on the relationship between crystallographic orientation and biasing in apatite fission-track measurements
  11. Borocookeite, a new member of the chlorite group from the Malkhan gem tourmaline deposit, Central Transbaikalia, Russia
  12. New thermochemical evidence on the stability of dickite vs. kaolinite
  13. Thermodynamics of Fe oxides: Part I. Entropy at standard temperature and pressure and heat capacity of goethite (α-FeOOH), lepidocrocite (γ-FeOOH), and maghemite (γ-Fe2O3)
  14. Thermodynamics of Fe oxides: Part II. Enthalpies of formation and relative stability of goethite (α-FeOOH), lepidocrocite (γ-FeOOH), and maghemite (γ-Fe2O3)
  15. An in situ neutron diffraction study of cation disordering in synthetic qandilite Mg2TiO4 at high temperatures
  16. Peristeritic plagioclase in North Sea hydrocarbon reservoir rocks: Implications for diagenesis, provenance and stratigraphic correlation
  17. Incorporation of Ni into natural goethite: An investigation by X-ray absorption spectroscopy
  18. Characterization of an early metamorphic stage through inclusions in zircon of a diamondiferous quartzofeldspathic rock from the Erzgebirge, Germany
  19. Gersdorffite (NiAsS) chemical state properties and reactivity toward air and aerated, distilled water
  20. The concentration and speciation of hydrogen in feldspars using FTIR and 1H MAS NMR spectroscopy
  21. The significance of mineral inclusions in large diamonds from Yakutia, Russia
  22. Letters. Evidence from surface phonons for the (2 × 1) reconstruction of the (101̄4) surface of calcite from computer simulation
  23. Transformation of SiO2 to the amorphous state by shearing at high pressure
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