Silicon coordination in rutile and TiO2-II at ambient and high pressures: Si-29 NMR

Jed L. Mosenfelder, Namjmjun Kim, Jonathan F. Stebbins

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The structural environment of silicon dissolved in rutile and α-PbO2-structured TiO2 (TiO2-II) was probed using 29Si MAS NMR on 29Si-enriched samples. At 1 atm, about 0.01 wt% SiO2 is incorporated into TiO2 as IVSi, presumably in interstitial sites. Rutile recovered from 6 GPa, 1600 °C contains about 0.6 wt% SiO2, incorporated both as VISi (∼90%) and IVSi (∼10%). TiO2-II, synthesized at 12 GPa, 1200 °C, contains only VISi. The chemical shift for VISi in TiO2-II is slightly less negative than that for rutile, and the peak is split, suggesting either a more complex mechanism of substitution or a different response to quenching or decompression in the lower-symmetry structure. Future thermodynamic studies of the TiO 2-SiO2 solid solution will have to take into account the mixed coordination environment of the Si in TiO2, at low pressures.

Original languageEnglish (US)
Pages (from-to)968-973
Number of pages6
JournalAmerican Mineralogist
Issue number7
StatePublished - Jul 1 2010


  • Crystal structure
  • High-pressure studies
  • NMR spectroscopy
  • Rutile
  • TiO-II

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