Investigation of synthetic Mg1.3V1.7O4 spinel with MgO inclusions: Case study of a spinel with an apparently occupied interstitial site

Hinako Uchida, Kevin Righter, Barbara Lavina, Matthew M. Nowell, Stuart I. Wright, Robert T Downs, Hexiong Yang

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

A magnesium vanadate spinel crystal, ideally MgV2O4, synthesized at 1 bar, 1200 °C and equilibrated under FMQ + 1.3 log fo2 condition, was investigated using single-crystal X-ray diffraction, electron microprobe, and electron backscatter diffraction (EBSD). The initial X-ray structure refinements gave tetrahedral and octahedral site occupancies of T(Mg0.9660.034) and M(V0.7113+ V0.1094+Mg0.180), respectively, along with the presence of 0.053 apfu Mg at an interstitial octahedral site (16c). Back-scattered electron (BSE) images and electron microprobe analyses revealed the existence of an Mg-rich phase in the spinel matrix, which was too small (≤3 μm) for an accurate chemical determination. The EBSD analysis combined with X-ray energy dispersive spectroscopy (XEDS) suggested that the Mg-rich inclusions are periclase oriented coherently with the spinel matrix. The final structure refinements were optimized by subtracting the X-ray intensity contributions (∼9%) of periclase reflections, which eliminated the interstitial Mg, yielding a structural formula for spinel TMgM(V1.3683+ V0.3164+Mg0.316)O4. This study provides insight into possible origins of refined interstitial cations reported in the literature for spinel, and points to the difficulty of using only X-ray diffraction data to distinguish a spinel with interstitial cations from one with coherently oriented MgO inclusions.

Original languageEnglish (US)
Pages (from-to)1031-1037
Number of pages7
JournalAmerican Mineralogist
Volume92
Issue number7
DOIs
StatePublished - Jul 2007

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spinel
interstitials
inclusions
periclase
x rays
Electron diffraction
electron probe analysis
electron
backscatter
diffraction
Cations
Electrons
electrons
cation
X-ray diffraction
crystal
cations
X ray diffraction
X rays
matrix

Keywords

  • Crystal chemistry
  • Electron backscatter diffraction
  • Inclusion
  • Periclase
  • Spinel
  • XRD

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics

Cite this

Investigation of synthetic Mg1.3V1.7O4 spinel with MgO inclusions : Case study of a spinel with an apparently occupied interstitial site. / Uchida, Hinako; Righter, Kevin; Lavina, Barbara; Nowell, Matthew M.; Wright, Stuart I.; Downs, Robert T; Yang, Hexiong.

In: American Mineralogist, Vol. 92, No. 7, 07.2007, p. 1031-1037.

Research output: Contribution to journalArticle

Uchida, Hinako ; Righter, Kevin ; Lavina, Barbara ; Nowell, Matthew M. ; Wright, Stuart I. ; Downs, Robert T ; Yang, Hexiong. / Investigation of synthetic Mg1.3V1.7O4 spinel with MgO inclusions : Case study of a spinel with an apparently occupied interstitial site. In: American Mineralogist. 2007 ; Vol. 92, No. 7. pp. 1031-1037.
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AB - A magnesium vanadate spinel crystal, ideally MgV2O4, synthesized at 1 bar, 1200 °C and equilibrated under FMQ + 1.3 log fo2 condition, was investigated using single-crystal X-ray diffraction, electron microprobe, and electron backscatter diffraction (EBSD). The initial X-ray structure refinements gave tetrahedral and octahedral site occupancies of T(Mg0.966□0.034) and M(V0.7113+ V0.1094+Mg0.180), respectively, along with the presence of 0.053 apfu Mg at an interstitial octahedral site (16c). Back-scattered electron (BSE) images and electron microprobe analyses revealed the existence of an Mg-rich phase in the spinel matrix, which was too small (≤3 μm) for an accurate chemical determination. The EBSD analysis combined with X-ray energy dispersive spectroscopy (XEDS) suggested that the Mg-rich inclusions are periclase oriented coherently with the spinel matrix. The final structure refinements were optimized by subtracting the X-ray intensity contributions (∼9%) of periclase reflections, which eliminated the interstitial Mg, yielding a structural formula for spinel TMgM(V1.3683+ V0.3164+Mg0.316)O4. This study provides insight into possible origins of refined interstitial cations reported in the literature for spinel, and points to the difficulty of using only X-ray diffraction data to distinguish a spinel with interstitial cations from one with coherently oriented MgO inclusions.

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