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Investigation of Synthetic Mg(1.3)V(1.7)O4 Spinel with MgO Inclusions: Case Study of a Spinel with an Apparently occupied Interstitial SiteA magnesium vanadate spinel crystal, ideally MgV2O4, synthesized at 1 bar, 1200 C and equilibrated under FMQ + 1.3 log f(sub o2) condition, was investigated using single-crystal X-ray diffraction, electron microprobe, and electron backscatter (EBSD). The initial X-ray structure refinements gave tetrahedral and octahedral site occupancies, along with the presence of 0.053 apfu Mg at an interstitial octahedral site . 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 (less than or equal to 3microns) for an accurate chemical determination. The EBSD analysis combined with X-ray energy dispersive spectroscop[y (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 (approx. 9%) of periclase reflections, which eliminated the interstitial Mg. This study provides insight into possible origins of refined interstitial cations reported in the 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.
Document ID
20080014310
Acquisition Source
Johnson Space Center
Document Type
Preprint (Draft being sent to journal)
Authors
Uchida, Hinako
(Arizona Univ. Tucson, AZ, United States)
Righter, Kevin
(NASA Johnson Space Center Houston, TX, United States)
Lavina, Barbara
(Nevada Univ. Las Vegas, NV, United States)
Nowell, Matthew M.
(EDAX-TSL Draper, UT, United States)
Wright, Stuart I.
(EDAX-TSL Draper, UT, United States)
Downs, Robert T.
(Arizona Univ. Tucson, AZ, United States)
Yang, Hexiong
(Arizona Univ. Tucson, AZ, United States)
Date Acquired
August 24, 2013
Publication Date
January 1, 2007
Subject Category
Geosciences (General)
Distribution Limits
Public
Copyright
Other

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