X-ray single-crystal structural characterization of MgCr2O4, a post-spinel phase synthesized at 23 GPa and 1600°Cстатья
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Дата последнего поиска статьи во внешних источниках: 20 мая 2014 г.
Аннотация:The crystal structure and chemical composition of a crystal of MgCr2O4 post-spinel phase synthesized in the model system Mg3Cr2Si3O12–Mg4Si4O12 at 23 GPa and 1600 1C have been investigated. Electron microprobe analysis confirmed the MgCr2O4 stochiometry of the studied phase. The compound was found to crystallize with the orthorhombic calcium-titanate (CaTi2O4) structure type, space group Bbmm, with lattice parameters a = 9.468(1), b = 9.670(1), c = 2.845(1) Å, V = 260.5(1) Å3, and Z¼4. The structure was refined to R1 = 0.046 using 286 independent reflections. Magnesium was found to fully occupy the eightfold-coordinated A site (with a mean bond distance of 2.289 Å) and Cr the octahedral B site (mean: 1.986 Å). The successful synthesis of MgCr2O4 with (CaTi2O4)-type structure and its structural character- ization demonstrate the stability of the new post-spinel phase. The absence of MgCr2O4 compounds with spinel structure coexisting with the post-spinel phase in theQ3 investigated run is discussed.