Crystal structures of Zn₂GeO₄ cubic/tetragonal spinel and Zn₂SiO₄ modified spinel phases

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Crystal structures of the cubic and tetragonal spinel phases of Zn₂GeO₄ and the modified spinel phase of Zn₂SiO₄ were refined by Rietveld analysis of synchrotron powder X–ray diffraction data. The Zn₂GeO₄ cubic spinel phase was found to have an inverse spinel configuration. The Zn₂GeO₄ tetragonal spinel phase is isostructural to Zn₂TiO₄, where half of Zn occupies the tetrahedral site, and the remaining Zn and Ge are ordered in two octahedral sites. In the modified spinel phase of Zn₂SiO₄, Zn occupies the octahedral sites. Independent individual cation–oxygen distances in the Zn₂GeO₄ tetragonal spinel and Zn₂SiO₄ modified spinel phases were calculated using the bond valence repartition method, and are in reasonable agreement with the refined structures.