A computation study of site occupancy in the commercial Mg28Ge7.55O32F15.04:Mn4+ phosphor

• First crystal field analysis of the Mn4+ energy levels in the commercial MFG phosphor was performed.
• Site occupancy problem for the Mn4+ impurity was solved.
• Mn4+ energy levels in all possible sites were calculated.
• The 2E–4A2 emission transition occurs at the highest energy in MFG among all known oxides.

This is the first attempt to provide detailed crystal field analysis of the Mn4+ energy levels in the commercial magnesium fluorogermanate (MFG) phosphor. The energy levels of the Mn4+ ion (3d3 configuration) were calculated for all available sites in the lattice and the results compared with the experimental spectroscopic data. It is concluded that the Mn4+ ions prefer to occupy the sixfold coordinated Ge1 and Mg2 sites of the MFG lattice. The ligand of the Ge1 and Mg2 sites is oxygen [Ge(1)O6 and Mg(2)O6]. The incorporation of fluorine ions in the host lattice does not change the covalence of the Mn4+ bonding. This can be understood on the basis of our computational result which focuses on the distribution of the Mn4+ ion among the available lattice sites.

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