A computation study of site occupancy in the commercial Mg₂₈Ge_7.55O₃₂F_15.04:Mn⁴⁺ phosphor

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.