Manganese valence and coordination structure in Mn,Mg-codoped γ-AlON green phosphor

The valence and coordination structure of manganese in a Mn,Mg-codoped γ-AlON spinel-type oxynitride green phosphor were studied by synchrotron X-ray diffraction and absorption fine structure measurements. The absorption edge position of the XANES revealed the bivalency of Mn. Two cation sites are available in the spinel structure for cation doping: a tetrahedral site and an octahedral site. The pre-edge of the XANES and the distance to the nearest neighbor atoms obtained from the EXAFS measurement showed that Mn was situated at the tetrahedral site. Rietveld analysis showed that the vacancy occupied the octahedral site. The preferential occupation of the tetrahedral site by Mn and the roles of N and Mg are discussed in relation to the spinel crystal structure. - Graphical Abstract: Fourier transform of EXAFS of Mn K-edge for Mn,Mg-codoped green phosphor and Mn coordination structure. Highlights: ► Mn, Mg-codoped γ-AlON green phosphor for white LED. ► The valence of Mn is divalent. ► Mn occupies the tetrahedral site in the spinel structure.