“MgAlON” spinel structure: A new crystallographic model of solid solution as suggested by 27Al solid state NMR

27Al high-resolution magic-angle spinning (MAS) nuclear magnetic resonance (NMR) experiments revealed that “MgAlON” spinel solid solutions have three different aluminium local structural environments. Two of them are characteristic of the MgAl2O4 spinel reference structure and involve of aluminium atoms in four- and six-fold oxygen co-ordinations. The presence of the third site is correlated firstly with oxygen/nitrogen substitution on the anionic lattice and secondly with the presence of magnesium in the spinel structure. This specific environment corresponds to a tetragonal site where the aluminium is surrounded by nitrogen atoms exclusively. Consequently, a model of solid solution is proposed for aluminium magnesium oxynitride and the chemical formulation of “MgAlON” samples is deduced.