As previously reported , metastable solid solutions based on cubic zinc oxide, quenched after synthesis at high pressure and high temperature, are characterized by the presence of nanoand/or micro-uniformities. For the Fe 2+ cation (3d 6 , electronic configuration t 2g 4 e g 2 ), possible reasons for the instability of the rock salt structure are the weakened preference of this cation for the octahedral coordination , its possible participation in redox reactions, disproportionation (partial decomposition into Fe 0 and Fe 3+ ), as well as the possibility of formation of complex ternary Zn-Fe-O oxides of various structural types, including spinels, which can be formed when iron is oxidized to the +3 oxidation state.