Formation of the Metastable Iron (III) Germanate Fe₂GeO₅ through Kinetic Control of the Oxidative Reaction

Synthesis of complex oxides requires high temperatures to overcome barriers due to the diffusion of solids. Therefore, the most stable polymorphs are obtained in general reactions. However, it is necessary to design kinetic reactions with low initial energy barriers and control the reaction path and products to synthesize novel and metastable oxides. We report the synthesis of a metastable Fe₂GeO₅ with a kyanite-type structure via kinetic control of oxidative reaction in Fe₂GeO₄. It is also found that Fe₂GeO₅ was not synthesized at all by the conventional method, high-pressure synthesis method, or coprecipitation method. Our result indicates that kinetic control of the oxidative reaction is a promising method for synthesizing metastable materials.