A preparation and polymorphic relations of sodium iron oxide (NaFeO2)

The formation of α-NaFeO2 and β-NaFeO2 below 700°C was found to depend strongly on the structure of starting iron oxide; α-Fe2O3 with hcp of oxygen yielded β-NaFeO2 with hcp and γ-Fe2O3 with ccp of oxygen yielded α-NaFeO2 with ccp by a reaction either with Na2CO3 or Na2O2. The doping of Na-ions into the γ-Fe2O3 structure and its rapid change to α-NaFeO2 were observed. The transformation from the metastable β-NaFeO2 to the stable α-form was very much sluggish in the solid state, but it was accelerated by the presence of the liquid Na2O2.