抄録
When one crystalline material changes to another with the loss or gain of part of the material, and there is accord in three dimensions between the initial and final lattices, then the transformation can be characterized as topotactic. In the topotactic transformation from γ-FeOOH to γ-Fe2O3, controlling features appear to be the close-packed oxygen frameworks in the interstices of which the mobile iron ions can migrate. The reaction between BaO·6Fe2O3 particles with the hexagonal shape and Fe(OH)2 fine particles in the aqueous solution generates Fe3O4 particles with the same shape as that of BaO·6Fe2O3. BaO·6Fe2O3 changes to Fe3O4 with the loss of Ba and O atoms in BaO·6Fe2O3, which comes from the reaction with protons generated by oxidation of Fe(OH)2 to Fe3O4.
