Hierarchical magnetic iron (III) oxides prepared by solid-state thermal decomposition of coordination polymers

By calcining Prussian Blue (PB) microcrystals with well-defined morphologies at different temperatures (300°C, 450°C and 600°C, respectively) in air, β-Fe ₂O ₃, γ-Fe ₂O ₃ and α-Fe ₂O ₃ with different shapes were successfully prepared. It was found that the heating rate played a critical role in the shape and hierarchical structure of the prepared iron(III) oxides. When the heating rate was as high as 10°C min ^-1, hierarchical iron(III) oxides could be obtained, while when the heating rate was as low as 1°C min ^-1, iron(III) oxides with smooth surfaces could be obtained. The hierarchical iron(III) oxides showed an interesting magnetic response at room temperature. The differences of magnetic properties for the hierarchical iron(III) oxides prepared at different temperatures should be caused by the composition of different phases.