A series of α-Fe₂O₃ crystalline materials with fascinating polyhedral morphologies, such as octahedral, cuboctahedral and truncated cubic structures, were prepared through a novel solid-phase sintering process. Our results demonstrated that the structural transformations among the polyhedra were easily controlled by the sintering times. This suggested that the Wulff polyhedra transformation could occur in a hexagonal crystal system. Furthermore, we found that the magnetic properties of the α-Fe₂O₃ crystals were associated with their size and shape.