Synthesis and formation mechanism of hematite hollow microspheres by a one-pot templateless surfactant-free hydrothermal process

Hollow microspheres of hematite (α-Fe₂O₃) were prepared by a simple hydrothermal treatment of ferrous ammonium sulphate hexahydrate ((NH₄)₂Fe(SO₄)₂·6H₂O) aqueous solution without any surfactants and additives at 180–200 °C. The products were characterized by XRD, FE-SEM and TEM. The results show that α-Fe₂O₃ hollow microspheres are about 1 μm in diameters and are composed of α-Fe₂O₃ nanoparticles with a diameter range from 50 nm to 150 nm. The effects of reaction parameters such as reaction time, temperature and [(NH₄)₂Fe(SO₄)₂·6H₂O] on the morphology of the final product were investigated. A potential formation mechanism of α-Fe₂O₃ hollow microspheres was also proposed, where the intermediate, urchin-like goethite, served as a sacrificial template for the formation of hollow structure. The reaction parameters-depended morphologies of the final products consisted well with the proposed formation mechanism.