Soft chemistry synthesis, structure and electrochemical characterization of iron phosphates Fe(H2PO4)3 and Fe(PO3)3

The iron phosphate, Fe(H2PO4)3, was synthesized through a precipitation route by means of acidic media. As the compound is highly hygroscopic, the structure was solved ab initio by powder X-ray diffraction under nitrogen flow at room temperature and 200 °C. This phase is antiferromagnetic below 30 K. It converts into Fe(PO3)3 at 550 °C, after dehydration. Electrochemical characterizations, performed on the last compound, show irreversible decomposition into metallic iron.