A novel route for FePO4 olivine synthesis from sarcopside oxidation

Abstract

Heterosite FePO4 is synthesized for the first time by direct thermal oxidation of sarcopside Fe3(PO4)2. Both FePO4 and Fe3(PO4)2 have a pseudo olivine structure. Complete isostructural conversion of sarcopside into FePO4 is achieved at a temperature of 450 °C within 3 days according to the reaction Fe3(PO4)2 + ¾ O2 → 2 FePO4 + ½ Fe2O3 which leads to the extraction of iron from the sarcopside structure. Appropriate heating ramp must be applied in order to avoid the crystallization of Fe7(PO4)6. Electrochemical performances of the oxidation product are consistent with those of olivine FePO4.