The process of the phase transformation from amorphous to crystalline FePO4·2H2O was studied in this research. It was found that Fe and P are predominantly present as FeHPO4+ and FeH2PO42+ and an induction period exists during the transition from amorphous to monoclinic form. The induction period and the time required for phase transformation were shortened with the increased temperature. Phase transformation could be kinetically described by the Johnson–Mehl–Avrami (JMA) dynamics model. The dissolution rate of amorphous FePO4·2H2O is the rate-limiting step of this process. the activation energy of phase transformation is calculated to be 9.619 kJ/mol. The results in this study provided more guidelines for the regulation of FePO4·2H2O precursors by precipitation method.
