Synthesis of NH4FePO4·H2O nano-plates via solid-state reaction at low temperature and its thermochemistry properties

Ammonium–iron(II) phosphate monohydrate was synthesized via solid-state reaction at low temperature and characterized by X-ray diffraction, infrared spectroscopy, chemical analysis and scanning electron microscope. Thermochemical study was performed by an isoperibol solution calorimeter at 298.15 K. The results show that the obtained product is NH4FePO4·H2O with plate shape of nanometer measure. According to Hessʹs law, a new thermochemical cycle was designed, and the standard enthalpy of formation of the titled complex at 298.15 K is Δ f H m ⦵   [ N H 4 FeP O 4 ⋅ H 2 O ( s ) , 298.15   K ] = − 1774.92 ± 0.39   kJ   mo l − 1 .