ИСТИНА

This work is a part of systematic studies of new materials syntesized on the basic of compounds of transition elements, which is carried out at Luginin’s laboratory of thermochemistry and Inorganic chemistry division of MSU. It is devoted to the study of thermochemical properties of NH4MPO4nH2O (M = Fe, Co, Ni, Mn). The choice of object of research is caused by its application as the precursors for LiMPO4 preparation, which is Li-ion batteries material. The thermodynamic properties of NH4MPO4nH2O are less well understood. The only work [1] devoted to the determination of the NH4FePO4H2O enthalpy of formation. According to the IUPAC classification, the data obtained in single work can be considered only as prelimenary. The enthalpies of formation of NH4MPO4nH2O (M = Co, Ni, Mn) were not determinated early. The samples of NH4MPO4nH2O were prepared by precipitation method. The precipitates were washed out by the distilled water and dried up. The synthesized samples were checked by X-ray and TG analysis. The X-ray examination supported the single-phase nature of samples. It is stated by using X-ray and TG analysis that n in NH4MPO4nH2O is equal to1 for M = Fe, Co, Mn, and n is equal to 6 for M = Ni. To determine the enthalpies of formation of investigated compounds, the enthalpies of reaction of NH4MPO4nH2O with 1 M hydrochloric acid were measured at 298.15 K in sealed swinging calorimeter with an isothermal coat. Temperature rise in each run was measured by platinum resistance thermometer. Thermometric sensitivity of circuit was 3105 K. The energy equivalent of calorimeter was determined by electric technique. The enthalpies of formation of NH4MPO4nH2O were calculated on basis of experimental data and the realiable literature data on thermochemical properties of ammonium, iron, cobalt, nickel, manganese chlorides and phosphoric acid solutions.