Thermodynamic properties of complex oxides in the La-Ni-O system

Complex oxides La2NiO4+δ , La3Ni2O7-δ , La4Ni3O10-δ and LaNiO3-δ , the members of Ruddlesden-Popper series La n+1Ni n O3n+1, were prepared using citrate precursors. The stability range of LaNiO3-δ in air as well as the oxygen nonstoichiometry of La3Ni2O7-δ and La4Ni3O10-δ as a function of temperature and oxygen partial pressure was determined by means of thermogravimetric technique. Decomposition temperatures of La3Ni2O7-δ , La4Ni3O10-δ and LaNiO3-δ in air were determined by conductivity measurement method. The boundary of stability for La4Ni3O10-δ was determined by EMF measurements of galvanic cell with oxygen conducting solid electrolyte. The isothermal (1400 K) projection of La-Ni-O system phase diagram to the plane 'log(PO2)-relative mole fraction of metal components' was suggested. - Graphical abstract: The crystal structure of La4Ni3O10