Synthesis of La2NiO4+δ oxides by sol–gel process: Structural and microstructural evolution from amorphous to nanocrystallized powders

In this paper, the structural and microstructural transition from amorphous to La2NiO4+δ nanocrystallized oxides synthesized by a polymeric route based on Pechiniʹs work has been studied by several experimental techniques including infrared spectroscopy and wide angle X-ray scattering. The synthesis parameters which govern this transition have been identified in order to synthesize La2NiO4+δ oxides with various mean crystallite sizes and non stoichiometry levels. Therefore, it has been demonstrated that the control of the nature and the content of organic compounds in the polymeric sols allows the preparation of La2NiO4+δ metastable phases with a mean crystallite size ranging from 100 to 220 nm and a non stoichiometry level ranging from 0.15 to 0.22 at 25 °C. As the cathodic performance strongly depends on the physical characteristics of the oxides, this study shows that our versatile process may be suitable to elaborate electrodes with different electrochemical behaviours.