In situ variable temperature X-ray diffraction studies on the transformations of nano-precursors to La–Ni–O phases

In situ variable temperature XRD (VT-XRD) measurements on the transformation of nano-precursors to LaNiO phases are presented. Experimental results showed that LaNiO3 and La2NiO4 phases were formed at ca. 700 °C via the reaction of La2O3 and NiO (from the initial nano-precursors), where a relatively low temperature of 700 °C was found for the synthesis of La2NiO4. The formation of La3Ni2O7 at higher temperature (up to 1150 °C) appeared to proceed through a further reaction of La2NiO4 with unreacted NiO, whilst the formation of La4Ni3O10 (at 1075 °C) proceeded via a further decomposition of LaNiO3. Although phase pure La3Ni2O7 and La4Ni3O10 were not directly obtained under the processing conditions herein, the results of this study allow for a better understanding of formation pathways, particularly for the higher order La–Ni–O phases.

Graphical abstractIn situ variable temperature XRD showing the phase formation pathway of Lan+1NinO3n+1 at evaluated temperatures.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► In situ VT-XRD was utilized to study the pathways for Lan+1NinO3n+1 formations. ► LaNiO3 and La2NiO4 phases were formed via the reaction of La2O3 and NiO, respectively. ► La3Ni2O7 phase was formed via further reaction of La2NiO4 phase with unreacted NiO. ► La4Ni3O10 phase was formed via further decomposition of LaNiO3 phase.