Sol-Gel-Process-Based Molten-Flux Synthesis of Plate-like La2NiO4+δ Particles

La2NiO4+delta particles with a plate-like morphology were prepared from a NaOH melt by molten-flux synthesis. For this purpose, the intermediates from a sol-gel process were used as reactants. Using powder X-ray diffraction, the sol-gel intermediates were identified as a mixture of tetragonal La2O2CO3 and cubic NiO. The existence of NiO was also confirmed by transmission electron microscopy in combination with electron-energy loss spectroscopy. The ultrafine mixed sol-gel intermediates were then mixed with NaOH powder and additional water in a nickel crucible and heated to 673 K for 8 h. The chemical reactions in the air during the molten-flux synthesis and the influence of the salt on the formation of La2NiO4+delta were examined by thermogravimetric analysis. The powder X-ray diffraction indicated a K2NiF4-type tetragonal structure with the 14/mmm space group for the reaction product. The scanning electron microscopy showed plate-like La2NiO4+delta crystals with a length and thickness of approximately 9 mu m and 2 mu m, respectively, while the energy-dispersive X-ray spectroscopy revealed a homogeneous distribution of lanthanum and nickel in the product powder. The influence of the processing parameters on the product generation, as well as on the size and morphology of the La2NiO4+delta particles, was systematically studied.

Automated summary

In this study, La2NiO4+delta particles with a plate-like morphology were prepared using molten-flux synthesis, and the influence of NaOH on the formation process was investigated. Various techniques including thermogravimetric analysis, powder X-ray diffraction, and electron microscopy were employed to study the structure, morphology, and composition distribution of the reaction product.