Crystalline Intermediate Phases in the Sol-Gel-Based Synthesis of La_2NiO_(4+δ)

摘要

X-ray diffraction and transmission electron microscopy were applied to investigate a sol-gel synthetic process for the mixed oxygen ion and electron conductor La_2NiO_(4+δ) with a K_2NiF_4 structure type. The development of the La_2NiO_(4+δ) is elucidated considering the influence of calcination temperatures and dwell times. Following the thermal decomposition of nitrate and organic precursors in an intermediate step, the lanthanum nickel oxide is obtained after a short dwell time above 750℃. This occurs by the transformation of an ultrafinely dispersed powder consisting of lanthanum oxycarbonate, lanthanum oxide, and nickel oxide. The pure La_2NiO_(4+δ) phase was obtained by similar solid-state reactions between nanocrystalline powder particles at just 950℃.