Analysis of the Reaction Process in the Formation of Lanthanum Nickel Oxide via a Mechanochemical Route

Abstract

This paper describes the analysis of lanthanum nickel oxide (LaNiO₃) formation process during heating of a precursor prepared via a mechanochemical (MC) route. To study the effect of the MC treatment on the solid-state reaction of the precursor, two kinds of precursor were prepared: one was a simple mixture of lanthanum hydroxide (La(OH)₃), nickel hydroxide (Ni(OH)₂), and sodium chloride (NaCl); the other was the mixture obtained by mechanochemical treatment of the simple mixture in a high-energy planetary ball mill. The MC-treated precursor consisted mainly of La(OH)₃, Ni(OH)₂, and NaCl, as did the simple mixture. However, the MC-treated precursor contained relatively low crystalline components and was well mixed compared with the simple mixture. After the heat treatment, LaNiO₃ was obtained from both precursors through three steps of endothermic solid-state reactions. The mechanochemical treatment suppressed the formation of relatively stable hexagonal lanthanum oxycarbonate (La₂O₂CO₃) phase as the intermediate, resulting in the formation of high crystallinity LaNiO₃ at relatively low temperature.