The formation of nanocrystalline orthoferrites of rare-earth elements XFeO3 (X = Y, La, Gd) via heat treatment of coprecipitated hydroxides

摘要

Heat treatment of coprecipitated hydroxides in air has afforded isometric nanocrystals of rhombic yttrium, lanthanum, and gadolinium ferrites with average crystallite size 40 +/- 4 nm. It has been stated that the formation of XFeO3 (X = Y, La, Gd) nanocrystals occurs via two mechanisms, from the corresponding coprecipitated hydroxide (main route) and from the products of partial carbonatization of the precursor (side route). It has been shown that the formation of XFeO3 (X = Y, La, Gd) nanocrystals via the main and the side routes occurs at 500 and 780A degrees D (o-YFeO3), 646 and 900A degrees D (o-LaFeO3), and at 769A degrees D (o-GdFeO3). Basing on the obtained data, we have suggested a scheme of chemical and physical transformations accompanying the formation of nanocrystals of yttrium, lanthanum, and gadolinium ferrites.