Preparation and Study of Coprecipitated Indium and Dysprosium Hydroxides by Thermal and X-ray Diffraction Analyses

X-ray diffraction and thermal analyses, electron microscopy, Brunnauer-Emmett-Teller method, and infrared spectroscopy were used to study the products of coprecipitated indium and dysprosium hydroxides obtained under different conditions of aging in the mother liquor. The paper analyzed the effect of aging conditions on the phase composition, degree of crystallinity, and dispersion of the resulting powders. Samples with a molar ratio of In(III):Dy(III) = 1:1 were studied after aging in the mother liquor under stirring for 10 min, 3 d, and 7 d without heating, and for 7 d at 70°C. No correlation was found between the aging time of the precipitates and the crystallite size. It was shown that the specific surface and the degree of crystallinity of the precipitates increased significantly at increased aging time. Two mechanisms of precipitate aging were verified: ordering of the structure of hydroxides with the transition from the X-ray amorphous state to the crystalline state and dehydration of metal hydroxides. The study evidenced significant absorption of carbon dioxide by hydroxides during precipitate aging with the formation of carbonates, which result in the release of carbon dioxide during thermal decomposition.