Kinetic schemes of chemical transformations and particle morphology upon interaction between Ln2(SO4)3 (Ln = La, Pr, Nd, Sm) and hydrogen

The phase compositions of samples obtained during the treatment of anhydrous sulfates Ln(2)(SO4)(3) (Ln = La, Pr, Nd, Sm) in a stream with an excess of hydrogen in the temperature range of 400 to 1100A degrees C at exposures of up to 420 min are determined. Kinetic schemes are compiled for the chemical transformations and changes of phase composition of the mixtures in coordinates of temperature and time that have six fields of the phase combinations: Ln(2)(SO4)(3), Ln(2)(SO4)(3) + Ln(2)O(2)SO(4), Ln(2)O(2)SO(4), Ln(2)O(2)SO(4) + Ln(2)O(2)S, Ln(2)O(2)S, and Ln(2)O(2)S + Ln(2)O(3). Single-phase samples of Ln(2)O(2)SO(4) compounds are obtained at temperatures (A degrees C) of 540-560 (La), 460-520 (Pr), 470-520 (Nd), and 480-520 (Sm). The temperatures (A degrees C) of Ln(2)O(2)S compounds are 580-920 (La), 600-900 (Pr), 600-900 (Nd), and 600-800 (Sm). It is shown via electron microscopy that particles of La-2(SO4)(3) in the shape of cylinders are converted into flakes of Ln(2)O(2)SO(4), predominantly flat Ln(2)O(2)S crystallites.