Kinetics of the transformation of Ln2O2SO4 into Ln2O2S (Ln = La, Pr, Nd, and Sm) in a hydrogen flow

The kinetic dependences of the yield of Ln(2)O(2)S (Ln = La, Pr, Nd, and Sm) upon the treatment of Ln(2)O(2)SO(4) in a hydrogen flow at 950, 1120, and 1170 K are constructed. The plots are approximated by Avrami-Erofeev equations, equations of compressed volume and compressed surface, and Jander's equation. The correctness of choosing these equations is evaluated using the numerical values of Fisher's criterion. Images of the particles of Nd2O2SO4 -> Nd2O2S transformation in the flow are obtained on an Ntegra Aura atomic force probe microscope. A mechanism of the crystal growth of the Nd2O2S phase from the nucleation site of the Nd2O2SO4 and Nd2O2S phase boundaries is proposed.