Kinetic diagrams of Ln2O2SO4 phase transformations in a H2 flow (Ln = La, Pr, Nd, Sm)

Kinetic diagrams of Ln₂O₂SO₄ (Ln = La, Pr, Nd, Sm) systems reduction in a H₂ flow are plotted for the first time in temperature-duration of treatment coordinates in which there are five areas of phase states. The temperatures of formation are established for products of the Ln₂O₂SO₄ + 4H₂ = Ln₂O₂S + 4H₂O reaction in the temperature range of 880–900 K and products of the Ln₂O₂SO₄ + H₂ = Ln₂O₃ + SO₂+ H₂O reaction in the temperature range of 1090–1220 K. The ranges of the temperature of formation of the homo-geneous Ln₂O₂S phase were found to decrease: 880–1220, 900–1200, 900–1180, and 900–1090 K in the sequence La-Pr-Nd-Sm.