THERMOCHEMICAL STABILITY OF RARE EARTH SESQUIOXIDES UNDER A MOIST ENVIRONMENT AT HIGH TEMPERATURE

摘要

Volatilization tests enabled to quantify the chemical and thermal stability of different rare earth sesquioxides, RE_2O_3 (where RE = Sc, Dy, Er, Yb) and to understand the corrosion process. These tests were carried out at temperatures ranging from 1000 to 1400°C in moist air with 50 kPa of water at atmospheric pressure, under a flowing gas velocity of 5 cm.s~(-1). Besides the volatilization rate, the nature of the volatile gaseous species was determined. Moreover, the proposed experimental method allowed to assess the Gibbs free energy of formation of these gaseous volatile species. Then, the partial pressures of hydroxide gaseous species were compared in order to identify the most stable species in moist environments.