THERMODYNAMIC STUDY OF THE CSCL-CECL3 SYSTEM BY KNUDSEN EFFUSION MASS-SPECTROMETRY

The vaporization of samples of different chemical and phase compositio ns covering the complete concentration range of the CsCl-CeCl3 system was investigated in the temperature range between 749 K and 1098 K by the use of Knudsen effusion mass spectrometry. The gaseous species CsC l, Cs2Cl2, CeCl3, Ce2Cl6 and CsCeCl4 were identified in the vapor and their partial pressures determined. The thermodynamic stability of CsC eCl4(g) was evaluated by second law treatment of the equilibrium parti al pressures. The thermodynamic activities of CsCl and CeCl3 were obta ined at 950 K in the two phase fields {liquid+Cs3CeCl6(s)} and {CsCe2C l7(s)+ CeCl3(s)} from the partial pressures of the vapor components. T he Gibbs free energies of formation from the constituent halides of th e pseudobinary phases Cs3CeCl6(s) and CsCe2Cl7(s) were evaluated from the thermodynamic activities of the components. The results are discus sed with other literature data for the studied system. (C) 1998 Elsevi er Science S.A. All rights reserved.