THERMODYNAMIC STUDY OF THE CSCL-NDCL3 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-NdCl3 system was investigated in the temperature range between 736 K and 1077 K by the use of Knudsen effusion mass spectrometry, The gaseous species CsC l, Cs2Cl2, NdCl3, Nd2Cl6 and CsNdCl4 were identified in the vapor and their partial pressures determined. The thermodynamic stability of CsN dCl4(g) was evaluated by second law treatment of the equilibrium parti al pressures. The thermodynamic activities of CsCl and NdCl3 at 950 K in the two phase fields {Liquid+Cs3NdCl6(s)} and {CsNd2Cl7(s)+NdCl3(s) } resulted from the partial pressures of the vapor components. The fre e enthalpies of formation of the pseudobinary phases Cs3NdCl6(s) and C sNd2Cl7(s) from the constituent halides were evaluated from the thermo dynamic activities of the components. The results are discussed with o ther literature data for the studied system. (C) 1998 Elsevier Science S.A. All rights reserved.