Mass-Spectrometric and Electrochemical Studies of Thermodynamic Properties of Liquid and Solid Phases in the System CaO-Al2O3


  • Presented at the 82nd Annual Meeting, The American Ceramic Society, Chicago, Illinois, April 28, 1980 (Basic Science Division No. 45-B-80).

  • The work of K. T. Jacob was supported in part by the Natural Sciences and Engineering Research Council of Canada. The mass spectrometry measurements were made possible by partial financial assistance of the Delegation Generate al la Recherche Scientifique and by an Ugine Acier scholarship to R. Lourtau.


The activities of CaO and Al2O3 in lime-alumina melts were studied by Knudsen cell-mass spectrometry at 2060 K. Emf of solid state cells, with CaF2 as the electrolyte, was measured from 923 to 1223 K to obtain the free energies of formation of the interoxide compounds. The results are critically evaluated in the light of data reported in the literature on phase equilibria, activities in melts, and stabilities of compounds. A coherent set of data is presented, including the previously unknown free energy of formation of CaO.6Al2O3 and the temperature dependence of activities in the liquid phase.