Potential of Knudsen Effusion Mass Spectrometry (KEMS) for Thermo Chemical Studies in Materials Science

The determination of valuable thermodynamic data for materials at elevated temperatures is a very important issue in Materials Science. This can be achieved by the elucidation of vaporization processes with high temperature mass spectrometry.

Knudsen Effusion Mass Spectrometry provides the identification of gaseous species present above condensed phases and permits the determination of their partial pressures up to a total pressure of 200 Pa.

The key for establishing model calculations using DG minimization tools like FactSage, Pandat or Thermocalc is the knowledge of the thermodynamic data of molecules and compounds. This includes the partial pressures of gaseous species, the standard enthalpies and entropies of formation of gaseous and condensed phases as well as their enthalpies and entropies of mixing and the knowledge of phases and chemical compounds which are formed upon reactions.

The method will be described and examples and an insight will be given how basic thermodynamic data are derived with the above mentioned method for the incorporation into thermodynamic databases. Examples of investigations carried out in our lab will be given.