Decomposition Pressure and Thermodynamic Stability of Thorium Oxyfluoride

Article abstract of DOI:10.1021/j100346a077

The decomposition pressure of the oxyfluoride-phase ThOF2(s) was measured by the torsion-effusion method over the range 1100-1250 K.The material vaporizes incongruently to yield ThF4(g) and ThO2(s).Vapor composition was verified by mass spectrometry and vapor molecular weight measurements.A small effusion orifice-area dependence indicates a slight kinetic barrier to the incongruent vaporization process.Derived equilibrium data show that ThOF2(s) is only marginally stable, with a Gibbs energy of formation of about 8 kJ mol^-1 from ThF4(s) and ThO2(s).