Thermodynamic modeling of the LiF–YF3 phase diagram

A thermodynamic optimization of the LiF–YF3 binary phase diagram was performed by fitting the Gibbs energy functions to experimental data that were taken from the literature, as well as from own thermoanalytic measurements (DTA and DSC) on HF-treated samples. The Gibbs energy functions for the end member compounds were taken from the literature. Excess energy terms, which describe the effect of interaction between the two fluoride compounds in the liquid phase, were expressed by the Redlich–Kister polynomial function. The calculated phase diagram and thermodynamic properties for the unique formed compound, LiYF4, are in reasonable agreement with the experimental data.

► Thermodynamic assessment of the LiF–YF3 system is given.
► Fusion enthalpy for LiF, YF3 and LiYF4.
► Analytical expression for LiYF4 heat capacity (CP).
► Excess energy parameters for the liquid phase were assessed by Redlich–Kister polynomial model.