Thermodynamic modeling of the LiF–YF3 phase diagram

Abstract

A thermodynamic optimization of the LiF−YF 3 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, LiYF 4 , are in reasonable agreement with the experimental data.

Experimental evaluation and thermodynamic assessment of the LiF–LuF3 phase diagram

“…The heat of fusion and polymorphic transition (∆H PT ) for LiF, LuF 3 and LiLuF 4 were calculated from the DSC peak area of these thermal effects for each compound. In a previous work, the experimental ∆H PT for LiF was reported and reasonable agreement with the literature value was found [13,17]. Compared to the literature data, the main difference in the results were noticed for LuF 3 thermal events.…”

Directional solidification of the eutectic LiF–LiYF4 using Bridgman and micro-pulling down techniques: Microstructural study and some properties

“…A wealth of halide eutectic systems exists, whose equilibrium phase diagrams were studied in the 60s and 70s, and more recently assessed using modern calorimetric equipment and calculation capabilities 20 . This allows us to choose among many systems with the aim of exploiting eutectics.…”

Growth of Self Organized Eutectic Fibers from LiF─Rare Earth Fluoride Systems

“…Thus, one can define a S' for the eutectic itself by calculating the difference of S for the mixture x eut just above and below T eut . For LiF/LiGdF 4 this was performed with the assessment data for the LiF-GdF 3 -LuF 3 system [13] and data for the LiF-YF 3 system where published recently [9]. For LiF-LiGdF 4 one calculates S' = 28.2 J/(molK) = 3.4R and for LiF-LiYF 4 S' = 34.4 J/(molK) = 4.1R.…”

“…The eutectics that are studied here are situated between the intermediate scheelite type LiREF 4 (RE = Y, Gd) and LiF. Both systems LiF−YF 3 [9] and LiF−GdF 3 [10] were re-investigated and for the first time a thermodynamic assessment for the Gibbs free energies G(T) of the line compounds LiF, YF 3 , LiYF 4 and G(T,x) of the {x YF 3 + (1-x) LiF} melt was performed. The scheelite type intermediate phase is a "borderline peritectic" where the liquidus of both YF 3 and LiYF 4 , as well as the peritectic line of LiYF 4 meet at one point.…”