Thermodynamic Investigation on the BaB2O4–BaF2–2NaF–Na2B2O4Reciprocal System

The BaB2O4–BaF2–2NaF–NaB2O4reciprocal system has been investigated by combination of experimental measurements with theoretical calculation. The Na2B2O4–2NaF binary and Na2B2O4–BaF2pseudo-binary phase diagrams are measured by means of DTA and X-ray diffraction. The thermodynamic functions for all sub-binary systems are derived from measured phase diagrams and thermodynamic data by CALPHAD technique, and the sub-binary phase diagrams are calculated according to phase equilibrium principle. Then, the thermodynamic functions for sub-binary systems are extrapolated to the BaB2O4–BaF2–2NaF–Na2B2O4reciprocal system, and the phase diagram of the reciprocal system is calculated. The calculated phase diagrams are verified by additional experiments.