PHASE-EQUILIBRIA IN THE GLASS-FORMING SYSTEM ZRF4-BAF2

The equilibrium phase diagram for the binary glass-forming system ZrF4-BaF2 described in this paper is based on data obtained by thermal analysis and X-ray diffraction. All experiments and the synthesis of binary compounds were performed in closed platinum vessels evacuated to 10(-4) Torr before sealing. Two eutectic points at X(BaF2) = 0.30 and 569 +/- 1-degrees-C and at X(BaF2) = 0.38 and 549 +/- 1-degrees-C were observed. The binary phase BaZr2F10 undergoes two phase transitions before melting congruently. BaZrF6 undergoes two phase transitions and melts incongruently. The glass-forming region is probably limited by solid-liquid equilibria. A thermodynamic model for the melt, based on equilibria between proposed complex species, is presented.