Phase relations in the system NaF-CaF2-NaAlSiO4-CaAl2Si2O8

The phase diagram of the pseudoternary reciprocal system NaF-CaF2-NaAlSiO4- CaAl2Si2O8 is reported in this paper. The phase relations in the system hav e been investigated by differential thermal analysis, quenching melts, Xray diffractometry, and optical and electron microscopies, The stable diagonal CaF2-NaAlSiO4 divides the system in two pseudoternary systems. The solidus temperatures in the two subsystems NaF-CaF2-NaAlSiO4 and CaF2-NaAlSiO4-CaA l2Si2O8 are 805 degrees +/- 2 degrees C and 1095 degrees +/- 4 degrees C, r espectively. An extensive region of liquid-liquid immiscibility is evident in the NaF-CaF2-NaAlSiO4 subsystem. The compositions of the two liquids fal l outside the compositional surface NaF-CaF2-NaAlSiO4-CaAl2Si2O8, but only a small deviation from the ternary behavior is observed.