MSnF4 (M = Pb++, Ba++, Sr++) : Thermal expansion and phase transitions

The unit-cell parameters of PbSnF4, BaSnF4 and SrSnF4 were measured from liquid N2 temperature up to 400° C. PbSnF4 undergoes two phase transitions at ∼ 260° and 380°C. One of the new phases (β) can be quenched to room temperature. All three phases have structures related to that of fluorite. Most of our results conflict with recent publication (Mat. Res. Bull., 13, 877 (1978)).