METASTABLE CRYSTALLIZATION OF LAZR2F11

Fusion and crystallization of the compound LaZr2F11 were investigated by differential thermal analysis and powder X-ray diffraction. The sta ble modification of LaZr2F11 was observed to melt congruently at 789+/ -4 degrees C. The melt was easily supercooled past the melting point, before a metastable phase, beta LaZr2F11, crystallized. On further coo ling beta-LaZr2F11 went through an exothermic solid-solid phase transi tion to the stable modification alpha-LaZr2F11. No solid-solid phase t ransition was observed during reheating of alpha-LaZr2F11. The melting point of beta-LaZr2F11 was observed approximately 10 K below the melt ing point of alpha-LaZr2F11. beta-LaZr2F11 was confirmed metastable at all temperatures, but nucleates more readily from the supercooled mel t than the stable modification alpha-LaZr2F11.