Polymorphisme de l'hexahydroaluminate trisodique Na3AlH6

Structural investigations on the cryolite-like compound Na₃AlH₆ have been carried out using high-temperature diffractometry. α-Na₃AlH₆ which crystallises in a monoclinic pseudo-cubic system under room-temperature conditions exhibits at 525 K a polymorphic transition into a f.c.c. form β-Na₃AlH₆. This result has been established by high-pressure-high-temperature studies. From structural point of view Na₃AlH₆-β is to be related to the high temperature modification of cryolite Na₃AlF₆