Thermal evolution of Mg-Al and Ni-Al layered double hydroxides: the structure of the dehydrated phase

Simulation of X-ray diffraction patterns on the basis of the models of one-dimensional disordered crystals was used to investigate the structure of the dehydrated phase produced by dehydration of Mg-Al and Ni-Al layered double hydroxides at a temperature of ∼473-498 K. It was found that the removal of water molecules transforms the initial structure, which is a mixture of 3R₁ and 2H₁ polytypes, into a structure that comprises preferentially fragments of 3R₂ and 1H polytypes and has some turbostratic disorder.