THERMAL DECOMPOSITION OF LAYERED DOUBLE HYDROXIDES Mg-Al, Ni-Al, Mg-Ga: STRUCTURAL FEATURES OF HYDROXIDE, DEHYDRATED, AND OXIDE PHASES

The analysis of the literature data reveals that, as a rule, layered double hydroxides prepared by co-precipitation have an imperfect structure; however, there are different viewpoints on the type of the defects. Thermal decomposition of Mg-Al, Mg-Ga, and Ni-Al hydroxides occurs through dehydration, dehydroxylation, and decarbonization. The first stage affords a layered dehydrated phase with a strongly disordered structure, which is a subject of controversy. Also, the question on the diffusion of cations during thermolysis is still open, i.e., whether the Mg-Al, Mg-Ga and Ni-Al systems degrade with the development of a nanoheterogenous oxide systems or a single-phase mixed oxide, but with very defective structure, is formed.