Topotactic preparation of textured alumina ceramics from dehydroxylation of gibbsite films

• Gibbsite nanoplatelets were assembled on their basal plane to form (001)-textured films.
• Textured alumina ceramics were prepared by sintering textured gibbsite films without addition of α-alumina seeds.
• Both pseudomorphic and topotactic aspects were exploited in bulk form instead of individual nanoparticulate size.
• Direct XRD evidence of the topotactic dehydroxylation from gibbsite to α-alumina is presented in this work.

In this paper, textured alumina ceramics were prepared from dehydroxylation of gibbsite films and the pseudomorphic and topotactic nature of the dehydroxylation of textured gibbsite films has been investigated. First, the precursor film with a (001)-textured structure was obtained via vacuum filtration deposition of diluted aqueous suspensions of gibbsite nanoplatelets. Subsequently, (001)-textured α-alumina ceramics were successfully achieved by sintering of the deposited gibbsite films without addition of α-alumina seeds. The Scanning Electron Microscope (SEM) and X-ray Diffraction (XRD) results show that, during the phase transition from gibbsite to α-alumina, both layered morphology and crystal's axis orientation have been retained to a considerable extent. For the first time, a direct XRD evidence of gibbsite topotactic dehydroxylation to the α-alumina phase is presented. It is believed that the method described here exploits gibbsite's pseudomorphic and topotactic dehydroxylation, not on individual particles scale but on a bulk form. The resulting structure can be considered as inorganic scaffolds which can have applications for fabrication of dense, textured alumina-based ceramics and other layered/textured nanocomposites.