Synthesis and Structure of the Gibbsite Intercalation Compounds [LiAl₂(OH)₆]X {X = Cl, Br, NO₃} and [LiAl₂(OH)₆]Cl·H₂O Using Synchrotron X-ray and Neutron Powder Diffraction

Treatment of gibbsite {γ-Al(OH)3} with the lithium salts LiX {X = Cl, Br, NO3} in water leads to intercalation of both the cations and anions into the host structure to give [LiAl2(OH)6]X·H2O {X = Cl, Br, NO3}. Thermogravimetric analysis indicates that these materials can be readily dehydrated to give highly hydroscopic, crystalline layered phases [LiAl2(OH)6]X {X = Cl, Br, NO3}. The structures of these dehydrated phases have been determined by synchrotron X-ray and neutron powder diffraction. The dehydrated intercalates with {X = Cl, Br} are isomorphous and crystallize in the P63/mcm space group. [LiAl2(OH)6]NO3 adopts a similar structure but crystallizes in space group P63/m due to disorder of the intercalated nitrate anions in the crystallographic ab plane. All the intercalates consist of eclipsed Al(OH)3 layers stacked along the c-axis with the halide or nitrate ions located at the cell edges and midway between the Al(OH)3 layers. The lithium ions have been located in the unfilled octahedral sites wit...