A mixed alkali metal titanate with the lepidocrocite-like layered structure. Preparation, crystal structure, protonic form, and acid-base intercalation properties

A mixed alkali metal titanate of composition A(x)Ti(2-x/3)Li(x/3c)O(4) (A = K, Rb, Cs) has been prepared and its ion-exchange/intercalation properties have been explored. Solid-state calcination of appropriate mixtures of TiO 2 and alkali metal carbonates produced the titanate at a stoichiometry of x = 0.80 for A = K, 0.75 for Rb, and 0.70 for Cs. Rietveld refinement on neu tron diffraction data confirmed that the orthorhombic structure is comprise d of lepidocrocite-related host layers of Ti2-x/3Lix/3O4 and charge-balanci ng A ions in the interlayer domain. Complete extraction of both alkali meta l ions was achieved by acid-leaching, producing a new protonic titanate of H4x/3Ti2-x/3O4. H2O. This phase is distinguished from isomorphous related c ompounds in terms of high proton content as a consequence of exchangeable L i ions located in the host framework. The material took up alkali metal ion s and organoammonium ions from aqueous media. These ion-exchange and interc alation reactions brought about expansion/contraction of the gallery height and lateral displacement of the layers. The resulting various types of lay er sequence can be understood in terms of the nature of the interlayer spec ies.