Synthesis and thermal stability studies of mixed A-site Dion-Jacobson triple-layered perovskites,A'LaNaNb3O10 (A' = H, Li, Na, K, Rb, CuCl)

The new mixed-metal Dion-Jacobson layered perovskite RbLaNaNb3O10 has been prepared by direct reaction. Rietveld refinement of X-ray diffraction data shows this compound to be tetragonal (a = 3.88703(7) angstrom, c = 15.1349(5) angstrom; S.G. P4/mmm) and isostructural to RbCa2Nb3O10 with La and Na statistically distributed over the Asite within the perovskite block. The compound can be topochemically manipulated, readily undergoing ion exchange reactions to produce the series A'LaNaNb3O10 (A' = H, Li, Na, K, CuCI). Thermal studies show that, with the exception of KLaNaNb3O10, the exchange products are all low temperature phases, decomposing below 800 degrees C with a decomposition pathway varying with the nature of the interlayer species. Significant to this study is the observation that the rare combination of site sharing trivalent and monovalent cations (La/Na) imparts an increased stability for the A'LaNaNb3O10 compounds relative to the corresponding A'Ca2Nb3O10 analogues - the thermal stability in LiLaNaNb3O10 for example is over 50 degrees C higher than that of LiCa2Nb3O10.