Synthesis, Structure, and Electrical Conductivity of A[A2B3O10](A=Rb, Cs; A=Sr, Ba; B=Nb, Ta): New Members of Dion–Jacobson-Type Layered Perovskites

New members of Dion–Jacobson (D-J)-type layered perovskites of the general formula Aʹ[A2B3O10] (Aʹ=Rb, Cs; A=Sr, Ba; B=Nb, Ta) were prepared by solid-state reactions between the metal oxides, nitrates, and carbonates under specific conditions. The crystal structures were determined using powder X-ray diffraction data in combination with Rietveld analysis. The c-axis lattice parameter increases as the size of the alkaline earth ion increases. Both Sr and Ba compounds crystallize in a tetragonal cell, while the corresponding Ca compounds crystallize in an orthorhombic cell. The electrical conductivity of the layered perovskites was determined using AC impedance analysis and DC methods. Among the compounds with the same alkali ion and different alkaline earth ions, the Ca compound exhibits a higher electrical conductivity than the corresponding Sr and Ba compounds. DC measurements reveal that the layered perovskites exhibit both ionic and electronic conduction.