Synthesis, crystal structure, and ionic conductivity of novel Ruddlesden-Popper related phases, Li4Sr3Nb5.77Fe0.23O19.77 and L4Sr3Nb6O20

We have synthesized two new lithium-containing oxides which are related to Ruddlesden-Popper phases, Li(4)Sr(3)Nbs(5.77)Fe(0.23)O(19.77) and Li4Sr3Nb6O20, With partial occupancy of the 12-coordinated sites by Sr, for the first time by direct solid-state reaction. While the single crystal and powder X-ray diffraction data indicate that these oxides crystallize in tetragonal cells (space group I4/mmm; a = 3.9585(2) Angstrom, c = 25.915(3) Angstrom and a = 3.953(2) Angstrom, c 26.041-(5) A for the respective oxides), the electron diffraction of some of the crystallites shows supercell reflections with a approximate to root 2a(p), c approximate to 25.9 Angstrom, probably indicating a twisting of the NbO6 octahedra in the ab-plane. Although, these oxides show no significant lithium ionic conduction at room temperature, they show distinct conductivity values at elevated temperatures.