Synthesis and crystal structure of new layered perovskite compounds: Li2La0.833(Nb1.5Ti0.5)O7 and Li2La2.25(Nb1.25Ti2.75)O13

Single crystals of Li2La0.833(Nb1.5Ti0.5)O7 and Li2La2.25(Nb1.25Ti2.75)O13 were grown in the system Li2O–La2O3–Nb2O5–TiO2. Both these compounds crystallize in the space group P42/mnm (No. 136), Z = 4: a = 5.5334(2), c = 18.3907(2) Å and a = 5.4915(6), and c = 33.812(4) Å, respectively. Their crystal structures, determined from single crystal X-ray diffraction data, are related to the Ruddlesden–Popper phases An+1BnO3n+1, which could be better written here as Li2[AxBnO3n+1]: Li2La0.833(Nb1.5Ti0.5)O7 is an n = 2 member and Li2La2.25(Nb1.25Ti2.75)O13 corresponds to an n = 4 member. In both structures, Nb5+ and Ti4+ ions statistically occupy distorted B octahedral sites of the perovskite, La3+ ions partially fill the cages of the perovskite, and Li+ ions are found in tetrahedral coordination between the perovskite layers.