Construction of a double-layered tetrahedral network within a perovskite host: Two-step route to the alkali-metal-halide layered perovskite, (LixCl)LaNb2O7

A two-step topotactic route is used to construct lithium halide layers within a perovskite host. Initially RbLaNb2O7 is converted to (CuCl)LaNb2O7 by ion exchange and then reductive intercalation with n-butyllithium is used to form (LixCl)LaNb2O7. The copper metal byproduct from the reduction step is removed by treatment with iodine. Rietveld refinement of neutron powder diffraction data revealed that an alkali-halide double layer with LiO2Cl2 tetrahedra forms between the perovskite slabs. Compositional studies indicate that the range for x in (LixCl)LaNb2O7 is 2⩽x<4, which appears consistent with the neutron data where only one lithium site was found in the structure.