Determination of the crystal structure of new layered oxyfluoride, RbCaNb2O6F by neutron diffraction

A new layered perovskite-type oxyfluoride, RbCaNb2O6F was prepared by conventional solid-state reaction. The crystal structure of RbCaNb2O6F was studied by performing neutron diffraction analyses. The structure of RbCaNb2O6F is derived from the stacking of [CaNb2O6F]- perovskite-type blocks which alternate with Rb+ ions along c-axis. The fluoride ion occupies the central site of corner-sharing NbO5F octahedra in the perovskite block. This layered perovskite compound is a new member of the Dion-Jacobson series with n=2 for the general formula A[A'n-1BnX3n+1]. The structural features of RbCaNb2O6F are discussed by comparison with other compounds of A[A'B2X7] family