A neutron diffraction study of structural distortions in the Ruddlesden–Popper phase Na2La2Ti3O10

Abstract

The structure of Na₂La₂Ti₃O₁₀(tetragonal, space group I4/mmm) has been re-examined using time-of-flight powder neutron diffraction in order to clarify uncertainties remaining from an X-ray diffraction study. One of the oxygen atoms is shown to be displaced significantly from its ideal position, the shift being consistent with the rotation of one of the TiO₆ octahedra by ca. 12.5° around the [001] direction. This rotation allows for a 2.5% increase in four of the Ti—O bond lengths and a corresponding decrease in the bond valence sum from 4.9 to 4.1. The structural distortion is similar to that observed previously at overbonded octahedral sites in related structures.