Stacking disorder in a layered carbonate phase: the structure of LaKOCO3 Original Research Article

The structure of LaKOCO3 prepared by using the molten salt synthesis was examined by neutron diffraction, X-ray diffraction and electron diffraction. LnKOCO3 has a layered structure strongly related to the T∗ structure known from transition metal oxides, whereby the transition metal/oxygen layers of the latter are completely substituted by carbonate layers. Unlike in other layered carbonate phases, the carbonate ions are ordered and immobile in terms of rotation at 300 K. While the long-range orientation order within the layers is well established, a statistical orientation of the layer units was found around the axis perpendicular to the layers. The consequences of this stacking disorder for the diffraction data were discussed.