A TEM Study of Birnessite-type K_0.33MnO₂

－In-plane Ordering and Layer Stacking－

抄録

Birnessite-type K_0.33MnO₂ was prepared by the solid state reaction of KOH and MnCO₃ in air. The XRD pattern of the sample calcined at 700°C can be indexed as a single phase of the monoclinic C2/m phase (a= 5.186Å, b = 2.851Å, c =7.154Å, β=101.74°). Their [001]_m zone ED patterns show superlattice spots indicating in-plane pseudo-hexagonal (√3×√3)_h-R30° and monoclinic (3×1)_m ordering. However, the lattice images do not show clear contrast of the superlattice. Although the [010]_m and [100]_m-zone ED patterns also showed clear superlattice spots, they show diffuse streaks due to the stacking disorder. The lattice images clearly revealed the details of the layer stacking. The thickness of the layers with the regular stacking is limited to several nano-meters because of the stacking disorder.