A single crystal X-ray and high resolution electron microscope study of Pb5Sb6S14

The structure of Pb5Sb6S14, first observed by HREM, has been refined by single crystal X-ray diffraction. It is a higher homologue of robinsonite, Pb4Sb6S13, with a = 28.367(8) Å, b = 4.024(1) Å, c = 22.044(7) Å, α = 89.59(2), β = 92.28(3), γ = 89.93(2), space group I1, Z = 4. Pb5Sb6S14 is built from two different ribbons composed of square pyramidal (Pb, Sb)S5 groups with the narrow ribbon identical to that in robinsonite and the other ribbon one pyramid wider. HREM studies indicate that during electron microscope observation Pb5Sb6S14 decomposes into three different polymorphs of PbS. High resolution electron micrographs allow models to be proposed for the transformations.