Structure and Properties of Ni0.25Pt3O4. A New Platinum Bronze

The first single-crystal preparation, structure determination, and electrical conductivity measurements of a platinum-metal bronze are described. The nickel-platinum bronze Ni0.25Pt3O4 has a cubic structure with a = 5.61 (2) å and crystallizes in space group PmZn or P43w, with two formula units per unit cell. The structure was solved using three-dimensional X-ray data, collected by counter methods. Refinement by full-matrix least-squares methods gave a final R factor of 5.6% on F for the 18 independent reflections. The structure can be described in terms of a filled β-tungsten type, where the “filling” oxygen atoms are in square-planar coordination around the platinum atoms. Nonintersecting chains of Pt atoms run parallel to all three cubic axes. The short Pt-Pt distance of 2.80 (1) A and the electrical resistivity data indicate extensive metallic bonding along the chains. The Ni atoms are situated in channels, each Ni atom being very weakly bonded to eight oxygen atoms.