Synthesis, electrical properties, and powder neutron crystal structure refinement of Pb1-xBixPt2O4 compounds (0 <= x <= 0.3)

摘要

Substitution of Pb for Bi in the recently characterized mixed-valence lead-platinum oxide PbPt2O4 was attempted and a Pb1-xBixPt2O4 solid solution was obtained for 0 less than or equal to x less than or equal to 0.3. Powder X-ray diffraction study showed that all substituted compounds crystallize with similar triclinic unit cell and PbPt2O4 lattice parameters. The structural model of Pb0.7Bi0.3Pt2O4 was refined from powder X-ray diffraction data using the Rietveld method and the results indicate the same crystal structure than PbPt2O4 with one mixed Pb/Bi atomic site. Neutron diffraction realized on the two limit compositions of the solid solution (x = 0 and 0.3) allowed to confirm the PbPt2O4 and Pb0.7Bi0.3Pt2O4 stoichiometries. Mean oxidation degree of Pt atoms in the [PtO4] infinite chains decreases from + 3 for PbPt2O4 to + 2.7 for Pb0.7Bi0.3Pt2O4- Conductivity measurements show a metallic behavior for all the compositions except the limit composition x = 0.3 for which a semiconducting behavior appears. (C) 2002 Elsevier Science (USA). [References: 26]