Neutron diffraction and X-ray absorption study of Ag5Pb2O6

Neutron diffraction and X-ray absorption measurements were carried out for a silver-lead oxide Ag5Pb2O6. The powder neutron diffraction patterns could be fitted to the trigonal P (3) over bar 1m structure, as was found by X-ray diffraction. From the bond-valence-sum (BVS) analysis, the valences of the Ag and Ph ions were estimated to be about 1 + and 3.7 +, respectively. The X-ray absorption measurements indicated that the ionic state of Ag is close to 1 +, while that of Pb stands between 3 + and 4 +. The deviation of the valence of the Ph ion from 4 + suggests a contribution of Ph orbitals to the metallic conduction as well as the possible superconductivity of this material, consistently with a recent band-structure calculation. (c) 2006 Elsevier Inc. All rights reserved.