LEAD-NMR STUDY OF BAPB1-X(SB BI)(X)O-3

Recent Mossbauer experiments on BaPb1-xSbxO3 revealed only the presenc e of Sb(V), while in BaPb1-xBixO3 in the semiconducting phase the Bi-c harge disproportionation is well established. We find a similar asymme try in the NMR spectra. The NMR spectra on semiconducting BaPb1-xSbxO3 clearly show the charge disproportionation of lead, while in BaPb1-xB ixO3 in the semiconducting phase only Pb(IV) is observed. The metallic phases of the Sb-doped compounds show one lead resonance line. Based on the NMR spectra and the elemental analysis a phase diagram for BaPb 1-xSbxO3 is proposed with a miscibility gap in the range of 0.35 < x < 0.50.