The defect chemical nature and electronic band structure of Yb-doped BaPrO3 have been examined as a candidate for cathode materials in solid oxide fuel cell using oxide protonics material as a solid electrolyte, because of a possible presence of mixed conductivity of holes (electrons) and protons. The FT-IR results have shown that the proton concentration increases with the increase of dopant concentration. The electrical conductivity measurements suggest that p-type conductivity dominates in both intrinsic and extrinsic regions, showing a linear increase of conductivity with the increase of dopant concentration. The photoemission spectroscopy measurements have shown the presence of sub-band at the top of valence band, suggesting that the valence band is composed of O2p and Pr4f multiplet. These results can be explained by a simple defect chemical model assuming both auto-ionization of Pr4+/Pr3+ in the intrinsic region and the charge compensation for acceptor dopant of Yb3+ on normal Pr4+ site by holes in the extrinsic region. (C) 2007 Elsevier B.V. All rights reserved.