Influence of the metal-to-non-metal transition on the surface degradation of BaPb1-xBixO3

A synchrotron-excited photoemission study of BaPb1-xBixO3 ceramics having compositions spanning the entire solid solution range has been carried out. Photoemission is used to monitor the changes in the density of states (DOS) in the valence band and Fermi level regions as a function of Pb content. A dramatic change in surface reactivity at the metal-to-non-metal transition point is revealed, with all metallic compositions displaying pronounced surface instability. These results are correlated with XPS data from artificially degraded samples, which show a pronounced variation in the surface concentration of BaCO3 (a degradation product) as a function of the Pb:Bi ratio in the region of the metal-to-non-metal transition.