EXAFS is used to study changes in local structure which occur on doping at the B site in two related perovskite oxides,. In the case of the stannate, data is taken at the Sr K, Sb K and Sn K edges. A combination of near-edge XAS and EXAFS measurements show that Sb dopes into the material as SbV . In the case of the bismuthate, data is taken at the low-intensity Bi L I and Pb L II edges, with the aim of resolving controversy surrounding the interpretation of EXAFS data taken at the overlapping L III edges. In BaBiO 3 , two BiMO bond lengths are observed, suggesting the presence of a charge density wave. In this material, equal proportions of these two bond lengths are present. However, as Pb is doped into the material, the proportion of oxygen bonded to Bi at the shorter of the two distances increases progressively.

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Ah**.net svnchmtmn-erritor( ~ nhntnnmk=inn ctimrlw _."", of R n D h ~ "I _,_. RI " _ J n. e e r ~l m i ~~ "" having compositions spanning t h e entire solid solution range has been carried out. Photoemission is used to monitor t h e changes in the density of states (00s) in t h e 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 ar!ificinliy degraded samples, which show a pronounced variation in the surface concentration of BaCO, (a degradation product) as a function of the Pb : Bi ratio in the region of t h e metal-to-non-metal transition.

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