XPS study of Ba0.6K0.4BiO3

Single crystal Ba 0.6 K 0.4 BiO 3 was studied by using XPS. The results show that there is no evidence for the presence of Bi 5+ in single crystal of Ba 0.6 K 0.4 BiO 3 ; instead, there is evidence for the presence of mixed valent Bi 3+ and Bi (3+)‐δ . Moreover, the Ols XPS results suggest the presence of mixed valent O 2− and O 1− , and the valence band spectrum suggests the high degree of covalency for Bi—O bonds.