EFFECTS OF SUBSTITUTION OF BI WITH PB IN BABI1-XPBXO3 ON CRYSTAL-STRUCTURE AND CONDUCTION BEHAVIOR

The crystal structure of BaBi1-xPb(x)O3 was investigated by X-ray diffraction. In the range 0.0 less-than-or-equal-to x less-than-or-equal-to 0.5, monoclinic symmetry containing two Bi sites was clearly observed. This suggests that Bi exhibits disproportionation to two different chemical states, 3+ and 5+, supplying no electron carrier in the range 0.0 less-than-or-equal-to x < 0.5. As x increases above 0.5, a continuous phase variation from monoclinic to orthorhombic was observed, which showed good agreement with a continuous variation of the temperature dependence of resistivity and a qualitatively similar X-ray absorption near-edge structure on composition x. This continuous effect of the substitution of Bi with Pb in BaBi1-xPb(x)O3 contrasted with the case of the substitution of Ba with K in Ba1-xK(x)BiO3, which shows a distinct phase transition involving electron carrier generation at x almost-equal-to 0.35.