OXIDE-ION MOTION IN BISMUTH SESQUIOXIDE (DELTA-BI2O3)

The delta-form of Bi2O3 and the melt were studied by EXAFS near the Bi -L(3) edge and by X-ray diffraction. EXAFS data analyses were made on the basis of a two-shell model. A non-linear least-squares fitting was carried out by the cumulant expansion up to fourth-order term. The Bi -O distances of the first and second shells slightly decrease with inc reasing temperature in spite of increase of the lattice constant. The cumulants of higher order are almost constant with temperature. Compar ison using primary differential of XANES by energy shows a slight chan ge between the delta-form and the melt indicating a change in symmetry of coordinating atoms.