Thermal Variation of Structure and Electrical Conductivity in Bi4YbO7.5
Journal article, 2013

The thermal behavior of the oxide ion-conducting solid electrolyte Bi4YbO7.5 was investigated using a combination of variable temperature X-ray and neutron powder diffraction, thermal analysis (DTA and TGA), and ac impedance spectroscopy. The title compound shows a fluorite-type structure throughout the measured temperature range (20-850 degrees C), with a phase separation at ca. 600 degrees C into a cubic delta-type phase and an orthorhombic phase of assumed stoichiometry Bi17Yb7O36. This type of transition is a relatively common feature in bismuth oxide-based systems and can limit their practical application. Here, the transition was carefully studied using isothermal measurements, which showed that it is accompanied by changes in oxide-ion stoichiometry, as well as significant disorder in the oxide ion sublattice in the delta-type phase. These results correlate with the observed electrical behavior. Analysis of the total neutron scattering through reverse Monte Carlo (RMC) modeling reveals details of the coordination environments for both cations. The oxide-ion vacancy distribution seems to be consistent with a favoring of < 100 > vacancy pairs, although < 110 > vacancy pairs exhibit the highest frequency as they have the maximum likelihood. A vacancy ordering model based on three vacancies per cell is presented.


neutron diffraction


defect structure

cubic bismuth oxides

fluorite structure



bismuth ytterbium oxide


bismuth oxide


defect structure



total scattering



M. Leszczynska

Warsaw University of Technology

X. Liu

Queen Mary University of London

W. Wrobel

Warsaw University of Technology

M. Malys

Warsaw University of Technology

M. Krynski

Warsaw University of Technology

Stefan Norberg

Chalmers, Chemical and Biological Engineering, Environmental Inorganic Chemistry

S. Hull

STFC Rutherford Appleton Laboratory

F. Krok

Warsaw University of Technology

I. Abrahams

Queen Mary University of London

Chemistry of Materials

0897-4756 (ISSN) 1520-5002 (eISSN)

Vol. 25 3 326-336

Subject Categories

Chemical Sciences



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