Simultaneous electrical impedance and optical absorption spectroscopy for rapid characterization of oxygen vacancies and small polarons in doped ceria
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d2cp04901e.pdf
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Author(s)
Kalaev, D.
Tuller, H. L.
Date Issued
2023
Publisher
Royal Society of Chemistry (RSC)
Citation
Kalaev, D. and Tuller, H. L. 2023. "Simultaneous electrical impedance and optical absorption spectroscopy for rapid characterization of oxygen vacancies and small polarons in doped ceria." 25 (7).
Version
Final published version
Abstract
Mixed ionic–electronic conductors (MIECs) play a central role in emerging energy conversion and
energy efficient computational technologies. However, it is both challenging and resource demanding
to characterize MIECs over the broad range of experimental conditions of interest, thereby significantly
limiting their study and applications. Here, a novel method of a simultaneous measurement of electrical
conductivity and optical absorption of thin films in out-of-equilibrium state, i.e. during a reduction
process, is employed for a comprehensive study of a MIEC oxide, PrxCe1xO2d (PCO). It enables, orders
of magnitude faster than by established techniques, characterization of the oxygen vacancy and small
polaron formation and transport as a function of temperature (demonstrated here down to 200 1C), in a
wide range of deviation from stoichiometry, d. For instance, at 600 1C the PCO properties were
obtained during a ten minute reduction process, in the pO2 range from 1 to 1013 bar. The experimental
results show that the oxygen vacancy mobility is constant while the small polaron mobility is linear in d,
in the whole pO2 range, which yields the total conductivity quadratic in d. Furthermore, the method was
applied to study the modification of PCO’s transport properties with composition change. It was shown
that increasing x from 0.1 to 0.2 suppresses the ionic mobility and, at the same time, enhances the small
polaron mobility. Finally, the optically determined d was used to define an instantaneous oxygen activity
in PCO that can be accessed in the out-of-equilibrium experiments. This work opens up new
possibilities to study the effects of microstructure, strain and other applied external stimuli on the
transport and thermodynamic properties of PCO and similar types of MIEC materials.
Subjects
Physical and Theoretical Chemistry
General Physics and Astronomy
MIT Department
Massachusetts Institute of Technology. Department of Materials Science and Engineering
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Creative Commons Attribution NonCommercial License 3.0
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DOI of Published Version
https://doi.org/10.1039/d2cp04901e
