Details

Autor(en) / Beteiligte

• Kalaev, D
• Tuller, H. L

Titel

Simultaneous electrical impedance and optical absorption spectroscopy for rapid characterization of oxygen vacancies and small polarons in doped ceria

Ist Teil von

• Physical chemistry chemical physics : PCCP, 2023-02, Vol.25 (7), p.5731-5742

Ort / Verlag

England: Royal Society of Chemistry

Erscheinungsjahr

2023

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• 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, Pr x Ce 1− x O 2− δ (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 °C), in a wide range of deviation from stoichiometry, δ . For instance, at 600 °C the PCO properties were obtained during a ten minute reduction process, in the p O 2 range from 1 to 10 −13 bar. The experimental results show that the oxygen vacancy mobility is constant while the small polaron mobility is linear in δ , in the whole p O 2 range, which yields the total conductivity quadratic in δ . 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 δ 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. Novel σ- α method, applied under non-steady state conditions, enables an accelerated and detailed study of oxygen vacancy and small polaron transport in praseodymium doped ceria as functions of oxygen non-stoichiometry and temperature.