Oxygen surface exchange kinetics measurement by simultaneous optical transmission relaxation and impedance spectroscopy: Sr(Ti,Fe)O3-x thin film case study

Nicola H. Perry, Jae Jin Kim, Harry L. Tuller

Research output: Contribution to journalArticlepeer-review

Abstract

We compare approaches to measure oxygen surface exchange kinetics, by simultaneous optical transmission relaxation (OTR) and AC-impedance spectroscopy (AC-IS), on the same mixed conducting SrTi0.65Fe0.35O3-x film. Surface exchange coefficients were evaluated as a function of oxygen activity in the film, controlled by gas partial pressure and/or DC bias applied across the ionically conducting yttria-stabilized zirconia substrate. Changes in measured light transmission through the film over time (relaxations) resulted from optical absorption changes in the film corresponding to changes in its oxygen and oxidized Fe (~Fe4+) concentrations; such relaxation profiles were successfully described by the equation for surface exchange-limited kinetics appropriate for the film geometry. The kchem values obtained by OTR were significantly lower than the AC-IS derived kchem values and kq values multiplied by the thermodynamic factor (bulk or thin film), suggesting a possible enhancement in k by the metal current collectors (Pt, Au). Long-term degradation in kchem and kq values obtained by AC-IS was also attributed to deterioration of the porous Pt current collector, while no significant degradation was observed in the optically derived kchem values. The results suggest that, while the current collector might influence measurements by AC-IS, the OTR method offers a continuous, in situ, and contact-free method to measure oxygen exchange kinetics at the native surfaces of thin films.

Original languageEnglish (US)
Pages (from-to)130-141
Number of pages12
JournalScience and Technology of Advanced Materials
Volume19
Issue number1
DOIs
StatePublished - Dec 31 2018

Keywords

  • Thin films
  • impedance spectroscopy
  • mixed ionic and electronic conductor
  • optical absorption
  • oxygen surface exchange
  • perovskite

ASJC Scopus subject areas

  • Materials Science(all)

Fingerprint

Dive into the research topics of 'Oxygen surface exchange kinetics measurement by simultaneous optical transmission relaxation and impedance spectroscopy: Sr(Ti,Fe)O<sub>3-x</sub> thin film case study'. Together they form a unique fingerprint.

Cite this