Voltage and partial pressure dependent defect chemistry in (La, Sr)FeO3−δ thin films investigated by chemical capacitance measurements. Issue 17 (19th April 2018)

• Record Type: Journal Article
• Authors: Schmid, Alexander; Rupp, Ghislain M.; Fleig, Jürgen
• Is Part Of: Physical chemistry chemical physics. Volume 20:Issue 17(2018)
• Page Start: 12016
• Page End: 12026
• Publication Date: 2018-04-19
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/c7cp07845e
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : Chemical capacitance measurements are used to study the defect chemistry of La0.6 Sr0.4 FeO3− δ thin films and their polarization ( η ) and p O2 dependence. Important point defects are oxygen vacancies ( ), electrons (e′) and holes (h˙). Abstract : La0.6 Sr0.4 FeO3− δ (LSF) thin films of different thickness were prepared by pulsed laser deposition on yttria stabilized zirconia (YSZ) and characterized by using three electrode impedance spectroscopy. Electrochemical film capacitance was analyzed in relation to oxygen partial pressure (0.25 mbar to 1 bar), DC polarization (0 m to −600 m) and temperature (500 to 650 °C). For most measurement parameters, the chemical bulk capacitance dominates the overall capacitive properties and the corresponding defect chemical state depends solely on the oxygen chemical potential inside the film, independent of atmospheric oxygen pressure and DC polarization. Thus, defect chemical properties (defect concentrations and defect formation enthalpies) could be deduced from such measurements. Comparison with LSF defect chemical bulk data from the literature showed good agreement for vacancy formation energies but suggested larger electronic defect concentrations in the films. From thickness-dependent measurements at lower oxygen chemical potentials, an additional capacitive contribution could be identified and attributed to the LSF|YSZ interface. Deviations from simple chemical capacitance models at high pressures are most probably due to defect interactions.