Defect chemistry and electrical properties of (La0.8 Ca0.2)0.95 Fe O3-δ

Kyung Joong Yoon, Peter A. Zink, Srikanth Gopalan, Uday B. Pal, Larry R. Pederson

Research output: Contribution to journalArticle

24 Citations (Scopus)

Abstract

A-site-doped lanthanum ferrite perovskites are considered to be promising cathode materials for the lower temperature operation of solid oxide fuel cells due to their high catalytic activity, mixed electronic and ionic conductivities at reduced temperature, and adjustable thermal-expansion coefficient. The defect chemistry and electrical properties of (La0.8 Ca0.2)0.95 Fe O3-δ were studied using thermogravimetry and dc electrical conductivity measurements at temperatures 550≤T≤850°C in the oxygen partial pressure range of 0.001≤ pO2 ≤1 atm. A point-defect model was developed, and the mass-action coefficients for the oxygen-exchange reaction at various temperatures were determined by fitting thermogravimetry data into the model. Equilibrium defect concentrations were calculated as a function of temperature and oxygen partial pressure based on the defect modeling results. Electrical conductivity measurements indicated that (La0.8 Ca0.2)0.95 Fe O3-δ is a p-type conductor. At low temperature, conductivity increased with temperature, which reflected thermally activated conduction behavior. At high temperatures, conductivity decreased with temperature because the conductivity was mainly affected by a decrease in the hole concentration due to the progressive formation of oxygen vacancies at the expense of holes. Hole mobility under various conditions was determined using electric conductivity data and equilibrium hole concentrations, and the relationship between the mobility and temperature indicated a nonadiabatic, small polaron hopping conduction mechanism with activation energies of 0.149-0.310 eV. The effects of temperature and oxygen partial pressure on the defect structure and electronic conduction were discussed in detail.

Original languageEnglish
JournalJournal of the Electrochemical Society
Volume156
Issue number7
DOIs
Publication statusPublished - 2009
Externally publishedYes

Fingerprint

Electric properties
electrical properties
chemistry
Defects
defects
conductivity
oxygen
partial pressure
Temperature
temperature
Partial pressure
Oxygen
Hole concentration
thermogravimetry
conduction
Thermogravimetric analysis
electrical resistivity
Low temperature operations
hole mobility
perovskites

ASJC Scopus subject areas

  • Electrochemistry
  • Electronic, Optical and Magnetic Materials
  • Materials Chemistry
  • Surfaces, Coatings and Films
  • Renewable Energy, Sustainability and the Environment
  • Condensed Matter Physics

Cite this

Defect chemistry and electrical properties of (La0.8 Ca0.2)0.95 Fe O3-δ. / Yoon, Kyung Joong; Zink, Peter A.; Gopalan, Srikanth; Pal, Uday B.; Pederson, Larry R.

In: Journal of the Electrochemical Society, Vol. 156, No. 7, 2009.

Research output: Contribution to journalArticle

Yoon, Kyung Joong ; Zink, Peter A. ; Gopalan, Srikanth ; Pal, Uday B. ; Pederson, Larry R. / Defect chemistry and electrical properties of (La0.8 Ca0.2)0.95 Fe O3-δ. In: Journal of the Electrochemical Society. 2009 ; Vol. 156, No. 7.
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