Electrical Conductivity Relaxation Study of Solid Oxide Fuel Cell Cathodes using Epitaxial (001)-Oriented Strontium-Doped Lanthanum Manganite Thin Films

Epitaxial single-crystal films of La0.7Sr0.3MnO3 (100) having smooth surface morphology were deposited on SrTiO3 (100) substrates by pulsed laser deposition (PLD). Electrical conductivity relaxation (ECR) measurements were carried out at elevated temperatures over a range of absolute oxygen pressures to determine the oxygen surface exchange coefficient. Steady-state conductivity data of the thin films show good agreement with the bulk material's properties. The values of the oxygen exchange coefficients (Kchem) are found to be similar for both oxidation and reduction process between 50 and 500 mTorr O2. The activation energy (Ea) of Kchem is 1.00±0.27 eV at temperatures above 600 °C and Kchem (T=612°C)≈1.2×10-6 cm/s.