Structural properties and electrochemical performance of strontium- and nickel-substituted lanthanum cobaltite

This study presents structural and defect properties as function of doping, temperature and pO2 in (La1 − x Srx)0.99 Co0.6 + xNi0.4 − xO3 − δ (x = 0; 0.1; 0.2; 0.3; 0.4). Thermograviomertric analysis showed a linear increase in δ with both T and x in the high temperature regime. The onset temperature of reduction was seen to increase with x which was confirmed with dilatometry and XANES. XANES measurements further indicated that reduction was exclusively associated with cobalt. A transition from polaronic to itinerant electronic conduction was measured with increasing x ranging from 2000–3500 Scm− 1 in the intermediate SOFC temperature range of 500–800 °C. The polarisation resistance when used as porous SOFC cathodes was measured to decrease with x. The activation energy of about 1.8 eV for all electrodes but (La0.6 Sr0.4)0.99 CoO3 − δ, for which it was about 1 eV.