Ceria is proposed as an additive for La0.8Sr0.2MnO3 (LSM) cathodes in order to increase both their thermal stability and electrochemical properties after co-sintering with an yttria-stabilized zirconia (YSZ) electrolyte at 1350 degrees C. Results show that LSM without CeO2 addition is unstable at 1350 degrees C, whereas the thermal stability of LSM is drastically improved after addition of CeO2. In addition, results show a correlation between CeO2 addition and the maximum power density obtained in 300 mu m thick electrolyte-supported single cells in which the anode and modified cathode have been co-sintered at 1350 degrees C. Single cells with cathodes not containing CeO2 produce only 7 mW cm(-2) at 800 degrees C, whereas the power density increases to 117 mW cm(-2) for a CeO2 addition of 12 mol%. Preliminary results suggest that CeO2 could increase the power density by at least two mechanisms: (1) incorporation of cerium into the LSM crystal structure, and (2) by modification or reduction of La2Zr2O7 formation at high temperature. This approach permits the highest LSM-YSZ co-sintering temperature so far reported, providing power densities of hundreds of mW cm(-2) without the need for a buffer layer between the LSM cathode and YSZ electrolyte. Therefore, this method simplifies the co-sintering of SOFC cells at high temperature and improves their electrochemical performance. (C) 2011 Elsevier B.V. All rights reserved.