Mg-doped La2Ce2O7-delta (LCO) is investigated to develop an easily sintered and chemically stable proton conductor for fabricating high-performance solid oxide fuel cells (SOFCs). All La2-xMgxCe2O7-delta ceramics possess a pure fluorite-type structure. The sintering activity of Mg-doped LCO increases obviously, and fully dense La1.85Mg0.15Ce2O7-delta (LMCO) electrolyte membrane is successfully prepared by co-firing at the temperature as low as 1300 degrees C for 5 h. Besides, LMCO exhibits the highest electrical conductivity of 7.41 x 10(-2) S cm(-1) in dry air and 1.55 x 10(-2) S cm(-1) in wet H-2 (similar to 3% H2O) at 700 degrees C among the investigated oxides, and retains excellent chemical stability against CO2 and H2O. The LMCO-based fuel cell also displays very encouraging power performance, reaching as high as 897 mWcm(-2) at 700 degrees C. The results demonstrate LMCO is a promising alternative as proton conductor for achieving both chemically stable and high-performance SOFCs with reduced sintering temperature. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.