In this study, the effects of Ti substitution for Ce on chemical and structural stability and electrical properties of proton-conducting solid electrolyte membrane BaCe0.8-xTixSm0.2O3-delta(BCST) are investigated. Our results show that both chemical and structural stability of the BCST samples in CO2 containing and moist atmospheres are remarkably enhanced with increasing the content of Ti which is higher electronegative than Ce. However, the proton conductivity of the sample decreases with increasing Ti content, which may be due to the increasing difficulty of lattice hydration and smaller grain size (corresponding to more grain boundaries) caused by Ti doping. The activation energy for proton migration increases with Ti content, which is mainly related with the weaker hydrogen bond. The results show that the BaCe0.75Ti0.05Sm0.2O3-delta has a great electrical conductivity (1.03 x 10(-2) S cm(-1) at 650 degrees C) and it also demonstrates good chemical and structural stability in CO2 and water containing atmospheres. Therefore, BaCe0.75Ti0.05Sm0.2O3-delta can be considered as a promising proton conducting electrolyte for intermediate temperature solid oxide fuel cells. (C) 2016 Elsevier B.V. All rights reserved.