Ce0.9Gd0.1O1.95 is widely used as an oxide-ion conductor in solid-state electrochemical cells, but the Gd dopant is costly. We aimed to reduce the Gd content in this type of conductor by carrying out tests on the Ce0.9Gd0.1-xYxO1.95 system. The sintering characteristics of Ce0.9Gd0.1O1.95 were better than those of Ce0.9Gd0.1O1.95. The electrical conductivity of Ce(0.9)Gd(0.1)O(1.95)at 600 degrees C was 0.0184 S cm(-1), which was approximately 71% of that of Ce0.9Gd0.1O1.95. Each co-doped Ce0.9Gd0.1-xYxO1.95 ceria sample investigated was found to form a single fluorite phase. With increasing Y content, the sintering characteristics of Ce0.9Gd0.1-xYxO1.95 had a tendency to approach to those of Ce0.9Gd0.1O1.95. The conductivity of Ce0.9Gd0.075Y0.025O1.95 at 600 degrees C was 0.0259 S cm(-1), the same as that of Ce0.9Gd0.1O1.95. After aging at 600 degrees C, rates of decrease in conductivity for Ce0.9Gd0.075Y0.025O1.95 were almost the same as those of Ce0.9Gd0.1O1.95. These results suggested that it is possible to reduce the Gd content in Ce(0.9)Gd(0.1)O(1.95)by 25% through substitution with Y. (c) 2017 The Electrochemical Society. All rights reserved.