To improve the protonic conductivity of CaZr0.95In0.05O3 - delta as well as the chemical and thermal stability of BaCe0.9Y0.1O3 (-) (theta), a composite ceramic 80% CaZr0.95In0.05O3 (-) (delta)-20% BaCe0.9Y0.1O3 (-) (theta) was synthesized by an optimized solid-state reaction method. The experimental results showed that the composite ceramics sintered at the temperature of 1400 degrees C obtained a relative density higher than 97%. A proton conductivity of the composite as high as 1.0 x 10(-3) S.cm(-1) at 800 degrees C was realized, which was more than twice that of CaZr0.95In0.05O3 (- delta). In addition, the chemical and thermal stability of composite ceramics in CO2 and H2O atmospheres appeared adequate under a wide range of operating conditions. (C) 2015 Elsevier B.V. All rights reserved.