Dense ceramic samples BaCe0.85 - xZrxEr0.15O3-alpha (0.0 <= x <= 0.4) have been synthesized by heat-treating the precursor prepared through a microemulsion route. The obtained ceramic samples showed a single phase of orthorhombic perovskite. It was found that the ceramic powders of BaCe0.85 - xZrxEr0.15O3-alpha were relatively stable when x >= 0.2 after exposure in 94% N-2 + 3% CO2 + 3% H2O atmosphere at 873.15 K for 20 h. The total conductivities of the ceramic samples decreased with increasing Zr content in the samples in wet hydrogen. Among the ceramic samples studied, BaCe0.65Zr0.2Er0.15O3-alpha displayed both a high chemical stability in 94% N-2 + 3% CO2 + 3% H2O atmosphere and an acceptable conductivity at 573.15-1073.15 K. The results indicated that BaCe0.65Zr0.2Er0.15O3-alpha. was almost pure ionic conductor at 773.15-1073.15 K in wet hydrogen atmosphere. The ionic conduction was contributed mainly by proton with transference numbers of 0.95-0.81 and partially by oxide ion with transference numbers of 0.02 to 0.08. In addition, BaCe0.65Zr0.2Er0.15O3-alpha was successfully applied to the ammonia synthesis at atmospheric pressure. The peak ammonia formation rate achieved 3.27 x 10(-9) mol s(-1) cm(-2) under a direct current of 1.0 mA at 723.15 K. (c) 2011 Elsevier B.V. All rights reserved.