Dense ceramic samples of BaCe1-x Ca (x) O3-alpha (x = 0.05, 0.10, 0.15, 0.20) have been synthesized by heat treating the precursor prepared from a microemulsion route under lower calcining and sintering temperatures than traditional high-temperature solid-state reaction. The samples exhibited single phase of orthorhombic perovskite. It was found that the samples were almost pure proton conductors in wet hydrogen at 300-600 A degrees C. Ammonia was synthesized successfully from nitrogen and hydrogen gases at atmospheric pressure using BaCe0.9Ca0.1O3-alpha as an electrolyte of ammonia synthesis reactor.