Complex oxides La1.95Ca0.05M2O7-delta (M = Ce, Zr) were prepared by sol-gel method and characterized by thermal analysis (TG-DTA), X-ray diffraction (XRD). On the sintered complex oxides as solid electrolyte, the conductivity was measured in various atmospheres, and ammonia was synthesized from nitrogen and hydrogen at atmospheric pressure in the solid states proton conducting cell reactor by electrochemical methods. The rates of ammonia formation were up to 2.0 x 10(-9) mol s(-1) cm(-2) for La1.95Ca0.05Zr2O7-delta and 1.3 x 10(-9) mol s(-1) cm(-2) for La1.95Ca0.05Ce2O7-delta, respectively, at 520 degrees C. (c) 2005 Elsevier Ltd. All rights reserved.