Mixed potential protonic-electronic conductivity in the Dion-Jacobson-type layered perovskites in hydrogen-containing atmosphere and their application in ammonia sensors

The electrical conductivities of Dion-Jacobson (D-J)-type layered perovskites ACa₂Nb₃O₁₀ (A = K, Rb, Cs) were investigated in the presence of different gas atmospheres. An increase in the electrical conductivity of about two to five orders of magnitude in both ammonia and hydrogen atmospheres as compared to air is observed in the investigated temperature regime 30-750 °C. Among the members studied, KCa ₂Nb₃O₁₀ exhibits the highest electrical conductivity with the lowest activation energy in hydrogen atmosphere. Open circuit voltage measurements using a hydrogen-air cell (H₂||air) reveal that as-prepared material exhibits mainly proton conductivity at low temperatures, while sample taken after the AC impedance measurements in hydrogen atmosphere and quenched to room temperature shows significant electronic contribution. The electrical conductivity changes as a function of the ammonia/hydrogen gas concentration. Accordingly, layered perovskites appear to be useful materials for practical applications (e.g., for gas sensors.)