AA ' 2M3O10 (A = K, Rb, Cs; A ' = Ca; M = Nb) layered perovskites: low-temperature proton conductors in hydrogen atmospheres

Electrical conductivity of the Dion-Jacobson (D-J) type layered perovskite oxides, AA(2)'M3O10 (A = K, Rb, Cs; A' = Ca; M = Nb, Ta), is determined by AC impedance analysis in hydrogen atmospheres and in air. The electrical conductivity behavior of the layered perovskite oxides in hydrogen is different from that in air. Among the layered perovskites, KCa2Nb3O10 exhibits the highest electrical conductivity, sigma, of 3.2 x 10(-4) S cm(-1) at 45 degreesC with an activation energy, E-a, of 0.25 eV in a hydrogen atmosphere. Open circuit voltage measurements at room temperature with hydrogen-oxygen gas concentration cells reveal that the mobile charge carriers are most likely protonic in origin. The electrical (proton) conductivity is comparable to that of fast lithium ionic conductors based on the perovskite structure such as (Li,La)TiO3 at the same temperature.