The conductivity of Dion-Jacobson-type layered perovskites, Nb3Ca2AO10 (where A was K, Rb or Cs), was investigated under various gas atmospheres. A 2- to 5-order of magnitude increase in the conductivity in NH3 and H atmospheres was observed, as compared to the behavior in air. Among the members of this series, the compound with the smallest alkali ion (Nb3Ca2KO10) exhibited the highest conductivity. A single activation energy, ranging from 0.25 to 0.80eV, was observed in air and H. In the case of NH3, a sharp increase in the conductivity was found at about 500C. The activation energy at 300 to 500C was attributed to ionic motion and, at higher temperatures (500-700C), to defect formation and ionic motion. The unusual electrical conductivity behavior in NH3 was explained in terms of a model which had been developed for alkali halides. EMF measurements revealed that the layered perovskites were ionic (proton) conductors. The conductivity varied as a function of the NH3 gas concentration.

Electrical Properties of ANb3Ca2O10 (A = K, Rb, Cs) Layered Perovskite Ceramics. V.Thangadurai, W.Weppner: Ionics, 2001, 7[1-2], 22-31