This proton-conducting electrolyte, Ba3Ca1.18Nb1.82O9, was shown to exhibit a conductivity of above 0.01S/cm, with a transport number that was greater than 0.98, at 600C. Concentration cell measurements which were performed at up to 800C, using various gases, revealed no sign of residual electronic conduction, and the total ionic transport number was close to unity. It was found that only 1/3 of the O-ion vacancies (those which were replaceable by protons) participated in conduction. The remaining, deeply-trapped O vacancies were essentially immobile.

Y.Du, A.S.Nowick: Solid State Ionics, 1996, 91[1-2], 85-91