The proton conductivity of doped perovskite metal oxides with the ABO3 structure, which were aliovalently doped with lanthanide oxides, could be understood in terms of an effective oxide-ion vacancy concentration which arose from dopant-site selectivity and the relative values of water incorporation energies. The conductivity results suggested that smaller lanthanide ions (Y3+, Yb3+) replaced B-site cations (Zr) and generated the oxide-ion vacancies (VO) which were necessary for proton incorporation as a result of charge compensation that gave rise to an enhanced proton conductivity. On the other hand, larger lanthanide dopant ions (Nd3+, La3+) appeared to replace A-site cations (Sr2+) and resulted in the generation of divalent cation vacancies. Such doping suppressed the oxide-ion vacancy concentration, and the proton conductivity was decreased. The results were consistent with the energetics of substitution reactions.

Dependence of Dopant Ion Selectivity on Incorporation of Protons in Doped Perovskite Oxides. A.Kumar: Indian Journal of Pure and Applied Physics, 2001, 39[4], 263-6