Fig. 1: High oxide-ion conductivity of Ba7Nb3.9Mo1.1O20.05.

a, b Complex impedance plots of Ba7Nb3.9Mo1.1O20.05 recorded in dry air at (a) 309 °C and (b) 598 °C. c Arrhenius plots of bulk conductivity σb, grain-boundary conductivity σgb and DC σtot of Ba7Nb3.9Mo1.1O20.05 in dry air. Activation energy for σb of Ba7Nb3.9Mo1.1O20.05 decreases with temperature from 0.454 to 0.185 eV as shown by the red numbers in panel c. Green line represents σb of Ba7Nb4MoO20 reported by Fop et al.40. d Oxygen transport number of Ba7Nb3.9Mo1.1O20.05. e Oxygen partial pressure P(O2) dependence of σtot of Ba7Nb3.9Mo1.1O20.05. f Comparison of bulk conductivities of Ba7Nb3.9Mo1.1O20.05 and other oxide-ion conductors.