Ionic conductivity of perovskite LaCoO₃ measured by oxygen permeation technique

Oxygen permeation measurement is demonstrated, not only for a mixed oxide ionic and electronic conductor, but also as a new alternative to determine ambipolar conductivities, which can be usually reduced to be partial conductivities (either ionic or electronic). As a model system and an end member of an important oxygen permeable La_1-xSr_xCoO_3-δ dense membrane system, LaCoO₃ dense ceramic was measured with respect to the thickness, temperature and oxygen partial pressure dependencies of its oxygen permeability. Within the thickness range used (down to 0.041cm), the oxygen permeation of LaCoO₃ was found to be purely controlled by bulk diffusion with activation energies between 260–300 kJ mol^-1. Its ionic conductivity and oxygen self-diffusion coefficient as functions of oxygen partial pressure were also derived from permeability data. P_O2^-0.46 and P_O2^-031 relations were found in the high pressure (1.01–10^-2bar) and low pressure (10^-2.8–10^-3.4bar) ranges, respectively.