IONIC-CONDUCTIVITY OF PEROVSKITE LACOO3 MEASURED BY OXYGEN PERMEATIONTECHNIQUE

Oxygen permeation measurement is demonstrated, not only for a mixed ox ide ionic and electronic conductor, but also as a new alternative to d etermine 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 La1-xSrxCoO3-delta dense membrane system, LaCoO3 dense ceramic was measured with respect to the thickness, temperature and oxygen partial pressure dependencie s of its oxygen permeability. Within the thickness range used (down to 0.041 cm), the oxygen permeation of LaCoO3 was found to be purely con trolled 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 permeab ility data. P-O2(-0.46) and P-O2(-0.31) relations were found in the hi gh pressure (1.01-10(-2) bar) and low pressure (10(-2.8)-10(-3.4)bar) ranges, respectively.