Electrochemical characterisation of MBaCo3ZnO7+δ (M = Y, Er, Tb) as SOFC cathode material with low thermal expansion coefficient

The electrochemical oxygen activation at high temperature was studied on a new class of oxygen-store material based on the system YBaCo4O7+δ. Three different porous layers made of YBaCo3ZnO7+δ, ErBaCo3ZnO7+δ and TbBaCo3ZnO7+δ were electrochemically tested as oxygen activation coatings and showed a very promising activity. The envisaged applications for these materials are principally as SOFC cathodes and as catalytic layer on oxygen membranes. The electrochemical performance followed the order Tb ⩾ Y > Er at any tested temperature. Area specific resistance for the best performing material (TbBaCo3ZnO7+δ) ranges from 30 mΩ cm2 at 850 °C to 0.46 Ω cm2 at 650 °C. High temperature XRD showed that the thermal expansion coefficient (25–900 °C) in air of TbBaCo3ZnO7 is 9.45 × 10−6 K−1, which evidences the good thermochemical compatibility of this cobalt-rich electrocatalyst with YSZ/GDC electrolytes.