Highly conductive barium zirconate-based carbonate composite electrolytes for intermediate temperature-protonic ceramic fuel cells

Two-phase composite materials consisting of a BZY matrix phase and a binary eutectic carbonate (Li-0.5Na)(2)CO3 phase are designed in order to promote the densification and ionic conductivity of BaZr0.85Y0.15O3 delta (BZY) proton conductors at intermediate temperature. In the presence of carbonate phase, a considerable change in microstructure for the densification of BZY electrolytes sintered at 670 degrees C for 4 h is clearly visible in SEM analysis. This sintering effect is due to the formation of molten phase associated with carbonates at low temperature (495 degrees C) by TG-DTA analysis. The conductivity of composite electrolytes is significantly higher than that of BZY over the entire temperature and atmosphere range studied by AC impedance and DC four-probe methods. In addition, the change of the carbonate content in the composite electrolyte presents a great influence on the conductivity. The composite containing 25 wt.% (Li-0.5Na)(2)CO3 shows the highest ionic conductivity of 0.176 S cm (1) at 550 degrees C and lowest activation energy of 0.127 eV in the temperature range of 500-650 degrees C. (C) 2013 Elsevier B.V. All rights reserved.