Proton transport properties at the grain boundary of barium zirconate based proton conductors for intermediate temperature operating SOFC

Proton transport properties across the grain boundary of barium zirconate based proton conductors were studied in accordance with the space charge concept. The analysis is performed at temperatures lower than 200 degrees C using a Mott-Schottky model. The barrier height of Y- and Gd-doped barium zirconate is in the range of 0.29 to 0.57 V, which higher than that of oxygen ionic conductors. The barrier height of the space charge layer shows a dependence on the dopant type and concentration. The dependence correlates with the enrichment of the dopant at the grain boundary. The results suggest that the enrichment of the dopant decreases the barrier height and is effective to improve proton transport properties across the grain boundary.