The Effect of Space Charge on Blocking Grain Boundary Resistance in an Yttrium-Doped Barium Zirconate Electrolyte for Solid Oxide Fuel Cells

The higher grain boundary resistance in the proton-conducting yttrium-doped barium zirconate is one of the major issues to be solved. A new strategy has been experimentally studied on the basis of space charge theory to understand the grain boundary resistance in pristine and 20 mol % yttrium-doped barium zirconate by varying the sintering temperature (1200, 1300, 1400, and 1500 degrees C). The electrical response upon applying a DC bias indicates the existence of space charge in the grain boundary region of barium zirconate. The Mott-Schottky analysis was performed at a lower temperature of 100 degrees C to infer the information from the grain boundary region. A parabolic reduction in normalized proton concentration was observed from the grain boundary to its core. The barrier height varied in the range of 0.55-0.15 V depending on the sintering temperature. The increase in dopant concentration along the grain boundary resulted in the reduction of barrier height as well as space charge width. Hence, the presence of yttrium and subsequent variation of the sintering temperature have a strong influence on space charge modulation and affect the grain boundary resistance.