Effects of Stoichiometry Variation on Transport Properties of Proton Conducting Ceramics for High Temperature Solid Oxide Cells

Solid Oxide Fuel Cells (SOFCs) are one of the most energy and space-efficient energy production technologies in the field and have applications in electric vehicles, power plants, and commercial and residential energy reserves. Intermediate-temperature SOFCs employ perovskites (crystals with the form ABO_3-δ) to act as electrolytes that can transport H⁺. Within the cell, air approaches the cathode side as fuel approaches the anode side, and the electrolyte passes H⁺ from the anode to the cathode side. This causes the electrons to be passed through a wire connecting the cathode and the anode sides to generate electrical power. Common issues of this kind of fuel cell are the transport properties associated with the electrolyte, i.e., low ionic conductivity and electronic leakage. The stoichiometry of Ba in Ba(Zr_0.4Ce_0.4Y_0.2)O₃ (BZCY – an SOFC electrolyte material) is varied to test the effects of this variance on transport properties, as Ba tends to evaporate during high-temperature processing. Cells are created with BZCY electrolytes of 0%, 3%, 6%, and 9% excess Ba. Both electrolyte-supported half cells and Ni-BZCY anode-supported full cells are constructed and evaluated to understand the correlation of Ba stoichiometry and the transport properties. The behavior of these cells under different conditions is discussed with respect to the effect of Ba stoichiometry.