Solid oxide fuel cells that contain mixed ionic-electronic conductors (MIECs) as electrolytes exhibit maximum efficiency at high ionic current density due to a small electronic leakage current. At low ionic current density the electronic current increases due to partial reduction of the electrolyte and efficiency decreases. This leads to restrictions in the optimum cell operating range and cell design. Provided the necessary materials and cell design parameters are known, the optimum cell design, especially the electrolyte thickness, can be predicted. The optimization of fuel cells with a mixedconducting ceria electrolyte is outlined. The cell optimization considered in this study includes operating range (V-I), MIEC thickness, and the electrochemical performance of the electrodes. Defect chemical considerations predict an optimum in MIEC thickness depending on the operating temperature.
Microstructure, cathodic polarization, and ohmic resistance on the cathode side of
ZrO2
‐based solid oxide fuel cells have been studied for the intermediate temperature operation range between 700 and 900°C. Starting powder characteristics, powder calcination temperature, and sintering temperature strongly influence the final microstructure of cathodes. Electrochemical performance depends on these processing parameters as well as on the cathode thickness and the contact spacing of current collectors. A decrease in effective electrode area occurs both on the microscopic level with coarse and inhomogeneous cathode microstructure and on the macroscopic level with a wide contact spacing of the current collectors. The smaller effective electrode area causes inhomogeneous current density distribution and results consequently in higher ohmic losses originating from the electrolyte and higher cathodic polarization. These losses are evaluated using
La0.85Sr0.15MnO3
cathodes with different microstructures and on the
ZrO2‐8
mole percent
Y2O3
electrolyte. The influence of current path constrictions on the ohmic and nonohmic losses is demonstrated using Pt current collectors of different geometric spacings.
The electrical conductivity of 3Y-TZP ceramics containing SiO2 and AI2O3 has been investigated by complex impedance spectroscopy between 500 and 1270 K. At low temperatures, the total electrical conductivity is suppressed by the grain boundary glass films. The equilibrium thickness of intergranular films is 1-2 nm, as derived using the "brick-layer" model and measured by HRTEM. A change in the slope of the conductivity Arrhenius plots occurs at the characteristic temperature Tb at which the macroscopic grain boundary resistivity has the same value as the resistivity of the grains. The temperature dependence of the conductivity is discussed in terms of a series combination of RC elements.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.