Anode-supported thin electrolyte cells are studied by electrochemical impedance spectroscopy ͑EIS͒. The aim is to describe how the losses of this type of cells are distributed at low current density ͑around open-circuit voltage͒ as a function of temperature. An equivalent circuit consisting of an inductance, a serial resistance ͑R s ͒, and five arcs to describe the polarization resistance is suggested. This equivalent circuit is based on previous studies of single electrodes in three-electrode and two-electrode symmetric cell setups. The equivalent circuit components have been assigned to the electrode processes, and the assignments were verified by extensive full cell studies in which the partial pressure of reactant gases on both the electrodes as well as temperature was systematically varied with the aim to identify frequency regions which are dominated by an electrode specific process. Furthermore, the model is applied on a good performing cell with area specific resistance ͑ASR͒ = 0.15 ⍀ cm 2 at 850°C and a poor performing cell with ASR = 0.29 ⍀ cm 2 at the same temperature. Both cells were fabricated using nominally the same procedure. The EIS analysis indicated that the difference in performance originates from microstructural differences on the cathode. This is further supported by the observation of large differences in the cathode microstructure by scanning electron microscope.

Bulk expansion of the anode upon oxidation is considered to be responsible for the lack of redox stability in high-temperature solid oxide fuel cells ͑SOFCs͒. The bulk expansion of nickel-yttria stabilized zirconia ͑YSZ͒ anode materials was measured by dilatometry as a function of sample geometry, ceramic component, temperature, and temperature cycling. The strength of the ceramic network and the degree of Ni redistribution appeared to be key parameters of the redox behavior. A model of the redox mechanism in nickel-YSZ anodes was developed based on the dilatometry data and macro-and microstructural observations.

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