Investigation of Gadolinia-Doped Ceria (GDC) Electrolyte by Electrochemical Impedance Spectroscopy

Electrochemical impedance spectroscopy (EIS) is widely used in the study of aqueous and solid state electrochemistry. Information such as sample conductivity and electrode effects can be studied by varying the frequency. Despite extensive use of EIS, two issues regarding the measurement and interpretation warrant discussion. They concern the high frequency inductive load and the use of constant phase element (CPE) for data fitting. The experimental work was conducted on polycrystalline gadolinia-doped ceria. In this work, subtracting lead impedance is shown to be an effective way to recover semi-circular behavior at high frequency, representative of grain boundary effects. The present work shows that in many instances for data interpretation, pure capacitance may be used in the equivalent circuit, instead of the often used CPE. The significance is that fitting can be achieved using one parameter rather than two needed for CPE.