Monitoring of the LSM/YSZ interface in SOFCs using limited-contact geometry in impedance spectroscopy

The electrochemical property of SOFC cathode composites based on LSM((La0.7Sr0.3)0.95MnO3) and YSZ(Y2O3-Stabilized ZrO2) was characterized by using limited-contact geometry of an electrode and electrolyte in AC two-point impedance analysis. The point-contacted configuration amplifies the responses occurring near the YSZ/cathode interface through the aligned point-contact of YSZ on the planar LSM/YSZ cathode. The point-contacted interface also amplifies the bulk resistance of the electrolyte and electrode which allows quantitative estimation of the electrode-related responses with regard to the amplified bulk resistance. The resultant impedance spectra were analyzed through an equivalent circuit model constructed by resistors and constant phase elements. The electrode-related polarizations were measured with respect to the cathode composition, temperature and oxygen partial pressure. The potentiality of modified impedance spectroscopy is discussed as an alternative approach toward more precise resolving of the electrode-polarization phenomena in solid oxide fuel cells.