Microstructure refinement of pulsed laser deposited La_0.6Sr _0.4CoO_3-δ thin-film cathodes for solid oxide fuel cell

In this study, the microstructural modification of pulsed laser deposited La_0.6Sr_0.4CoO_3-δ (LSC64) thin-film cathodes for solid oxide fuel cells (SOFCs) to improve the lateral conduction and to reduce the surface composition degradation is investigated. A high-temperature deposited 100 nm-thick denser LSC64 layer is added over 2.4 μm-thick porous cathode to cover and bridge the cathode domains. According to the cell performance analyses using current-voltage-power measurements, the performance of the cell modified with an additional denser layer is increased compared with the cell without the denser layer in all operating temperature range. The degree of improvement of peak power density is bigger than 10% at 650-550 C and is about 6% at 500 C. This performance enhancement can be attributed to the electrochemical property improvement, especially oxygen surface exchange property, rather than to the conduction improvement, based on the electrochemical impedance analysis. Improved crystallinity and composition integrity of the denser LSC64 layer is considered to enhance the surface exchange property of the cathode.