General Features of Co-Based Perovskite Cathode

Another merit of using (La, SrjCoOj (LSC) is its high electronic conductivity. At high temperatures, with high Sr content, the electronic conductivity of LSC shows metallic behavior i.e., the conductivity decreases with increasing temperature [38]. It is represented well with a itinerant electron model. The absolute value of the conductivity ranges from 10 to 3 x 10 S cm , which is useful for effective current collection. 

Although LSC is an attractive material for a SOFC cathode, its use is restricted because of the instability of LSC on zirconia-based electrolytes. It is well known that LSC reacts with YSZ and forms SrZrOs at the interface. When YSZ or ScSZ is used as the electrolyte, a protective interlayer is indispensable. 

Ceria doped with gadolinia (GDC) or samaria (SDC) is used as the interlayer in some intermediate-temperature SOFCs. Even with the interlayer, however, issues of long-term stability may still remain [39]. If LaGaOs-based oxide is used as the electrolyte, the interface stability problem is less significant. LSC-related cathodes are widely used on LaGa03. For long-term stability, however, the interdiffusion of Co and Ga should be avoided. 

Another problem is the large thermal expansion coefficient of (La, Sr)Co03, as discussed in the previous section. To avoid the problem of thermal expansion, (La, Sr)(Co, Fe)03 is chosen in practical systems. 

2 Electrochemical Reaction of a Model Electrode A (La,Sr)CoOs Dense Film 

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