Characteristics of LaCo0.4Ni0.6-xCuxO3-δ ceramics as a cathode material for intermediate-temperature solid oxide fuel cells

In this study, the effects of Cu-ion substitution on the densification, microstructure, and physical properties of LaCo0.4Ni0.6-xCuxO3-delta ceramics were investigated. The results indicate that doping with Cu ions not only enhances the densification but also promotes the grain growth of LaCo0.4Ni0.6-xCuxO3-delta ceramics. The Cu substitution at x <= 0.2 can suppress the formation of La4Ni3O10, while the excess Cu triggers the formation of La2CuO4.032 phase. The p-type conduction of LaCo0.4Ni0.6-xCuxO3-delta ceramic was significantly raised by Cu substitution because the acceptor doping (Cu-Ni(')) triggered the formation of hole carriers; this effect was maximized in the case of LaCo0.4Ni0.4Cu0.2O3-delta composition (1480 S cm(-1) at 500 degrees C). Thermogravimetric data revealed a slight weight increase of 0.29% for LaCo0.4Ni0.4Cu0.2O3-delta compact up to 871 degrees C; this is due to the incorporation of oxygen that creates metal vacancies and additional h carriers, partially compensating the conductivity loss due to the spin-disorder scattering. As the temperature of the LaCo0.4Ni0.4Cu0.2O3-delta compacts rose above 871 degrees C, significant weight loss with temperature was observed because of the release of lattice oxygen to the ambient air as a result of Co (IV) thermal reduction accompanied by the formation of oxygen vacancies. A solid oxide fuel cell (SOFC) single cell with Sm0.2Ce0.8O2-delta (electrolyte) and LaCo0.4Ni0.4Cu0.2O3-delta (cathode) was built and characterized. The Ohmic (0.256 Omega cm(2)) and polarization (0.434 Omega cm(2)) resistances of the single cell at 700 degrees C were determined; and the maximum power density was 0.535 W cm(-2). These results show that LaCo0.4Ni0.4Cu0.2O3-delta is a very promising cathode material for SOFC applications.