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 LaCo 0.4 Ni 0.6-x Cu x O 3-δ ceramics were investigated. The results indicate that doping with Cu ions not only enhances the densification but also promotes the grain growth of LaCo 0.4 Ni 0.6-x Cu x O 3-δ ceramics. The Cu substitution at x ≤ 0.2 can suppress the formation of La 4 Ni 3 O 10 , while the excess Cu triggers the formation of La 2 CuO 4.032 phase. The p-type conduction of LaCo 0.4 Ni 0.6 O 3-δ ceramic was significantly raised by Cu substitution because the acceptor doping ( C u N i ' ) triggered the formation of hole carriers; this effect was maximized in the case of LaCo 0.4 Ni 0.4 Cu 0.2 O 3-δ composition (1480 S cm −1 at 500 °C). Thermogravimetric data revealed a slight weight increase of 0.29% for LaCo 0.4 Ni 0.4 Cu 0.2 O 3-δ compact up to 871 °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 LaCo 0.4 Ni 0.4 Cu 0.2 O 3-δ compacts rose above 871 °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 Sm 0.2 Ce 0.8 O 2-δ (electrolyte) and LaCo 0.4 Ni 0.4 Cu 0.2 O 3-δ (cathode) was built and characterized. The Ohmic (0.256 Ω cm 2 ) and polarization (0.434 Ω cm 2 ) resistances of the single cell at 700 °C were determined; and the maximum power density was 0.535 W cm −2 . These results show that LaCo 0.4 Ni 0.4 Cu 0.2 O 3-δ is a very promising cathode material for SOFC applications. [ABSTRACT FROM AUTHOR]