Preparation of LaGaO3-based perovskite oxide film by a pulsed-laser ablation method and application as a solid oxide fuel cell electrolyte

LaGaO3-based perovskite oxide films are deposited on a dense substrate consisting of NiO, Fe3O4, and Sm-doped CeO2 (SDC). After in situ reduction, NiO and Fe3O4 are reduced to form an alloy and during reduction, the substrate becomes porous, and therefore can be used as a porous electrode substrate in a solid oxide fuel cell (SOFC). Since the reaction between NiO and LaGaO3-based oxide is known, an interlayer of SDC is introduced between the LaGaO3 film and the substrate. The LaGaO3/SDC bilayer film exhibits electrical conductivity close to that of a bulk one. A single fuel cell using the LaGaO3/SDC bilayer film shows an open-circuit potential of 1.1 V, which is close to the theoretical value. A quite large power density of 0.6 W cm(-2) is achieved at 773 K with a LaGaO3 film of 5 mu m in thickness. The effects of LaGaO3 film thickness on power generation are further studied. Although the open-circuit potential increases, the maximum power density decreases with increasing thickness. On the other hand, the open-circuit potential becomes lower with thicknesess below 5 mu m. This suggests that the reaction between NiO and the LaGaO3 film occurs with an excessively thin film. Therefore, the largest power density is obtained with a film thickness of 5 mu m. The effects of interlayer compound are also examined. The application of La(Sr)Ga(Fe)O-3 (LSGF) is also effective in obtaining high power density, but the maximum value is less than that achieved with a SDC interlayer. A two-cell stack is successfully demonstrated. (c) 2006 Elsevier B.V. All rights reserved.