Influence of synthesis route on morphology and electrical properties of LaNi 0.6Fe 0.4O 3

Abstract

Recently LaNi 1− x Fe xO 3 materials have been suggested as good candidates for cathodes for Intermediate Temperature Solid Oxide Fuel Cells. The electrical conductivity and the morphology of LaNi 0.6Fe 0.4O 3 samples have been studied as a function of preparation route and calcination temperature. The conductivity, mainly electronic, strongly depends on the densification of the material, which is influenced by the preparation procedure. DFT calculations indicate that the conduction bands of LaNi 0.6Fe 0.4O 3 are mainly made up of Fe and Ni 3d states and that there is a small bandwidth (2.3 eV) around the Fermi level. Moreover, a small polaron mechanism for the electronic conduction in this material is suggested by the simulations. Three different preparation methods have been investigated: the glycine–nitrate process, the gel–citrate complexation route and the coprecipitation route. The glycine–nitrate synthesis produces non-homogenous LaNi 0.6Fe 0.4O 3 materials. Good specific conductivity is obtained only after high temperature treatments that homogenise and sinter the material. The gel–citrate complexation route leads to homogenous LaNi 0.6Fe 0.4O 3 samples, which however are resistant to sinterization/densification. Finally, homogenous LaNi 0.6Fe 0.4O 3 is obtained with coprecipitation synthesis. This synthesis is particularly promising since the morphology of the obtained precipitate favours the sinterization at low temperatures. These temperatures are low enough to prevent the undesirable reaction with ZrO 2-based electrolyte.