Synthesis and electrical properties of Ln2CuO4+ d (Ln: Nd or La) mixed conductor sputter deposited coatings

Abstract

Abstract Nd2CuO4 and La2CuO4 are potential candidates as cathode material for intermediate temperature-solid oxide fuel cells. Nd–Cu and La–Cu oxides were co-sputtered on rotating substrates from metallic La, Nd and Cu targets in the presence of a reactive argon–oxygen gas mixture. Structural and chemical features of these films have been determined by X-ray diffraction and energy-dispersive spectroscopy. Their electrical resistivity was measured using the four-point probe method. As-deposited Nd–Cu based coatings are amorphous and, after annealing, crystallise in K2NiF4+ d -type structure for Nd/Cu atomic ratio of 2, with more or less Nd2O3 or CuO, depending on whether Nd or Cu is in excess, respectively. As-deposited La–Cu based coatings are also amorphous and crystallise in La2CuO4 for La/Cu >2 or in LaCuO3±d perovskite-type structure when Cu is in excess. The electrical measurements show a clear relation between resistivity and structure of the coatings. After annealing, crystallised neodymium-based coatings show higher resistivity than lanthanum-based ones. Finally, LaCuO3±d exhibit higher resistivity than La2CuO4.