Study of the La1−xSrxMnO3 Cathode Film Prepared by a Low Power Plasma Spray Method with Liquid Solution Precursor for a Solid Oxide Fuel Cell

A perovskite La1−xSrxMnO3 cathode thin film for an oxygen ion conducting solid oxide fuel cell was prepared using a low power (8.8 kW) liquid solution plasma spray method. Usually, a 30–50 kW Ar plasma torch with temperature higher than all the melting points of solid precursors is essential to synthesis oxides thin film. However, using the liquid precursors as the feeding materials, the required power can be reduced and save a lot of thermal budget. The precursors are water solutions of lanthanum nitrate hexahydrate, manganese(II) nitrate tetrahydrate, and strontium nitrate. The atomic percentage of La in the plasma sprayed La1−xSrxMnO3 cathode film is lower than that of La in the feeding precursor into the torch, which is due to the low boiling temperature of La(NO3)3 precursor. The oxygen stoichiometry of La1−xSrxMnO3−δ deduced from the valence state of Mn measured by X-ray absorption spectroscopy shows an oxygen deficit structure. The measured low resistivity of 0.07–0.09 Ωcm at room temperature for this La1−xSrxMnO3−δ is essential for oxygen ion transport in the cathode thin film of a solid-state fuel cell.