Lanthanum nickelate thin films deposited by spray pyrolysis: Crystallization, microstructure and electrochemical properties

Thin films from the Lan+1NinO3n+1 system exhibit favorable dielectric and electrochemical properties that may prove useful for a variety of devices ranging from ferroelectrics to low-temperature solid oxide fuel cells. The present work covers the compositional, microstructural and electrochemical characterization of thin lanthanum nickelate films deposited by spray pyrolysis. In accordance with the phase diagram, LaNiO3−δ or La4Ni3O10−δ films were obtained during annealing of spray deposited films at temperatures between 540 °C and 1100 °C. Whereas LaNiO3−δ films exhibited a high metallic conductivity, La4Ni3O10−δ films were semiconducting. Electrochemical impedance spectroscopy indicated an increase of the area specific oxygen reduction resistance with the annealing temperature. The study highlights how the phase and microstructure of thin films from the Lan+1NinO3n+1 system can be tailored by annealing of initially amorphous films. LaNiO3−δ films have a high potential for application in electrochemical devices operating at low temperatures where high electrical conductivity is required.