Ageing of lanthanum strontium copper orthoferrite powders for sensing layers

Nanosized powders of lanthanum strontium copper orthoferrites La0.8Sr0.2Fe1-xCuxO3-w(LSFC) have been recently proposed as sensing component in chemical sensors for humidity detection. The LSFC powders were prepared by citrate auto-combustion of dry gel obtained from a solution of corresponding nitrates in a citric acid solution. The aged powders were investigated by chemical and structural analysis using X-ray Photoelectron Spectroscopy (XPS), Infrared Spectroscopy and X-Ray Powder Diffraction as a total loss of their sensing properties has been observed after about one year storage of the sensors at room temperature in the laboratory. The detection of surface hydroxides and carbonates species as well as very large Sr and Cu excess within the surface area were important results.