X-ray Photoelectron Spectroscopy Study of Europium Niobate Thin Film Prepared by Chemical Solution Deposition

Transparent europium niobate EuNbO₄ (ENO_F) thin film (~100 nm) was prepared by sol-gel/spin-coating process on alumina substrates with PbZrO₃ (PZ) interlayer and annealing at 1000°C. The X-ray diffraction (XRD) analyses verified the formation of the monoclinic M-EuNbO₄ and tetragonal T-EuNb₅O₁₄ phases in ENO precursor and ENO_F film. The surface morphology of powder precursor and microstructure of film were investigated by SEM analyses. Surface chemistry was investigated by X-ray photoelectron spectroscopy (XPS). The XPS demonstrated two valence states of Eu (Eu³⁺/Eu²⁺) in powder precursor as nanophosphor for lighting and display technologies. Eu concentration (at. %) decreases from 10 % in the precursor to 2 % in the film considering the substrate contains C, Al, Si, Pb, and Zr elements (40 %) at Nb (6 %) and O (52 %). The single valence state of Eu³⁺ was confirmed in ENO film designed for the application in environmental electrolytic thin-film devices.