Characterization of luminescent SrAl2O4 films doped with terbium and europium ions deposited by ultrasonic spray pyrolysis technique

SrAl2O4, SrAl2O4:Tb3+ and SrAl2O4:Eu3+:Eu2+ films were synthesized by means of the ultrasonic spray pyrolysis technique. These samples, characterized by X-Ray Diffraction, showed the monoclinic phase of the strontium aluminate. Images of the surface morphology of these films were obtained by SEM and the chemical composition was measured by EDS and XPS. The photoluminescence and cathodoluminescence characteristics of the films were studied as a function of the terbium and europium concentrations. The optimal PL emission intensities were reached at 8 at% for terbium doped films and 6 at% for europium doped samples. The CL emission spectra for europium doped films showed the typical bands of Eu3+ ions and also a broadband centered at 525 nm which is attributed to Eu2+ ions. XPS measurements confirm the presence of Eu3+ and Eu2+ in europium doped SrAl2O4 films, without having been subjected to a reducing atmosphere. Chromatic diagrams exhibited green color for SrAl2O4:Tb3+ films, red and yellow colors for SrAl2O4:Eu3+:Eu2+ films. The PL decay curves were also obtained: the averaged decay time was 2.7 ms for SrAl2O4:Tb3+ films and 1.9 ms for SrAl2O4:Eu3+ films. Similar results were obtained by the stretched exponential model.