Luminescent properties of ZrO₂:Dy³⁺ and ZrO₂:Dy³⁺+Li⁺ films synthesized by an ultrasonic spray pyrolysis technique

ZrO₂:Dy³⁺ and ZrO₂:Dy³⁺+xLi⁺ films were synthesized by an ultrasonic spray pyrolysis process. X-Ray Diffraction studies, as a function of the deposition temperature, indicate a meta-stable tetragonal crystal structure of the zirconia, as the substrate temperature was increased. Photoluminescence and cathodoluminescence characteristics of the films were studied as a function of deposition parameters such as the substrate temperature and the dysprosium and lithium concentrations. For an excitation wavelength of 286 nm, all the luminescent emission spectra show peaks located at 485, 584, 670 and 760 nm, which are the characteristic 4f→4f intra-transitions of Dy³⁺ ions and they correspond to electronic transitions ⁴F_9/2→⁶H_15/2, ⁴F_9/2→⁶H_13/2, ⁴F_9/2→⁶H_11/2 and ⁴F_9/2→⁶H_9/2, respectively. The lithium incorporation in the ZrO₂:Dy³⁺ films produced an improvement in the intensity of the luminescent emission. As the deposition temperature is increased, a rise of the luminescence intensity is observed. Also, it is noted, a quenching of the luminescence, with increasing doping concentration. The elemental chemical composition of the layers, as determined by energy dispersive spectroscopy, is reported as well. In addition, the surface morphology characteristics of the films, as a function of the deposition temperature, are presented.