Multicolored photoluminescence and structural properties of zirconium oxide films co-doped with Tb³⁺ and Eu³⁺ ions

The photoluminescence and structural properties of ZrO₂ films doped with Eu³⁺ and Tb³⁺ ions, deposited by ultrasonic spray pyrolysis technique, are reported. X ray diffraction analysis showed that the films are polycrystalline and exhibit the ZrO₂ tetragonal metastable phase. The surface morphology characteristics of the films are strongly dependent on the deposition temperature, going from a rough surface formed by ramifications at low temperatures to a denser material with ramifications and the appearance of spherical features at higher temperatures. In addition, the elemental composition of the films as determined by energy dispersive spectroscopy, is reported. The photoluminescence spectra present the characteristic emission peaks associated with the Tb³⁺ and Eu³⁺ dopants as well as a broad emission peaked at 440 nm associated with radiative transitions within the ZrO₂ matrix. As the deposition temperature is increased, it was observed an increasing intensity of the photoluminescence emission. Also a concentration quenching was observed for both dopants. The photoluminescence emission spectra for the ZrO₂ films co-doped with Eu³⁺ and Tb³⁺ ions, showed emission lines that are a combination of those observed for each ion individually plus the blue broad band associated with the host lattice. Decay times were measured for double doped samples. The CIE chromaticity diagrams for these films showed colors falling in the blue, green, yellow, red-orange, bluish-white and yellowish-white regions depending on the doping characteristics of the films.