@conference{
author = "Radmilović, Nadežda and Stamenković, Tijana and Lojpur, Vesna and Dinić, Ivana and Mančić, Lidija",
year = "2022",
abstract = "The process where long-wavelength excitation radiation is converted into shorter wavelength output radiation is known as photon upconversion (UC). Research of up conversion materials is mainly focused on chloride, bromide, fluoride and oxide compounds doped with Pr3+, Nd3+, Dy3+, Ho3+, Er3+ and Yb3+ as activators [1]. Activators are incorporated in the form of rear earth elements (REE) at a proper position in the host lattice. The unique emission mechanism of REE is associated with the incompletely filled 4f shell which enables large numbers of sharp intra-4f electronic transitions and the existence of abundant, long-living electronic excited states. Oxides possess relatively low phonon energy, high thermal stability and admirable intrinsic luminescence properties compared to chlorides and fluorides as host crystal lattice [2,3]. Various host latticed and dopant metal ions have been implemented for obtaining new UC compounds and in our work we studied Ln2MoO6 (Ln=Y,Gd) and Sr2Gd2O4 doped with various concentrations of Yb3+ at constant Er3+ concentration. Synthesized powders were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and luminescence emission and excitation spectroscopy. XRD analyses showed that SrGd2O4 single phase is obtained at 1100 °C, Gd2MoO6 phase starts to form at 750 °C and the pure phase is obtained at 900 °C, while Y2MoO6 was obtained at the lowest temperature of 600 °C. TEM analyses gave insight into particle size - powders obtained at lowest temperatures (Y2MoO6) have the smallest particle size in the range of ~10 nm (Figure 1a), while SrGd2O4 exhibited grain sizes in 150-200 nm range (Figure 1b). The EDS mapping confirmed presence of Yb3+, uniformly distributed in host lattice. Photoluminescence spectra of SrGd2O4 showed emission peaks that can be assigned to the trivalent Er3+ f-f electronic transitions in the following way: two green emission bands at 523 and 551 nm while the red emission band at 661 nm. Continual intensification of UC with the increase of Yb3+ content indicates that the SrGd2O4 host matrix easily accommodates high dopant concentration without quenching. Photoluminescence properties showed that co-doped Y2MoO6 has double emitting luminescence with green emission band at 546 and 560 nm (2H11/2, 4S3/2 → 4I15/2) and red emission band at 655 nm (4F9/2 → 4I15/2); Gd2MoO6 showed double emitting luminescence with two green emission bands at 525 and 546 nm as well as a red emission band at 657 nm. The green UC emission intensity increased gradually with the increment of Yb3+ ion concentration. In comparison, the optimal doping concentration for the red UC emission was found to be 2.5 at %, which was much higher than that of the green UC emission. While the change of Yb3+ ion concentration does not influence the band position, it led to the change of the emission intensity. Increase of Yb3+ concentration in the host lattice leads to change of the green to red ratio, showing the ability for fine-tuning of the color output. Therefore, these materials can be used in lasers and devices for optical communications because of the infrared-to-visible light conversion.",
publisher = "Belgrade : Serbian Academy of Sciences and Arts",
journal = "Program & Book of Abstracts / Second International Conference ELMINA 2022, Belgrade, Serbia, August 22nd-26th, 2022",
title = "Different Up-conversion Oxides Co-doped with Er3+/Yb3+ Synthesized at High Temperatures",
pages = "194-195",
url = "https://hdl.handle.net/21.15107/rcub_dais_14276"
}