Influence of the Coordination Environment of Lanthanides and Size Factors on the Properties of Lanthanide-Containing Fluorophores and Hybrid Systems Based on Them

What priority area of ​​science and technology does it correspond to: new substances and materials.

Research: fundamental.

Prospect for further execution: to be continued as a target fundamental.

Research level: no analogues in Ukraine.

Patent: no

What additional actions require further research: Optimization of synthesis conditions and chemical composition and materials based on Al2O3 activated with Eu3+/Eu2+ ions requires additional funding and exams in prototypes of optoelectronic devices.

Brief description, advantages, further prospects for application.

Samples of nanosized δ*-Al2O3 doped with Eu3+/Eu2+ ions were obtained by gas-phase combustion. Changes in particle morphology and luminescent properties of materials as a result of thermally stimulated phase transformations δ*→θ→α-Al2O3 have been studied. It has been established that the δ*-, θ-, and α-phases coexist in the range of ~1100–1200°C. Full transition to thermostable – modification occurs as a result of firing at 1300°C for ≥6 hours. It is shown that the particles before firing have a spherical shape with a diameter of 10-70 nm. The transformation into α-Al2O3 leads to an increase in the size of crystallites and the formation of vermicular (red-shaped) microstructures. Luminescence spectroscopy methods have shown that in the synthesis products some of the ions in Europe are stabilized in the +2 oxidation state and emit radiation in the spectral range of 360–450 nm with a maximum at ~410 nm. The decay kinetics of this luminescence is characterized by a constant τ= ~400 ns, which is close to the typical values ​​for the 5d→4f transitions of Eu2+ ions in inorganic compounds.

It has been established that the phase transition δ*,θ → α-Al2O3 does not lead to significant changes in the luminescence spectra of Eu3+ ions, and the inhomogeneous broadening of the bands of the 5D0→7Fj transitions in Eu3+ ions in δ*, θ and α-Al2O3 as a result of a significant difference between the ionic radii of Al3+ and Eu3+. It is concluded that, due to the favorable size distribution of particles and their spherical morphology, nanosized Al2O3:Eu3+/Eu2+ synthesized by gas-phase combustion is a promising precursor for obtaining transparent luminescent ceramics.

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