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The fluorophosphate glasses with composition of Ba(PO 3) 2 – AlF 3 –CaF 2 – MgF 2 –BaF 2 – SrF 2 –YbF 3 – ErF 3 were synthesized and their spectroscopic properties were studied. The main attention here was paid to studying the luminescence kinetics Yb3+ (1040 nm) and Er3+ (1550 nm, 655 nm and 540 nm). It has been found that the population of the 4I 13/2 (Er3+) level and the relaxation of the 2F 5/2 (Yb3+), 4F 9/2 , and 2H 11/2 +4S 3/2 (Er3+) levels are close to exponential and the probabilities of these processes are well approximated by linear functions with respect to the ytterbium concentration. All this led to the conclusion that the migration-accelerated energy transfer makes a significant contribution to the population and deactivation of these energy levels. A scheme of the main energy transfer channels in an ensemble of ytterbium and erbium ions and the corresponding system of rate equations are proposed. On the basis of these equations, mathematical modeling of the luminescence kinetics of ytterbium and erbium ions was carried out and the energy transfer parameters were estimated. • Er3+ and Yb3+ doped fluorophosphate glasses spectroscopic properties were studied. • Mathematical modeling of the luminescence kinetics of Er3+ and Yb3 was carried out. • Energy transfer parameters between Er3+ and Yb3 were estimated. [ABSTRACT FROM AUTHOR]

Phase pure BaF2 doped with Ce3+ (0.1%) nanocrystals are synthesized using an ionic liquid (IL) ([C4mim][BF4]) assisted solvothermal method where the IL is not only used as a reaction medium and a capping agent, but also as a reaction partner. Subsequently, upon calcining the as-prepared nanocrystals at various temperatures (200, 400, 600 and 800 °C), athough the crystal phase remains the same, however, a significant change in the lattice strain and morphology is observed. Tensile strain appears in the nanocrystals calcined at temperatures up to 400 °C, but a reversal of the strain, i.e. compressive strain, takes place when calcination is performed at 600 °C and onwards. Nanoflakes are obtained until calcination at 400 °C. However on calcination at 600 °C and beyond, a drastic modification in the morphology is observed. Layer or step-like structures appear due to secondary nucleation of nanoparticles. Meanwhile, the photoluminescence (PL) intensity of Ce3+ ions gradually decreases with the calcination temperature and finally vanishes at 600 °C/800 °C. To investigate the reasons for the quenching of the PL intensity, thermally stimulated luminescence (TSL) and thermally stimulated exoelectron emission (TSEE) measurements are performed. The TSL and TSEE results indicate that in addition to the domination of deeper electron traps that appear as a high-temperature shift of TSEE glow peaks for both 600 °C and 800 °C, some new types of defects like F vacancies (F-centers) can be present, especially in the 800 °C calcined sample. The conditions leading to the quenching of Ce3+ luminescence in the nanoparticles are analyzed and discussed. [ABSTRACT FROM AUTHOR]

The kinetic parameters of core-valence luminescence for BaF 2 nanoparticles with different sizes were studied under synchrotron radiation excitation with photon energy of 18.8 eV at room temperature. In contrast to BaF 2 single crystals the decay kinetics of nanoparticles is shown to be non-exponential indicating the luminescence quenching. We assume that the quenching of core-valence luminescence is caused by the diffusion of core holes to nanoparticle surface. The diffusion length of the core holes in BaF 2 has been estimated as 2–3 nm using diffusion model of luminescence quenching in nanoparticles. • Decay kinetics of core-valence luminescence of BaF 2 nanoparticles is studied. • Core-valence luminescence quenching is considered as result of core hole migration to surface. • Core hole diffusion length is estimated. [ABSTRACT FROM AUTHOR]