Seminar Announcement: Dobroslawa Kasprowicz

Data pubblicazione: 29-giu-2015 10.20.30

Announcement

Wednesday, 17 June 2015, 15:00

Sala Grande Palazzina B via alla Cascata 56/C

"Micro-Raman investigations of KGd(WO₄)₂ crystals triply-doped with Pr³⁺, Tm³⁺, Tb³⁺, Ho³⁺, Er³⁺ and Yb³⁺ ions and their NIR-VIS up-conversion luminescence"

Dobroslawa Kasprowicz

Faculty of Technical Physics, Poznan University of Technology University of Technology,

Poznan, Poland

Abstract

During the lecture the spectroscopic properties of triply-doped KGd(WO₄)₂ single crystals and micro-crystalline powders, doped with Er³⁺/Yb³⁺/Tm³⁺, Tb³⁺/Yb³⁺/Tm³⁺, Pr³⁺/Yb³⁺/Tm³⁺ and Ho³⁺/Yb³⁺/Tm³⁺ ions, studied by the μ-Raman spectroscopy and optical spectroscopy methods will be presented. The investigated samples were obtained by the Top Seeded Solution Growth method, while the powders were synthesized by the Pechini method. It was shown that all these systems exhibit multicolor up-conversion fluorescence under 980 nm laser irradiation. The multicolor light emission was obtained by the simultaneous emission of red, green and blue radiation, the intensity of which varies with the type of ions, their concentration, and the size of crystals. The analysis of the dependence of fluorescence intensity on the excitation power resulted in the conclusion about a possible transfer of excitation energy between lanthanide ions in the up-conversion processes. The vibrational properties of triply-doped KGd(WO₄)₂ crystals have been investigated using Renishaw In-Via Raman spectrometer. The room temperature Raman spectra of investigated materials were recorded in the spectral range of 100 – 1000 cm ^-1 /internal and external vibrations. The vibrational studies of the KGd(WO₄)₂ host lattice are particularly important due to their role in transfer of excitation energy between lanthanide ions in the energy conversion process. The results have been discussed in terms of the influence of doping composition of rare earth ions and the crystal size reduction on the crystal structure, lattice dynamics and the luminescence of investigated materials.