The target of obtaining suitable matrix for the incorporation of Gd3+ ions may be of relevant importance in several areas from development of UV-emitting laser to magnetic and magneto-optical application. In this view, nanostructured glassceramic composites represent an interesting class of materials since they combine together the optimal properties of crystals as host materials for rare-earth ions with chemical and mechanical stability and workability of glasses. In this work, we present recent results on energy transfer process between gallium oxide nanocrystals embedded in an amorphous ger-mano-silicate glass matrix and the f-f transitions of gadolinium ions. Samples were prepared by melt-quenching method with typical composition 7.5Li2O–2.5Na2O–20Ga2O3–35GeO2–35SiO2 (mol%) and doped with 0.2 mol% of Gd2O3. As-prepared samples are completely amorphous, while thermal treatment at 694 °C for 15 minutes causes the precipitation of gallium oxide as -Ga2O3 in form of nano-crystals with diameter of about 5 nm [1,2]. Ga2O3 is a wide-bandgap oxide (EG = 4.9 eV) characterized by an intrinsic strong blue luminescence centred at about 460 nm and originated by recombination at donor and acceptor sites and excited by band-to-band transitions [3]. Gadolinium emission falls at 313 nm and it is due to 6P7/2 → 8S7/2 radia-tive relaxation. Energy transfer between the above-mentioned excitation channel of -Ga2O3 and rare-earth ion luminescence has been investigated by time-resolved photo-luminescence (PL) emission and excitation (PLE) spectroscopy. Clear-cut evidences of such process have been studied as a function of gallium content and nanostructuring. Time-resolved PLE spectra have been collected in order to evaluate energy transfer quantum yield. Moreover, Gd emission efficiency has been compared with respect to ions dispersed in pure silica matrix, confirming that incorporation of Gd ions in nano-crystals enhance their optical activity by partial suppression of non-radiative channels.
Lorenzi, R., Azarbod, A., De Trizio, L., Ignat'Eva, E., Sigaev, V., Paleari, A., et al. (2015). Energy transfer process between γ-Ga2O3 nanocrystals and Gd3+ ions in nanostructured germano-silicate glassceramic.. Intervento presentato a: LUMDETR 2015 - 9th International Conference on Luminescent Detectors and Transformers of Ionizing Radiation, Tartu (EST).
Energy transfer process between γ-Ga2O3 nanocrystals and Gd3+ ions in nanostructured germano-silicate glassceramic.
LORENZI, ROBERTOPrimo
;PALEARI, ALBERTO MARIA FELICEPenultimo
;
2015
Abstract
The target of obtaining suitable matrix for the incorporation of Gd3+ ions may be of relevant importance in several areas from development of UV-emitting laser to magnetic and magneto-optical application. In this view, nanostructured glassceramic composites represent an interesting class of materials since they combine together the optimal properties of crystals as host materials for rare-earth ions with chemical and mechanical stability and workability of glasses. In this work, we present recent results on energy transfer process between gallium oxide nanocrystals embedded in an amorphous ger-mano-silicate glass matrix and the f-f transitions of gadolinium ions. Samples were prepared by melt-quenching method with typical composition 7.5Li2O–2.5Na2O–20Ga2O3–35GeO2–35SiO2 (mol%) and doped with 0.2 mol% of Gd2O3. As-prepared samples are completely amorphous, while thermal treatment at 694 °C for 15 minutes causes the precipitation of gallium oxide as -Ga2O3 in form of nano-crystals with diameter of about 5 nm [1,2]. Ga2O3 is a wide-bandgap oxide (EG = 4.9 eV) characterized by an intrinsic strong blue luminescence centred at about 460 nm and originated by recombination at donor and acceptor sites and excited by band-to-band transitions [3]. Gadolinium emission falls at 313 nm and it is due to 6P7/2 → 8S7/2 radia-tive relaxation. Energy transfer between the above-mentioned excitation channel of -Ga2O3 and rare-earth ion luminescence has been investigated by time-resolved photo-luminescence (PL) emission and excitation (PLE) spectroscopy. Clear-cut evidences of such process have been studied as a function of gallium content and nanostructuring. Time-resolved PLE spectra have been collected in order to evaluate energy transfer quantum yield. Moreover, Gd emission efficiency has been compared with respect to ions dispersed in pure silica matrix, confirming that incorporation of Gd ions in nano-crystals enhance their optical activity by partial suppression of non-radiative channels.
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