Presentation on theme: "A new route for the hydrothermal synthesis of Eu doped tin oxide nanoparticles D. Tarabasanu-Mihaila 1 *, L. Diamandescu 1, M. Feder 1, S. Constantinescu."— Presentation transcript:
A new route for the hydrothermal synthesis of Eu doped tin oxide nanoparticles D. Tarabasanu-Mihaila 1 *, L. Diamandescu 1, M. Feder 1, S. Constantinescu 1, V.S. Teodorescu 1, S. Georgescu 2, A. Banuta 1 1 National Institute of Materials Physics, P.O. BOX MG-7, Bucharest, Romania 2 National Institute of Laser Plasma & Radiation Physics, P.O. BOX MG-36, Bucharest, Romania STATE OF THE ART AND OBJECTIVE EXPERIMENTAL TEM / EDX LUMINESCENCE CONCLUSION Eu doped SnO 2 nanoscaled powders were obtained in an extended solubility range (up to ~20 at.% Eu) directly, by a new hydrothermal route at moderate temperature (250 C); The nanocrystalline Eu:SnO 2 powders have the cassiterite structure (rutile type); The mean particle size is ~ 3-5 nm for as resulted hydrothermal samples and ~ 5-10 nm for the calcinated powders; Eu +3 ions can substitute for Sn 4+ or can enter interstitially in the SnO 2 nanostructure. At Eu/Sn concentration ratio = 1/1 (50 at % Eu), well crystallized cubic Eu 2 Sn 2 O 7 (compound of interest in high temperature catalytic application) has been obtained. Acknowledgements. This work was prepared with the support of the Romanian Ministry of Education and Research, under the Core Program PN *Corresponding author: MÖSSBAUER SPECTROSCOPY ON 151 Eu ) A 10-a editie a Seminarului National de nanostiinta si nanotehnologie 18 mai 2011 Biblioteca Academiei Romane SnO 2 is an attractive semiconductor, host lattice for optical active rare earths ions owing to its chemical stability and electronic and optical properties (wide band gap of 3.6 eV, high transparency in the visible light region). SnO 2 based luminescent materials (phosphors) have been synthetized by various methods: sol-gel, radio-frecvency sputtering, microwave assisted-solvothermal route, coprecipitation etc. [1-3]. Eu +3 ions exhibit an intense red light emission arising from 5 D 0 7 Fj transition; Eu +3 doped SnO 2 emits an unique reddish-orange color. The solubility limit of Eu +3 in SnO 2 is low (0,5-8 at%) because of the difference in the ionic radius and chemical valence state of Eu +3 and Sn +4. At higher doping concentration, the excess of Eu +3 may seggregate on the nanoparticle surface as separated phases. This study reports on the new route for the hydrothermal synthesis of Eu:SnO 2 nanocrystalline oxides, extending the solubility range to 20 at % Eu, together with the structural and morphological characterization of the obtained nanostructures. Luminescence spectra for the hydrothermal sample 3 at % Eu: SnO 2, as resulted (a) and after calcination at 650 °C (b). References 1.E. A. Morais, L. V. A. Scalvi, A. Tabata, Photoluminescence of Eu 3+ Ion in SnO 2 Obtained by Sol–Gel, J. Mater. Sci., 43, 1 (2008) 345– T. H. Moon, S. T. Hwang, D. R. Jung, Hydroxyl-Quenching Effects on the Photoluminescence Properties of SnO 2 :Eu 3+ Nanoparticles, J. Phys. Chem. C,111,11 (2007) 4164– D.H. Park, Y.H. Cho, Y.R. Do, B.T. Ahn, Characterization of Eu- Doped SnO 2 Thin Films Deposited by Radio-Frequency Sputtering for a Transparent Conductive Phosphor Layer, J.Electrochem. Soc.,153, 4 (2006) H63–H67. TEM images and EDX spectrum of the sample with 6 at % Eu; the atomic ratio Eu/Sn given by EDX: 5.9/ /93.2. Hydrothermal synthesis route Mössbauer spectrum on 151 Eu for the hydrothermal sample at 6 at % Eu: SnO 2 (left) in comparison with Eu 2 O 3 Mössbauer spectrum (right) showing the presence of many inequivalent Eu sites in the SnO 2 structure.