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Journal of Nanomaterials
Volume 2007, Article ID 16391, 8 pages
Research Article

Upconversion Properties of Nanocrystalline ZrO2:Yb3+, Er3+ Phosphors

1Department of Chemistry, University of Turku, Turku FI-20014, Finland
2Department of Biotechnology, University of Turku, Tykistökatu 6, Turku FI-20520, Finland
3Graduate School of Materials Research, Turku, Finland

Received 30 October 2007; Accepted 26 November 2007

Academic Editor: Wiesław Stręk

Copyright © 2007 Iko Hyppänen et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Combustion and sol-gel methods were used to prepare the upconverting nanocrystalline ZrO2:Yb3+,Er3+ phosphors. The crystal structure was studied by X-ray powder diffraction and the crystallite sizes were estimated with the Scherrer formula. Impurities and nanomaterials' thermal degradation were analyzed with FT-IR spectroscopy and thermal analysis, respectively. Upconversion luminescence and luminescence decays were studied with IR-laser excitation at 977 nm. All nanomaterials possessed the cubic ZrO2 fluorite-type structure except for a small monoclinic impurity obtained with the sol-gel method. The conventional NO3 and OH impurities were observed for the combustion synthesis products. The ZrO2:Yb3,Er3+ nanomaterials showed red (630–710 nm) and green (510–570 nm) upconversion luminescence due to the 4F9/24I15/2 and (2H11/2,4S3/2)4I15/2 transitions of Er3+, respectively. The products of the combustion synthesis exhibited the most intense luminescence intensity and showed considerable afterglow. It was concluded that excitation energy is partially trapped in the system and subsequently bleached thermally to the luminescent Er3+ center to yield “persistent upconversion”.