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Optical properties of nanocrystalline YAG:Ce
|Heiko Paul , Dominik Kessler , Ulrich Herr|
Ulm University, Albert-Einstein-Allee 47, Ulm 89081, Germany
Due to its high quantum efficiency (QE) for luminescence, conventional coarse-grained YAG:Ce finds widespread use in light conversion and scintillator applications. Preparing YAG:Ce in nanocrystalline form may impart modified optical properties of advantage to technological applications, but the latter depend on highly efficient energy conversion. In this work, the effect of the particle size on quantum efficiency as well as on the optical lifetime of the YAG:Ce emission will be characterized and discussed.Nanocrystalline YAG:Ce with an average particle size of 20 to 50 nm is synthesized by the chemical vapor reaction (CVR) method and subsequently analyzed by different techniques. Photoluminescence (PL) is used to investigate the relative quantum efficiency, emission properties and excitation behavior of different samples, while lifetime measurements of the luminescence intensity reveal information about the relaxation mechanisms of the excited Ce states. X-ray diffraction (XRD) is performed to examine the structure and grain size of the material. Furthermore, analysis of the chemical composition and doping concentration is performed by energy dispersive x-ray analysis (EDX) in a scanning electron microscope.
Comparing the nanocrystalline samples to a coarse-grained reference sample, we find a significant influence of the particle size on quantum efficiency. It turns out that the investigated nanocrystalline samples exhibit a lower QE at ambient temperature than the coarse-grained reference. The results of the optical lifetime measurements are discussed in relation to this reduction in QE.
Presentation: Poster at E-MRS Fall Meeting 2007, Acta Materialia Gold Medal Workshop, by Heiko Paul
See On-line Journal of E-MRS Fall Meeting 2007
Submitted: 2007-05-11 20:01 Revised: 2009-06-07 00:44