Available online at www.sciencedirect.com Radiation Measurements 38 (2004) 539 – 543 www.elsevier.com/locate/radmeas Simultaneous excitation of Ce 3+ and Eu 3+ ions in Tb 3 Al 5 O 12 Miroslaw Batentschuk a ; 1 , Andres Osvet a ; ∗ , Gabi Schierning a , Andreas Klier a , J urgen Schneider b , Albrecht Winnacker a a Department of Material Science, Institute 6, University of Erlangen-Nuernberg, Martensstrasse 7, Erlangen D91058, Germany b Freiburger Materialforschungszentrum, Stefan-Meier-Strasse 21 Freiburg D79104, Germany Received 28 November 2003; received in revised form 8 December 2003; accepted 8 December 2003 Abstract Y3Al5O12:Ce 3+ (YAG:Ce) and Tb3Al5O12:Ce 3+ (TAG:Ce) both show the typical Ce 3+ ion luminescence of the allowed Ce 3+ d–f transition. Eu 3+ codoping, however, reveals dierent results for both matrices: in YAG:Ce,Eu, only the luminescence of the Ce 3+ ion occurs by excitation within the Ce 3+ absorption bands. Here, the Eu 3+ luminescence cannot be sensitized by the Ce 3+ ion. But in TAG:Ce,Eu, both Ce 3+ and Eu 3+ luminescence are measured at several excitation wavelengths: an excitation within the Tb-sublattice results in both Ce 3+ and Eu 3+ luminescence, which is not surprising as an energy transfer from Tb 3+ to Ce 3+ and Eu 3+ is well known in literature. In addition, an excitation in the lowest 5d level of Ce 3+ delivers Eu 3+ luminescence at room temperature. This means that the Ce 3+ ion can be used as a sensitizer in the TAG lattice that transfers its energy via the Tb sublattice to the activator Eu 3+ . c  2003 Elsevier Ltd. All rights reserved. Keywords: Terbium aluminium garnet; Energy transfer 1. Introduction Y3Al5O12:Ce 3+ (YAG:Ce) is used as a phosphor for white light emitting diodes using the principle of luminescence conversion (LUCOLED). However, the color impression of a LUCOLED on the base of a blue diode and YAG:Ce is too “cold”, a red component is missing. The common way to improve the emission spectra of lighting devices is with co-activation of the conversion phosphors, for ex- ample with Eu 3+ which shows an intense line emission in the red. An intense 5d– 4f photoluminescence of Ce 3+ on the Tb 3+ site in Tb3Al5O12 (TAG) powder has been reported recently (Kummer et al., 2001), as well as the possibility of its use as a luminescence converter. Compared with YAG:Ce, the spectrum of the TAG:Ce 3+ is slightly shifted to the red, ∗ Corresponding author. Tel.: +49-913-185-27726; fax: +49-913-185-28495. E-mail addresses: mirobat@ww.uni-erlangen.de (M. Batentschuk), andres.osvet@ww.uni-erlangen.de (A. Osvet). 1 Also to be corresponded to. Tel.: +49-913-185-27726. probably because of a reduced local symmetry. However, this shift is not sucient to compensate for the lack of a red component. A codoping with Pr has already been applied successfully (Ellens and Zwaschka, 2001). Results of co-doping both TAG:Ce and YAG:Ce with Eu 3+ are presented in this contribution. Although the YAG and the TAG matrices behave very similarly concerning the Ce 3+ luminescence, there are immense dierences in the case of Eu 3+ co-activation: while in YAG:Ce,Eu the Eu 3+ luminescence cannot be sensitized by Ce 3+ , in TAG:Ce,Eu both Tb 3+ and Ce 3+ serve as sensitizers. 2. Experimental 2.1. Preparation of the phosphors The powder samples were prepared by a conven- tional solid-state reaction. According to the nominal composition of Tb3Al5O12:Ce,Eu, the starting materials Tb2O3; 5; Al2O3; Ce2O3 and Eu2O3 (99% for Al2O3, 99.9% for all other oxides) were weighed and milled. Synthesis took place in a furnace heated by induction using a sealed 1350-4487/$ - see front matter c  2003 Elsevier Ltd. All rights reserved. doi:10.1016/j.radmeas.2003.12.009