Glass - Back to the Future!



Presenting Author:
Andreas Herrmann
<andreas.herrmann@uni-jena.de>

article posted 28 Jan 2016


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Ce3+:YAG and Ce3+:LuAG glass ceramics for use in white LEDs
produced by a sintering technique and Ce3+:YAG precipitation
from a glass

Andreas Herrmann*1, Ashkan Keshavarzi1, Christian Rüssel1, Peter Pachler2


Commercial Ce3+ doped yttrium aluminum garnet (Ce3+:YAG) and lutetium aluminum garnet (Ce3+:LuAG) powders were mixed with powdered soda-lime silicate glass with the molar composition 15.5 Na2O / 10.7 CaO / 73.8 SiO2. The mixtures were sintered at temperatures in the range from 800 to 1000 °C for 10 and 30 min (Fig. 1).


XRD-patterns proved that the ceramic samples contain only the respective garnet phases. Fluorescence spectra clearly show a dissolution of the phosphors during the sintering process, especially at 1000 °C. However, if the processing time is short, almost no fluorescence intensity is lost in comparison to samples sintered at 800 °C (Fig. 2). The emission intensity of Ce3+ ions in the glassy phase can easily be used as a measure of this dissolution process, since the Ce3+:NCS-glass emission peak is in a much different spectral range than the emission of the Ce3+:YAG and Ce3+:LuAG phosphors (Fig. 2).



Additionally, the dissolution process is strongly affected by the chemical composition of the glass. The efficiency in lm/W of the ceramic samples increases with the sample thickness and is for the Ce3+:LuAG sample nearly as high as for polymer embedded samples, while it is slightly smaller for the Ce3+:YAG samples. Therefore, low Tg glasses are not necessarily required for embedding of fluorophors. The results are compared to similar glass ceramics produced by precipitation of the Ce3+:YAG phase from a glass.

Institutions

1 Otto-Schott-Institut für Materialforschung, Jena University, Fraunhoferstr. 6, 07743 Jena, Germany

2 Tridonic Jennersdorf GmbH, Technologiepark 10, 8380 Jennersdorf, Austria