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
doped yttrium aluminum garnet (Ce3+
:YAG) and lutetium aluminum
:LuAG) powders were mixed with powdered soda-lime silicate glass with
the molar composition 15.5 Na2
O / 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).
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
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).
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.
1 Otto-Schott-Institut für Materialforschung, Jena University, Fraunhoferstr. 6, 07743 Jena, Germany
2 Tridonic Jennersdorf GmbH, Technologiepark 10, 8380 Jennersdorf, Austria