Fachhochschule Münster
University of Applied Sciences
Utrecht University
Philips Lighting
COMPARATIVE STUDY OF THE AFTERGLOW
OF STRONTIUM ALUMINATES
Danuta Dutczak, Thomas Jüstel, Andries Meijerink, and Cees Ronda
University of Applied Sciences Münster, D-48565 Steinfurt, Germany
Utrecht University, Budapestlaan 6, 3584 CD Utrecht, The Netherlands
I t d ti
Introduction
This
In recent years afterglow phosphors have attracted considerable
work
deals
with
Eu2+ in
persistent
luminescence
and
different strontium aluminate hosts,
attention due to their potential applications in various fields, including
thermoluminescence of
emergency signs, light sources, luminous paint or optical data storage
such as SrAl2O4, SrAl4O7, SrAl12O19, Sr4Al14O25. All persistent
[1]. At the beginning of the 20th century the ZnS:Cu phosphor were
phosphors were synthesized by conventional high temperature
developed as a long afterglow pigment. In the last 20 years, research on
solid-state or combustion method under a reducing atmosphere.
persistent luminescent phosphors has been switched strongly to
The
aluminates doped with rare earth ions, which show a much brighter and
luminescence (TSL) were recorded to characterize the type,
longer afterglow [2].
intensity and duration of the afterglow .
400nm
1,0
473nm 490nm 520nm
1
2+
photoluminescence
max=138°C
SrAl12O19:Eu
(PL)
and
thermally
stimulated
2+
SrAl12O19:Eu
2+
0
2+
Sr4Al14O25:Eu
Normalized Intensity
Normalized Intensity
SrAl4O7:Eu
0,8
2+
SrAl2O4:Eu
0,6
0,4
0,2
50
1
350
400
450
500
550
600
Wavelength [nm]
650
150
200
250
300
max=94°C
350
400
2+
SrAl4O7:Eu
0
50
100
1 max =90°C
1
150
200
250
max2=235°C
300
350
400
2+
Sr4Al14O25:Eu
Hexagonal SrAl12O19 (SrO-6Al2O3)
0
50
1
00
0,0
100
100
150
200
250
300
max=125°C
350
400
2+
SrAl2O4:Eu
0
700
50
100
150
200
250
300
350
400
Temperature [°C]
Emission spectra of xSrO-yAl2O3 doped with Eu2+
TL spectra of xSrO-yAl2O3 doped with Eu2+
Monoclinic SrAl4O7 (SrO-2Al2O3)
1
2+
SrAl12O19:Eu
180
200
220
240
260
280
2+
Sr4Al14O25:Eu
2+
SrAl4O7:Eu
5.9eV
0
140
1
2+
SrAl4O7:Eu
300
160
180
200
220
240
260
280
300
2+
Sr4Al14O25:Eu
2+
Intensity
Normalized Intensity
160
SrAl12O19:Eu
5
10
7.3eV
0
140
1
2+
SrAl2O4:Eu
4
10
Orthorhombic Sr4Al14O25 (4SrO-7Al2O3)
6.0 eV
0
140
1
0
140
160
180
200
220
240
260
280
300
2+
SrAl2O4:Eu
3
10
6.4eV
160
180
200
220
240
Wavelength [nm]
260
280
0
300
Excitation spectra of xSrO-yAl2O3 doped with Eu2+
1
2
3
Time [min]
4
5
Sr
O
Al
Decay curves of xSrO-yAl2O3 doped with Eu2+
Monoclinic SrAl2O4 (SrO-Al2O3)
Conclusions
It was found that the emission of Eu2+ ions varies from the blue to
TL measurements showed that SrAl12O19:Eu and SrAl4O7:Eu
the green depending on the host lattice due to crystal-field splitting and
show solely a single glow peak at 138 and 94 °C, respectively. In
covalent interaction with the surrounding Oxygen anions.
anions
contrast to that,
that the more alkaline strontium aluminates exhibit two
Bright and persistent afterglow at room temperature was only
glow peaks, viz. at 90 and 235 °C for Sr4Al14O25:Eu and at 125 and
observed for SrAl2O4 and Sr4Al14O25 phosphors doped with Eu2+, while
200 °C for SrAl2O4:Eu. We attribute these high temperature glow
Eu2+ doped SrAl12O19 and SrAl4O7 show rather weak afterglow.
peaks to the strong afterglow at room temperature.
[1] Sang-Do Han, Krishan C. Singh, Tai-Yeon Cho, Jihye Gwak, Journal
of Luminescence 2008 128 301-305,
[2] Yuanhua Lin, Zilong Tang, Zhongtai Zang Materials Letters 2001 51 14-18.