ISSN 10637834, Physics of the Solid State, 2011, Vol. 53, No. 1, pp. 127–130. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © S.V. Nizhankovsky, A.Ya. Dan’ko, Yu.V. Zorenko, V.V. Baranov, L.A. Grin’, V.F. Tkachenko, P.V. Mateichenko, 2011, published in Fizika Tverdogo Tela,
2011, Vol. 53, No. 1, pp. 121–124.
127
1. INTRODUCTION
Owing to the appropriate combination of high den
sity, mechanical strength, chemical stability, and good
scintillation characteristics, crystals based on lutetium
aluminates and silicates have been widely used in
nuclear physics and medical engineering, in particu
lar, in positron emission tomography and devices for
recording and visualizing Xray and gamma radiations
[1]. In recent years, lutetium aluminum garnet
Lu
3
Al
5
O
12
(commonly designated as LuAG) has been
investigated extensively. This compound was used in
the design of the heavy scintillator Lu
3
Al
5
O
12
: Ce
3+
(6.73 g/cm
3
) with a light output of up to 16000 pho
tons/MeV and a decay time of 60–70 ns and the faster
scintillator Lu
3
Al
5
O
12
: Pr
3+
with a light output of up to
24 000 photons/MeV and a decay time (~20 ns) that is
two times shorter than the decay time of lutetium sili
cates [2]. A further improvement of functional charac
teristics of scintillators based on these crystals is sub
stantially limited by the presence of antisite defects
(AD) Lu
Al
(Lu cations in positions of Al cations),
which act as intrinsic luminescence centers in the UV
spectral range [3] and as trapping centers [4]. The
reabsorption of the intrinsic luminescence by dopant
ions and trapping of charge carriers lead to a signifi
cant increase in the contribution from the slow lumi
nescence component and to a decrease in the light
output [3, 4].
One of the ways to solve this problem can be the
search for more optimum compositions of scintillators
based on lutetium aluminum garnet crystals. In partic
ular, the contribution from slow scintillation compo
nents was decreased in Lu
3
(Al
1–
x
Ga
x
)
5
O
12
: Pr
3+
gar
nets by modifying the composition of these garnet
crystals with gallium ions [5]. In the present work, we
studied crystals of (Lu
1–
x
Gd
x
)
3
Al
5
O
12
solid solutions
doped with Ce
3+
and Pr
3+
ions. The prerequisite for
the modification of the garnet composition with gado
linium was based on the results obtained earlier by
Feofilov et al. [6], according to which the concentra
tion of antisite defects depends substantially on the
ionic radius of the dominant garnet cation and
becomes minimum in the case of gadolinium. Much
attention was focused on the investigation of the influ
ence of the substitution of gadolinium ions for lute
tium cations on the growth conditions, as well as on
the optical and luminescence properties of these crys
tals.
2. EXPERIMENTAL TECHNIQUE
2.1. Crystal Growth
Crystals of (Lu
1–
x
Gd
x
)
3
Al
5
O
12
: Ce
3+
, Pr
3+
solid
solutions were grown by the modified horizontal
directional crystallization method (“gasphase” tech
nology of horizontal directional crystallization). The
technology is based on the use of protective reducing
gaseous media and carboncontaining heatinsulating
DISLOCATIONS
Growth and the Luminescence Properties of a Lutetium Gadolinium
Garnet Doped with Ce
3+
and Pr
3+
Ions
S. V. Nizhankovsky
a
, A. Ya. Dan’ko
a
,
*, Yu. V. Zorenko
b
, V. V. Baranov
a
,
L. A. Grin’
a
, V. F. Tkachenko
a
, and P. V. Mateichenko
a
a
State Scientific Institution “Institute for Single Crystals,” National Academy of Sciences of Ukraine,
pr. Lenina 60, Kharkov, 61178 Ukraine
* email: Danko@isc.kharkov.ua
b
Ivan Franko National University of Lviv, ul. Universitetskaya 1, Lvov, 79000 Ukraine
Received January 15, 2010
Abstract
—Crystals of lutetium gadolinium garnet solid solutions (Lu
1–
x
Gd
x
)Al
5
O
12
(0
≤
x
≤
0.6) doped with
Ce
3+
and Pr
3+
ions have been prepared by the horizontal directional crystallization method, and their optical
and luminescence properties have been investigated. It has been established that the introduction of gadolin
ium into the lutetium garnet lattice leads to a decrease in the antisite luminescence (Lu
Al
centers) in the UV
spectral range and to sensitization of the Ce
3+
ion luminescence. By contrast, the presence of gadolinium
results in the quenching of the Pr
3+
luminescence due to the nonradiative excitation transfer from Pr
3+
ions
to Gd
3+
ions.
DOI:
10.1134/S1063783411010215