Author's personal copy
Journal of Alloys and Compounds 509 (2011) 8478–8482
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Journal of Alloys and Compounds
j our na l ho me p ag e: www.elsevier.com/locate/jallcom
Growth and characterization of tetragonal structure modification of
-Gd
2
Si
2
O
7
:Ce
V. Baumer
a
, I. Gerasymov
b
, O. Sidletskiy
b,∗
, O. Voloshina
b
, S. Neicheva
b
a
State Scientific Institution “Institute for Single Crystals” National Academy of Sciences of Ukraine, 60, Lenin Ave., Kharkiv, 61001, Ukraine
b
Institute for Scintillation Materials National Academy of Sciences of Ukraine, 60, Lenin Ave., Kharkiv, 61001, Ukraine
a r t i c l e i n f o
Article history:
Received 27 December 2010
Received in revised form 1 June 2011
Accepted 6 June 2011
Available online 12 June 2011
Keywords:
Scintillation materials
-Gd2Si2O7
Crystal structure
Luminescence
a b s t r a c t
Growth procedure, crystal structure, and luminescent properties of tetragonal -Gd
2
Si
2
O
7
:0.5 at.% Ce
(a = 6.65740(10)
˚
A, c = 24.2715(3)
˚
A, sp.gr. P4
3
) are studied. Tetragonal modification of this compound is
obtained for the first time. Essentially it is isostructural to -Sm
2
Si
2
O
7
and some other known disilicates
(Ca, La, Ce, Pr, Nd). Obtained samples demonstrate high luminescence yield under X-rays and fast decay.
© 2011 Elsevier B.V. All rights reserved.
1. Introduction
Radiation monitoring, high-energy physics, medical diagnostics
devices, well logging, etc. are the basic domains of scintillation
materials application. At present, rare earth silicates RE
2
SiO
5
and
aluminates RE
3
Al
5
O
12
, REAlO
3
(RE = Y, Gd, Lu) activated with Ce
3+
or Pr
3+
are widely applied in many fields [1]. Search for new materi-
als with improved scintillation characteristics is of big importance.
Cerium-doped lutetium scandium orthoborate (Lu
1-x
Sc
x
)BO
3
[2],
gadolinium silicate Gd
9.33
(SiO
4
)
6
O
2
(GSAP:Ce) [3], Ce, Na-codoped
lutetium silicate Lu
2
SiO
5
[4] are the recent examples of new scin-
tillation materials based on complex oxides. Ce-doped rare earth
pyrosilicates (disilicates) RE
2
Si
2
O
7
are among the most promising
new scintillators. They possess lower crystallization temperatures
and lower cost of starting components in comparison to those for
oxyorthosilicates. Pyrosilicates demonstrate attractive scintillation
characteristics at monitoring of -radiation [5,6] and thermal neu-
trons [7], in particular, outstanding light yield stability at elevated
temperatures. Recently, growth procedure, and scintillation and
luminescence characteristics of Ce-doped Gd
2
Si
2
O
7
(GPS) [8] and
Y
2
Si
2
O
7
[9], Pr
3+
-doped Lu
2
Si
2
O
7
(LPS) [10,11] and Gd
2
Si
2
O
7
[12],
and Eu-doped Y
2
Si
2
O
7
and La
2
Si
2
O
7
[13] were reported.
Rare earth pyrosilicates demonstrate big variety of crystalline
structures depending on rare earth cation radius and conditions of
obtaining. Hence, process of GPS:Ce crystal growth, as well as other
∗
Corresponding author. Tel.: +380 57 341 04 42; fax: +380 57 340 44 74.
E-mail address: sidletskiy@isma.kharkov.ua (O. Sidletskiy).
pyrosilicates with RE cation size more than 0,87
˚
A, is complicated
because of incongruent melting of RE
2
O
3
–SiO
2
compositions with
molecular ratio 1:2. In accordance with the phase diagram (Fig. 1),
with the cooling of the melt, 2Gd
2
O
3
·3SiO
2
crystals precipitate from
the melt when the temperature reaches the liquidus curve for the
initial composition Gd
2
O
3
·2SiO
2
. There are two known methods to
overcome this problem. The first one was demonstrated in [8,15,16]
where GPS:Ce or GPS:Pr single crystals were obtained by the Float-
ing Zone and Czochralski methods from stoichiometric melt with
heavy (up to 25 at.%) Ce
3+
and Pr
3+
doping, correspondingly. It was
assumed [15] that the heavy doping changes phase diagram and
enables direct crystallization of single crystalline samples from
the melt. Depending on Ce concentration, orthorhombic, triclinic,
and monoclinic modifications of Gd
2
Si
2
O
7
:Ce can be obtained [16].
However, high Ce concentration in this method evidently should
lead to concentration quenching and drop of light yield. The second
approach is to crystallize GPS, or mixed pyrosilicate (LaGPS) from
melt-solution with the self-flux of SiO
2
(silicon oxide concentration
71–73.6 mol.%) [17,18]. This method allows one to grow crystals
with low Ce concentrations and higher luminescence intensities
[19]. The one of the highest luminescence yields in comparison
with other structures (orthorhombic, triclinic) was demonstrated
on tetragonal mixed pyrosilicate Gd
2x
La
2-2x
Si
2
O
7
:Ce [19]. There-
fore, search for other compositions with this type of structure
is a topic of scientific and practical interest. This work describes
the growth procedure and characterization of Ce-doped tetrag-
onal gadolinium pyrosilicate (-Gd
2
Si
2
O
7
) without La addition.
This crystalline structure has never been observed before with
GPS:Ce.
0925-8388/$ – see front matter © 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jallcom.2011.06.016