cccccc

1. Thermoluminescence and optically stimulated luminescence
characteristics of Al2O3 doped with Tb
J.V. Soares a
, C.F. Gugliotti a
, Y.S. Kawashima a
, S.H. Tatumi b
, J.C.R. Mittani b, *
a
Technological Faculty of S~ao Paulo, Praça Cel. Fernando Prestes, 30, S~ao Paulo-SP, Brazil
b
Federal University of S~ao Paulo, Baixada Santista, Av. Almirante Saldanha da Gama, 89, Santos, Brazil
h i g h l i g h t s
Al2O3:Tb with several terbium concentrations was produced using the evaporation method.
The sample doped with 3 mol% of terbium presented highest luminescence.
The luminescence in the visible region is due to electron transitions of Tb3þ
.
The 190
C TL peak as well OSL signal showed a linear behavior for gamma doses between 1 and 20 Gy.
The minimum detectable dose for Al2O3:Tb was 3 mGy for TL and 40 mGy for OSL.
a r t i c l e i n f o
Article history:
Available online 23 May 2014
Keywords:
Al2O3
Thermoluminescence
Optically stimulated luminescence
TL spectra
Fluorescence
a b s t r a c t
In the present work policrystals of a À Al2O3 doped with terbium were synthesized using the solvent
evaporation method. The samples were prepared using Al(NO3)3$9H2O and Tb(NO3)3$5H2O reagents,
with Tb concentrations between 1 and 5 mol% and thermally treated at high temperature above
~1400
C. X-ray diffraction measurements showed the a-phase formation of samples. TL glow curve
presented an intense peak at ~190
C and two other with low intensity at 290 and 350
C after gamma
irradiation. The best doping concentration which presented high luminescence was the sample doped
with 3 mol% of Tb. TL spectra and fluorescence measurements showed similar luminescence spectra with
lines attribute to Tb3þ
ions. A linear behavior to gamma dose between 1 and 20 Gy was observed in TL,
using 190
C peak as well as in OSL signal, this last carried out using 532 nm wavelength stimulation.
© 2014 Elsevier Ltd. All rights reserved.
1. Introduction
In the last years, insulate materials doped with rare earth ions
have received increasing attention due to their technological
importance. Among these, materials oxides doped with rare earth
have received more attention due to the attractive properties such
as high chemical stability, ease of synthesis etc. (Konrad et al.,
1999). One of these materials is Al2O3 because it offers an excel-
lent mechanical property and good chemical stability; therefore, it
can be considered a good candidate to be used as a host material of
rare earth ions (Rai et al., 2012).
Actually, Al2O3 doped with carbon is being used with optically
stimulated luminescence (OSL) technique in dosimetry and the
material have shown some advantages, such as luminescence effi-
ciency, sensitivity, stability, control of the luminescence emitted,
etc. (McKeever and Moscovitch, 2003) when compared with ther-
moluminescence technique.
Conventionally, the Al2O3:C used in OSL dosimetry is prepared
by crystal growth techniques, which require sophisticated equip-
ment, temperatures above 2000 C and highly reduced
atmospheres.
However, in literature, it can be found several other ways to
synthesize the material with low cost and easy to handle such as
pechini (Bitencourt et al., 2010) solegel (Kaplyanskii et al., 1998;
Gonçalves et al., 2010), solvent evaporation (Azorín et al., 2002),
electrochemical route (Azevedo et al., 2004), combustion synthesis
(Hirata et al., 2005), etc.
On this way, in the present work Al2O3 doped with Tb was
prepared using solvent evaporation method and characterized us-
ing TL, OSL, TL spectra and fluorescence techniques looking the
radiation dosimetry.
* Corresponding author.
E-mail addresses: juan.mittani@unifesp.br, juan.mittani@gmail.com,
juanmittani603@hotmail.com (J.C.R. Mittani).
Contents lists available at ScienceDirect
Radiation Measurements
journal homepage: www.elsevier.com/locate/radmeas
http://dx.doi.org/10.1016/j.radmeas.2014.05.015
1350-4487/© 2014 Elsevier Ltd. All rights reserved.
Radiation Measurements 71 (2014) 78e80

2. 2. Experimental
Al2O3 doped with Terbium was synthesized using the solvent
evaporation method. The samples were prepared using
Al(NO3)3.9H2O and Tb(NO3)3.5H2O reagents obtained from Sigma-
eAldrich, with Terbium concentrations between 1 and 5 mol%. The
mixture was thermal treated at high temperature (~1400 C) for
two hours using a heating rate of 3 C minÀ1
. The final product was
crushed and sieved to select powder grains with sizes between 50
and 200 mm.
The crystalline structure of the samples was investigated by X-
ray diffraction using the MiniFlex™ II analyzer from Rigaku, with
Cu Ka radiation (l ¼ 1.5418 Å). The data were collected by scanning
2q from 3 to 80 at room temperature. The results of the X-ray
diffraction pattern confirmed the formation of a-phase in the
samples.
TL and OSL measurements were carried out using a TL/OSL
Daybreak system model 1100 series reader equipped with a pho-
tomultiplier tube EMI 9235QB and optical filter Schott BG-39
(2 mm thick) and Corning 7e59 (4 mm thick). The heating rate
used in TL measurements was 5 C sÀ1
from RT to 450 C. OSL
measurements were carried out at room temperature using a green
laser as stimulation (532 nm, ~5 mW cmÀ2
at the sample position).
It was used 60 channels where the counts per channel were during
10 s each one.
TL spectra and fluorescence measurements were done using the
CARY 500 spectrophotometer. Fluorescence measurements were
done using UV stimulation between 295 and 350 nm (5 nm step)
and the luminescence emission detected from 400 to 800 nm in a
pulse mode with total decay time 0.02 s; delay time 0.2 ms and gate
time 10 ms.
The samples were irradiated to different doses between 1 and
20 Gy for dose response and 23 kGy for TL spectra at room tem-
perature using a 60
Co gamma source.
3. Results and discussions
Luminescence intensity of ~190 C TL peak as a function of
terbium concentration is shown in Fig. 1. From the results, it is
observed that the peak intensity enhances with the increment of Tb
concentration, attains a high intensity to the sample doped with
3 mol% and then decreases with increasing of Terbium due to the
quenching concentration.
Fig. 1. Intensity of 190 C TL peak as function of Tb concentration.
Fig. 2. Fluorescence of Al2O3 pure and doped (3 mol% of Tb) stimulated with 310 nm
wavelength.
Fig. 3. TL spectra of Al2O3:Tb after high gamma dose irradiation.
Fig. 4. TL glow curves of Al2O3:Tb for several gamma doses between 1 and 20 Gy
(heating rate 5C sÀ1
).
J.V. Soares et al. / Radiation Measurements 71 (2014) 78e80 79

3. Fluorescence measurements of pure and doped (3 mol% of
terbium) samples stimulated with 310 nm wavelength is shown in
Fig. 2. The doped sample spectrum shows emission lines peaking at
489, 545, 588 and 622 nm due to electron transitions of 5
D4 / 7
F6,
5
D4 / 7
F5, 5
D4 / 7
F4, and 5
D4 / 7
F3 levels from Tb3þ
respectively,
plus superposed emissions between 650 and 750 nm due to crystal
point defects in the sample. The same spectrum was observed for
other stimulation wavelengths between 295 and 350 nm, however,
with low intensities. On the other hand, the pure sample showed
only superposed emissions between 650 and 750 nm with high
intensity when compared to the doped sample.
TL emission spectra after gamma irradiation with high dose is
shown in Fig. 3. The TL spectrum shows similar emission lines as
fluorescence plus two new emission lines peaking at 383 and
422 nm, both also due to Tb3þ
. All these emission lines have high
intensity for temperatures between 160 and 220 C, with
maximum on ~190 C, thus indicating that the luminescence peak
at this temperature is due to Tb dopant.
Fig. 4 shows the TL glow curve of Al2O3:Tb (3 mol%) for various
g-irradiations ranged from 1 to 20 Gy. All the glow curves exhibit an
intense peak at ~190 C plus two low intense peaks at 290 and
350 C. The behavior of 190 C peak as a function of the dose was
linear, as observed in Fig. 5, and showed a minimum detected dose
of the 3 mGy which was calculated using three times the standard
deviation of zero dose reading.
The OSL decay curves for various g-irradiations ranged from 1 to
20 Gy is shown in Fig. 6, and the behavior of OSL intensity (first
point of the curve) as a function of the dose in Fig. 5. Likewise as TL,
the OSL signal shows a linear behavior to the gamma doses and a
minimum detected dose of 40 mGy, calculated in the same way as
TL.
4. Conclusions
From the results, we can conclude that the solvent evaporation
method seems suitable for preparation of Al2O3:Tb due to the ad-
vantages such as low cost and easy to handle.
Most of the luminescence of the material comes from Tb dopant
(380 and 600 nm), and due to the use of optical filters in front of the
PMT for TL and OSL measurements (optical transmission ~340 and
450 nm), just a part of the luminescence spectra is detected, thus
diminishing the luminescence intensity and sensitivity of the
material.
The sample presented linear behavior for gamma doses be-
tween 1 and 20 Gy with minimum detected dose of 3 mGy for TL
and 40 mGy for OSL.
Acknowledgements
The authors wish to thank Ms. E. Somessari and Mr. C. Gaia,
Instituto de Pesquisas Energeticas e Nucleares (IPEN), Brazil, for
kindly carrying out the irradiation of samples and Conselho
Nacional de Desenvolvimento Científico e Tecnologico CNPq for
undergraduate fellowship.
References
Azevedo, W.M., Carvalho, D.D., Khoury, H.J., Silva Jr., E.F., 2004. Photoluminescence
characteristics of rare earth doped nanoporous aluminum oxide. Appl. Surf. Sci.
234, 457e461.
Azorín, J., Esparza, A., Falcony, C., Rivera, T., García, M., Martínez, E., 2002. Prepa-
ration and thermoluminescence properties of aluminum oxide doped with
europium. Radiat. Prot. Dosim. 100, 277e279.
Bitencourt, J.F.S., Ventieri, A., Gonçalves, K.A., Pires, E.L., Mittani, J.C., Tatumi, S.H.,
2010. A comparison between neodymium doped alumina samples obtained by
Pechini and sol-gel methods using thermo-stimulated luminescence and SEM.
J. Non-Cryst. Solids 356, 2956e2959.
Gonçalves, K.A., Bitencourt, J.F.S., Mittani, J.C., Tatumi, S.H., 2010. Study of Radiation
Induced Effects in the Luminescence of Nanostructurated Al2O3:Yb,Er crystals.
IOP Conf. Series: Materials Science and Engineering, 15.
Hirata, G., Perea, N., Tejeda, M., Gonzalez-Ortega, J.A., McKittrick, J., 2005. Lumi-
nescence study in Eu-doped aluminum oxide phosphors. Opt. Mater. 27,
1311e1315.
Kaplyanskii, A.A., Kulinkin, A.B., Kutsenko, A.B., Feofilov, S.P., Zakharchenya, R.I.,
Vasilevskaya, T.N., 1998. Optical spectra of triplycharged rare-earth ions in
polycrystalline corundum. Phys. Sol. State 40, 1310e1316.
Konrad, A., Fries, T., Gahn, A., Kummer, F., Herr, U., Tidecks, R., Sammer, K., 1999.
Chemical vapor synthesis and luminescence properties of nanocrystalline cubic
Y2O3. Eur. J. Appl. Physiol. 86, 3129e3133.
Mckeever, S.W.S., Moscovitch, M., 2003. On the advantages and disadvantages of
optically stimulated luminescence dosimetry and thermoluminescence
dosimetry. Radiat. Prot. Dosim. 104, 263e270.
Rai, R.K., Upadhyay, A.K., Kher, R.S., Dhoble, S.J., 2012. Mechanoluminescence,
thermoluminescence and photoluminescence studies on Al2O3: Tb phosphors.
J. Luminescence 132, 210e214.
Fig. 5. TL and OSL intensity of Al2O3:Tb (3 mol% of Tb) as function of dose and mini-
mum detectable dose.
Fig. 6. OSL signal of Al2O3:Tb using 532 nm laser stimulation for several gamma doses
between 1 and 20 Gy.
J.V. Soares et al. / Radiation Measurements 71 (2014) 78e8080