New SrPb3Br8 crystals: Growth, crystal structure and optical properties

Article abstract of DOI:10.1016/j.jallcom.2016.05.024

SrBr₂-PbBr₂ system was investigated. A new compound of SrPb₃Br₈ was obtained and investigated by powder and single crystal XRD and spectroscopic methods. SrPb₃Br₈ crystals have orthorhombic symmetry with Pnma space group, a = 8.0056 (4) ?, b = 4.7359 (2) ?, c = 9.5208 (5) ?. These crystals are transparent from ≈360 nm, the band gap is 3.20 eV and calculated density is 6.242 g/cm³. Electronic structure of SrPb₃Br₈ was elucidated based on data of X-ray photoelectron spectroscopy (XPS) and X-ray emission spectroscopy (XES). In particular, XPS core-level and valence-band spectra were measured for pristine and Ar⁺ ion-irradiated surfaces of SrPb₃Br₈ crystals. The XPS results reveal high hygroscopicity of the SrPb₃Br₈ single crystal surface. Comparison on a common energy scale of the XPS valence-band spectrum of SrPb₃Br₈ the XES Br Kβ₂ band representing the energy distribution of the Br 4p states in this bromide indicate that the principle contributions of the Br 4p states occur in the upper portion of the valence band, with also their significant contributions in other valence-band portions.

Full text of DOI:10.1016/j.jallcom.2016.05.024

Accepted Manuscript
New SrPb Br crystals: Growth, crystal structure and optical properties
3
8
Ludmila I. Isaenko, Alina A. Goloshumova, Alexander P. Yelisseyev, Yuri V. Shubin,
O.Y. Khyzhun, Dmitrii Yu. Naumov, Alexandra Yu. Tarasova
PII:
S0925-8388(16)31343-3
10.1016/j.jallcom.2016.05.024
JALCOM 37542
DOI:
Reference:
To appear in: Journal of Alloys and Compounds
Received Date: 19 January 2016
Revised Date: 21 April 2016
Accepted Date: 3 May 2016
Please cite this article as: L.I. Isaenko, A.A. Goloshumova, A.P. Yelisseyev, Y.V. Shubin, O.Y. Khyzhun,
D.Y. Naumov, A.Y. Tarasova, New SrPb Br crystals: Growth, crystal structure and optical properties,
3
8
Journal of Alloys and Compounds (2016), doi: 10.1016/j.jallcom.2016.05.024.
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New SrPb3Br8 crystals: growth, crystal structure and
optical properties
Ludmila I. Isaenko1,2, Alina A. Goloshumova1, *, Alexander P. Yelisseyev1, Yuri V. Shubin2,3, O.Y.
Khyzhun 4, Dmitrii Yu. Naumov3, Alexandra Yu. Tarasova1
1V.S. Sobolev Institute of Geology and Mineralogy of Siberian Branch of Russian Academy of
Sciences, 43, Russkaya Street, Novosibirsk, 630058, Russia
2Novosibirsk State University, 2, Pirogova Street, Novosibirsk, 630090, Russia
3Nikolaev Institute of Inorganic Chemistry Siberian Branch of Russian Academy of Sciences,
3, Acad. Lavrentiev Ave., Novosibirsk, 630090, Russia
4
Frantsevych Institute for Problems of Materials Science, National Academy of Sciences of
Ukraine, 3 Krzhyzhanivsky Street, UA-03142 Kyiv, Ukraine
Abstract
SrBr2 - PbBr2 system was investigated. A new compound of SrPb3Br8 was obtained and
investigated by powder and single crystal XRD and spectroscopic methods. SrPb3Br8 crystals
have orthorhombic symmetry with Pnma space group, a = 8.0056(4) Å, b = 4.7359(2) Å, c =
9.5208(5) Å. These crystals are transparent from ≈360 nm, the band gap is 3.20 eV and
calculated density is 6.242 g /cm3. Electronic structure of SrPb3Br8 was elucidated based on data
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of X-ray photoelectron spectroscopy (XPS) and X-ray emission spectroscopy (XES). In
particular, XPS core-level and valence-band spectra were measured for pristine and Ar+ ion-
irradiated surfaces of SrPb3Br8 crystals. The XPS results reveal high hygroscopicity of the
SrPb3Br8 single crystal surface. Comparison on a common energy scale of the XPS valence-band
spectrum of SrPb3Br8 the XES Br Kβ2 band representing the energy distribution of the Br 4p
states in this bromide indicate that the principle contributions of the Br 4p states occur in the
upper portion of the valence band, with also their significant contributions in other valence-band
portions.
Keywords
A. Inorganic materials; B. Crystal growth; C. Crystal structure; C. Optical properties; D. X-
ray diffraction; D. Photoelectron spectroscopies
1. Introduction
An intense search for new active media for solid state lasers generating in mid-infrared range
revealed a family of double halogenides of alkali metals APb2Br5, where A=K, Rb. The cycle of
works on obtaining of this group of crystals was initiated 15 years ago. As a result crystals with a
unique set of properties were developed [1]. These compounds appeared to be chemically stable
and transparent in a wide range (0.35-30 µm). They have a low-energy phonon spectrum which
results in minimum heat losses and high quantum yield of the radiative processes. The conditions
of the matrix effective doping with rare-earth elements were found and a group of crystals
promising as laser media for visible and infrared ranges was created [2-5]. RbPb2Br5 (RPB) and
KPb2Br5 (KPB) crystals have a density of 5.62 and 5.83 g/cm3, respectively. Loose packing of
the ions with large radius provides comprehensive facilities for variation of crystals composition
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and properties and opens prospects for their use not only as active laser matrices, but also as
promising scintillation materials. High density and the possibility of crystal doping with rare-
earth ions are important characteristics of effective scintillation crystal. Scintillation crystals are
now an important part of many applications, including the detection of gamma radiation with
high energy resolution to identify isotopes. Many research works are devoted to obtain effective
stable material with optimal scintillation properties (high energy resolution, light yield, etc.).
There are some specific requirements for gamma spectroscopy, such as a high atomic number
(which provides a good stopping power for gamma rays) and the absence of natural radioactivity
[6]. Strontium ions are easily replaced with rare-earth ions in crystal lattices because of the
similarity in their ionic radii. Therefore replacing of alkali ions (K and Rb) with strontium in the
matrices of listed bromides is considered as the way to obtain a new potential scintillation
material. The SrBr2-PbBr2 system was not studied to date and there are no data in literature. In
the present work new SrPb3Br8 crystal was grown for the first time, its crystal structure and some
spectroscopic properties were investigated. In particular, X-ray photoelectron spectroscopy
(XPS) and X-ray emission spectroscopy (XES) were used in the present work to measure the
XPS core-level and valence-band spectra as well as the XES Br Kβ2 band (Br 4p states) of the
SrPb3Br8 crystal.
2. Experimental details
To obtain crystals of ternary compounds SrBr2 and PbBr2 were used as initial materials.
Binary bromides were prepared by dissolving SrCO3 (99.99%) and pre-purified Pb(NO3)2 in
hydrobromic acid HBr (99,99%). For further purification synthesized bromides were subjected to
the repeated directed crystallization with a preliminary removal of contaminated parts. The
purified components were placed in a quartz ampoule, which then was evacuated, sealed and
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placed in a horizontal furnace. Then the mixture was melted at the temperature of 380°C and
stirred up during 24 hours for complete composition homogenization. The resulting material was
loaded into a quartz growth container. Crystals were grown by the vertical Bridgman method.
The vertical temperature gradient in the growth zone was about 20°/cm, the speed of the ampoule
lowering into the cold zone was 2-5 mm/day. As a result sufficiently pure and transparent crystal
boule up to ø15×100 mm in size was obtained (Fig. 1). Crystal boule is homogeneous, but in its
middle part there are turbid blocks several millimeters in size.
To determine phase composition of obtained boules the powder X-Ray diffraction analysis
was used. Samples were cut from conic, middle and end parts of the crystal boule and then were
grinded to dispersed powders. The PXRD analysis of the samples was performed at room
temperature on a Shimadzu XRD-7000 diffractometer (CuKα radiation, Ni filter on the reflected
beam, scintillation detector with amplitude discrimination). The patterns were recorded in the
step mode in the angular range 2θ = 10–85°, with a step 0.05. The phase nature of the prepared
compound was determined by indexing the powder diffraction patterns of the complexes using
the single crystal XRD data. Indexing of the diffraction patterns for the products of hydrolysis
was carried out using the data reported in the PDF database [7]. Unit cell parameters were refined
by the full-profile technique within the whole diffraction range using the PowderCell 2.4
software [8].
Clean and optically transparent sample 0.13×0.07×0.02 mm3 in size was cut from the middle
part of the grown boule and used for single crystal XRD experiment. Single crystal data were
collected with the МоКα-radiation using a Bruker APEX DUO diffractometer equipped with a
graphite monochromator. All calculations were performed using SHELXTL software {Bruker
AXS Inc. (2004), APEX (Version 1.08), SAINT (Version 7.03), SADABS (Version 2.11) и
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SHELXTL (Version 6.12) Bruker Advanced X-Ray Solutions – Madison, Wisconsin, USA}.
Coordination numbers of cations in studied structures were defined by the Dirichlet polyhedra
method using the Xshell software [9]. For graphic visualization the BS program (Balls & Sticks
ver. 1.42 by Sung J. Kang & Tadashi C. Ozawa) was used.
Transmission spectra were recorded at 300 K in the UV to near IR and mid-IR spectral ranges
using a Shimadzu PC-2501 and a Fourier-tranform Infralum FT-801 spectrometers, respectively.
Plates of SrPb3Br8 and PbBr2 300 and 60 microns thick, respectively, with cleaved natural faces
were used for these measurements. Absorption spectra were then calculated taking into account
the multiple reflections from the opposite parallel flat faces of the plates. We analyzed the so
called Tauc plot of (αhυ)n vs hυ in the region of the short-wavelength edge of the transparency
region, where α is the absorption coefficient deduced from the transmission data and hυ is the
photon energy. The index of power (n) for the Tauc plot determines the type of the band-to-band
electron transitions [10].
Features of the electronic structure of the SrPb3Br8 crystal were clarified based on XPS and
XES measurements. The XPS core-level and valence-band spectra of SrPb3Br8 were measured
using the UHV-Analysis-System produced by SPECS Surface Nano Analysis Company (Berlin,
Germany). The System is equipped with a hemispherical PHOIBOS 150 analyzer and the XPS
spectra were recorded in an ion-pumped chamber at a base pressure less than 7×10–10 mbar. The
XPS spectra were excited by a Mg Kα source of X-ray radiation (E=1253.6 eV) were attained at
a constant pass energy of 35 eV. The spectrometer energy scale was calibrated following the
technique reported in detail in [5]. The C 1s line (284.6 eV) of adventitious carbon was used as a
reference to account for the charging effects as it is offered for ternary lead-bearing bromides
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[11, 12]. To remove surface contaminations, we have performed the bombardment of SrPb3Br8
single crystal surface by Ar+ ions with the energy of 3.0 keV over 5 min at the ion current
density of 17 µA/cm2 (a total Ar+ flux was estimated to be 5.3×1016 ions/cm2). This method of
surface cleaning is the same used earlier for a number of ternary lead-containing bromides [5, 11,
12]. In addition, following the experimental studies and first-principles band-structure
calculations of ternary Pb-bearing bromides indicating that their electronic structures are defined
by significant contributions of the Br 4p states throughout the whole valence band region [11-
14], we have also measured XES Br Kβ2 band (K → MII,III transition) that represents
peculiarities of the energy distribution of the valence Br p states. In the present work, the XES Br
Kβ2 band was recorded with energy resolution of about 0.3 eV employing a Johann-type DRS-
2M spectrograph equipped with an X-ray BHV-7 tube (gold anode) operating at accelerating
voltage, Ua = 45.0 kV, and anode current, Ia = 72.5 mA. The disperse element was a quartz
crystal with the (0001) reflecting plane.
3. Results and discussion
The results of powder x-ray phase analysis are shown at Fig. 2. There is one main phase on
diffraction patterns of all three samples. Its peaks correspond to the reference diffraction pattern
of lead bromide, but their position is shifted towards smaller angles. This indicates an increase of
unit cell parameters in comparison with the structure of pure lead bromide. In more detail, this
phase was studied by single crystal x-ray diffraction analysis. Besides there are additional weak
peaks attributable to other unidentified phase on the diffraction pattern of the sample made from
the middle part of crystal boule (Fig. 2, ♦). Low intensity of peaks indicates its low content of
about 20% in the sample.
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According to powder X-Ray diffraction results crystal structure of the main phase is rather
similar to lead bromide. To estimate the difference between them X-Ray diffraction analysis was
carried out for PbBr2 and crystals of obtained compound. The results and structure refinement
data are given in Table 1.
Single crystal X-Ray diffraction analysis showed that obtained compound is SrPb3Br8 crystal
of orthorhombic system with Pnma space group. Strontium and lead ions each have one
nonequivalent position in crystal structure, bromine ions have two positions. As a result of
Dirichlet polyhedra constructing it was found that the coordination number of cations is 9. Table
2 shows cation-anion bond lengths in SrPb3Br8 crystal in comparison with similar characteristics
for PbBr2 crystal. According to bond lengths two coordination spheres for each cation can be
selected. The first one is formed by seven bromine ions, and the second coordination sphere
includes another two Br- ions. Coordination polyhedra of Sr2+ and Pb2+ cations are monocapped
tetragonal prisms.
SrPb3Br8 crystal structure is slightly changed crystal structure of PbBr2, where part of lead
ions is substituted by Sr2+ ions (Fig. 3). In this case lead coordination polyhedra, which are
occupied by strontium, become distorted, cation-anion bond lengths for Sr2+ and Pb2+ ions are
different (Table 2).
The positions of both cations differ from Pb2+ ion position in pure lead bromide structure: as
opposed to the latter in the structure of ternary compound Sr2+ and Pb2+ are slightly displaced,
therefore SrPb3Br8 lattice is slightly distorted in comparison with PbBr2 (Fig. 4).
On the basis of single crystal x-ray diffraction data the diffraction pattern for SrPb3Br8 crystal
was calculated (Fig. 2, SrPb3Br8). It corresponds completely to the main phase on the diffraction
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patterns obtained by powder x-ray analysis. This confirms that the main phase in the obtained
crystal boule conforms SrPb3Br8.
Transmission spectra were recorded for thin SrPb3Br8 and PbBr2 plates, which were 300 and
60 ꢀm thick, respectively (Fig. 5). and absorption spectra were calculated on their basis. Both
crystals become transparent from ≈0.36 ꢀm and they stay transparent up to 20 ꢀm at least. For
SrPb3Br8 the transparency grows smoothly as wavelength increases up to 1.5 ꢀm whereas at
longer wavelengths one can see some structure: broad bands near 2.5 and 15 ꢀm and narrow
lines at 2.89, 6.26 and 8.05 ꢀm. According to Tennison et al [15] these lines in the mid-IR are
associated with water molecules and O-H vibrations (Table 3). Strong absorption at about 2.89
ꢀm is caused by stretch vibrations in H2O molecules and OH groups. Absorption features at 6.26
ꢀm and 15 ꢀm correspond to ν2, bend vibrations and L2 librations in H2O, respectively. Origin of
the 8.05 ꢀm absorption line is not clear to date.
A Tauc plot [16] was used to determine the optical bandgap. Unfortunately the absorption
spectra both for SrPb3Br8 and PbBr2 did not show a flattening in the coordinates of (α×hν)2 = f
(hν) or (α×hν)0.5 = f (hν) as was expected for the cases of direct or indirect band-to-band
electronic transitions, respectively. However, we found that the absorption dependence versus
photon energy was close to an exponential one (Fig. 6). Following F. Urbach [17, 18] such shape
of the α (hν) spectrum typically is associated with electronic transitions from the valence to
conduction band tail in disordered solids. It is necessary to note that a shortwave absorption edge
is located near 3.2 eV for PbBr2, which is considerably lower than the Eg= 4.2 eV value, obtained
from the reflection and luminescence excitation spectra [19, 20]. A possible reason of such
difference may be an intense band of excitonic absorption, located near 3.95 eV in PbBr2 [19,
20]. Similar situation takes place in SrMgF4 single crystal: absorption edge is near 10.5 eV
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whereas Eg= 12.5 eV according to results of reflection and luminescence excitation spectroscopy
[21, 22]. Taking into account close values for shortwave absorption edge for SrPb3Br8 and PbBr2
single crystals (Fig. 5), we expect that bandgap values for these crystals are also similar (about
4.2 eV from [19, 20]).
Thus, spectroscopic studies indicate the presence of impurities of oxygen-containing
compounds. Strontium-containing halides are highly hygroscopic [23, 24], therefore oxygen-
containing compounds could be formed at the stage of synthesis or sample preparation.
Considering the composition of the starting components in the system, it can be assumed that the
detected second phase of unidentified composition is an oxygen-containing compound of
strontium.
The above suggestions are confirmed by the present XPS results. Fig. 7 presents the survey
XPS spectra of both pristine and Ar+ ion-bombarded surfaces of the studied SrPb3Br8 crystal.
From the figure, it is apparent that all the features of the survey XPS spectra, except of carbon
and oxygen 1s levels and KLL Auger lines, are attributed to the core-levels of atoms constituting
the SrPb3Br8 compound. As one can see from Fig. 7, relative intensities of the XPS O 1s and C
1s core-level lines are rather high on the pristine surface of the SrPb3Br8 crystal to adsorbed
oxygen-containing species, hydrocarbons and water. Further, as Fig. 8a presents, the maximum
of the XPS Pb 4f7/2 core-level spectrum is detected on the pristine SrPb3Br8 crystal surface at the
binding energy of about 138.9 eV. This fact indicates that lead atoms on the pristine SrPb3Br8
surface are mainly in the formal valence +3 [25-27]. Figs. 7 and 8 reveal that the surface
treatment with 3.0 keV Ar+ ions over 5 min at ion current density fixed at 14 µA/cm2 causes
decreasing relative intensities of the XPS C 1s and O 1s lines as well as relative content of Pb3+
ions in the topmost SrPb3Br8 crystal layers. As a result of such a bombardment, the relative
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contents of Pb2+ and Pb3+ ions become comparative (see Fig. 8a). However, the Ar+ ion-
bombardment do not alter charge states of Sr and Br atoms because the binding energies of the
XPS Br 3p3/2 and Sr 3p3/2 core-level spectra do not change within the accuracy of the present
measurements, namely ±0.1 eV (Figs. 8b and 8c). Fig. 9 shows that the mentioned Ar+
irradiation does not cause significant changes of the energy distribution of the electronic states
within the valence band region as well. As can be seen from Fig. 9, the Ar+ ion-bombardment
makes visible two fine-structure peculiarities A and B of the XPS valence-band spectrum that are
not resolved on the spectrum of the pristine surface of the SrPb3Br8 crystal. It is worth
mentioning that the SrPb3Br8 compound looks to be very different from other ternary lead-
bearing bromides, namely Tl3PbBr5 and APb2Br5 (A = K, Rb, Tl), which were proved to possess
very low hygroscopicity [11-14, 28].
Results of comparison of the X-ray emission Br Kβ2 band and the XPS valence-band
spectrum of SrPb3Br8 provided that a common energy scale is used are plotted in Fig. 10. The
technique of matching the above X-ray spectra of the SrPb3Br8 crystal on a common energy scale
is similar to that used earlier for a number of ternary lead-contained bromides (see, e.g. Refs.
[13, 14]), and it is generally used in experimental studies of solids using the XPS and XES
method [29]. The experimental XPS and XES results depicted in Fig. 10 show that the principal
contributions of the Br 4p states occur in the upper portion of the valence band, with also
significant contributions of the valence Br p states throughout the whole valence band region of
SrPb3Br8. Similar conclusion was made when studying the electronic structure of a number of
ternary lead-bearing bromides Tl3PbBr5 and APb2Br5 (A = K, Rb, Tl) [11-14, 28]. Regrettably,
available facilities do not allow measurements of the energy distribution of the valence s and p
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states associated with lead and strontium atoms that are expected to be the other contributors to
the valence band of the SrPb3Br8 compound.
4. Conclusions
Ternary compound of SrPb3Br8 composition is crystallized in SrBr2 - PbBr2 system. SrPb3Br8
crystal structure has Pnma symmetry, a = 8.0056(4) Å, b = 4.7359(2) Å, c = 9.5208(5) Å. These
crystals are transparent from ≈360 nm, bandgap is estimated as 3.20 eV. Calculated density is
6.242 g/cm3 and allows one to consider the SrPb3Br8 crystals as a potential scintillation material.
The present XPS results indicate that all features of the survey spectra of SrPb3Br8, except of
carbon and oxygen 1s levels and KLL Auger lines, are attributed to the core-levels of atoms
constituting the compound under consideration. Further, the XPS measurements indicate that the
SrPb3Br8 crystal surface is highly hygroscopic. Matching the XPS valence-band spectrum on a
common energy scale with the X-ray emission Br Kβ2 band, which represents the energy
distribution of the Br 4p states, allows for concluding that the Br 4p states contribute mainly in
the upper portion of the valence band of SrPb3Br8, with also their significant contributions in
other valence-band portions. The study of SrBr2-PbBr2 system will be continued.
Acknowledgements
This work is supported by Russian Foundation of Basic Research (grant № 16-32-00545).
Authors thank V.M. Pashkov for help with crystal growth.
AUTHOR INFORMATION
Corresponding Author
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*Phone/Fax: +7 383 306 63 88. E-mail: alingol-nsk@yandex.ru
REFERENCES
[1] M.C. Nostrand, R.H. Page, W.F. Payne, W.F. Krupke, S. Schunemann, L.I. Isaenko,
Spectroscopic data infrared transitions in CaGa2S4:Dy3+ and KPb2Cl5:Dy3+, ASSL TOPS XIX,
Washington, D.C., 1998, p 524.
[2] L.I. Isaenko, A.A. Merkulov, S.V. Melnikova, V.M. Pashkov, A.Yu. Tarasova, Effect of K
↔ Rb Substitution on Structure and Phase Transition in Mixed KxRb1−xPb2Br5, Cryst. Growth
Des. 9 (2009) 2248–2251.
[3] I.N. Ogorodnikov, A.A. Smirnov, V.A. Pustovarov, L.I. Isaenko, A.Y. Tarasova, V.Y.
Yakovlev, Transient optical absorption and luminescence in APb(2)Cl(5) (A = K, Rb) crystals,
Phys. Solid State. 51 (2009) 1640-1648.
[4] A.Yu. Tarasova, Yu.V. Seryotkin, V.M. Pashkov, L.I. Isaenko, Coefficients of thermal
expansion of KPb2Cl5 and RbPb2Br5 crystals, JTAC. 104 (2011) 795-796.
[5] A.Yu. Tarasova, L.I. Isaenko, V.G. Kesler, V.M. Pashkov, N.M. Denysyuk, O.Yu. Khyzhun,
A.P. Yelisseyev, Electronic structure and fundamental absorption edges of KPb2Br5,
K0.5Rb0.5Pb2Br5 and RbPb2Br5 single crystals, J. Phys. Chem. Solids. 73 (2012) 674-682.
[6] E.D. Bourret-Courchesne, G.A. Bizarri, R. Borade, G. Gundiah, E.C. Samulon, Z. Yan, S.E.
Derenzo, Crystal growth and characterization of alkali-earth halide scintillators, J. Cryst. Growth
352 (2012) 78 – 83.
[7] Powder Diffraction File, PDF-2/Release 2009, 2009: International Centre for Diffraction
Date, USA.
[8] G. Nolze, W. Kraus, Powder Diffr. 13 (1998) 25.
12

ACCEPTED MANUSCRIPT
[9] N.E. Kashcheeva, D.Y. Naumov, E.V. Boldyreva, Software for calculating Dirichlet domains
and examples of its application for the analysis of crystal structures of
cobalt(III)nitropentaammines, Z. Kristallogr. 214 (1999) 534 – 541.
[10] D.L. Wood, J. Tauc, Weak absorption tails in amorphous semiconductors, Phys. Rev. B. 5
(1972) 3144 – 3151.
[11] O.Y. Khyzhun, V.L. Bekenev, O.V. Parasyuk, S.P. Danylchuk, N.M. Denysyuk, A.O.
Fedorchuk, N. AlZayed, I.V. Kityk, Single crystal growth and the electronic structure of
orthorhombic Tl3PbBr5: A novel material for non-linear optics, Opt. Mater. 35 (2013) 1081–
1089.
[12] O.Y. Khyzhun, V.L. Bekenev, N.M. Denysyuk, I.V. Kityk, P. Rakus, A.O. Fedorchuk, S.P.
Danylchuk, O.V. Parasyuk, Single crystal growth and the electronic structure of TlPb2Br5, Opt.
Mater. 36 (2013) 251–258.
[13] A.A. Lavrentyev, B.V. Gabrelian, V.T. Vu, N.M. Denysyuk, P.N. Shkumat, A.Y. Tarasova,
L.I. Isaenko, O.Y. Khyzhun, Electronic structure and optical properties of RbPb2Br5, J. Phys.
Chem. Solids. 91 (2016) 25–33.
[14] A.A. Lavrentyev, B.V. Gabrelian, V.T. Vu, N.M. Denysyuk, P.N. Shkumat, A.Y. Tarasova,
L.I. Isaenko, O.Y. Khyzhun, Specific features of the electronic structure and optical properties of
KPb2Br5: DFT calculations and X-ray spectroscopy measurements, Opt. Mater. 53 (2016) 64–72.
[15] J. Tennyson, P.F. Bernath, L.R. Brown, A. Campargue, A.G. Császár, L. Daumont, R.R.
Gamache, J.T. Hodges, O.V. Naumenko, O.L. Polyansky, L.S. Rothman, A.C. Vandaele, N.F.
Zobov, A database of water transitions from experiment and theory (IUPAC Technical Report),
Pure Appl. Chem. 86 (2014) 71-83.
13

ACCEPTED MANUSCRIPT
[16] J. Tauc, Optical properties and electronic structure of amorphous Ge and Si, Mater. Res.
Bull. 3 (1967) 37-46.
[17] F. Urbach, The long-wavelength edge of photographic sensitivity and of the electronic
absorption of solids, Phys. Rev. 92 (1953) 1324-1329.
[18] S. John, C. Soukoulis, M.H. Cohen, E.N. Economou, Theory of Electron Band Tails and the
Urbach Optical-Absorption Edge, Phys. Rev. Lett. 57 (1986) 1777-1780.
[19] R. Kink, T. Avarma, V. Kisand, A. Lohmus, I. Kink, I. Martinson, Luminescence of cation
excitons in PbCl2 and PbBr2 crystals in a wide excitation VUV region, J. Phys.: Condens. Matter.
10 (1998) 693–700.
[20] M. Iwanaga, M. Watanabe, T. Hayashi, Charge separation of excitons and the radiative
recombination process in PbBr2 crystals, Phys. Rev. B 62 (2000) 10766-10773.
[21] I.N. Ogorodnikov, V.A. Pustovarov, S.I. Omelkov, L.I. Isaenko, A.P. Yelisseyev, A.A.
Goloshumova, S.I. Lobanov, A far ultraviolet spectroscopic study of the reflectance,
luminescence and electronic properties of SrMgF4 single crystals, J. Lumin. 145 (2014) 872-879.
[22] A.P. Yelisseyev, X. Jiang, L.I. Isaenko, L. Kang, B. Lei, Z. Lin, A.A. Goloshumova, S.I.
Lobanov, D.Y. Naumov, Structures and optical properties of two phases of SrMgF4, Phys. Chem.
Chem. Phys. 17 (2015) 500-508.
[23] V.A. Pustovarov, I.N. Ogorodnikov, A.A. Goloshumova, L.I. Isaenko, A.P. Yelisseyev, A
luminescence spectroscopy study of scintillation crystals SrI2 doped with Eu2+, Opt. Mater. 34
(2012) 926-930.
[24] N.J. Cherepy, B.W. Sturm, O.B. Drury, T.A. Hurst, S.A. Sheets, L.E. Ahle, C.K. Saw, M.A.
Pearson, S.A. Payne, A. Burger, L.A. Boatner, J.O. Ramey, E.V. van Loef, J. Glodo, R.
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Hawrami, W.M. Higgins, K.S. Shah, W.W. Moses, Performance of Europium-Doped Strontium
Iodide, Transparent Ceramics and Bismuth-loaded Polymer Scintillators, Proc. SPIE. 7449
(2009) 74490F.
[25] K.S. Kim, T.J. O’Leary, N. Winograd, X-Ray Photoelectron Spectra of Lead Oxides,
Analyt. Chem. 45 (1973) 2214 – 2218.
[26] J.M. Thomas, M.J. Tricker, Electronic structure of the oxides of lead. Part 2.—An XPS
study of bulk rhombic PbO, tetragonal PbO, β-PbO2 and Pb3O4, J. Chem. Soc., Faraday Trans.
71 (1975) 329-336.
[27] S. Rondon, P.M.A. Sherwood, Core Level and Valence Band Spectra of PbO by XPS, Surf.
Sci. Spectra 5 (1998) 97.
[28] N.M. Denysyuk, V.L. Bekenev, M.V. Karpets, O.V. Parasyuk, S.P. Danylchuk, O.Y.
Khyzhun, Electronic structure of the high-temperature tetragonal Tl3PbBr5 phase, J. Alloys
Compd. 576 (2013) 271–278.
[29] A. Meisel, G. Leonhardt, R. Szargan, X-Ray Spectra and Chemical Binding, Springer-
Verlag, Berlin/Heidelberg, 1989.
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Figure captions
Fig. 1. Strontium bromine plumbite crystals. An arrow points at turbid blocks.
Fig. 2. XRD pattern of middle and end parts of crystal boule, calculated one of SrPb3Br8 single
crystal, standard one of PbBr2. ♦ - unidentified phase.
Fig. 3. SrPb3Br8 crystal structure.
Fig. 4. Coordination of Pb2+ (a) and Sr2+ (b) ions in SrPb3Br8 structure and Pb2+ ions in PbBr2
structure (c).
Fig. 5. Transmission spectra for SrBr3Br8 (1) and PbBr2 (2) plates, 300 and 60 µm thick,
respectively.
Fig. 6. Absorption spectra for SrBr3Br8 (1) and PbBr2 (2) plates, 300 and 60 µm thick,
respectively, near the absorption edge.
Fig. 7. Survey XPS spectra recorded for (1) pristine and (2) Ar+ ion-bombarded surface of
SrPb3Br8 crystal.
Fig. 8. Detailed XPS (a) Pb 4f, (b) Br 3p and (c) Sr 3p3/2 core-level spectra recorded for (1)
pristine and (2) Ar+ ion-bombarded surface of SrPb3Br8 crystal.
Fig. 9. Detailed XPS valence-band spectra recorded for (1) pristine and (2) Ar+ ion-bombarded
surface of SrPb3Br8 crystal.
Fig. 10. Comparison on a common energy scale of the XPS valence-band spectrum and the X-
ray emission Br Kβ2 band of SrPb3Br8 crystal.
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Table 1. Crystal data and structure refinement for SrPb3Br8 and PbBr2.
Empirical formula
Formula weight
Wavelength, Å
Crystal system
Space group
Sr Pb3 Br8
1356.84
Pb Br2
367.01
0.71073
0.71073
Orthorhombic
P n m a
Orthorhombic
P n m a
Unit cell dimensions
a = 8.0056(4) Å
α = 90°.
a = 8.0256(4) Å
α = 90°.
b = 4.7359(2) Å
β = 90°.
b = 4.7103(3) Å
β = 90°.
c = 9.5208(5) Å
γ = 90°.
c = 9.5398(5) Å
γ = 90°.
3
360.97(3)
360.63(3)
Volume, Å
Z
1
4
Density (calculated), g/cm3
Sample size, mm3
6.242
6.760
0.19 x 0.14 x 0.12
0.18 x 0.10 x 0.08
from 3.32 to 28.27°
2395
Theta range for data collection from 3.32 to 28.26°
Reflections collected
Independent reflections
Refinement method
2217
504 [R(int) = 0.0471]
504 [R(int) = 0.0351]
2
Full-matrix least-squares on F
2
1.177
1.187
Goodness-of-fit on F
Final R indices [I>2sigma(I)] R1=0.0298, wR2=0.0798
R indices (all data) R1=0.0310, wR2=0.0804
R1=0.0224, wR2=0.0576
R1=0.0227, wR2=0.0577
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Table 2. Interatomic distances in SrPb3Br8 and PbBr2.
SrPb3Br8
Sr-Br Pb-Br
PbBr2
Pb-Br
2.942
3.008
3.008
3.190
3.190
3.269
3.274
3.896
3.896
3.049
3.116
3.116
3.146
3.243
3.244
3.244
3.660
3.660
2.939
3.013
3.013
3.194
3.194
3.268
3.276
3.894
3.894
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Table 3. The interpretation of absorption bands in SrPb3Br8.
№ Wave-
length, ꢀm
2.89
Wave-
Interpretation
number, cm-1
1
3460
H2O, ν3,
asymmetric
stretch
O-H group
stretch
2
3
6.26
15
1597
666
H2O, ν2, bend
H2O,
L2 librations
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