Properties of a new nanosized tin sulphide phase obtained by mechanochemical route

Article abstract of DOI:10.1016/S0925-8388(01)01910-7

The paper deals with the properties of a new 4H-SnS₂ phase (N-phase) synthesized together with berndtite 4H-SnS₂ by a mechanochemical route from elemental tin and sulphur. The surface and bulk properties of SnS₂ phases were verified by surface area measurements, particle size analysis, electron microscopy, XRD, M?ssbauer spectroscopy and chemical dissolution methods. The particles of synthesized product are 12-18 nm in size and during milling, secondary particles (aggregates) are formed that are 20-60 μm in size. The particle size and a high developed surface area (7-21 m² g^-1) greatly influence the solid-liquid reaction and solid transformations of mechanosynthesized tin sulphide products.

Full text of DOI:10.1016/S0925-8388(01)01910-7

Journal of Alloys and Compounds 337 (2002) 76–82
L
www.elsevier.com/locate/jallcom
Properties of a new nanosized tin sulphide phase obtained by
mechanochemical route
´ˇa ,
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´
ˇ
´
b
c
d
a
b
a
*
P. Balaz , L. Takacs , T. Ohtani , D.E. Mack , E. Boldizarova , V. Soika , M. Achimovicova
a
ˇ
Institute of Geotechnics, Slovak Academy of Sciences, 043 53 Kosice, Slovakia
bUniversity of Maryland, Baltimore County, Baltimore, MD 21250, USA
cOkayama University of Science, Laboratory for Solid State Chemistry, Okayama 700, Japan
dTechnical University Braunschweig, Institute of Physics and Theoretical Chemistry, 381 106 Braunschweig, Germany
Received 5 January 2001; received in revised form 13 September 2001; accepted 18 September 2001
Abstract
The paper deals with the properties of a new 4H-SnS2 phase (N-phase) synthesized together with berndtite 4H-SnS2 by a
mechanochemical route from elemental tin and sulphur. The surface and bulk properties of SnS2 phases were verified by surface area
¨
measurements, particle size analysis, electron microscopy, XRD, Mossbauer spectroscopy and chemical dissolution methods. The particles
of synthesized product are 12–18 nm in size and during milling, secondary particles (aggregates) are formed that are 20–60 mm in size.
The particle size and a high developed surface area (7–21 m2 g21) greatly influence the solid–liquid reaction and solid transformations of
mechanosynthesized tin sulphide products.
2002 Elsevier Science B.V. All rights reserved.
Keywords: Nanostructures; Mechanical alloying; X-ray diffraction; Magnetic measurements
1. Introduction
via mechanochemical processes [9–12]. The application of
intensive milling is one of the promising routes for the
preparation of advanced materials of nanosized dimensions
with unusual properties. Some sulphides, including tin
sulphides were synthesized by this procedure [13–35].
The aim of the present work is to evaluate the bulk and
surface properties as well as the reactivity of a new tin
sulphide prepared by ball milling.
Metal sulphides may be applied as advanced materials
for many applications, e.g. intercalation precursors (TiS2,
TaS2, NbS2), precursors for synthesis of high temperature
superconductors (La2S3), luminescence materials (CdS:
Mn, Cu, Pb), diagnostic materials (Ag2S), solar energy
materials (ZnS, CuInS2), materials for photoelectrolysis
(FeS2), high-energy density batteries (TiS2) and further
materials for opto-electric and magnetic applications [1].
Tin sulphides belong to materials which exhibit variable
physico-chemical properties, such as polytypism, poly-
morphism and non-stoichiometry [2]. Some of them, e.g.
SnS2 consists of two layers of closely packed sulphur
anions with sandwiched tin cations in octahedral coordina-
tion. The sulfides of this type have a number of empty sites
in their structure and hence they are interesting host
lattices for intercalation [3–8].
2. Experimental
2.1. Synthesis
For the mechanochemical synthesis of the new tin
sulphide phase the following chemicals were used: tin
(powder, 2100 mesh, Alfa Ventron, Germany) and
elemental sulphur (powder, Lachema, Czech Republic).
The starting mixture was prepared from the elements
according to the weight ratio Sn:S51:1.85. The mixture
was homogenized by mixing in methanol for 60 min. After
drying, 4 g of powder was milled in a planetary mill
URF-AGO 2 (Russia) using 110 steel balls with 5 mm
diameter. The rotational speed of the planet carrier was
In recent years, a number of papers have been published
on developing methods to synthesize inorganic materials
*
Corresponding author. Tel.: 1421-95-633-0790; fax: 1421-95-632-
3402.
E-mail address: balaz@saske.sk (P. Balaz).
´ˇ
0925-8388/02/$ – see front matter
PII: S0925-8388(01)01910-7
2002 Elsevier Science B.V. All rights reserved.

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P. Balaz et al. / Journal of Alloys and Compounds 337 (2002) 76–82
77
700 min21, 1000 ms22 providing a centrifugal acceleration
on the thimble axes. Milling was performed in argon
atmosphere for 30–120 min.
2.2. Characterization techniques
The powder X-ray diffraction measurements were per-
formed on Rigaku Rad-B using Cu Ka radiation at (0.3
kW power, 0.58/min scanning speed). The ZDS software
product was used for crystalline size determination based
on the analysis of selected X-ray diffraction profiles using
the variance method.
Fig. 1. XRD pattern of the mechanochemically synthesized tin sulphide
phase, milling time 60 min; B, berndite 4H-SnS2; N, new 4H-SnS2 phase
(N-phase).
¨
Tin Mossbauer spectra were recorded in transmission
geometry using a conventional microcomputer-controlled
spectrometer in constant acceleration mode. A 119Sn g-ray
source was used. The velocity scale was calibrated relative
to BaSnO3. A proportional counter was used to detect the
3. Results and discussion
3.1. XRD and surface properties
¨
transmitted g-rays. Mossbauer spectral analysis software
The X-ray diffraction pattern of the mechanochemically
prepared tin sulphide sample is given in Fig. 1. About half
of the peaks were identified based on JCPDS card 21-1231.
This structure corresponds to the pattern of the 4H
polytype of tin sulphide: berndtite SnS2. The other strong
and sharp peaks at d 5 0.3114, 0.2583 and 0.2369 nm,
with relative intensities of I/I0 5 0.72, 0.94 and 0.28,
respectively, do not originate from that phase. Whitehouse
and Balchin [38] reported that the milling process used to
prepare powder specimens made the identification of SnS2
polytypes difficult, except for the 2H modification. None
of the X-ray patterns reported in Ref. [38] corresponds to
the lines indicated by N in Fig. 1. It was concluded in our
previous paper [26] that a new SnS2 phase was created
during high energy milling of the starting mixture of
elemental tin and sulphur. The lines marked with ‘N’
originate from this phase.
In Table 1 the data on the crystallite size of the samples
milled for different times are given. For the calculation of
crystallite size of a new 4H-SnS2 phase (N-phase) the peak
at d 5 0.2583 nm was selected. The crystallite size values
of the 4H-SnS2 and N-phases are similar.
The values of specific surface areas for the synthesized
tin–sulphur compounds are of 1–2 orders of magnitude
larger than in the case of the reaction precursors, i.e.
elementary tin and sulphur: the values of 0.11 and 0.16 m2
Recoil [36] was used for the quantitative evaluation of the
spectra. The Voigt-based fitting method provided the
distribution of the hyperfine parameters for multiple sites.
The specific surface area was determined by the low
temperature nitrogen adsorption method in a Gemini 2360
sorption apparatus (Micromeritics, USA).
The particle size distribution was measured by a laser
diffraction system using a Helos and Rodos granulometer
(Sympatec, Germany).
Scanning electron micrographs were obtained on a BS
300 scanning electron microscope (Tesla, Czech Republic).
The reactivity of mechanochemically synthesized tin
sulphide was tested for dissolution within sodium sulphide
and sodium hydroxide solution. During the sulphidic tin
solubilization in this environment soluble thiostannates and
sodiumtinhydroxide compounds of the Na2(SnS3),
Na4(SnS4) and Na2Sn(OH)6 type can be formed [37].
Reaction conditions: 300 ml solution of 25 g l21 Na2S1
12.5 g l21 NaOH, weight of sample 400 mg, dissolution
time 30 min, temperature 30–608C.
The experimental results on tin dissolution were fitted to
the kinetic equation
2 ln (1 2 ´Sn) 5 ktL
(1)
where the ´Sn, k (s21) and tL (s) stand for the conversion
fraction, rate constant, and dissolution time, respectively.
The temperature dependence of the dissolution rate was
fitted to the Arrhenius equation in order to determine the
apparent activation energy.
Thermal characterization was carried out on a DTA-50
differential thermal analyser (Shimadzu, Japan). The typi-
cal sample mass was 35 mg. Al2O3 was used as reference
material. The sensor of the DTA was a Pt–PtRh differen-
tial thermocouple with 0.1 mV sensitivity. The measure-
ments were carried out at a heating rate of 408C min21 in
70 ml min21 argon flow.
Table 1
Crystalline size, D and specific surface area, SA of SnS2 phases after
milling for different time, t
t
D, nm
SA
min
m2 g21
4H-SnS2
N-phase
30
45
60
90
120
18
14
17
15
16
17
13
13
12
15
7.2
16.7
16.0
21.0
14.1

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78
P. Balaz et al. / Journal of Alloys and Compounds 337 (2002) 76–82
Fig. 2. Photomicrograph of tin sulphide phase, milling time 30 min.
g21 were determined for Sn and S, respectively. The
specific surface of the sample milled for 30 min is 7.2 m2
g21 while the same value for the sample milled for 120
Figs. 3 and 4. Careful inspection of the microphotographs
reveals that the mechanosynthesized samples are in fact
aggregates composed of sub-micron particles formed by
small crystallite grains. The particle size distribution in
Figs. 5 and 6 show that a rather inhomogenous, trimodal
distribution of aggregates is present with the maxima at
1.2, 6.8 and 16.5 mm for samples synthesized by milling
for both 30 and 120 min.
min is equal to 21.0 m2 g21
.
There is a close correlation between the crystallite size
D of the N-phase and the SA values of synthesized samples
(Fig. 2).
The microphotographs of both samples are given in
Fig. 3. Photomicrograph of tin sulphide phase, milling time 120 min.

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P. Balaz et al. / Journal of Alloys and Compounds 337 (2002) 76–82
79
Fig. 4. Particle size distribution of the mechanochemically synthesized tin sulphide phase, milling time 30 min.
¨
¨
3.2. Mossbauer properties of the N-phase
Mossbauer spectra after mechanochemical synthesis for
30–120 min are characterized by a dominant singlet with
IS51.02 mm s21. The singlet is slightly deformed as it is
the superposition of two compounds with parameters
corresponding to different forms of SnS2. The value of the
isomer shift indicates the presence of polar covalent bonds
[39]. The representation of the minor phase is in the
amount of 6–10% (Table 3). By confrontation with the
results of XRD measurements one can conclude that the
¨
Mossbauer spectra of the mechanosynthesized products
milled for 30, 60 and 120 min, respectively, are given in
Fig. 7 together with the Mossbauer pattern of elemental
¨
tin.
The main component of the spectrum of elemental tin is
a singlet with isomer shift IS52.5 mm s21. A minor
singlet corresponding to Sn21 in SnO2 is also visible, its
relative intensity is 6.1% (Table 2).
¨
minor SnS2 phase identified by Mossbauer spectroscopy is
Fig. 5. Particle size distribution of the mechanochemically synthesized tin sulphide phase, milling time 120 min.

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P. Balaz et al. / Journal of Alloys and Compounds 337 (2002) 76–82
80
Fig. 6. Relationship between the crystallite size of N-phase, D and the
specific surface area, SA.
with great probability the N-phase identified by the XRD
method.
It follows from the site populations analysis given in
Table 2 that besides sulphidic products, also an oxidic
phase can be identified among the products of mech-
anosynthesis. For milling times of 30–90 min the amount
of SnO2 is equal to |6% (in addition to the fraction of
oxide present in starting b-Sn).
The applied experimental techniques are not able to
explain why a limiting fraction of the N-phase exists in the
mechanosynthesized products. There is possibly a mech-
anochemical equilibrium between 4H-berndtite SnS2 and
the new SnS2 phase (N-phase), which may be the conse-
quence of several factors. External conditions such as the
applied energy of milling and internal factors such as the
decrease of crystallite size and steric limitations among
SnS2 phases may be of importance and play a crucial role.
3.3. Reactivity of mechanosynthesized phases
3.3.1. Dissolution reaction
The mechanosynthesized samples were subjected to
dissolution in alkaline sodium sulphide solution. Fig. 8
shows the relationship between the degree of tin solubiliza-
tion ´Sn and dissolution time tL. The reaction propagation
is very fast: depending on the history of the sample, 50%
or more of tin was dissolved after only 5 min or more of
reaction.
The dissolution kinetics was fitted to Eq. (1) in order to
calculate the rate constant k. The k values are shown as a
function of milling time in Fig. 9. An attempt to eliminate
the influence of surface area by introducing the specific
rate constant kS (the rate constant divided by the specific
surface area) is also given in this figure. However, the
¨
Fig. 7. Mossbauer spectra of tin compounds: elemental tin standard (a),
mechanosynthesized tin sulphide phase milled for (b) 30 min, (c) 60 min,
(d) 120 min.
influence of surface area is not decisive in this case and the
structural imperfections must also play an important role
[40].

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P. Balaz et al. / Journal of Alloys and Compounds 337 (2002) 76–82
81
Table 2
¨
Mossbauer distribution analysis of tin compounds calculated from site
populations
Milling time
(min)
Site populations (%)
a
b-Sn
SnS2
SnO2
–
30
45
60
90
93.87
–
6.1
11.9
12.2
11.9
12.4
20.7
–
–
–
–
–
88.1
87.8
88.1
87.6
79.3
120
a 4H-berndtite SnS2 plus N-phase.
Table 3
¨
Mossbauer analysis of tin sulphide phases calculated from distribution
parameters
Milling time
(min)
%
Major phase (4H-SnS2)
Minor phase (N-phase)
30
45
60
90
120
93.6
89.6
90.5
89.5
91.3
6.4
10.4
9.5
10.5
8.7
Fig. 9. Influence of milling time, tG on the rate constant, k and the
specific rate constant, kS of tin dissolution from the mechanochemically
synthesized tin sulphide phase.
The temperature sensitivity of tin solubilization of the
mechanochemically synthesized samples was characterized
by calculations of the apparent activation energy E. The
values E 5 65 and 45 kJ/mol were found for samples
milled for 45 and 90 min, respectively. According to the
literature [41,42] these values correspond to values typical
for heterogeneous reactions where the rate of chemical
reaction is the rate determining step.
3.3.2. Thermal transformation
The XRD characterization was performed for the sample
mechanosynthesized for 45 min and annealed in argon in
the DTA regime. After heating to 7008C the phase
identified as SnS2 loses much sulphur and it consists of
large-grain SnS and Sn2S3 identified by X-ray diffraction
measurements. The chemical transformation of tin sulphide
phase may be described by the equation
4SnS2 → Sn2S3 1 2SnS 1 3S
(2)
4. Conclusions
1. New 4H-SnS2 and berndtite 4H-SnS2 phases were
prepared from elemental tin and sulphur by mechanoch-
emical processing. The new phase has relatively strong
and sharp peaks in the XRD pattern and its occurrence
¨
is supported by Mossbauer spectroscopy.
2. The grains of the synthesized sulphides are 12–18 nm
in size. During milling secondary particles (aggregates)
are formed that are 20–60 mm in size.
Fig. 8. Influence of dissolution time, tL on the recovery of tin, ´Sn from
the mechanochemically synthesized tin sulphide phase, milling time: 1,
45 min; 2, 60 min; 3, 90 min; 4, 120 min.
3. The particle size and the related large specific surface
area (7–21 m2
g
21) strongly influence the chemical

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P. Balaz et al. / Journal of Alloys and Compounds 337 (2002) 76–82
82
[16] V. Rusanov, Ch. Chakurov, J. Solid State Chem. 79 (1989) 181.
dissolution of tin from mechanochemically synthesized
sulphides.
4. The thermal decomposition of SnS2 phases is character-
ized by the loss of elemental sulphur and the formation
of large grained SnS and Sn2S3 compounds.
[17] L. Takacs, M.A. Susol, J. Solid State Chem. 121 (1996) 394.
[18] L. Takacs, Mater. Sci. Forum 269–272 (1998) 513.
[19] L. Takacs, Hyperfine Interact. 111 (1998) 245.
¨
[20] L. Takacs, V.K. Garg, Mossbauer studies of ball milled Fe12xS11x
,
¨
in: M. Miglierini, D. Petridis (Eds.), Mossbauer Spectroscopy in
Materials Science, Kluwer Academic, Dordrecht, 1999, pp. 143–
150.
[21] T. Kosmac, D. Maurice, T.H. Courtney, J. Am. Ceram. Soc. 76
(1993) 2345.
Acknowledgements
´ˇ
´
ˇ
[22] P. Balaz, T. Havlık, Z. Bastl, J. Briancin, J. Mater. Sci. Lett. 14
This work was partly supported (P.B., M.A., E.B.) by
the Slovak Grant Agency for Science VEGA (grant no.
2/2103/22) and by the National Science Foundation (L.T.,
V.S., grant DMR-9712141). The authors are indebted to
Prof. K.D. Becker for his supporting interest in their work.
(1995) 344.
´ˇ
´
ˇ
[23] P. Balaz, T. Havlık, J. Briancin, R. Kammel, Scripta Metall. Mater.
32 (1995) 1357.
´ˇ
´
´
[24] P. Balaz, Z. Bastl, T. Havlık, J. Lipka, I. Toth, Mater. Sci. Forum
235–237 (1997) 217.
´ˇ
ˇ´
´
[25] P. Balaz, T. Ohtani, Z. Bastl, E. Boldizarova, J. Solid State Chem.
144 (1999) 1.
´ˇ
[26] P. Balaz, T. Ohtani, Mater. Sci. Forum 343–346 (2000) 389.
´ˇ
[27] P. Balaz, Extractive Metallurgy of Activated Minerals, Elsevier,
References
Amsterdam, 2000.
[28] T. Tsuzuki, J. Ding, P.G. McCormick, Physica B 239 (1997) 378.
[29] T. Tsuzuki, P.G. McCormick, Appl. Phys. A65 (1997) 607.
[30] T. Tsuzuki, P.G. McCormick, Nanostruct. Mater. 12 (1999) 75.
[31] R. Lin, J.Z. Jiang, R.K. Larsen, S. Morup, F.J. Berry, Hyperfine
Interact. C 3 (1998) 45.
[32] J.Z. Jiang, R.K. Larsen, R. Lin, S. Morup, I. Chorkendorff, K.
Nielsen, K. Hansen, K. West, J. Solid State Chem. 138 (1998) 114.
[33] T. Ohtani, M. Motoki, K. Koh, K. Ohsima, Mater. Res. Bull. 30
(1995) 1495.
´ˇ
[1] P. Balaz, Metall 54 (2000) 190.
[2] F. Jellinek, React. Solids 5 (1988) 323.
[3] J. Morales, C. Perez-Vicente, J.L. Tirado, J. Solid State Ionics 51
(1992) 133.
[4] L. Herman, J. Morales, L. Pattanayak, J.L. Tirado, J. Solid State
Chem. 100 (1992) 262.
[5] C. Barriga, P. Lavela, J. Morales, J.L. Tirado, Solid State Ionics
63–65 (1993) 450.
¨
¨
[6] W. Muller-Warmuth, R. Schollhorn (Eds.), Progress in Intercalation
[34] T. Ohtani, K. Maruyama, K. Ohshima, Mater. Res. Bull. 32 (1997)
343.
Research, Kluwer Academic, Dordrecht, 1994.
[7] J. Rouxell, A. Meerschant, G.A. Wiers, J. Alloys Comp. 229 (1995)
144.
[35] T. Ohtani, A. Tsubota, K. Ohshima, Mater. Res. Bull. 34 (1999)
1143.
[8] C. Julien, C. Perez-Vicente, Solid State Ionics 89 (1996) 337.
[9] N.J. Welham, J. Mater. Res. 13 (1998) 1607.
[10] N.J. Welham, J. Alloys Comp. 274 (1998) 303.
¨
[36] K. Lagarec, D.G. Rancourt, Mossbauer Spectral Analysis Software
for Windows, version 1.0, University of Ottawa, Department of
Physics, Ottawa, 1998.
[37] H. Remy, Inorganic Chemistry, Publishing House of the Technical
Literature, Prague, 1967, in Czech.
[38] C.R. Whitehouse, A.A. Balchin, J. Mater. Sci. 14 (1979) 2516.
[39] A.G. Maddock, Mossbauer Spectroscopy, Principles and Applica-
tions of the Techniques, Horwood, Chichester, 1997.
[40] M. Senna, Part. Part. Syst. Charact. 6 (1989) 163.
[41] F. Habashi, Kinetics of Metallurgical Processes, Metallurgie Ex-
ˇ
´
[11] V. Sepelak, U. Steinicke, D.Ch. Uecker, S. Wissmann, K.D. Becker,
J. Solid State Chem. 135 (1998) 52.
ˇ
´
[12] P. Druska, U. Steinicke, V. Sepelak, J. Solid State Chem. 146 (1999)
13.
¨
[13] Ch. Chakurov, G.G. Gospodinov, Z. Bontschev, J. Solid State
Chem. 41 (1982) 244.
[14] Ch. Chakurov, V. Rusanov, G. Gospodinov, J. Solid State Chem. 59
´
(1985) 265.
´
´
tractive Quebec, Quebec, 1999.
[15] Ch. Chakurov, V. Rusanov, G. Gospodinov, J. Solid State Chem. 71
(1987) 522.
[42] J.W. Evans, Miner. Sci. Eng. 11 (1979) 207.