Dielectric permittivity of (Ag₃AsS₃)x(As₂S₃)₁₋x superionic glasses and composites
Complex dielectric permittivity of (Ag₃AsS₃)x(As₂S₃)₁₋x (x = 0.3−0.9) superionic glasses and composites at 300 K were studied. A decrease of the real part of dielectric permittivity with frequency by almost five orders of magnitude as well as one dispersion region in glasses and two dispersion re...
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2014
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Studenyak, I.P. Neimet, Yu.Yu. Orliukas, A.F. Kežionis, A. Kazakevičius, E. Šalkus, T. 2017-05-30T06:00:43Z 2017-05-30T06:00:43Z 2014 Dielectric permittivity of (Ag₃AsS₃)x(As₂S₃)₁₋x superionic glasses and composites / I.P. Studenyak, Yu.Yu. Neimet, A.F. Orliukas, A. Kezionis, E. Kazakevicius, T. Salkus // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2014. — Т. 17, № 2. — С. 174-178. — Бібліогр.: 20 назв. — англ. 1560-8034 PACS 77.80.Bh, 78.40.Ha https://nasplib.isofts.kiev.ua/handle/123456789/118368 Complex dielectric permittivity of (Ag₃AsS₃)x(As₂S₃)₁₋x (x = 0.3−0.9) superionic glasses and composites at 300 K were studied. A decrease of the real part of dielectric permittivity with frequency by almost five orders of magnitude as well as one dispersion region in glasses and two dispersion regions in composites, which is reflected in the dielectric loss spectra, were observed. Frequency dependences of dielectric permittivity within the range from 10 Hz to 3x109 Hz were analyzed in the framework of the Cole-Cole model. Compositional behaviour of Cole-Cole parameters in (Ag₃AsS₃)x(As₂S₃)₁₋x (x = 0.3−0.9) superionic glasses and composites was studied. The most substantial changes were observed with the transition from (Ag₃AsS₃)₀.₄(As₂S₃)₀.₆ glass to (Ag₃AsS₃)₀.₅(As₂S₃)₀.₅ composite and from (Ag₃AsS₃)₀.₆(As₂S₃)₀.₄ composite to (Ag₃AsS₃)₀.₈(As₂S₃)₀.₂ composite. en Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України Semiconductor Physics Quantum Electronics & Optoelectronics Dielectric permittivity of (Ag₃AsS₃)x(As₂S₃)₁₋x superionic glasses and composites Article published earlier |
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Dielectric permittivity of (Ag₃AsS₃)x(As₂S₃)₁₋x superionic glasses and composites |
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Dielectric permittivity of (Ag₃AsS₃)x(As₂S₃)₁₋x superionic glasses and composites Studenyak, I.P. Neimet, Yu.Yu. Orliukas, A.F. Kežionis, A. Kazakevičius, E. Šalkus, T. |
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Dielectric permittivity of (Ag₃AsS₃)x(As₂S₃)₁₋x superionic glasses and composites |
| title_full |
Dielectric permittivity of (Ag₃AsS₃)x(As₂S₃)₁₋x superionic glasses and composites |
| title_fullStr |
Dielectric permittivity of (Ag₃AsS₃)x(As₂S₃)₁₋x superionic glasses and composites |
| title_full_unstemmed |
Dielectric permittivity of (Ag₃AsS₃)x(As₂S₃)₁₋x superionic glasses and composites |
| title_sort |
dielectric permittivity of (ag₃ass₃)x(as₂s₃)₁₋x superionic glasses and composites |
| author |
Studenyak, I.P. Neimet, Yu.Yu. Orliukas, A.F. Kežionis, A. Kazakevičius, E. Šalkus, T. |
| author_facet |
Studenyak, I.P. Neimet, Yu.Yu. Orliukas, A.F. Kežionis, A. Kazakevičius, E. Šalkus, T. |
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2014 |
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English |
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Semiconductor Physics Quantum Electronics & Optoelectronics |
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Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
| format |
Article |
| description |
Complex dielectric permittivity of (Ag₃AsS₃)x(As₂S₃)₁₋x (x = 0.3−0.9)
superionic glasses and composites at 300 K were studied. A decrease of the real part of
dielectric permittivity with frequency by almost five orders of magnitude as well as one
dispersion region in glasses and two dispersion regions in composites, which is reflected
in the dielectric loss spectra, were observed. Frequency dependences of dielectric
permittivity within the range from 10 Hz to 3x109 Hz were analyzed in the framework of
the Cole-Cole model. Compositional behaviour of Cole-Cole parameters in
(Ag₃AsS₃)x(As₂S₃)₁₋x (x = 0.3−0.9) superionic glasses and composites was studied. The
most substantial changes were observed with the transition from (Ag₃AsS₃)₀.₄(As₂S₃)₀.₆
glass to (Ag₃AsS₃)₀.₅(As₂S₃)₀.₅ composite and from (Ag₃AsS₃)₀.₆(As₂S₃)₀.₄ composite to
(Ag₃AsS₃)₀.₈(As₂S₃)₀.₂ composite.
|
| issn |
1560-8034 |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/118368 |
| citation_txt |
Dielectric permittivity of (Ag₃AsS₃)x(As₂S₃)₁₋x superionic glasses and composites / I.P. Studenyak, Yu.Yu. Neimet, A.F. Orliukas, A. Kezionis, E. Kazakevicius, T. Salkus // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2014. — Т. 17, № 2. — С. 174-178. — Бібліогр.: 20 назв. — англ. |
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| first_indexed |
2025-11-25T20:35:27Z |
| last_indexed |
2025-11-25T20:35:27Z |
| _version_ |
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| fulltext |
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2014. V. 17, N 2. P. 174-178.
© 2014, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
174
PACS 77.80.Bh, 78.40.Ha
Dielectric permittivity of (Ag3AsS3)x(As2S3)1-x superionic glasses
and composites
I.P. Studenyak1, Yu.Yu. Neimet1, A.F. Orliukas2, A. Kežionis2, E. Kazakevičius2, T. Šalkus2
1Faculty of Physics, Uzhhorod National University,
46, Pidhirna str., 88000 Uzhhorod, Ukraine
2Vilnius University, Faculty of Physics,
9, Saulėtekio al., LT-10222 Vilnius, Lithuania
E-mail: studenyak@dr.com
Abstract. Complex dielectric permittivity of (Ag3AsS3)x(As2S3)1-x (x = 0.3−0.9)
superionic glasses and composites at 300 K were studied. A decrease of the real part of
dielectric permittivity with frequency by almost five orders of magnitude as well as one
dispersion region in glasses and two dispersion regions in composites, which is reflected
in the dielectric loss spectra, were observed. Frequency dependences of dielectric
permittivity within the range from 10 Hz to 3109 Hz were analyzed in the framework of
the Cole-Cole model. Compositional behaviour of Cole-Cole parameters in
(Ag3AsS3)x(As2S3)1-x (x = 0.3−0.9) superionic glasses and composites was studied. The
most substantial changes were observed with the transition from (Ag3AsS3)0.4(As2S3)0.6
glass to (Ag3AsS3)0.5(As2S3)0.5 composite and from (Ag3AsS3)0.6(As2S3)0.4 composite to
(Ag3AsS3)0.8(As2S3)0.2 composite.
Keywords: superionic glasses, composites, dielectric permittivity, Cole-Cole parameters.
Manuscript received 31.01.14; revised version received 14.05.14; accepted for
publication 12.06.14; published online 30.06.14.
1. Introduction
Chalcogenide glasses, doped with metals, have attracted
wide interest due to increased ionic conductivity. Such
characteristic features of chalcogenide glasses as the
presence of ion conduction pathways, phase separation,
high mobility of conductive ions in the matrix of the
chalcogenide glass make them applicable for creation of
solid electrolyte batteries, electrochemical sensors, fuel
cells, electrochromic displays, etc. [1]. It should be noted
that in comparison with crystalline solid electrolytes,
chalcogenide glasses are more technological, simple and
lower-cost in production. The remarkable place among
them is taken by the glasses of Ag–As–S ternary system
due to high values of electrical conductivity being
mostly ionic [2].
Electrical conductivity of materials in the Ag-As-S
system, prepared by different methods (doping of As2S3
with Ag, silver dissolution), was studied by several
researchers [2-10]. It was shown that the electrical
conductivity of (Ag2S)x(As2S3)1-x glasses increases to
display a step-like jump of nearly 5 orders of magnitude
within the narrow concentration range 9% < x < 15%
[9]. At x < 5% the electrical conductivity is typical for a
semiconducting glass, while at x > 15% it is
representative of an ionic conductor. Interrelation
between structural peculiarities and ionic transport were
studied in Refs. [9, 10]. Recently, silver ion diffusion
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2014. V. 17, N 2. P. 174-178.
© 2014, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
175
was considered by S. Stehlik et al. using the random-
walk model [11].
In Ref. [12], it was shown that after heating the
(Ag3AsS3)x(As2S3)1-x (x = 0.3 − 0.6) glasses and
composites up to more than 450 K and subsequent
cooling down to room temperature, formation of
nanocrystals on the surface takes place, which leads to a
sharp decrease of optical transparency. The temperature
studies of optical absorption edge in (Ag3AsS3)x(As2S3)1-x
glasses and composites were carried out in the work
[13]. Besides, the frequency, temperature and
compositional investigations of electrical conductivity in
(Ag3AsS3)x(As2S3)1-x glasses and composites were
performed in [14].
Now, it is of a great importance and actuality to
obtain information concerning the dielectric response of
the Ag–As–S system. Hence, the present study is
focused on the investigation of the dielectric permittivity
of (Ag3AsS3)x(As2S3)1-x (x = 0.3−0.9) superionic glasses
and composites in a wide frequency range from 10 Hz to
3 GHz at room temperature.
2. Experimental
Synthesis of vitreous compounds in the Ag3AsS3–As2S3
system was carried out at temperatures 820-840 K with
24-h melt homogenization time from the corresponding
components, which were synthesized beforehand from
highly pure elemental substances. Glassy alloys were
mixed periodically and subsequently cooled in the icy
water (273 K). Six alloys in the concentration range of
x = 0.3–0.9 for (Ag3AsS3)x(As2S3)1-x superionic glasses
and composites were chosen for the study.
Measurements of complex dielectric permittivity were
carried out within the range of frequencies 10 Hz–3 GHz
at room temperature by a coaxial impedance
spectrometer set-up [15].
3. Results
The frequency dependences of the real part of complex
dielectric permittivity exhibit frequency dispersion
and the low-frequency plateau corresponding to the
limiting low-frequency bulk dielectric constant s
should be reached (Fig. 1a). At still lower frequencies,
the capacitance of the electrode, connected in series with
the sample, causes a rapid increase of dielectric constant
with decreasing frequency [16]. Composites
(Ag3AsS3)x(As2S3)1-x with x = 0.5, 0.6 and 0.8, 0.9 have
two very distinct dispersion regions, which is well seen
on the frequency dependence of dielectric loss
(Fig. 1). With the frequency increase for the glasses and
composites (Ag3AsS3)x(As2S3)1-x with x = 0.3–0.9, a
decrease of by almost 5 orders of magnitude was
revealed.
As one can see from Fig. 1b, the frequency
dependences of the imaginary part of complex dielectric
permittivity for (Ag3AsS3)0.3(As2S3)0.7 and
(Ag3AsS3)0.4(As2S3)0.6 glasses display one maximum at
the frequencies ν = 120 Hz and 337 Hz, respectively.
With further addition of Ag3AsS3 to the As2S3 glassy
matrix, the composites in Ag3AsS3–As2S3 system are
formed. In (Ag3AsS3)0.5(As2S3)0.5 and
(Ag3AsS3)0.6(As2S3)0.4 composites, the maximum of the
frequency dependence of moves stepwise to the
higher frequency region and is observed at ν = 6559 Hz
for (Ag3AsS3)0.5(As2S3)0.5 and at ν = 4956 Hz for
(Ag3AsS3)0.6(As2S3)0.4 (Figs 1b and 2). Besides, for the
above mentioned composites the additional peculiarities
in a form of an asymmetry and a shoulder on the high-
frequency wings of maxima are observed (see insert
to Fig. 1b). It should be noted that for
(Ag3AsS3)0.8(As2S3)0.2 and (Ag3AsS3)0.9(As2S3)0.1 two
maxima are revealed on the frequency dependences of
the imaginary part of complex dielectric permittivity.
They are observed at ν1 = 139 Hz and ν2 = 39244 Hz for
(Ag3AsS3)0.8(As2S3)0.2 and at ν1 = 69 Hz and ν2 =
59354 Hz for (Ag3AsS3)0.9(As2S3)0.1 at the frequency
dependences of (Fig. 1b).
Fig. 1. Frequency dependences of the real (a) and imaginary
(b) parts of the complex dielectric permittivity for various
x = 0.3 (1), 0.4 (2), 0.5 (3), 0.6 (4), 0.8 (5), 0.9 (6) in
(Ag3AsS3)x(As2S3)1-x glasses and composites at T = 300 K.
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2014. V. 17, N 2. P. 174-178.
© 2014, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
176
Table. Cole-Cole parameters ε∞, Δε, α and 0 of the (Ag3AsS3)x(As2S3)1-x glasses and composites (x = 0.3, 0.4, 0.5, 0.6, 0.8,
0.9) at 300 K.
x, Ag3AsS3 ε∞ Δε α 0, ms
Disp. reg. → 1 and 2 1 2 1 2 1 2
0.3 13.40 41430 – 0.183 – 6.03 –
(I)
0.4 13.90 88090 – 0.185 – 5.84 –
0.5 15.15 279272 2334 0.222 0.186 2.58 0.02
(II)
0.6 16.18 343028 2605 0.220 0.206 3.33 0.02
0.8 14.20 225620 571 0.198 0.223 6.91 0.009
(III)
0.9 13.41 261134 613 0.204 0.226 8.66 0.007
Dispersion regions: 1 – from 10 to 2×105 rad/s, 2 – from 2×105 to 1010 rad/s.
Fig. 2. Compositional dependences of maxima frequences of
the imaginary part of complex dielectric permittivity for
(Ag3AsS3)x(As2S3)1-x glasses and composites at 300 K.
The obtained results on the dielectric permittivity
are in a good agreement with the results of X-ray
studies, which shows that the glasses of Ag–As–S
system become separated after adding the proustite
Ag3AsS3 crystal to the base As2S3 glass [14]. One can
distinguish three different structural states in the whole
compositional range of the Ag3AsS3−As2S3 system,
namely: glassy state for x = 0−0.4 (І), composite state
with crystalline smithite AgAsS2 inclusions for 0.4 <
x 0.6 (ІІ), and a composite state with crystalline
smithite AgAsS2 and proustite Ag3AsS3 inclusions for
0.6 < x < 1 (ІІІ). Compositional changes of dielectric
permittivity at the transitions from х = 0.4 to 0.5 are
related to the transition from the glassy structure at x0.4
to the composite one with AgAsS2 crystalline inclusions
at x 0.5. Peculiarities of compositional behavior of
dielectric permittivity at the transition from х = 0.6 to 0.8
are due to the presence of crystalline AgAsS2 and
Ag3AsS3 inclusions in As2S3 glassy matrix. Therefore,
the compositional studies of dielectric permittivity in
(Ag3AsS3)x(As2S3)1-x glasses and composites revealed
the most significant changes occurring at the transitions
from х = 0.4 to 0.5 and from х = 0.6 to 0.8 (Figs 1
and 2). The above highlighted results were confirmed by
the presence of the corresponding bands in the X-ray
diffraction patterns of superionic (Ag3AsS3)x(As2S3)1-x
glasses and composites [14].
4. Discussion
For the advance analysis of the dielectric relaxation
processes in (Ag3AsS3)x(As2S3)1-x glasses and
composites, the well-known Cole-Cole equation was
used [17]:
1
0 )(1
)(
)(
i
s ,
where i is the complex dielectric permittivity
( is the dielectric constant and – dielectric loss), ε∞
– high frequency limiting value of dielectric permittivity
at ω → ∞, εs – low frequency static dielectric
permittivity at ω → 0, 2 – angular frequency (ν –
experimental frequency), 0 – most probabilistic mean
relaxation time of the corresponding relaxation process
(among all the relaxation times from the relaxation
distribution function), and, finally, α is a characteristic
parameter (parameter of a width of the Cole-Cole
relaxation distribution function) that assumes values
between 0 and 1. The value Δε = εs – ε∞, a finite change
of the dielectric constant, is also known as a dielectric
strength, or polarizability. It should be noted that ε∞ is
also a contribution from all phonon modes and electron
polarization, whereas Δε is a contribution of relaxation
processes to the static dielectric permittivity. An increase
in the dielectric constant with a frequency decrease,
leading to a saturation at a constant value, εs = ε∞ + Δε,
was observed in crystalline ionic conductors [18, 19].
It should be mentioned that the frequency
dependences of in composites with x = 0.5–0.9 can
be separated into the following two dispersion regions:
(1) from 10 to 2×105 rad/s, and (2) from 2×105 to
1010 rad/s (Fig. 1). These regions are divided by a
vertical dash lines in all the following Fig. 3. This
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2014. V. 17, N 2. P. 174-178.
© 2014, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
177
corresponds to the maximum with high-frequency
asymmetry and a shoulder for composites with x = 0.5,
0.6 as well as two distinct maxima for composites with
x = 0.8, 0.9 on the frequency dependences of (Fig. 1).
This fact supports our results about the phase separation
or appearance of crystalline phases. Thus, one has to
take two different fitting procedures per graph with
respect to the presence of different phases. One should
note that for glasses with x = 0.3, 0.4 this process is yet
not visible, that is why the X-ray diffraction spectra of
the respective glasses reveal no signs of crystalline
inclusions [14].
Fig. 3. Compositional dependences of the Cole-Cole
parameters (a) ε∞ and Δε, (b) α and (c) 0 for
(Ag3AsS3)x(As2S3)1-x glasses and composites at 300 K
calculated for two dispersion regions: (1) from 10 to
2×105 rad/s, and (2) from 2×105 to 1010 rad/s.
The Cole-Cole parameters determined after
performing the fitting procedures are given in Table,
while their compositional dependences are highlighted in
Fig. 3. Hereby, Fig. 3 shows three compositional states,
according to the X-ray studies: the state of amorphous
glasses (I) demonstrates one dispersion region and can
be fitted by a single Cole-Cole function; the states of
composites (II) and (III) demonstrate two dispersion
regions, which should be fitted by two different Cole-
Cole functions.
The compositional dependences presented in Fig. 3
show that the dielectric strength as well as ε∞
nonlinearly varied and reached the highest values in the
state (ІІ). An increase of parameter α with the transition
from amorphous to composite structure (from x = 0.3,
0.4 to x = 0.5, 0.6) is an expected fact, as far as
composite structure with crystalline inclusions is more
disordered comparing to glasses, and, hence, have larger
distribution of relaxation times. The parameter α of the
second dispersion region demonstrates a permanent
enhancement with the x increase. This substructure,
characterized by the second dispersion region, becomes
more disordered with the increase of silver content. At
the same time, the parameter α of the first dispersion
region displays a decrease after an appearance of
proustite Ag3AsS3 in the composite with the increase of
x in the (Ag3AsS3)x(As2S3)1-x material. It was shown in
[20] that the values of parameter α like those obtained
here for (Ag3AsS3)x(As2S3)1-x glasses and composites are
inherent to mixed ionic materials that have one-
dimensional ion conducting pathways.
The presence of two different frequency regions in
our consideration implies a presence of two different
dielectric relaxation processes as well. Therefore, in our
results we marked out two modes (which correspond to
two used Cole-Cole functions for fitting), the most
probable relaxation times of which are given in Fig. 3.
Variations of 0 are inversely proportional to the
corresponding variations of νmax in Fig. 2. The
compositional dependence of relaxation times 0 has a
minimum in the state (ІІ). Although it is clear that the
values of the frequency shoulder at x = 0.5, 0.6 in the
frequency region 2 cannot be regarded as fully proper
ones. It is worth to remind that the parameter α also
represents the distribution of relaxation times. Further,
as we see from Fig. 3, the broadening of the distribution
function, i.e. the parameter α increase, is accompanied,
as a rule, by shortening the mean relaxation time 0 .
5. Conclusions
Frequency dependences studies of complex dielectric
permittivity at 300 K in (Ag3AsS3)x(As2S3)1-x superionic
glasses and composites with х = 0.3−0.9 were carried
out. A decrease of the real part of dielectric permittivity
with frequency by almost 5 orders of magnitude was
revealed. One dispersion region for the real part of
dielectric permittivity in glasses and two dispersion
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2014. V. 17, N 2. P. 174-178.
© 2014, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
178
regions in composites were observed. They showed
single maxima in the dielectric loss function of glasses
with x = 0.3 and 0.4, single maxima and peculiarities in
the form of high-frequency asymmetry and the shoulder
in composites with x = 0.5 and 0.6, as well as two
maxima in composites with x = 0.8 and 0.9.
Frequency dependences of the dielectric
permittivity within the range from 10 to 3109 Hz were
analyzed in the framework of the Cole-Cole model.
Compositional behaviour of the Cole-Cole parameters in
(Ag3AsS3)x(As2S3)1-x (x = 0.3−0.9) superionic glasses
and composites was studied. Different structural states
(glassy, composite) of the investigated materials were
considered, and the Cole-Cole fitting procedure involved
two dielectric relaxation processes for the composite
states. The parameters , ε∞, and α reach their highest
values in the state (II), whereas 0 gets its minimum. The
most essential changes of above mentioned parameters
are observed at the transition from glass with x = 0.4 to
composite with x = 0.5 as well as from composite with
x = 0.6 to composite with x = 0.8.
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Non-Cryst. Solids, 353, p. 1232-1237 (2007).
8. S. Stehlik, J. Kolar, M. Bartos, M. Vlcek,
M. Frumar, V. Zima and T. Wagner, Conductivity
in Ag–As–S(Se, Te) chalcogenide glasses // Solid
State Ionics, 181, p. 1625-1630 (2010).
9. C. Holbrook, P. Chen, D.I. Novita and
P. Boolchand, Origin of conductivity threshold in
the solid electrolyte glass system (Ag3S)x(As2S3)1-x
// IEEE Trans. Nanotechnology, 6(5), p. 530-535
(2007).
10. A. Pradel, N. Kuwata and M. Ribes, Ion transport
and structure in chalcogenide glasses // J. Phys.:
Condens. Matter, 15, p. S1561-S1571 (2003).
11. S. Stehlik, K. Shimakawa, T. Wagner and
M. Frumar, Diffusion of Ag ions under random
potential barriers in silver-containing chalcogenide
glasses // J. Phys. D: Appl. Phys. 45, 205304
(2012).
12. I. Studenyak, Yu. Neimet, C. Cserhati, S. Kökényesi,
E. Kazakevicius, T. Salkus, A. Kezionis and
A. Orliukas, Structural and electrical investigations
of (Ag3AsS3)x(As2S3)1-x superionic glasses // Cent.
Eur. J. Phys. 10, p. 206-209 (2012).
13. I.P. Studenyak, M. Kranjcec, Yu.Yu. Neimet,
M.M. Pop, Optical absorption edge in
(Ag3AsS3)x(As2S3)1-x superionic glasses //
Semiconductor Physics, Quantum Electronics &
Optoelectronics, 15(2), p. 147-151 (2012).
14. I.P. Studenyak, Yu.Yu. Neimet, M. Kranjčec,
A.M. Solomon, A.F. Orliukas, A. Kežionis,
E. Kazakevičius, and T. Šalkus, Electrical
conductivity studies in (Ag3AsS3)x(As2S3)1-x
superionic glasses and composites // J. Appl. Phys.
115, 033702 (2014).
15. A. Kežionis, E. Kazakevičius, T. Šalkus,
A.F. Orliukas, Broadband high frequency
impedance spectrometer with working temperatures
up to 1200 K // Solid State Ionics, 188, p. 110-113
(2011).
16. J.R. Dygas, Dielectric function of ionic conductors
studied by impedance spectroscopy // Solid State
Ionics, 176, p. 2065-2078 (2005).
17. K.S. Cole and R.H. Cole, Dispersion and
absorption in dielectrics I. Alternating current
characteristics // J. Chem. Phys. 9, p. 341-351
(1941).
18. K.E.D. Wapenaar and J. Schoonman, Conductivity
enhancement in Ba1-xLaxF2+x solid electrolytes //
Solid State Ionics, 5, p. 637-640 (1981).
19. J.B. Bates and J.C. Wang, Dielectric response of
ionic conductors // Solid State Ionics, 28-30,
p. 115-119 (1988).
20. D.L. Sidebottom, Dimensionality dependence of
the conductivity dispersion in ionic materials //
Phys. Rev. Lett. 83, p. 983 (1999).
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2014. V. 17, N 2. P. 174-178.
PACS 77.80.Bh, 78.40.Ha
Dielectric permittivity of (Ag3AsS3)x(As2S3)1-x superionic glasses
and composites
I.P. Studenyak1, Yu.Yu. Neimet1, A.F. Orliukas2, A. Kežionis2, E. Kazakevičius2, T. Šalkus2
1Faculty of Physics, Uzhhorod National University,
46, Pidhirna str., 88000 Uzhhorod, Ukraine
2Vilnius University, Faculty of Physics,
9, Saulėtekio al., LT-10222 Vilnius, Lithuania
E-mail: studenyak@dr.com
Abstract. Complex dielectric permittivity of (Ag3AsS3)x(As2S3)1-x (x = 0.3−0.9) superionic glasses and composites at 300 K were studied. A decrease of the real part of dielectric permittivity with frequency by almost five orders of magnitude as well as one dispersion region in glasses and two dispersion regions in composites, which is reflected in the dielectric loss spectra, were observed. Frequency dependences of dielectric permittivity within the range from 10 Hz to 3(109 Hz were analyzed in the framework of the Cole-Cole model. Compositional behaviour of Cole-Cole parameters in (Ag3AsS3)x(As2S3)1-x (x = 0.3−0.9) superionic glasses and composites was studied. The most substantial changes were observed with the transition from (Ag3AsS3)0.4(As2S3)0.6 glass to (Ag3AsS3)0.5(As2S3)0.5 composite and from (Ag3AsS3)0.6(As2S3)0.4 composite to (Ag3AsS3)0.8(As2S3)0.2 composite.
Keywords: superionic glasses, composites, dielectric permittivity, Cole-Cole parameters.
Manuscript received 31.01.14; revised version received 14.05.14; accepted for publication 12.06.14; published online 30.06.14.
1. Introduction
Chalcogenide glasses, doped with metals, have attracted wide interest due to increased ionic conductivity. Such characteristic features of chalcogenide glasses as the presence of ion conduction pathways, phase separation, high mobility of conductive ions in the matrix of the chalcogenide glass make them applicable for creation of solid electrolyte batteries, electrochemical sensors, fuel cells, electrochromic displays, etc. [1]. It should be noted that in comparison with crystalline solid electrolytes, chalcogenide glasses are more technological, simple and lower-cost in production. The remarkable place among them is taken by the glasses of Ag–As–S ternary system due to high values of electrical conductivity being mostly ionic [2].
Electrical conductivity of materials in the Ag-As-S system, prepared by different methods (doping of As2S3 with Ag, silver dissolution), was studied by several researchers [2-10]. It was shown that the electrical conductivity of (Ag2S)x(As2S3)1-x glasses increases to display a step-like jump of nearly 5 orders of magnitude within the narrow concentration range 9% < x < 15% [9]. At x < 5% the electrical conductivity is typical for a semiconducting glass, while at x > 15% it is representative of an ionic conductor. Interrelation between structural peculiarities and ionic transport were studied in Refs. [9, 10]. Recently, silver ion diffusion was considered by S. Stehlik et al. using the random-walk model [11].
In Ref. [12], it was shown that after heating the (Ag3AsS3)x(As2S3)1-x (x = 0.3 − 0.6) glasses and composites up to more than 450 K and subsequent cooling down to room temperature, formation of nanocrystals on the surface takes place, which leads to a sharp decrease of optical transparency. The temperature studies of optical absorption edge in (Ag3AsS3)x(As2S3)1-x glasses and composites were carried out in the work [13]. Besides, the frequency, temperature and compositional investigations of electrical conductivity in (Ag3AsS3)x(As2S3)1-x glasses and composites were performed in [14].
Now, it is of a great importance and actuality to obtain information concerning the dielectric response of the Ag–As–S system. Hence, the present study is focused on the investigation of the dielectric permittivity of (Ag3AsS3)x(As2S3)1-x (x = 0.3−0.9) superionic glasses and composites in a wide frequency range from 10 Hz to 3 GHz at room temperature.
2. Experimental
Synthesis of vitreous compounds in the Ag3AsS3–As2S3 system was carried out at temperatures 820-840 K with 24-h melt homogenization time from the corresponding components, which were synthesized beforehand from highly pure elemental substances. Glassy alloys were mixed periodically and subsequently cooled in the icy water (273 K). Six alloys in the concentration range of x = 0.3–0.9 for (Ag3AsS3)x(As2S3)1-x superionic glasses and composites were chosen for the study. Measurements of complex dielectric permittivity were carried out within the range of frequencies 10 Hz–3 GHz at room temperature by a coaxial impedance spectrometer set-up [15].
3. Results
The frequency dependences of the real part of complex dielectric permittivity
e
¢
exhibit frequency dispersion and the low-frequency plateau corresponding to the limiting low-frequency bulk dielectric constant
s
e
should be reached (Fig. 1a). At still lower frequencies, the capacitance of the electrode, connected in series with the sample, causes a rapid increase of dielectric constant with decreasing frequency [16]. Composites (Ag3AsS3)x(As2S3)1-x with x = 0.5, 0.6 and 0.8, 0.9 have two very distinct dispersion regions, which is well seen on the frequency dependence of dielectric loss
e
¢
¢
(Fig. 1). With the frequency increase for the glasses and composites (Ag3AsS3)x(As2S3)1-x with x = 0.3–0.9, a decrease of
e
¢
by almost 5 orders of magnitude was revealed.
As one can see from Fig. 1b, the frequency dependences of the imaginary part of complex dielectric permittivity e
¢
¢
for (Ag3AsS3)0.3(As2S3)0.7 and (Ag3AsS3)0.4(As2S3)0.6 glasses display one maximum at the frequencies ν = 120 Hz and 337 Hz, respectively. With further addition of Ag3AsS3 to the As2S3 glassy matrix, the composites in Ag3AsS3–As2S3 system are formed. In (Ag3AsS3)0.5(As2S3)0.5 and (Ag3AsS3)0.6(As2S3)0.4 composites, the maximum of the frequency dependence of e
¢
¢
moves stepwise to the higher frequency region and is observed at ν = 6559 Hz for (Ag3AsS3)0.5(As2S3)0.5 and at ν = 4956 Hz for (Ag3AsS3)0.6(As2S3)0.4 (Figs 1b and 2). Besides, for the above mentioned composites the additional peculiarities in a form of an asymmetry and a shoulder on the high-frequency wings of
e
¢
¢
maxima are observed (see insert to Fig. 1b). It should be noted that for (Ag3AsS3)0.8(As2S3)0.2 and (Ag3AsS3)0.9(As2S3)0.1 two maxima are revealed on the frequency dependences of the imaginary part of complex dielectric permittivity. They are observed at ν1 = 139 Hz and ν2 = 39244 Hz for (Ag3AsS3)0.8(As2S3)0.2 and at ν1 = 69 Hz and ν2 = 59354 Hz for (Ag3AsS3)0.9(As2S3)0.1 at the frequency dependences of
e
¢
¢
(Fig. 1b).
Fig. 1. Frequency dependences of the real
e
¢
(a) and imaginary ((( (b) parts of the complex dielectric permittivity for various x = 0.3 (1), 0.4 (2), 0.5 (3), 0.6 (4), 0.8 (5), 0.9 (6) in (Ag3AsS3)x(As2S3)1-x glasses and composites at T = 300 K.
Fig. 2. Compositional dependences of maxima frequences of the imaginary part of complex dielectric permittivity for (Ag3AsS3)x(As2S3)1-x glasses and composites at 300 K.
The obtained results on the dielectric permittivity are in a good agreement with the results of X-ray studies, which shows that the glasses of Ag–As–S system become separated after adding the proustite Ag3AsS3 crystal to the base As2S3 glass [14]. One can distinguish three different structural states in the whole compositional range of the Ag3AsS3−As2S3 system, namely: glassy state for x = 0−0.4 (І), composite state with crystalline smithite AgAsS2 inclusions for 0.4 < x ( 0.6 (ІІ), and a composite state with crystalline smithite AgAsS2 and proustite Ag3AsS3 inclusions for 0.6 < x < 1 (ІІІ). Compositional changes of dielectric permittivity at the transitions from х = 0.4 to 0.5 are related to the transition from the glassy structure at x(0.4 to the composite one with AgAsS2 crystalline inclusions at x ( 0.5. Peculiarities of compositional behavior of dielectric permittivity at the transition from х = 0.6 to 0.8 are due to the presence of crystalline AgAsS2 and Ag3AsS3 inclusions in As2S3 glassy matrix. Therefore, the compositional studies of dielectric permittivity in (Ag3AsS3)x(As2S3)1-x glasses and composites revealed the most significant changes occurring at the transitions from х = 0.4 to 0.5 and from х = 0.6 to 0.8 (Figs 1 and 2). The above highlighted results were confirmed by the presence of the corresponding bands in the X-ray diffraction patterns of superionic (Ag3AsS3)x(As2S3)1-x glasses and composites [14].
4. Discussion
For the advance analysis of the dielectric relaxation processes in (Ag3AsS3)x(As2S3)1-x glasses and composites, the well-known Cole-Cole equation was used [17]:
a
-
¥
¥
*
wt
+
e
-
e
+
e
=
w
e
1
0
)
(
1
)
(
)
(
i
s
,
where
e
¢
¢
+
e
¢
=
e
*
i
is the complex dielectric permittivity (
e
¢
is the dielectric constant and e
¢
¢
– dielectric loss), ε∞ – high frequency limiting value of dielectric permittivity e
¢
at ω → ∞, εs – low frequency static dielectric permittivity at ω → 0,
pn
=
w
2
– angular frequency (ν – experimental frequency), (0 – most probabilistic mean relaxation time of the corresponding relaxation process (among all the relaxation times from the relaxation distribution function), and, finally, α is a characteristic parameter (parameter of a width of the Cole-Cole relaxation distribution function) that assumes values between 0 and 1. The value Δε = εs – ε∞, a finite change of the dielectric constant, is also known as a dielectric strength, or polarizability. It should be noted that ε∞ is also a contribution from all phonon modes and electron polarization, whereas Δε is a contribution of relaxation processes to the static dielectric permittivity. An increase in the dielectric constant with a frequency decrease, leading to a saturation at a constant value, εs = ε∞ + Δε, was observed in crystalline ionic conductors [18, 19].
It should be mentioned that the frequency dependences of
e
¢
in composites with x = 0.5–0.9 can be separated into the following two dispersion regions: (1) from 10 to 2×105 rad/s, and (2) from 2×105 to 1010 rad/s (Fig. 1). These regions are divided by a vertical dash lines in all the following Fig. 3. This corresponds to the maximum with high-frequency asymmetry and a shoulder for composites with x = 0.5, 0.6 as well as two distinct maxima for composites with x = 0.8, 0.9 on the frequency dependences of e
¢
¢
(Fig. 1). This fact supports our results about the phase separation or appearance of crystalline phases. Thus, one has to take two different fitting procedures per graph with respect to the presence of different phases. One should note that for glasses with x = 0.3, 0.4 this process is yet not visible, that is why the X-ray diffraction spectra of the respective glasses reveal no signs of crystalline inclusions [14].
Fig. 3. Compositional dependences of the Cole-Cole parameters (a) ε∞ and Δε, (b) α and (c) (0 for (Ag3AsS3)x(As2S3)1-x glasses and composites at 300 K calculated for two dispersion regions: (1) from 10 to 2×105 rad/s, and (2) from 2×105 to 1010 rad/s.
The Cole-Cole parameters determined after performing the fitting procedures are given in Table, while their compositional dependences are highlighted in Fig. 3. Hereby, Fig. 3 shows three compositional states, according to the X-ray studies: the state of amorphous glasses (I) demonstrates one dispersion region and can be fitted by a single Cole-Cole function; the states of composites (II) and (III) demonstrate two dispersion regions, which should be fitted by two different Cole-Cole functions.
The compositional dependences presented in Fig. 3 show that the dielectric strength
e
D
as well as ε∞ nonlinearly varied and reached the highest values in the state (ІІ). An increase of parameter α with the transition from amorphous to composite structure (from x = 0.3, 0.4 to x = 0.5, 0.6) is an expected fact, as far as composite structure with crystalline inclusions is more disordered comparing to glasses, and, hence, have larger distribution of relaxation times. The parameter α of the second dispersion region demonstrates a permanent enhancement with the x increase. This substructure, characterized by the second dispersion region, becomes more disordered with the increase of silver content. At the same time, the parameter α of the first dispersion region displays a decrease after an appearance of proustite Ag3AsS3 in the composite with the increase of x in the (Ag3AsS3)x(As2S3)1-x material. It was shown in [20] that the values of parameter α like those obtained here for (Ag3AsS3)x(As2S3)1-x glasses and composites are inherent to mixed ionic materials that have one-dimensional ion conducting pathways.
The presence of two different frequency regions in our consideration implies a presence of two different dielectric relaxation processes as well. Therefore, in our results we marked out two modes (which correspond to two used Cole-Cole functions for fitting), the most probable relaxation times of which are given in Fig. 3. Variations of (0 are inversely proportional to the corresponding variations of νmax in Fig. 2. The compositional dependence of relaxation times (0 has a minimum in the state (ІІ). Although it is clear that the values of the frequency shoulder at x = 0.5, 0.6 in the frequency region 2 cannot be regarded as fully proper ones. It is worth to remind that the parameter α also represents the distribution of relaxation times. Further, as we see from Fig. 3, the broadening of the distribution function, i.e. the parameter α increase, is accompanied, as a rule, by shortening the mean relaxation time
0
t
.
5. Conclusions
Frequency dependences studies of complex dielectric permittivity at 300 K in (Ag3AsS3)x(As2S3)1-x superionic glasses and composites with х = 0.3−0.9 were carried out. A decrease of the real part of dielectric permittivity with frequency by almost 5 orders of magnitude was revealed. One dispersion region for the real part of dielectric permittivity in glasses and two dispersion regions in composites were observed. They showed single maxima in the dielectric loss function of glasses with x = 0.3 and 0.4, single maxima and peculiarities in the form of high-frequency asymmetry and the shoulder in composites with x = 0.5 and 0.6, as well as two maxima in composites with x = 0.8 and 0.9.
Frequency dependences of the dielectric permittivity within the range from 10 to 3(109 Hz were analyzed in the framework of the Cole-Cole model. Compositional behaviour of the Cole-Cole parameters in (Ag3AsS3)x(As2S3)1-x (x = 0.3−0.9) superionic glasses and composites was studied. Different structural states (glassy, composite) of the investigated materials were considered, and the Cole-Cole fitting procedure involved two dielectric relaxation processes for the composite states. The parameters
e
D
, ε∞, and α reach their highest values in the state (II), whereas (0 gets its minimum. The most essential changes of above mentioned parameters are observed at the transition from glass with x = 0.4 to composite with x = 0.5 as well as from composite with x = 0.6 to composite with x = 0.8.
References
1.
K.L. Ngai, J. Habasaki, Y. Hiwatari and C. Leon, A combined molecular dynamics simulation, experimental and coupling model study of the ion dynamics in glassy ionic conductors // J. Phys.: Condens. Matter, 15, p. S1607-S1632 (2003).
2.
E. Bychkov, D.L. Price, C.J. Benmore and A.C. Hannon, Ion transport regimes in chalcogenide and chalcohalide glasses: From the host to the cation-related network connectivity // Solid State Ionics, 154–155, p. 349-359 (2002).
3.
E.A. Kazakova and Z.U. Borisova, Electrocondutivity of (Ag3S)x(As2S3)1-x glass systems // Fizika Khimiia Stekla, 6, p. 424-427 (1980), in Russian.
4.
E. Bychkov, A. Bychkov, A. Pradel and M. Ribes, Percolation transition in Ag-doped chalcogenide glasses: Comparison of classical percolation and dynamic structure models // Solid State Ionics, 113-115, p. 691-695 (1998).
5.
Yu. Drugov, V. Tsegelnik, A. Bolotov, Yu. Vlasov and E. Bychkov, 110Ag tracer diffusion study of percolation transition in Ag2S–As2S3 glasses // Solid State Ionics, 136–137, p. 1091-1096 (2000).
6.
E. Bychkov, Superionic and ion-conducting chalcogenide glasses: Transport regimes and structural features // Solid State Ionics, 180, p. 510-516 (2009).
7.
M. Krbal, T. Wagner, T. Srba, J. Schwarz, J. Orava, T. Kohoutek, V. Zima, L. Benes, S.O. Kasap and M. Frumar, Properties and structure of Agx(As0.33S0.67)1-x bulk glasses // J. Non-Cryst. Solids, 353, p. 1232-1237 (2007).
8.
S. Stehlik, J. Kolar, M. Bartos, M. Vlcek, M. Frumar, V. Zima and T. Wagner, Conductivity in Ag–As–S(Se, Te) chalcogenide glasses // Solid State Ionics, 181, p. 1625-1630 (2010).
9.
C. Holbrook, P. Chen, D.I. Novita and P. Boolchand, Origin of conductivity threshold in the solid electrolyte glass system (Ag3S)x(As2S3)1-x // IEEE Trans. Nanotechnology, 6(5), p. 530-535 (2007).
10.
A. Pradel, N. Kuwata and M. Ribes, Ion transport and structure in chalcogenide glasses // J. Phys.: Condens. Matter, 15, p. S1561-S1571 (2003).
11.
S. Stehlik, K. Shimakawa, T. Wagner and M. Frumar, Diffusion of Ag ions under random potential barriers in silver-containing chalcogenide glasses // J. Phys. D: Appl. Phys. 45, 205304 (2012).
12.
I. Studenyak, Yu. Neimet, C. Cserhati, S. Kökényesi, E. Kazakevicius, T. Salkus, A. Kezionis and A. Orliukas, Structural and electrical investigations of (Ag3AsS3)x(As2S3)1-x superionic glasses // Cent. Eur. J. Phys. 10, p. 206-209 (2012).
13.
I.P. Studenyak, M. Kranjcec, Yu.Yu. Neimet, M.M. Pop, Optical absorption edge in (Ag3AsS3)x(As2S3)1-x superionic glasses // Semiconductor Physics, Quantum Electronics & Optoelectronics, 15(2), p. 147-151 (2012).
14.
I.P. Studenyak, Yu.Yu. Neimet, M. Kranjčec, A.M. Solomon, A.F. Orliukas, A. Kežionis, E. Kazakevičius, and T. Šalkus, Electrical conductivity studies in (Ag3AsS3)x(As2S3)1-x superionic glasses and composites // J. Appl. Phys. 115, 033702 (2014).
15.
A. Kežionis, E. Kazakevičius, T. Šalkus, A.F. Orliukas, Broadband high frequency impedance spectrometer with working temperatures up to 1200 K // Solid State Ionics, 188, p. 110-113 (2011).
16.
J.R. Dygas, Dielectric function of ionic conductors studied by impedance spectroscopy // Solid State Ionics, 176, p. 2065-2078 (2005).
17.
K.S. Cole and R.H. Cole, Dispersion and absorption in dielectrics I. Alternating current characteristics // J. Chem. Phys. 9, p. 341-351 (1941).
18.
K.E.D. Wapenaar and J. Schoonman, Conductivity enhancement in Ba1-xLaxF2+x solid electrolytes // Solid State Ionics, 5, p. 637-640 (1981).
19.
J.B. Bates and J.C. Wang, Dielectric response of ionic conductors // Solid State Ionics, 28-30, p. 115-119 (1988).
20.
D.L. Sidebottom, Dimensionality dependence of the conductivity dispersion in ionic materials // Phys. Rev. Lett. 83, p. 983 (1999).
Table. Cole-Cole parameters ε∞, Δε, α and (0 of the (Ag3AsS3)x(As2S3)1-x glasses and composites (x = 0.3, 0.4, 0.5, 0.6, 0.8, 0.9) at 300 K.
x, Ag3AsS3�
ε∞�
Δε�
α�
(0, ms�
�
Disp. reg. →�
1 and 2�
1�
2�
1�
2�
1�
2�
�
(I)�
0.3�
13.40�
41430�
–�
0.183�
–�
6.03�
–�
�
�
0.4�
13.90�
88090�
–�
0.185�
–�
5.84�
–�
�
(II)�
0.5�
15.15�
279272�
2334�
0.222�
0.186�
2.58�
0.02�
�
�
0.6�
16.18�
343028�
2605�
0.220�
0.206�
3.33�
0.02�
�
(III)�
0.8�
14.20�
225620�
571�
0.198�
0.223�
6.91�
0.009�
�
�
0.9�
13.41�
261134�
613�
0.204�
0.226�
8.66�
0.007�
�
Dispersion regions: 1 – from 10 to 2×105 rad/s, 2 – from 2×105 to 1010 rad/s.
© 2014, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
174
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