Ag2CdI4: Synthesis, characterization and investigation the strain lattice and grain size

Article abstract of DOI:10.1016/j.jallcom.2016.01.085

In this work the Ag₂CdI₄ nanostructures have been synthesized via a solid state reaction from reaction of AgI and CdI₂ as precursors. The effect of the mole ratio of precursors, time and temperature of reaction has been optimized to achieve the best product on morphology and purity. Nanostructures have been characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman (FT-IR) techniques, X-ray energy dispersive spectroscopy (EDS) and Ultraviolet spectroscopy (UVvis). The XRD patterns of nanostructures have been used to estimate the grain sizes and strain lattice. Grain size of nanostructures is in range of 5–17 nm and the strain of lattice is changed in range of 0.0024–0.014. The band gap of these nanostructures has been estimated by DRS spectrum about 5.4 eV. Raman spectroscopy has been confirmed the XRD results and show that the Ag₂CdI₄ nanostructures have been synthesized. SEM and TEM images have been used for investigation of morphology of product. Results show that the best morphology and purity have been achieved in 12 h and 200 °C in 1:1 mol ratio of precursors.

Full text of DOI:10.1016/j.jallcom.2016.01.085

Accepted Manuscript
Ag CdI : Synthesis, characterization and investigation the strain lattice and grain size
2
4
Mojgan Ghanbari, Sousan Gholamrezaei, Masoud Salavati-Niasari
PII:
S0925-8388(16)30085-8
10.1016/j.jallcom.2016.01.085
JALCOM 36436
DOI:
Reference:
To appear in: Journal of Alloys and Compounds
Received Date: 20 November 2015
Revised Date: 23 December 2015
Accepted Date: 9 January 2016
Please cite this article as: M. Ghanbari, S. Gholamrezaei, M. Salavati-Niasari, Ag CdI : Synthesis,
2
4
characterization and investigation the strain lattice and grain size, Journal of Alloys and Compounds
(2016), doi: 10.1016/j.jallcom.2016.01.085.
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Ag2CdI4: Synthesis, characterization and investigation the strain lattice and grain size
Mojgan Ghanbari1, Sousan Gholamrezaei2, Masoud Salavati-Niasari*,1
1 Institute of Nano Science and Nano Technology, University of Kashan, Kashan, P.O. Box 87317-51167, I. R. Iran
2 Young Researchers Club, Arak Branch, Islamic Azad University, Arak, Iran
*Corresponding author: Tel.: +98 31 5591 2383, Fax: +98 31 55913201.
E-mail address: salavati@kashanu.ac.ir
Abstract
In this work the Ag2CdI4 nanostructures have been synthesized via a solid state reaction from reaction of AgI
and CdI2 as precursors. The effect of the mole ratio of precursors, time and temperature of reaction have been
optimized to achieve the best product on morphology and purity. Nanostructures have been characterized using
X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM),
Raman (FT-IR) techniques, X-ray energy dispersive spectroscopy (EDS) and Ultraviolet spectroscopy (UV-
vis). The XRD patterns of nanostructures have been used to estimate the grain sizes and strain lattice. Grain
size of nanostructures are in range of 5 – 17 nm and the strain of lattice are changed in range of 0.0024 – 0.014.
The band gap of this nanostructures has been estimated by DRS spectrum about 5.4 eV. Raman spectroscopy
has been confirmed the XRD results and show that the Ag2CdI4 nanostructures have been synthesized. SEM
and TEM images have been used for investigation of morphology of product. Results show that the best
morphology and purity have been achieved in 12 h and 200 ºC in 1:1 mole ratio of precursors.
Keywords: Nanostructures; Solid state; Ag2CdI4; Electron microscopy.
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1. Introduction
In recent years super ionic conductors containing silver have attracted a lot of attention because of their
application in solid state batteries as solid electrolytes [1, 2]. Because of the phenomena that the transformation
of luminescence center changes by concentration of silver ion, these crystals are in first of interest [3-5]. The
silver mobility properties of crystals show a local irradiation that confirmed by both experimental and
computational efforts.
A2BI4 (A= Ag, Cu; B = Hg, Cd) are considered as a type of solid electrolytes that show phase transition at
moderate temperatures [7]. Recently Ag2CdI4 is synthesized as a super ionic conductor with silver ion. The
conductivity value of Ag2CdI4 is about 10-7 (Ω.cm-1) at room temperature, the phase transition occur in 80ºC
and the conductivity value in this temperature is 10-3 (Ω.cm-1) [8]. By the combination of inter grainy space
and crystalline grains the microstructures formed consequently. In recent years a lot of researches focused on
influence of inter grain space volume on thermal, conductivity and physical properties of these crystals [9-10].
When the crystalline grains have nano size, new futures observed in super ionic crystals [11]. Therefore in last
ten years, different methods developed to produce super ionic nanostructures with high value of ionic
conductivity [12-14]. By decreasing the size of super ionic crystals increase the grain boundaries and pores in
morphologies of nanostructures [15]. In this work we synthesized the Ag2CdI4 nanostructures by a simple solid
state method in low temperature and investigated the grain size, morphology and the strain of lattice.
2. Experimental
2.1.Materials
All the chemicals such as Lithium iodide (LiI), Silver nitrate (AgNO3), Cadmium nitrate (Cd(NO3)2) were of
analytical grade and were purchased from Merck Company (pro-analysis) and used without further
purification.
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2.2. Physical measurements
XRD patterns were recorded from a diffractometer of Philips Company with X'PertPro filtered by Cu Ka
radiation (λ = 1.54 Å). Microscopic morphology of products was achieved by a LEO 1455VP scanning
electron microscope. Prior to taking images, the samples were coated by a very thin layer of Pt to make the
sample surface conductor and prevent charge accumulation, and obtaining a better contrast.
2.3. Synthesis of precursors
2.3.1. Synthesis of AgI
The AgI precursor have been achieved by a co-precipitation method from LiI and AgNO3. For synthesis of AgI
stoichiometry amount of AgNO3 and LiI were dissolved in separate Beakers in distilled water and one of the
solutions were added to other solutions. The results solution were remained to crystalize the AgI precipitate.
2.3.2. Synthesis of CdI2
The preparation approaches and crystalize method for CdI2 is similar to AgI preparation.in this method
Cd(NO3)2 were used as Cd precursors.
2.3.3. Synthesis of Ag2CdI4
For preparation of Ag2CdI4, AgI and CdI2 were mixed together with a curtained ratio and grinned in mortar for
2h and the result powder were heated at a relatively low temperature (200 ˚C) in the air. An average
temperature increase of 30 ˚C is recorded every minute, before the temperature reached 200 ˚C, and after
keeping the thermal treatment at 200 ˚C for defined time, it was authorized to cool naturally in the room
temperature. Different effective parameters on synthetic approaches changed and the results of these changes
investigated. These reaction condition listed in Table 1.
3. Results and discussion
3.1. XRD patterns: Strain lattice and grain size
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Figure 1a shows the XRD patterns of AgI and CdI2 precursors. XRD pattern show that the AgI precursor have
been made up from AgI with the literature values of JCPDS No. 01-0503 and JCPDS No. 09-0374 without any
purification. The XRD pattern of CdI2 that shown in Figure 1b illustrates the product has hexagonal structure
with the literature value of JCPDS No. 02-1200 without any purifications.
In Figure 2a the XRD patterns of Sample No 1 that synthesizes in 200 ºC for 24 h and the mole ration of AgI :
CdI2 is 1:1. Product have been made up from Ag2CdI4 and a low amount of AgI and CdI2 remained in product.
The Ag2CdI4 have been crystalized in tow structures by literature values of JCPDS No. 37-1092 and 36-1112.
X-ray diffraction measurements were carried out in a Philips X’Pert High Score diffractometer using Cu Kα (λ
◦
= 1.5405 Å) radiation over 20–140 C. To adjust the shift of zero angle, the silicon crystal was used as a
standard sample. The crystallite size and lattice strain were estimated using the Williamson-Hall method [16]:
Where βs is the full-width at half-maximum of the diffraction peak, θ is the diffraction angle, λ is the X-ray
wavelength, d is the crystallite size, and ε is the lattice strain. βs can be given as:
Where βi is the width at half-maximum of the Si powder peaks used for calibration and βe is the evaluated
width. Thus, it is clear that when we plot βs cos θ against sin θ we get a straight line with slope (ε) and
intercept Kλ/d. The crystallite size (d) can be calculated from Kλ/d (K and λ are determinate) and lattice strain
is slop line (ε) [17]. The grain size for Ag2CdI4 by literature value JCPDS No. 37-1092 has been estimated
about 5.5 nm and this size for Ag2CdI4 by literature value JCPDS No. 36-1112 has been estimated about 86
nm. The strain lattice for 5.5 nm crystals is about 0.0114 and the strain lattice for 86 nm crystals is about
0.0172 (Figure 2b, c).
Because of presence the precursors in product the mole ratio of product have been changed and the product
have been synthesized in tow mole ratio of AgI:CdI2. Figure 3a, b show the XRD patterns of Sample No 2 and
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Sample No. 3 that synthesized in presence of different mole ration of precursors. In these conditions the
amount of precursors in product are very high and amount of Ag2CdI4 is very low. Therefor the best mole ratio
for preparation of Ag2CdI4 is 1:1 in 200 ºC and 24 h.
Figure 4 shows the XRD pattern of Sample No. 4 that prepared from AgI and CdI2 with the mole ratio of 1:1 in
150 ºC for 24 h. product has been made up from Ag2CdI4 and CdI2. The grain size and strain of lattice for
Ag2CdI4 in this structure are 17.5 nm and 0.0024 respectively. The grain size of this Ag2CdI4 with literature
value of 37-1092 that synthesized in 150 ºC in comparison with other product in 200 ºC have been increased
and the best temperature for preparation of Ag2CdI4 is 200 ºC.
For preparation of Ag2CdI4 as pure phase in product have been optimized the time of reaction and the lower
time 18 h and 12 h were examined in reaction. Figure 5a shows the XRD patterns of product in the mole ratio
of 1:1 in 18 h. in this condition product have been made up from AgI and Ag2CdI4 and CdI2 have been
eliminated from product. The grain size in this condition has been estimated about 8.2 nm and the strain lattice
in this condition are about 0.0024 (Figure 5b). Figure 5c shows the XRD pattern of sample No 6 that
synthesized in 200 ºC for 12 h, this product is pure and made up from Ag2CdI4 in two different phase by
JCPDS No. 37-1092 and 47-0870, Ag2CdI4 by JCPDS No. 37-1092 is major product. The grain size for major
and minor product have been estimated 11.6 and 3.8 nm respectively and the strain lattice for these phases are
about 0.0043 and 0.0175 respectively (Figure 5 d, e). Table 2 show the grain size and strain lattice of different
samples by JCPDS No. 37-1092.
3.2. SEM and TEM images: morphology
Figure 6 illustrates the SEM images of products. Figure 6a has been shown the SEM images of Sample No 1.
Product has been made up from nanoparticles but a low amount of bigger nanostructures have been seen in
product images. In Figure 6b and 6c the images of product that synthesized in different mole ratio of
precursors. The morphology of product in these conditions are not suitable and not regular. The morphology of
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sample No 4 that prepared in 150 ºC have been shown in Figure 6d. Product in this condition have not regular
morphology and are agglomerate structures. Figure 6e shows the morphology of product in 18 h. As-prepared
nanostructures have nanoparticles morphology but a low amount of irregular nanostructures have been seen in
SEM images. In Figure 6f has been shown the SEM images of Sample No 6 that achieved in 12 h. as-prepared
Ag2CdI4 in this condition are very small nanoparticles that arrayed in very regular structures.
Figure 7 has been shown the TEM images of Sample No 1. Nanoparticles that synthesized in this condition
have about 30 nm diameters. The product has not regular shape and the morphology of product are not
suitable.
Figure 8 illustrates the TEM images of optimized product (Sample No. 6). As-prepared Ag2CdI4 nanoparticles
in this condition has about 15 nm diameters and array in regular nanostructures.
3.3. DES spectrum: purity
Chemical purity of as-prepared Ag2CdI4 nanoparticles (sample No 1 and sample No 6) has been investigated
by Electron Diffraction X-ray spectroscopy (EDS). Figure 9a and 9b shows the product involved Ag, Cd, I and
O. Additional amount of O is caused because of surface oxidation of product in atmosphere [18].
3.4. Optical property: DRS spectrum
The optical absorption spectrum of Ag2CdI4 nanoparticles represents in Figure. 10a. The DRS spectrum was
used to further access their quality and electronic structure information. It demonstrates a major absorption
peaks about 220 nm and different low intensity absorption peaks in 300 – 400 nm. The absorption that
occurred in 226 nm is due to the fundamental absorption within the band gap of this material. The others
absorption bands have been attributed to the impurities or vacancies [19-20]. The optical band gap of Ag2CdI4
has been evaluated using the optical density (OD) vs. energy (E) plot (Figure 10b). The value of band gap
energy for this nanoparticle is ~ 5.4 eV [21].
3.5.Raman spectrum
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Figure 11 shows the raman spectrum of sample No 6. The characteristic absorption of as-prepared Ag2CdI4
have been occurred in 10 cm-1 – 110 cm-1. The vibrational modes of Ag2CdI4 have been assigned by
considering the nanostructures as vibration modes of AgI and (CdI4)2-. The band at 119 cm-1 can be allocated
to the symmetric stretching of (CdI4)2- that are in good agreement with other tetrahedral compound with
(CdI4)2- [22]. The range of 70 - ll0 cm-1 consists of two bands at the positions 76 cm-1 and 95 cm-1, these bands
are assigned to symmetric stretching modes of Agl [23]. The bands at and 37 cm-1 and 52 cm-1 can be assigned
to Cd-I deformation type bands. The band at 16 cm-1 is assigned to the E symmetry of Ag+ translational mode
[24].
4. Conclusion
Ag2CdI4 nanostructures have been made up from reaction of CdI2 and AgI2 in solid states reaction. The XRD
patterns of nanostructures have been used to estimate the grain sizes and strain lattice. Grain size of
nanostructures are in range of 5 – 17 nm and the strain of lattice are changed in range of 0.0024 – 0.014. The
band gap of this nanostructures has been estimated by DRS spectrum about 5.4 eV. Raman spectroscopy has
been confirmed the XRD results and show that the Ag2CdI4 nanostructures have been synthesized.
Acknowledgment
Authors are grateful to the council of Iran National Science Foundation and University of Kashan for
supporting this work by Grant No (159271/567).
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Figure and Table Captions
Table 1. Different reaction condition for solid state preparation of Ag2CdI4
Table 2. Grain size and strain lattice of product
Figure 1. XRD patterns of (a) AgI (b) CdI2
Figure 2. (a) XRD pattern (b,c) Williamson-Hal diagram of Sample No. 1
Figure 3. XRD pattern of sample No (a) 3 (b) 4
Figure 4. (a) XRD pattern (b) Williamson–Hal diagram of Sample No. 4
Figure 5. (a) XRD pattern (b) Williamson–Hal diagram of Sample No. 5 (C) XRD pattern (d,e) Williamson–
Hal diagram of Sample No. 6
Figure 6. SEM images of sample No (a) 1 (b) 2 (c) 3 (d) 4 (e) 5 (f) 6
Figure 7. TEM image of Sample No 1
Figure 8. TEM image of Sample No 1
Figure 9. EDS spectrum of Sample No (a) 1 (b) 2
Figure 10. (a) DRS spectrum and (b) optical density ( (αhν)2 ) vs. energy (E) plot of Sample No 6
Figure 11. Raman spectrum of Sample No 6
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Table 1.
Sample. No
Precursors Ratio
Time
24 h
24 h
24 h
24h
Temperature
200 ºC
1
2
3
4
5
6
AgI + CdI2
2AgI + CdI2
AgI + 2CdI2
AgI + CdI2
AgI + CdI2
AgI + CdI2
200 ºC
200 ºC
150 ºC
18 h
12 h
200ºC
200 ºC
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Sample No
Grain Size (nm)
Strain Lattice
Table 2
1
4
5
6
5.5
17.5
8.2
0.014
0.0024
0.0024
0.0043
11.6
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Figure 1
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Figure 2
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Figure 3
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Figure 4
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Figure 5
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Figure 6
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Figure 7
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Figure 8
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Figure 9
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Figure 10
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Figure 11
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ꢀ Ag2CdI4 nanostructures have been synthesized by low temperature solid state method.
ꢀ The reaction has been optimized for purity, morphology, and grain size and strain lattice.
ꢀ Effective parameters have been optimized such as time, temperature and mole ratio.