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Archives of Applied Science Research, 2011, 3 (3):321-326
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ISSN 0975-508X
CODEN (USA) AASRC9
Electric and FTIR studies on magnesium hydrogen maleate hexahydrate
(MHMH) single crystals
B. Rajagopal*1, A. V. Sharma2 and M. V. Ramana3
1
Department of Physics, Kavitha Degree College, Khammam, A.P., INDIA
Department of Physics, Andhra University, Visakhapatnam, A.P., INDIA
3
Department of Physics, SR & BGNR Govt College, Khammam, A.P., INDIA
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2
ABSTRACT
In the present investigation, dielectric and FTIR of MHMH crystals have been studied for the
first time. The dielectric constant, loss tangent and ac conductivity were measured and found
that the MHMH crystals have superior optical quality and shows the possibility of using the
prepared compounds for high frequency applications. FTIR studies on MHMH single crystals
confirm carboxylate groups.
Keywords: Electrical studies, FTIR spectra.
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INTRODUCTION
Metal derivatives of unsaturated dicarboxylic acids constitute an abundant group of compounds
that are of interest from the viewpoint of both coordination and macromolecular chemistry. The
maleates are of practical importance because of their use as coatings with specific properties,
efficient catalysts and are also of medicinal significance [1]. Magnesium Hydrogen Maleate
Hexahydrate (hereafter MHMH) single crystal is considered for the investigations on electric and
FTIR studies for the first time. M.P. Gupta et al [2] and F. Vanhouteghem etal [3] worked on
the structure of MHMH crystal. The synthesis and crystal structures on alkali metal maleates
were studied by Michel Fleck et al [4] recently.
MATERIALS AND METHODS
Experimental
Crystal Growth
MHMH single crystals were grown by the procedure described by Post and Trotter [5-6] from
the aqueous solution containing magnesium carbonate and maleic acid (AnalaR grade) in 1: 2
ratios. The crystals were grown from slow evaporation of saturated aqueous solution at room
temperature.
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Arch. Appl. Sci. Res., 2011, 3 (3):321-326
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Characterisation
A.C. electrical characteristics of MHMH single crystals were measured using Multifrequency
Hioki 3532-50 LCR Hi-Tester. Using the LCR meter the data of fourteen parameters such as |Z|,
|Y|, θ, Rp(DCR), Rs (ESR, DCR), G, X, B, Lp, Ls, Cp, Cs, D (tan δ) and Q can be measured at
different temperatures. FTIR spectra of MHMH crystals were recorded using Perkin Elmer FTIR
spectrum one spectrophotometer in the range 450 cm-1 to 4000 cm-1 in KBr medium.
RESULTS AND DISCUSSION
Dielectric properties
The dielectric constant ε' [7] was measured in the frequency range 50 Hz to 1M Hz at
different temperatures. The dielectric constant was calculated by using the relation,
ε' =
. . . (1)
where C is capacitance , t is thickness, A is area of flat surface, εo is permittivity of free space
(εo = 8.85 x 10-12 F/m).
The loss tangent tan δ (D) in the frequency range 50 Hz to 1 MHz at different temperatures
was taken from the data using LCD meter.
The a.c. conductivity was measured in the frequency range 50 Hz to 1 MHz at different
temperatures measured using the formula
σac = 2πf tan δ ε0 ε‫׳‬
. . . (2)
The variation of dielectric constant ε`, loss tangent (tan δ) and ac conductivity with frequency
and various temperatures is shown in figure 1, figure 2 and figure 3 respectively. The values of
dielectric constant, loss tangent and a.c. conductivity at various temperatures and frequencies
were shown in table 1, table 2 and table 3 respectively.
35
ε' 308K
ε' 323K
ε' 343K
ε' 363K
ε' 383K
30
Dielectric constant ε'
25
20
15
10
5
0
1.5
3
log f
4.5
6
Figure 1. dielectric constant (ε') versus frequency at different temperatures in MHMH crystal
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It is evident from the figure 1 that the dielectric constant is high in the lower frequency region
and decreases continuously with increase in frequency and increases with temperature. In the
lower frequency region the dielectric constant is high due to the combination of all the
polarizations such as electronic, ionic, dipolar and space charge [8-9]. The low value of dielectric
constant at higher frequencies may be due to the loss of significance of these polarizations
gradually. From the figure 2 it is evident that the loss tangent is low at higher frequencies. This
can be attributed to superior optical quality and the possibility of using the samples for high
frequency applications [10]. From the figure 3 it is evident that the a.c. conductivity increases
continuously with frequency and increases with temperature. At higher temperature, the
increased conductivity could be due to the reduction in the space charge polarization [11].
loss tangent tanδ
4
tanδ 308K
tanδ 323K
tanδ 343K
tanδ 363K
tanδ 383K
3
2
1
0
1.5
3
4.5
log f
6
Figure 2. loss tangent (tan δ) versus frequency at different temperatures in MHMH crystal
0.000005
σac 308K
σac 323K
σac 343K
0.000004
σac 363K
ac conductivity σac
σac 383K
0.000003
0.000002
0.000001
0.000000
1.5
3
log f
4.5
6
Figure 3. ac conductivity (σac) versus frequency at different temperatures in MHMH crystal
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Table 1. Dielectric constant (ε‫ )׳‬of MHMH crystals at different frequencies and at different temperatures
log f
2
3
4
5
6
308K
ε'
3.94
2.11
1.42
1.17
1.02
323K
ε'
4.01
2.10
1.42
1.18
1.03
343K
ε'
4.76
2.22
1.45
1.20
1.06
363K
ε'
5.51
2.35
1.49
1.22
1.09
383K
ε'
11.07
3.11
1.65
1.27
1.13
Table 2. Loss tangent (tan δ) of MHMH crystals at different frequencies and at different temperatures
log f
2
3
4
5
6
308K
tan δ
0.56
0.33
0.19
0.10
0.07
323K
tan δ
0.61
0.33
0.19
0.11
0.07
343K
tan δ
0.71
0.36
0.2
0.11
0.08
363K
tan δ
0.81
0.39
0.20
0.11
0.09
383K
tan δ
2.16
0.61
0.27
0.13
0.1
Table 3. A.C. conductivity (σac) of MHMH crystals at different frequencies and at different temperatures
log f↓
2
3
4
5
6
→ ac conductivity (Ω-1m-1) at different temperatures
σac308K
σac323K
σac343K
σac363K
σac383K
1.20x10-08 1.30 x10-08 1.90 x10-08 2.50 x10-08 2.53 x10-08
3.90 x10-08 3.90 x10-08 4.50 x10-08 5.10 x10-08 1.06 x10-07
1.50 x10-07 1.50 x10-07 1.58 x10-07 1.69 x10-07 2.43 x10-07
6.96 x10-07 7.02 x10-07 7.34 x10-07 7.38 x10-07 8.94 x10-07
4.35 x10-06 4.58 x10-06 4.91 x10-06 5.55 x10-06 5.63 x10-06
FTIR Spectra
The Magnesium Hydogen Maleate single crystal was qualitatively studied for the presence of
functional groups [12] in the molecule using the Fourier transform infrared (FTIR) spectrum
which was recorded using a Perkin-Elmer spectrometer technique in the range 4000–450 cm1
.The characteristic assignment of wavenumbers of the FTIR spectrum of MHMH crystal is
shown in figure 4 and characteristic assignments are presented in table 4.
The band observed at 3397 cm-1 and 3053 cm-1 are assigned to O–H (hydroxyl) stretching. The
band at 2926 cm-1 is assigned to the alkenyl(=C-H) stretching. The bands observed at 1566 and
1395 cm-1 have been assigned to C=C stretching and symmetric carboxylate COO- stretching
vibrations and that observed at 1672 cm-1 is due to the acid stretch. The asymmetric stretch
COO- due to carboxylate anion, which is to appear near 1550 cm-1, is overlapped with the band
at 1566 cm-1 and appears broad in the infrared spectrum.
It is expected to have a peak corresponding to O-H stretching in the region 3400-2400 cm-1 and
the bands appearing in the region 1700-1350 cm−1 are assigned to symmetric and asymmetric
stretching vibrations of the carboxylate group.
The bands at 1223, 1168, 1083 and 937 cm-1 are assigned to in-plane bending C-O-H, C-H
bending, carbonyl (C=O) bending and out-of-plane bending C-O-H respectively. The bands at
870,730 and 581 cm-1 are assigned to hydroxyl (O-H), carboxylate anion (COO¯ ) and carbonyl
(C=O) deformations respectively. All these assignments are in good agreement with that of the
assignments made in the literature [13-14].
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100
90
80
2926
70
937
%T transmission
60
3053
50
40
1223
1168
30
1083
1395
20
582
871
731
1672
10
1371
3397
0
3900
3400
1566
2900
2400
1900
1400
900
400
wavenumber (cm-1)
Figure 4. FTIR of MHMH crystal
Table 4. Assignment of wavenumber to FTIR spectra of MHMH crystal
υ(O-H)
Wavenumber(cm-1)
3397, 3053
υ(=C-H)
υs(COO)
υ(C=C)
υas(COO)
δ(C-O-H) in-plane
υ(C-O)
2926
1672
1566
1395, 1371
1223
1168
δ(C-H)
δ(C-O-H) out-of-plane
δ(C-H)out-of-plane
π(COO)
π(C=O)
1083
937
871
730
581
ASSIGNMENT
hydroxyl stretching
alkenyl strtching
carboxylate assymmetric stretching
Alkene stretching
carboxylate symmetric stretching
C-O-H in-plane bending
Carbon-oxygen stretching
Alkene bending
C-O-H out-of-plane bending
C-H out-of-plane bending
carboxylate deformation
carbonyl deformation
According to resonance as shown in figure 5, it is important to realize that the carboxylate anion
does not show the normal carbonyl and normal C-O single bond stretches in the present
investigations of MHMH crystal [15].
Figure 5. The carboxylate anion is represented as a resonance hybrid
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CONLUSION
The dielectric constant and loss tangent of MHMH crystal decrease with increase in frequency of
the applied electric field and ac conductivity increases with increase of frequency. MHMH
crystals found to have good optical quality and are useful for high frequency applications. The
functional group of MHMH crystal is identified with FTIR spectra.
REFERENCES
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[3] F. Vanhouteghem, A.T.H. Lenstra and P. Schweiss. Acta cryst., 1987, B43, p 523.
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64b, 5, p 517.
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