Spectral, thermal and hardness studies on unidirectional grown dichlorido diglycine zinc dihydrate single crystal

Article abstract of DOI:10.1016/j.physb.2010.12.007

Bulk semi-organic single crystal of dichlorido diglycine zinc dihydrate has been grown by unidirectional crystal growth method from aqueous solution. The phase of the grown crystal was identified using single crystal XRD analysis. The functional groups present in the crystal were confirmed using FTIR and ¹H NMR analysis. Transmission study shows 70% of transmission in the entire visible region, which reveals the good optical quality of the grown crystal. A stable broad peak in the range of violetgreen emission was observed in the emission spectrum, which is due to the existence of defects in the crystal. The thermal and mechanical properties of the grown crystal were studied using TG/DTA and the Vickers microhardness tester, respectively.

Full text of DOI:10.1016/j.physb.2010.12.007

Physica B 406 (2011) 836–840
Contents lists available at ScienceDirect
Physica B
journal homepage: www.elsevier.com/locate/physb
Spectral, thermal and hardness studies on unidirectional grown dichlorido
diglycine zinc dihydrate single crystal
n
J. Mary Linet , S. Jerome Das
Department of Physics, Loyola College, Nungambakkam, Chennai 600 034, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Bulk semi-organic single crystal of dichlorido diglycine zinc dihydrate has been grown by unidirectional
crystal growth method from aqueous solution. The phase of the grown crystal was identified using single
Received 20 October 2010
Received in revised form
1
crystal XRD analysis. The functional groups present in the crystal were confirmed using FTIR and H NMR
1
December 2010
analysis. Transmission study shows 70% of transmission in the entire visible region, which reveals the
good optical quality of the grown crystal. A stable broad peak in the range of violet–green emission was
observed in the emission spectrum, which is due to the existence of defects in the crystal. The thermal and
mechanical properties of the grown crystal were studied using TG/DTA and the Vickers microhardness
tester, respectively.
Accepted 2 December 2010
Available online 9 December 2010
Keywords:
Growth from solution
Optical materials and properties
Mechanical properties
&
2010 Elsevier B.V. All rights reserved.
1
. Introduction
frequency conversion applications [14]. To the best of our knowl-
edge, no reports are available on the growth of DCDGZ crystal using
unidirectional solution growth method. In the present study, bulk
single crystal of DCDGZ has been grown along /0 0 1S direction
using unidirectional crystal growth method for the first time and
has achieved enhanced crystal size of good optical quality. The
phase of the grown crystal was confirmed by single crystal XRD
analysis. The functional groups present in the crystal were con-
The organic amino acid materials constitute a family in which
ꢀ
+
2 3
glycine (CH COO NH ) is the simplest of all the amino acids. It is
the only amino acid without a center of chirality and has a high
melting point due to its dipolar nature [1]. The glycine molecule is
amphoteric in nature; however, it acts as unidentate ligand
through the carboxylate group and it seems that the amino moiety
is not involved in the metal coordination [2]. Recent literature
1
firmed by FTIR and H NMR spectral analysis. The optical quality of
reports show that glycine combines with metal salts like CaCl
2
[3],
the crystal was studied by transmission and emission spectra. In
addition, a detailed discussion of thermal analysis and microhard-
ness study are presented in this paper.
BaCl [4], SrCl [5], CoBr [6], ZnSO [7] and LiSO [8] and forms new
2
2
2
4
4
complex materials. Zinc chloride dihydrate co-ordinates with
glycine to form a complex material, dichlorido diglycine zinc
dihydrate (DCDGZ), which crystallizes in the monoclinic crystal
˚
2. Experiment
system with space group C2/c and lattice parameters a¼14.4167 A,
˚
˚
b¼6.9068 A, c¼12.9531 A and
b¼117.9401 [9]. The crystalline
2.1. Synthesis and solubility studies
perfection has been studied using high resolution X-ray analysis
that shows that the specimen has a low angular grain boundary
spread around 14 arcsec [10]. Unidirectional crystal growth
method has been established by Sankaranarayanan and Ramasamy
The DCDGZ salt was synthesized according to the following
reaction by mixing commercially available glycine and zinc chlor-
ide dihydrate (99.9%) in 2:1 molar ratio using double distilled water
as solvent.
[
11] for the growth of single crystal with desired orientation at low
temperature. This technique offers the main benefit of growing a
crystal along a specific orientation instead of natural facets. It
results in reducing the wasteful portion of the crystal for device
applications and the high percentage of solute–solvent conversion
efficiency [12,13]. Phase matching direction KDP crystal has been
grown using this technique and has achieved 90% of usable yield for
þ
ꢀ
2
2CH
2
NH
2
COOHþZnCl
2
U2H
2
O-ðCH
2
NH COO Þ ZnCl
2 2
U2H O
3
ð1Þ
The resultant product of DCDGZ was purified by successive
recrystallization process using double distilled water and care was
taken to avoid decomposition during heating by maintaining the
solution at 60 1C.
n
Solubility studies were carried out using the synthesized salt of
DCDGZ and double distilled water as solvent. The solution was kept
Corresponding author. Tel.: +91 44 2817 5662; fax: +91 44 2817 5566.
E-mail address: linet.mary@gmail.com (J. Mary Linet).
0921-4526/$ - see front matter & 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.physb.2010.12.007

J. Mary Linet, S. Jerome Das / Physica B 406 (2011) 836–840
837
3
. Results and discussion
.1. Single crystal X-ray analysis
The grown crystal was subjected to single crystal X-ray diffraction
3
analysis using ENRAF NONIUS CAD4 single crystal X-ray diffract-
ometer. The result shows that the crystal belongs to the mono-
˚
˚
clinic system with cell parameters a¼14.414(2) A, b¼6.907(2) A,
˚
c¼12.953(2) A,
b¼117.991 and point group 2/m and space group
C2/c, which are in good agreement with the literature report [9].
3.2. FTIR analysis
Fig. 1. Solubility of DCDGZ.
The FTIR spectral analysis of the grown crystal was recorded in
ꢀ
1
the range 400–4000 cm using Bruker IFS 66v spectrophotometer
employing KBr pellet technique and the resultant spectrum is depicted
ꢀ
1
in Fig. 3. The sharp peak at 3458 cm is due to the hydrogen bonded
OH group. In comparison with the absorption due to the carboxylate
ꢀ
1
group of
g-glycine observed at 608, 1397, and 1593 cm , these
ꢀ
1
peaks are found to be shifted at 602, 1395 and 1633 cm , respec-
+
3
tively, in the case of DCDGZ. Similarly, the peaks due the NH
group of
ꢀ
1
g
3
-glycine observed at 1133 and 3175 cm were shifted to 1137 and
194 cm , respectively, for DCDGZ. This observation confirms that
ꢀ
1
glycine exists in the zwitterionic form. The comparison of IR bands
Fig. 2. Photograph of as-grown DCDGZ single crystal.
with
g-glycine is shown in Table 1. The peaks at 1043, 903 and
in a constant temperature bath maintained at 30 1C (accuracy
7
0.05 1C) and continuously stirred using motorized magnetic
stirrer, to have uniform temperature and concentration throughout
the volume of the solution. After attaining supersaturation, the
equilibrium concentration of the solute was analyzed gravimetri-
cally [15]. The same procedure was repeated for various tempera-
ture ranges from 35 to 50 1C with 5 1C interval. The variation of
solubility with temperature is shown in Fig. 1.
2.2. Crystal growth
Bulk growth has been adopted using unidirectional crystal
growth method as reported by Sankaranarayan and Ramasamy
11] and the detailed description of the crystal growth setup is
[
reported elsewhere [16]. According to the solubility data, the
saturated solution was prepared at 38 1C. The prepared solution
was filtered using Whatman filter paper of porosity 2.5 mm to
remove extraneous solid colloidal particles that can act as a source
of spontaneous nucleation. The filtered solution was overheated to
Fig. 3. FTIR spectrum of DCDGZ single crystal.
4
5 1C for 10 h, which further helps in reducing the possibility of
nucleation during growth. Spontaneously obtained good quality
seed of /0 0 1S direction was fitted at the bottom of the ampoule.
The seed-fitted ampoule was immersed in the crystal growth setup
at room temperature. To avoid thermal stress on the seed crystal
the temperature of the bath was gradually raised up to the
operating temperature. Upon reaching it, the saturated solution
was filled in the ampoule. The temperature at the top and bottom of
the ampoule was maintained at 42 and 38 1C, respectively, for the
complete duration of the growth run, which helps to create a
thermal gradient inside the growth apparatus. The concentration
gradient gets shifted towards the seed crystal due to the action of
gravity, which helps in the growth, and the concentration of the
solution at the top keeps on increasing due to slow evaporation,
which induces buoyancy convection that further helps in increas-
ing the concentration towards the growing crystal. A crystal of size
Table 1
FTIR spectral data for DCDGZ crystal.
ꢀ
1
IR band (cm
-glycine
)
Assignment
g
DCDGZ
ꢀ
506
608
685
893
502
602
t
o
d
(COO
)
ꢀ
(COO )
ꢀ
)
706
(COO
903
u(CC)
1044
1043
1137
1341
1395
1633
1444
2643
3014
3194
3458
u
a
(CCN)
+
1133
1336
1397
1593
u
s
3
(NH )
o
(CH
2
)
ꢀ
ꢀ
u
s
(COO
)
)
u
d
a
(COO
(CH2)
1438
2664
u
u
u
s 2
(CH )
3000
a
a
2
(CH )
1
08 mm length and 12 mm diameter was grown with an average
+
3
–
175
3
(NH )
growth rate of 3.6 mm per day. The photograph of as grown crystal
is shown in Fig. 2.
2
OH(H O)

8
38
J. Mary Linet, S. Jerome Das / Physica B 406 (2011) 836–840
ꢀ
1
2643 cm
are attributed to CCN, CC and CH
2
stretching groups of
The recorded emission spectrum of excitation wavelength 230 nm
DCDGZ, respectively.
is shown in Fig. 6. A stable broad peak in the range of violet–green
emission is observed in the room temperature photoluminescence.
The broad peak ranges from 350 to 6000 nm with a maximum at
1
3
.3. H NMR spectral analysis
398 nm and the results indicate that DCDGZ crystal has violet
1
emission. The maximum intensity that appears at 398 nm is
The H NMR spectrum was recorded using Bruker Advance III
n
1
attributed to n–p transition of carbonyl group [17]. The peak
5
2
00 MHz FTNMR spectrophotometer using D O as solvent. The H
found at 556 nm indicates green emission and may be assigned as
NMR spectrum of DCDGZ (Fig. 4) shows three characteristic peaks
at 4.702 , 3.492 and 2.650 . The peaks at 4.702 and 3.492 are
due to the hydrogen of NH (methylene) groups, respec-
n
2+
p–p
transition due to the interaction between the metal (Zn
)
d
d
d
d
d
+
and ligand molecules [18]. The remaining small peaks at 439 nm
may be attributed to the presence of unknown defects [19].
3
and CH
2
tively. The larger peak area of the amino group is due to the
presence of three hydrogen atoms and the smaller peak area
corresponds to methylene group that contains two hydrogen
atoms. The water molecule peak is shifted downfield to 2.650
due to hydrogen bonding.
d
3.6. Thermal analysis
TG/DTA of the grown crystal was carried out between room
3
.4. Transmission analysis
temperature and 1000 1C at a heating rate of 10 1C/min using NETZSCH
STA 409 C/CD in nitrogen atmosphere. The compound undergoes four
stages of weight loss as observed in the TG curve at 130, 254, 586 and
720 1C as shown in Fig. 7. The following decomposition pattern has
been formulated to account for the weight losses.
Optical properties of materials are important as they provide
information on the electronic band structures, localized states and
types of optical transitions. The cut and polished plate of the grown
crystal was subjected to transmission measurements in the
spectral region of 200–1100 nm using Varian Cary 5E spectro-
photometer. Fig. 5 shows the transmission spectrum of DCDGZ
crystal. The characteristic absorption peak is prominent at 250 nm,
and there is no absorption between 250 and 1100 nm. The good
transmission (80%) of the crystal in the entire visible region shows
good optical quality of the grown crystal.
Step 1
9
1 to 1301C
ðNH
3
CH
2
COOÞ ZnCl
2
U2H
2
Oꢀꢀꢀꢀꢀꢀꢀꢀ! ðNH
3
CH
2
COOÞ ZnCl
2
2
þ2H Om
2
2
Formula weight ¼ 322:48
36:0
Weight loss ¼ 11:1%
3.5. Photoluminescence studies
The photoluminescence spectrum was recorded using JOBIN
YVON FLUROLOG-3-11 Spectroflurometer at room temperature.
Fig. 6. Emission spectrum of DCDGZ.
1
Fig. 4. H NMR spectrum of DCDGZ.
Fig. 5. Transmission spectrum of DCDGZ.
Fig. 7. TG/DTA curve of DCDGZ crystal.

J. Mary Linet, S. Jerome Das / Physica B 406 (2011) 836–840
839
Step 2
ðNH CH
1
30 to 3801C
3
2
COOÞ ZnCl
2
2
ꢀꢀꢀꢀꢀꢀꢀꢀ!ZnCO
3
þNH
4
CNOþ2CH
ꢁ 50:4
Weight loss ¼ 31:3%
3
Clm
2
Step 3
3
80 to 7001C
ZnCO
3
þNH
4
CNOꢀꢀꢀꢀꢀꢀꢀꢀ!ZnþHCNþCO
2
mþNH
3
mþO
2
m
Total mass unit ¼ 92:0
Weight loss ¼ 28:9%
Step 4
4
7001C
ZnþHCNꢀꢀꢀꢀꢀꢀꢀꢀ! ZnþHmþCNm
Total mass unit ¼ 27:0
Fig. 8. Variation of Hv with applied load P.
Weight loss ¼ 8:4%
The first experimental weight loss observed between 91 and
1
30 1C in the TG curve, corresponds to a weight loss of 11%, which is
due to the evolution of two water molecules from the crystal
system. The theoretical weight loss predicted from the formulated
pattern is 11.17%. The second stage of weight loss of 31% observed
at 254 1C is due to the elimination of two molecules of methyl
chloride and formation of zinc carbonate and ammonium cyanate.
The corresponding calculated theoretical weight loss is 31.3%. The
third weight loss observed at 586 1C is due to the decomposition of
ammonia, carbon dioxide, oxygen and formation of zinc and
hydrogen cyanide. The experimental weight loss in this stage is
3
0%, which is almost equal to the theoretical weight loss of 28.9%.
Finally, the weight loss of 8% at 720 1C is due to the decomposition
of carbon and cyanide, the corresponding theoretical weight loss is
8
.4%. The remaining 20% of residue is zinc. In all the four steps of
decomposition, the differences between the experimental and the
formulated weight losses 0are very small and in addition, it is
evident from the TG study that the compound is formed in the
stoichiometric ratio and the compound contains adsorbed water
molecules. The differential thermal analysis curve depicts three
exothermic peaks at 94, 134 and 231 1C. The first peak represents
the evolution of one water molecule and the second peak is due to
the elimination of the second water molecule and the third one is
due to the evolution of methyl chloride. Furthermore, this analysis
confirms that the crystal is thermally stable up to 91 1C.
Fig. 9. Plot of log P vs. log d.
Table 2
Hardness parameters of DCDGZ.
Meyer index number (n)
Hardness H
v
W (g)
A
1
Corrected
m ) hardness H
0
2
2
(Kg/mm )
(g/
m
2
(
kg/mm )
Low loads High loads
3.7. Microhardness measurements
2.835
1.502
67
ꢀ19.87
0.039
72.3
Hardness of the crystal carries information about the strength,
molecular binding, yield strength and elastic constants of the
material. The microhardness of DCDGZ crystal was determined using
the Vickers microhardness tester fitted with a diamond pyramidal
indenter. Indentations were made for the applied loads varying from
Meyer’s index number (n) and when the exponent no2 there is
normal ISE behavior, when n42 there is a reverse ISE behavior and
when n¼2 the hardness is independent of the applied load, which is
given by Kick’s law. Fig. 9 shows the plot of log Pvs. log d for the grown
crystal and is presented by two segments in the plot for Pr150 g and
P4150 g. The estimated values of n are shown in Table 2.
According to Onistch, for hard materials n lies between 1 and
1.6 and soft material it is above 1.6 [22]. So the values of n in Table 2
imply that DCDGZ is a hard crystal.
25 to 300 g for a constant time of 5 s and the diagonal lengths of the
indented impressions were measured. The average diagonal length of
the indented impressions was calculated and the Vickers microhard-
ness number was found from the following relation:
P
2
Hv ¼ 1854:4 d kg=mm2
ð2Þ
where P is the applied load (in kg) and d is the average diagonal length
of the indented impressions (in m). The microhardness profile as a
According to Hays–Kendall’s approach load dependent hard-
ness may be expressed by [23]
m
function of applied load is shown in Fig. 8. From the profile it is
observed that the hardness of the crystal increases with applied load
up to 150 g and becomes load independent for PZ150 g. Thisisdue to
the reverse indentation size effect [20]. The relationship between load
dn
P ¼ W þA
where W is the minimum load initiate plastic deformation, A
1
ð3Þ
1
is the
load independent constant and the exponent n¼2. The values of W
n
2
and size of indentation is given by Meyer’s law, P¼Ad , where P is
and A
1
can be calculated by plotting the experimental P against d
load, d is diagonal length of the impression, A and n are constants for a
particular material [21]. The slope of log P vs. log d plot gives the
plot. These two values have been estimated from the plot drawn
2
0
between P and d as shown in Fig. 10. The corrected hardness H has

8
40
J. Mary Linet, S. Jerome Das / Physica B 406 (2011) 836–840
Acknowledgement
The authors are grateful to SAIF, IIT Madras, for characterization
studies.
References
[
[
[
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¼ 1854:4A
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H
0
1
ð4Þ
[
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4
. Conclusion
Optically good quality semi-organic single crystal dichlorido
[
[
11] K. Sankaranarayanan, P. Ramasamy, J. Cryst. Growth 280 (2005) 467.
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diglycine zinc dihydrate has been grown by unidirectional crystal
growth method from aqueous solution. Single crystal X-ray ana-
lysis shows that the crystal belongs to the monoclinic system
[
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˚
˚
˚
with lattice parameters a¼14.414 A, b¼6.907 A, c¼12.953 A and
¼117.991. The presence of the functional groups was confirmed
[
[
b
1
using FTIR and H NMR analysis. Transmission study shows 70% of
transmission in the entire visible region, which exhibits good
optical quality of the grown crystal. A stable broad peak in the range
of violet–green emission was observed in the emission spectrum,
which is due to the existence of defects in the crystal. The thermal
analysis shows that the crystal is thermally stable up to 91 1C. The
microhardness measurement shows that the Vickers microhard-
[
19] A. Meijerink, G. Blasse, M. Glasbeek, J. Phys. Condens. Matter 2 (1990)
6
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[
[
2
ness value is 72 kg/mm .
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