- Email: [email protected]
Indigenously developed vertical semi transparent Bridgman setup for the growth of single crystals
Accepted Manuscript Title: Indigenously developed Vertical Semi Transparent Bridgman Setup for the growth of Single Crystals Authors: A. Saranraj, R. Murugan, S. Sahaya Jude Dhas, M. Jose, S.A. Martin Britto Dhas PII: DOI: Reference:
S2352-4928(17)30064-8 https://doi.org/10.1016/j.mtcomm.2017.11.003 MTCOMM 234
To appear in: Received date: Revised date: Accepted date:
13-4-2017 6-11-2017 6-11-2017
Please cite this article as: A.Saranraj, R.Murugan, S.Sahaya Jude Dhas, M.Jose, S.A.Martin Britto Dhas, Indigenously developed Vertical Semi Transparent Bridgman Setup for the growth of Single Crystals, Materials Today Communications https://doi.org/10.1016/j.mtcomm.2017.11.003 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Indigenously developed Vertical Semi Transparent Bridgman Setup for the growth of Single Crystals A. Saranraj1, R. Murugan1 , S. Sahaya Jude Dhas2, M. Jose1, S. A. Martin Britto Dhas*1 1
Department of Physics, Abraham Panampara Research Centre, Sacred Heart College, Tirupattur - 635 601, India
Department of Physics, Saveetha Engineering College, Chennai – 602 105, India
*
SC RI PT
2
corresponding author: Telephone +91-8903101253, Email: [email protected]
Melting Zone
Bottom
A
CC
EP
TE
D
Top
M
A
N
U
Graphical Abstract
1. Thread 2. Inner tube 3. Ampoule 4. Outer tube 5. Nichrome wire 6. Sensor 7. Temperature Controller
Schematic diagram of vertical semi transparent Bridgman setup
Highlights The indigenously constructed Bridgeman setup is a semi transparent type and cost effective. A stop clock is modified as translation assembly.
SC RI PT
Organic NLO materials such as Benzophenone and Acenaphthene are grown using the constructed Bridgeman srtup.
U
Abstract
N
An effective and economically viable vertical semi transparent Bridgman setup has been designed and fabricated by employing a furnace made up of a single Nichrome coil. We made an
A
effort with a new approach by adapting a translation mechanism for the ampoule coupled with a
M
stop clock. This set up is suitable device for growing organic crystal from melt as it makes use of ampoule translation assembly. Organic nonlinear materials of acenaphthene and benzophenone
D
were grown using this set up. Transparent single crystals were successfully grown as a result of suitable thermal gradient achieved by means of thermal gradient furnace assembly. The grown
translation
assembly,
crystal
growth,
Bridgeman
setup,
Acenaphthene,
EP
Keywords:
TE
single crystals were rationalized using X-ray diffraction, spectroscopic and thermal analysis.
Benzophenone
CC
1. Introduction
Crystals have evolved and emerged as major constituents of accepted giant pillars of
A
modern technology which grows with a rapid rate so that the need of growing quality crystals with low cost has gained momentum resulting to an impetus opportunity in such a way that the researchers involved in crystal growth have shown very much interest in achieving it. The modern technological development depends very much on the availability of suitable single crystals which are being used in lasers, semiconductors, magnetic devices, optical devices, superconductors, telecommunication, etc. The relevant scientific research in the field of crystal
growth covers a wide spectrum of work on nucleation, growth rates, translation rates, segregation, growth interfaces, stability and crystalline defects [1]. Solution growth technique has been employed traditionally to grow larger size organic crystals of high quality as they possess good nonlinear optical properties so that these crystals are being used in technological applications. However, in the case of some organic materials, solution growth methods are not
SC RI PT
suitable for growing crystals due to undesired compound associations which occur during the growth process and also solvent inclusions into the crystals in such a way that these problems can in turn reduce the optical quality [2]. The growth of organic crystals is difficult in comparison with the growth of inorganic crystals due to their low thermal conductivity and great super cooling tendencies. In such cases, melt growth plays an important role in the making of single crystals which are chemically stable even after they melt. Due to the fact that the grown
U
crystals have reliable optical quality and a fast growth rate, melt techniques are being tailored for
N
most of the crystals [3].
A
Bridgman introduced melt technique in 1925 and ever since there have been so many
M
modifications made and it continues to be the most vibrant method even today as it is found to be the simplest technique for the growth of crystal from the melt. The reasons for this popularity are
D
that the technique produces crystals with good dimensional tolerance during the fast growth and employ relatively simple technology. The materials to be grown is encapsulated in quartz tube
TE
and suspended in the furnace which is provided with a suitable temperature gradient for the growth [4].
EP
In the literature, it has been found that there were many changes and modifications implemented on the original setup of Bridgman in the past for the translation assembly so as to
CC
achieve improved precision. A translation assembly had been developed to achieve the precision of 0.001 mm/h using a nano-stepper motor drive which was coupled with a pulse frequency
A
modulation type electronic circuit controller to enable the translation for the growth vessel [5]. Another crucible lowering rate of 0.5 – 4 mm/h translation rate were achieved by different translation techniques [6-12]. In the present work, we made an attempt to modify the design of translation mechanism which is indigenously developed in our laboratory with a simple approach using a stop clock in such a way that it is much more cost effective and we could succeed in achieving it at the rate of 1.66 mm/hr. The construction details of the single zone transparent
furnace are briefed and the same set up was used to grow acenaphthene and benzophenone crystals. 2. Experimental Section The necessary features of the modified Vertical Semi Transparent Bridgeman growth
Bottom
U
Melting Zone
TE
D
M
A
N
Top
SC RI PT
apparatus designed and fabricated in our laboratory are shown schematically in Fig. 1
1. Thread
2. Inner tube 3. Ampoule 4. Outer tube 5. Nichrome wire 6. Sensor 7. Temperature Controller
EP
Fig. 1 Schematic diagram of modified vertical Bridgman setup It consists of three major components as that of temperature controller, furnace and translation
CC
assembly.
Design of Furnace assembly
A
The furnace temperature was controlled and maintained using a micro electronics
temperature controller as a thermocouple with an accuracy of ± 1°C, can control the temperature up to 1200°C. A borosilicate glass tube measuring 500 mm length, 70 mm diameter with a wall thickness of 2 mm was used as a furnace. The glass tube was wound with Nichrome wire of thickness 0.5mm. Initially, the space between the successive windings was kept at 30 mm for the upper part of the tube and then it was gradually decreased to 15 mm towards the middle part
which is the melting zone providing required temperature. The space between the windings was again gradually increased to 40 mm and then to 50 mm towards the lower end of the tube (inset of Fig. 1). The temperature gradient is established in such a way that the middle portion of the furnace would have the maximum temperature while the top and bottom have relatively lower temperatures. The melting zone provides the necessary temperature required for the melting of
SC RI PT
the sample. To avoid the loss of heat to the environment, it is covered with a thermal insulator.
A gradual change in temperature from top to bottom of the furnace and also the corresponding change in temperature gradient of the furnace can be effectively employed for a wide range of temperatures by changing the distance between the windings of the coil. To ensure constant temperature at both the hot and cold zones of the furnace, the temperature profile analysis was performed for the furnace (Fig. 2). From this plot, one can easily understand that
U
the temperature profile of the furnace is slowly increasing and reaching the maximum (i.e. little
N
above the melting point of the sample) and then slowly decreasing with respect to the distance along the furnace length. Obviously, the symmetrical nature of the plot indicates the change in
A
CC
EP
TE
D
M
A
temperature gradient is uniform and after number of trials, temperature profile is optimized.
Fig. 2 Temperature profile of constructed furnace Translation Mechanism
The ampoule is to be lowered slowly from the hot zone of the furnace to the cold zone. Crystallization begins at the tip of the ampoule and the continuous and uniform growth of the crystal is usually based on the first formed nucleus. In all the reports available in the literatures, the speed and smoothness of translation of the conventional stepper motor are generally increased by micro stepping mode which involves high cost and complicated technology. In the
SC RI PT
present work, we have used a simple technique to achieve a translation of 1.66 mm per hours. In order to achieve this, we have constructed a pulling mechanism equipped with a stop clock along with the hanging ampoule. The stop clock makes use of the thread that is tied with the hour hand shaft which has the circumference of 1.66 mm. As the hour hand shaft rotates, the thread rolls on the shaft slowly so that the ampoule is lowered to the distance of 1.66 mm for every one rotation of the shaft. Thus the translation speed of ampoule is maintained at the rate of 1.66 mm/hr could
U
be achieved. The melt on the tip of the ampoule started solidifying as it approached the freezing
N
point. The solid part was transparent enough in such a way that the quality assessment of the crystal was possible while it was growing.
M
A
3. Crystal Growth
Benzophenone and Acenaphthene, which are promising nonlinear optical materials, were
D
used for crystal growth. The two compounds in powder form were loaded in two different single wall ampoules and then the loaded ampoule was evacuated and sealed. When the temperature
TE
reaches above the melting point of the sample was melt. The ampoule was allowed to move downward in the furnace at a suitable temperature gradient. A vertical temperature gradient of
EP
~2.87 °C/cm was achieved in the constructed transparent furnace. The movement of the ampoule was fixed as 1.66 mm/h throughout the growth process to cover the entire length of the furnace.
CC
While ampoule is moving downwards (lower temperature zone) crystallization started and the growth process was allowed to continue gradually with the favorable conditions so that the
A
crystal grew up to the entire length of the melt region well inside the ampoule. A bulk size benzophenone single crystal of diameter up to 12 mm and length 84 mm was
able to be grown by employing this setup. The photograph of benzophenone crystal is shown in Fig. 3 (a). By following the same procedure, a bulk size single crystal of acenaphthene with diameter up to 15 mm and length 58 mm was also grown by using the single zone Vertical Semi Transparent Bridgman setup. The photograph of acenaphthene crystal is shown in Fig. 3 (b).
SC RI PT
b)
M
A
N
U
a)
D
Fig. 3 Photograph of as grown single crystal a) Benzophenone b) Acenaphthene
TE
4. Characterization
Nonius CAD-4/MACH 3 diffractometer with MoKα (λ=0. 71073 Å) radiation was used
EP
to obtain the cell parameters of the grown crystals and powder X-ray diffraction (XRD) study was carried out by employing a BRUKER diffractometer with CuKa radiation (1.5418Å). The
CC
FTIR spectra of the sample were recorded with KBr phase in the frequency region of 400-4000 cm-1 using Perkin Elmer Spectra 2. Thermo gravimetric analysis (TGA) was carried out for the grown crystal samples using Perkin Elmer STA 6000 thermal analyzer. Fine powders of the
A
crystals were used for the analysis in the temperature range of room temperature to 280oC, with a heating rate of 10oC/min. 5. Results and Discussion 5.1 X-ray Diffraction studies
The grown benzophenone belongs to the orthorhombic crystal system with noncentrosymmetric space group P212121. The obtained cell parameters using single crystal X-ray diffraction studies are in good agreement with the literature values (Table 1). Powder XRD pattern of benzophenone is indexed as shown in Fig. 4 (a). The diffraction
SC RI PT
pattern, d spacing and hkl values for every diffraction peak in the spectrum are described. Using the orthorhombic crystallographic equation, the lattice parameter values of benzophenone are calculated and compared with the reported value [7] and it is found to be in accordance with the literature values. Table 1 illustrates the calculated values and the reported values.
The grown acenaphthene belongs to the orthorhombic crystal system possessing noncentrosymmetric space group Pcm21. The obtained cell parameters using single crystal X-ray
U
diffraction studies are in excellent conformity with the literature values (Table 2).
N
The Powder XRD pattern of the grown crystal is shown in figure 4 (b). The diffraction
A
pattern, d spacing and hkl values for each diffraction peak in the spectrum are identified. With
M
the orthorhombic crystallographic equation, the lattice parameter values of acenaphthene are calculated and compared with the reported values. The positions of the peaks are in good agreement with the corresponding peaks found in the literature. Table 2 shows that the calculated
A
CC
EP
TE
D
values are very much in line with the literature values [13].
Fig. 4 (a) X-ray diffraction spectrum of benzophenone
Fig. 4 (b) X-ray diffraction spectrum of acenaphthene
Table 1. Lattice parameters values of benzophenone b (Å)
c (Å)
7.98
10.28
12.12
7.97
10.19
12.13
7.90
10.17
12.03
Reference
SC RI PT
a (Å)
Single XRD
Powder XRD [7]
Table 2. Lattice parameters values of acenaphthene b (Å)
c (Å)
8.28
14.01
7.22
Single XRD
8.30
14.02
7.23
Powder XRD
8.30
14.01
7.27
[14]
Reference
M
A
N
U
a (Å)
D
5.2 FTIR spectrum
TE
FTIR spectrum of benzophenone single crystal is presented in Fig. 5 (a) and compared with the reported values [15, 16]. Aromatic C-H stretching is observed in the spectrum at 3056
EP
cm-1. The recorded peak at 1651 cm-1 is ascribed to carbonyl (C=O) stretching. Skeletal vibrations of aromatic rings are located at 1444 cm-1 and at 1597cm-1. The peaks found at
CC
1028,1075,1147,1272 and 1322 cm-1 are all due to in plane bending modes of aromatic C-H bonds. The peaks observed below 1000 cm-1 illustrate the occurrences of out of plane bending
A
modes. The assignments of obtained frequencies are in conformity with the characteristic transmission bands of reported benzophenone. The FTIR spectra of acenaphthene crystal is shown in Fig. 5 (b). The observed values of the spectra are analyzed and also compared with the standard spectra of the functional groups [15]. The Peaks at 3056 cm-1 and at 2928 cm-1 can be assigned for CH stretching. The band at 1600 cm-1 may be attributed to a combination of CC stretching. CH bending in CH2 group is
observed at 1418 cm-1 and also at 836 cm-1. The peak at 783 cm-1 is due to CH out of plane bending. The presence of CH2 twisting is observed at 1371 cm-1. The vibration spectrum
N
U
SC RI PT
observed below 744 cm-1 is assigned to skeletal out of plane bending [17].
Fig. 5 (b) FTIR spectrum of grown
A
Fig. 5 (a) FTIR spectrum of grown
acenaphthene crystal
M
benzophenone crystal 5.3 TG analysis
D
The grown benzophenone thermo- gravimetric analysis (TGA) curve (Fig. 6 (a)) of this
TE
sample indicates that the sample is stable up to 149oC and without any weight loss. This indicates that there is no inclusion of water in the crystal lattice. An intense single step mass loss
EP
between 160- 273 oC is observed and it corresponds to the decomposition of benzophenone. The thermo- gravimetric analysis (TGA) curve obtained for grown acenaphthene is
CC
shown in Fig. 6 (b). The curve clearly shows that the grown crystal is stable between the temperature ranges of ambient to 127 oC. It is revealed that the loss of mass in acenaphthene
A
started around 127 oC and single step decomposition occurred at 220 oC.
Fig. 6 (a) TG plot of benzophenone
Fig. 6 (b) TG plot of acenaphthene
SC RI PT
6. Conclusion A low cost modified vertical semi transparent Bridgman setup has been designed and fabricated for the growth of single crystals. The constructed single zone of transparent furnace was made out of Nichrome wire. The solid-liquid interface position and shape could be monitored during the growth thereby the investigation of the important growth parameters such as vertical furnace temperature gradient and translation rate could be carried out. The translation
U
rate and the temperature profile were optimized. Transparent and good optical qualities of
N
benzophenone and acenaphthene single crystals have been successfully grown by the constructed setup. The grown crystals were confirmed by single crystal XRD and Powder XRD and also the
A
functional groups of these crystals were analyzed by FTIR. The thermal analysis (TGA) is
M
carried out for the grown benzophenone and acenaphthene single crystals.
D
References
TE
[1] K. Byrappa, T. Ohachi, Crystal growth Technology, Springer- Verlag Berlin Heidelberg Newyork.
[2] Georg Muller, Experimental analysis and modeling of melt growth processes. J. Cryst.
EP
Growth 237–239 (2002) 1628–1637. [3] A. Arulchakkaravarthi, C.K. Lakshmanaperumal, P. Santhanaraghavan, P. Jayavel, R.Selvan,
CC
K. Sivaji, R. Gopalakrishnan, P. Ramasay, Investigations on the growth of anthracene and transstilbene single crystals using vertical Bridgman technique. Mater. Sci. Eng. B95(2002) 236-241.
A
[4] Olson, H. Edwin, "Low-cost bridgman-type single-crystal growing apparatus. Ames Laboratory Technical Reports. Paper 28 (1960). [5] T. Suthan, N.P. Rajesh, P.V. Dhanaraj, C.K. Mahadeven, Growth and characterization of naphthalene single crystals grown by modified vertical Bridgman method. Spectrochim. Acta Part A 75 (1960) 69-73.
[6] B.J. McArdle, J.N. Sherwood, A.C. Damask, The Growth And Perfection of Phenanthrene Single Crystals. J. Cryst. Growth 22 (1974). 193. [7] M. Arivanadhan, K. Sanaranarayanan, K. Ramamoorthy, C. Sanjeeviraja, P. Ramasamy, A
novel
way
of
Bridgman-Stockbarger
modifying
Technique
the
and
thermal
studies
gradient
on
its
in
effect
Vertical on
the
SC RI PT
growth of benzophenone single crystals. Cryst. Res. Technol. 39 (2004) 692-698.
[8] J. Choi, M.D. Aggarwal, W.S. Wang, R. Metzl, K. Bhat, Benjamin G. Penn, O. Donald, Frazier, A Simple Inexpensive Bridgman-Stockbarger Crystal Growth System for Organic Materials. J. Am. Chem. Soc. (1996) 1054-7487.
[9] J. Choi, M.D. Aggarwal, W.S. Wang, Benjamin G. Penn and Donald O. Frazier, Binary Organic Single Crystals for Nonlinear Optical Application. J. Korean Phys. Soc. 32 (1998) 433-
U
435.
N
[10] B. Marcinia, The Growth of Some Aromatic Hydrocarbons Single Crystals from the Melt. Cryst. Res. Technol. 26 (1991) 855-862.
A
[11] J.N. Sherwood, S.J. Thomson, Growth of single crystals of anthracene. J. Sci. Instrum. 37
M
(1960) 242.
[12] W.M. Higgins, J. Glodo, E. Van Loef, M. Klugerman, T. Gupta, L. Cirignano, P. Wong,
D
K.S. Shah, Bridgman growth of LaBr3:Ce and LaCl3:Ce crystals for high-resolution gamma-ray
TE
spectrometers. J. Cryst. Growth 287 (2006) 239–242. [13] R. Ramesh Babua, N. Balamurugan, N. Vijayan, R. Gopalakrishnan, G. Bhagavannarayan, P.
Ramasamy,
Studies
on
acenaphthene
(C12H10)
single
crystals
grown
by
EP
vertical Bridgman technique. J. Cryst. Growth 285 (2005) 649–660. [14] S. Karuppusamy, K. Dinesh Babu, V. Nirmal Kumar, R. Gopalakrishnan, Thermal kinetic
CC
and dielectric parameters of acenaphthene crystal grown by vertical Bridgman technique. Appl. Phys. A 122 (2016) 498.
A
[15] K. Sankaranarayanan, P. Ramasamy, Unidirectional seeded single crystal growth from solution of benzophenone. J. Cryst. Growth 280 (2005) 467–473. [16] G. Socrates, Infrared Characteristic Group Frequencies, Wiley-Interscience: Chichester, (1980). [17] L. Colombo, Infrared Spectra in Polarized Light of Acenaphthene Crystals and Assignment of Molecular Vibrations. J. Chem. Phys. 39 (1963) 1942.
S2352-4928(17)30064-8 https://doi.org/10.1016/j.mtcomm.2017.11.003 MTCOMM 234
To appear in: Received date: Revised date: Accepted date:
13-4-2017 6-11-2017 6-11-2017
Please cite this article as: A.Saranraj, R.Murugan, S.Sahaya Jude Dhas, M.Jose, S.A.Martin Britto Dhas, Indigenously developed Vertical Semi Transparent Bridgman Setup for the growth of Single Crystals, Materials Today Communications https://doi.org/10.1016/j.mtcomm.2017.11.003 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Indigenously developed Vertical Semi Transparent Bridgman Setup for the growth of Single Crystals A. Saranraj1, R. Murugan1 , S. Sahaya Jude Dhas2, M. Jose1, S. A. Martin Britto Dhas*1 1
Department of Physics, Abraham Panampara Research Centre, Sacred Heart College, Tirupattur - 635 601, India
Department of Physics, Saveetha Engineering College, Chennai – 602 105, India
*
SC RI PT
2
corresponding author: Telephone +91-8903101253, Email: [email protected]
Melting Zone
Bottom
A
CC
EP
TE
D
Top
M
A
N
U
Graphical Abstract
1. Thread 2. Inner tube 3. Ampoule 4. Outer tube 5. Nichrome wire 6. Sensor 7. Temperature Controller
Schematic diagram of vertical semi transparent Bridgman setup
Highlights The indigenously constructed Bridgeman setup is a semi transparent type and cost effective. A stop clock is modified as translation assembly.
SC RI PT
Organic NLO materials such as Benzophenone and Acenaphthene are grown using the constructed Bridgeman srtup.
U
Abstract
N
An effective and economically viable vertical semi transparent Bridgman setup has been designed and fabricated by employing a furnace made up of a single Nichrome coil. We made an
A
effort with a new approach by adapting a translation mechanism for the ampoule coupled with a
M
stop clock. This set up is suitable device for growing organic crystal from melt as it makes use of ampoule translation assembly. Organic nonlinear materials of acenaphthene and benzophenone
D
were grown using this set up. Transparent single crystals were successfully grown as a result of suitable thermal gradient achieved by means of thermal gradient furnace assembly. The grown
translation
assembly,
crystal
growth,
Bridgeman
setup,
Acenaphthene,
EP
Keywords:
TE
single crystals were rationalized using X-ray diffraction, spectroscopic and thermal analysis.
Benzophenone
CC
1. Introduction
Crystals have evolved and emerged as major constituents of accepted giant pillars of
A
modern technology which grows with a rapid rate so that the need of growing quality crystals with low cost has gained momentum resulting to an impetus opportunity in such a way that the researchers involved in crystal growth have shown very much interest in achieving it. The modern technological development depends very much on the availability of suitable single crystals which are being used in lasers, semiconductors, magnetic devices, optical devices, superconductors, telecommunication, etc. The relevant scientific research in the field of crystal
growth covers a wide spectrum of work on nucleation, growth rates, translation rates, segregation, growth interfaces, stability and crystalline defects [1]. Solution growth technique has been employed traditionally to grow larger size organic crystals of high quality as they possess good nonlinear optical properties so that these crystals are being used in technological applications. However, in the case of some organic materials, solution growth methods are not
SC RI PT
suitable for growing crystals due to undesired compound associations which occur during the growth process and also solvent inclusions into the crystals in such a way that these problems can in turn reduce the optical quality [2]. The growth of organic crystals is difficult in comparison with the growth of inorganic crystals due to their low thermal conductivity and great super cooling tendencies. In such cases, melt growth plays an important role in the making of single crystals which are chemically stable even after they melt. Due to the fact that the grown
U
crystals have reliable optical quality and a fast growth rate, melt techniques are being tailored for
N
most of the crystals [3].
A
Bridgman introduced melt technique in 1925 and ever since there have been so many
M
modifications made and it continues to be the most vibrant method even today as it is found to be the simplest technique for the growth of crystal from the melt. The reasons for this popularity are
D
that the technique produces crystals with good dimensional tolerance during the fast growth and employ relatively simple technology. The materials to be grown is encapsulated in quartz tube
TE
and suspended in the furnace which is provided with a suitable temperature gradient for the growth [4].
EP
In the literature, it has been found that there were many changes and modifications implemented on the original setup of Bridgman in the past for the translation assembly so as to
CC
achieve improved precision. A translation assembly had been developed to achieve the precision of 0.001 mm/h using a nano-stepper motor drive which was coupled with a pulse frequency
A
modulation type electronic circuit controller to enable the translation for the growth vessel [5]. Another crucible lowering rate of 0.5 – 4 mm/h translation rate were achieved by different translation techniques [6-12]. In the present work, we made an attempt to modify the design of translation mechanism which is indigenously developed in our laboratory with a simple approach using a stop clock in such a way that it is much more cost effective and we could succeed in achieving it at the rate of 1.66 mm/hr. The construction details of the single zone transparent
furnace are briefed and the same set up was used to grow acenaphthene and benzophenone crystals. 2. Experimental Section The necessary features of the modified Vertical Semi Transparent Bridgeman growth
Bottom
U
Melting Zone
TE
D
M
A
N
Top
SC RI PT
apparatus designed and fabricated in our laboratory are shown schematically in Fig. 1
1. Thread
2. Inner tube 3. Ampoule 4. Outer tube 5. Nichrome wire 6. Sensor 7. Temperature Controller
EP
Fig. 1 Schematic diagram of modified vertical Bridgman setup It consists of three major components as that of temperature controller, furnace and translation
CC
assembly.
Design of Furnace assembly
A
The furnace temperature was controlled and maintained using a micro electronics
temperature controller as a thermocouple with an accuracy of ± 1°C, can control the temperature up to 1200°C. A borosilicate glass tube measuring 500 mm length, 70 mm diameter with a wall thickness of 2 mm was used as a furnace. The glass tube was wound with Nichrome wire of thickness 0.5mm. Initially, the space between the successive windings was kept at 30 mm for the upper part of the tube and then it was gradually decreased to 15 mm towards the middle part
which is the melting zone providing required temperature. The space between the windings was again gradually increased to 40 mm and then to 50 mm towards the lower end of the tube (inset of Fig. 1). The temperature gradient is established in such a way that the middle portion of the furnace would have the maximum temperature while the top and bottom have relatively lower temperatures. The melting zone provides the necessary temperature required for the melting of
SC RI PT
the sample. To avoid the loss of heat to the environment, it is covered with a thermal insulator.
A gradual change in temperature from top to bottom of the furnace and also the corresponding change in temperature gradient of the furnace can be effectively employed for a wide range of temperatures by changing the distance between the windings of the coil. To ensure constant temperature at both the hot and cold zones of the furnace, the temperature profile analysis was performed for the furnace (Fig. 2). From this plot, one can easily understand that
U
the temperature profile of the furnace is slowly increasing and reaching the maximum (i.e. little
N
above the melting point of the sample) and then slowly decreasing with respect to the distance along the furnace length. Obviously, the symmetrical nature of the plot indicates the change in
A
CC
EP
TE
D
M
A
temperature gradient is uniform and after number of trials, temperature profile is optimized.
Fig. 2 Temperature profile of constructed furnace Translation Mechanism
The ampoule is to be lowered slowly from the hot zone of the furnace to the cold zone. Crystallization begins at the tip of the ampoule and the continuous and uniform growth of the crystal is usually based on the first formed nucleus. In all the reports available in the literatures, the speed and smoothness of translation of the conventional stepper motor are generally increased by micro stepping mode which involves high cost and complicated technology. In the
SC RI PT
present work, we have used a simple technique to achieve a translation of 1.66 mm per hours. In order to achieve this, we have constructed a pulling mechanism equipped with a stop clock along with the hanging ampoule. The stop clock makes use of the thread that is tied with the hour hand shaft which has the circumference of 1.66 mm. As the hour hand shaft rotates, the thread rolls on the shaft slowly so that the ampoule is lowered to the distance of 1.66 mm for every one rotation of the shaft. Thus the translation speed of ampoule is maintained at the rate of 1.66 mm/hr could
U
be achieved. The melt on the tip of the ampoule started solidifying as it approached the freezing
N
point. The solid part was transparent enough in such a way that the quality assessment of the crystal was possible while it was growing.
M
A
3. Crystal Growth
Benzophenone and Acenaphthene, which are promising nonlinear optical materials, were
D
used for crystal growth. The two compounds in powder form were loaded in two different single wall ampoules and then the loaded ampoule was evacuated and sealed. When the temperature
TE
reaches above the melting point of the sample was melt. The ampoule was allowed to move downward in the furnace at a suitable temperature gradient. A vertical temperature gradient of
EP
~2.87 °C/cm was achieved in the constructed transparent furnace. The movement of the ampoule was fixed as 1.66 mm/h throughout the growth process to cover the entire length of the furnace.
CC
While ampoule is moving downwards (lower temperature zone) crystallization started and the growth process was allowed to continue gradually with the favorable conditions so that the
A
crystal grew up to the entire length of the melt region well inside the ampoule. A bulk size benzophenone single crystal of diameter up to 12 mm and length 84 mm was
able to be grown by employing this setup. The photograph of benzophenone crystal is shown in Fig. 3 (a). By following the same procedure, a bulk size single crystal of acenaphthene with diameter up to 15 mm and length 58 mm was also grown by using the single zone Vertical Semi Transparent Bridgman setup. The photograph of acenaphthene crystal is shown in Fig. 3 (b).
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b)
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a)
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Fig. 3 Photograph of as grown single crystal a) Benzophenone b) Acenaphthene
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4. Characterization
Nonius CAD-4/MACH 3 diffractometer with MoKα (λ=0. 71073 Å) radiation was used
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to obtain the cell parameters of the grown crystals and powder X-ray diffraction (XRD) study was carried out by employing a BRUKER diffractometer with CuKa radiation (1.5418Å). The
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FTIR spectra of the sample were recorded with KBr phase in the frequency region of 400-4000 cm-1 using Perkin Elmer Spectra 2. Thermo gravimetric analysis (TGA) was carried out for the grown crystal samples using Perkin Elmer STA 6000 thermal analyzer. Fine powders of the
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crystals were used for the analysis in the temperature range of room temperature to 280oC, with a heating rate of 10oC/min. 5. Results and Discussion 5.1 X-ray Diffraction studies
The grown benzophenone belongs to the orthorhombic crystal system with noncentrosymmetric space group P212121. The obtained cell parameters using single crystal X-ray diffraction studies are in good agreement with the literature values (Table 1). Powder XRD pattern of benzophenone is indexed as shown in Fig. 4 (a). The diffraction
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pattern, d spacing and hkl values for every diffraction peak in the spectrum are described. Using the orthorhombic crystallographic equation, the lattice parameter values of benzophenone are calculated and compared with the reported value [7] and it is found to be in accordance with the literature values. Table 1 illustrates the calculated values and the reported values.
The grown acenaphthene belongs to the orthorhombic crystal system possessing noncentrosymmetric space group Pcm21. The obtained cell parameters using single crystal X-ray
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diffraction studies are in excellent conformity with the literature values (Table 2).
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The Powder XRD pattern of the grown crystal is shown in figure 4 (b). The diffraction
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pattern, d spacing and hkl values for each diffraction peak in the spectrum are identified. With
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the orthorhombic crystallographic equation, the lattice parameter values of acenaphthene are calculated and compared with the reported values. The positions of the peaks are in good agreement with the corresponding peaks found in the literature. Table 2 shows that the calculated
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values are very much in line with the literature values [13].
Fig. 4 (a) X-ray diffraction spectrum of benzophenone
Fig. 4 (b) X-ray diffraction spectrum of acenaphthene
Table 1. Lattice parameters values of benzophenone b (Å)
c (Å)
7.98
10.28
12.12
7.97
10.19
12.13
7.90
10.17
12.03
Reference
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a (Å)
Single XRD
Powder XRD [7]
Table 2. Lattice parameters values of acenaphthene b (Å)
c (Å)
8.28
14.01
7.22
Single XRD
8.30
14.02
7.23
Powder XRD
8.30
14.01
7.27
[14]
Reference
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a (Å)
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5.2 FTIR spectrum
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FTIR spectrum of benzophenone single crystal is presented in Fig. 5 (a) and compared with the reported values [15, 16]. Aromatic C-H stretching is observed in the spectrum at 3056
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cm-1. The recorded peak at 1651 cm-1 is ascribed to carbonyl (C=O) stretching. Skeletal vibrations of aromatic rings are located at 1444 cm-1 and at 1597cm-1. The peaks found at
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1028,1075,1147,1272 and 1322 cm-1 are all due to in plane bending modes of aromatic C-H bonds. The peaks observed below 1000 cm-1 illustrate the occurrences of out of plane bending
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modes. The assignments of obtained frequencies are in conformity with the characteristic transmission bands of reported benzophenone. The FTIR spectra of acenaphthene crystal is shown in Fig. 5 (b). The observed values of the spectra are analyzed and also compared with the standard spectra of the functional groups [15]. The Peaks at 3056 cm-1 and at 2928 cm-1 can be assigned for CH stretching. The band at 1600 cm-1 may be attributed to a combination of CC stretching. CH bending in CH2 group is
observed at 1418 cm-1 and also at 836 cm-1. The peak at 783 cm-1 is due to CH out of plane bending. The presence of CH2 twisting is observed at 1371 cm-1. The vibration spectrum
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observed below 744 cm-1 is assigned to skeletal out of plane bending [17].
Fig. 5 (b) FTIR spectrum of grown
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Fig. 5 (a) FTIR spectrum of grown
acenaphthene crystal
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benzophenone crystal 5.3 TG analysis
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The grown benzophenone thermo- gravimetric analysis (TGA) curve (Fig. 6 (a)) of this
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sample indicates that the sample is stable up to 149oC and without any weight loss. This indicates that there is no inclusion of water in the crystal lattice. An intense single step mass loss
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between 160- 273 oC is observed and it corresponds to the decomposition of benzophenone. The thermo- gravimetric analysis (TGA) curve obtained for grown acenaphthene is
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shown in Fig. 6 (b). The curve clearly shows that the grown crystal is stable between the temperature ranges of ambient to 127 oC. It is revealed that the loss of mass in acenaphthene
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started around 127 oC and single step decomposition occurred at 220 oC.
Fig. 6 (a) TG plot of benzophenone
Fig. 6 (b) TG plot of acenaphthene
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6. Conclusion A low cost modified vertical semi transparent Bridgman setup has been designed and fabricated for the growth of single crystals. The constructed single zone of transparent furnace was made out of Nichrome wire. The solid-liquid interface position and shape could be monitored during the growth thereby the investigation of the important growth parameters such as vertical furnace temperature gradient and translation rate could be carried out. The translation
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rate and the temperature profile were optimized. Transparent and good optical qualities of
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benzophenone and acenaphthene single crystals have been successfully grown by the constructed setup. The grown crystals were confirmed by single crystal XRD and Powder XRD and also the
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functional groups of these crystals were analyzed by FTIR. The thermal analysis (TGA) is
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carried out for the grown benzophenone and acenaphthene single crystals.
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References
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[1] K. Byrappa, T. Ohachi, Crystal growth Technology, Springer- Verlag Berlin Heidelberg Newyork.
[2] Georg Muller, Experimental analysis and modeling of melt growth processes. J. Cryst.
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Growth 237–239 (2002) 1628–1637. [3] A. Arulchakkaravarthi, C.K. Lakshmanaperumal, P. Santhanaraghavan, P. Jayavel, R.Selvan,
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K. Sivaji, R. Gopalakrishnan, P. Ramasay, Investigations on the growth of anthracene and transstilbene single crystals using vertical Bridgman technique. Mater. Sci. Eng. B95(2002) 236-241.
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[4] Olson, H. Edwin, "Low-cost bridgman-type single-crystal growing apparatus. Ames Laboratory Technical Reports. Paper 28 (1960). [5] T. Suthan, N.P. Rajesh, P.V. Dhanaraj, C.K. Mahadeven, Growth and characterization of naphthalene single crystals grown by modified vertical Bridgman method. Spectrochim. Acta Part A 75 (1960) 69-73.
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growth of benzophenone single crystals. Cryst. Res. Technol. 39 (2004) 692-698.
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[10] B. Marcinia, The Growth of Some Aromatic Hydrocarbons Single Crystals from the Melt. Cryst. Res. Technol. 26 (1991) 855-862.
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[11] J.N. Sherwood, S.J. Thomson, Growth of single crystals of anthracene. J. Sci. Instrum. 37
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K.S. Shah, Bridgman growth of LaBr3:Ce and LaCl3:Ce crystals for high-resolution gamma-ray
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spectrometers. J. Cryst. Growth 287 (2006) 239–242. [13] R. Ramesh Babua, N. Balamurugan, N. Vijayan, R. Gopalakrishnan, G. Bhagavannarayan, P.
Ramasamy,
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vertical Bridgman technique. J. Cryst. Growth 285 (2005) 649–660. [14] S. Karuppusamy, K. Dinesh Babu, V. Nirmal Kumar, R. Gopalakrishnan, Thermal kinetic
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and dielectric parameters of acenaphthene crystal grown by vertical Bridgman technique. Appl. Phys. A 122 (2016) 498.
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[15] K. Sankaranarayanan, P. Ramasamy, Unidirectional seeded single crystal growth from solution of benzophenone. J. Cryst. Growth 280 (2005) 467–473. [16] G. Socrates, Infrared Characteristic Group Frequencies, Wiley-Interscience: Chichester, (1980). [17] L. Colombo, Infrared Spectra in Polarized Light of Acenaphthene Crystals and Assignment of Molecular Vibrations. J. Chem. Phys. 39 (1963) 1942.