ISRN Condensed Matter Physics

Volume 2014 (2014), Article ID 678567, 5 pages

http://dx.doi.org/10.1155/2014/678567

Research Article

Growth and Analysis of NSH and KMNSH Crystals by Slow Evaporation Technique

V. Masilamani, J. Shanthi, and V. Sheelarani

Department of Physics, Avinashilingam Institute for Home Science and Higher Education for Women, Coimbatore 641043, India

Received 18 December 2013; Accepted 12 February 2014; Published 24 March 2014

Academic Editors: H. D. Hochheimer, S. Krukowski, and V. Stephanovich

Copyright © 2014 V. Masilamani et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract.

Nickel sulphate hexahydrate (NSH) and potassium magnesium nickel sulphate hexahydrate (KMNSH) single crystals were grown by slow evaporation method. The grown NSH crystal was found to crystallize in tetragonal system with space group P4₁ 2₁ 2 and KMNSH in monoclinic system with space group P₁2₁/c. The optical band gap energies of the grown crystals using UV-Vis spectral results for the doped and undoped NSH crystals were calculated. The presence of various functional groups in the crystal was identified by FTIR analysis. The thermal behaviour of the grown crystal has been studied by TGA/DTA analysis.

1. Introduction

Ultraviolet (UV) light filters are used in missile approach warning systems which locate and track UV energy emitting sources and are used as sensors for helicopters or transport aircraft. Commercially available nickel sulphate hexahydrate crystals are widely used as sensors. The biggest problem for these sensors arises due to low thermal stability of nickel sulphate crystals which is 76°C. The potassium nickel sulphate hexahydrate (KNSH) crystals which have higher thermal stability as 97°C are used in missile approach warning systems and as sensors in spaceships [1, 2]. Several other crystals such as cesium nickel sulphate hexahydrate (CNSH) [3], iron nickel sulphate twelvehydrate (FNSH) [4], rubidium nickel sulphate hexahydrate (RNSH) [5], and ammonium cobalt nickel sulphate hexahydrate (ACNSH) [6] are also reported as UV filter materials. Similar research work carried out on potassium sulphate [7, 8], potassium cobalt nickel sulphate hexahydrate (KCNSH) [9, 10], bis thiourea magnesium sulphate (BTMS) [11], and magnesium sulphate heptahydrate [12] crystals is also reported. In the search of newer crystalline materials with better filter transmission property and higher thermal stability, the growth of potassium magnesium nickel sulphate crystal has been carried out in this research work.

2. Experimental Procedure

NiSO₄·6H₂O, K₂SO4, and MgSO₄·7H₂O of AR grade (purity > 98.0%) were used. Approximate molar ratio of materials was taken using digital balance and dissolved in double distilled water. The solution of pH value 5 was stirred for nearly 2 hourswith magnetic stirrer to ensure homogeneity. Heating the solution to 60°C is carried out to promote the reaction and then is cooled to 40°C slowly. An abduction is formed according to the reaction given as follows:

The homogenised solution was filtered twice using Whatman filter paper number 1 and then allowed to evaporate at 40°C temperature using a constant temperature bath. Then the solution is transferred to the petridish and allowed to evaporate without disturbance. Optically good quality NSH, KMNSH single crystals have been grown within a period of 11 days and 8 days, respectively, and are shown in Figures 1(a) and 1(b).

(a)

(b)

Figure 1: (a) Photography of the grown NSH crystal and (b) photography of grown KMNSH crystal.

3. Results and Discussion

X-ray diffraction studies of grown crystal were carried out with PANalytical X-ray diffractometer using CuKα (a.u.) radiation. The FTIR spectrum of both crystals was recorded in the range 400–4000 cm⁻¹ using SHIMADZU IR AFFINITY-1 spectrometer by KBr pellet technique. Optical properties of the crystals were studied using UV-Visible spectrophotometer. Thermal analysis for the grown crystals was also carried out.

3.1. Powder X-Ray Diffraction

The grown NSH and KMNSH crystals were crushed to a uniform fine powder and subjected to powder X-ray diffractometer to identify the reflecting planes. Lattice parameters obtained from XRD data are listed in Table 1. It is observed that structure of KMNSH is monoclinic with space group P₁2₁/c and NSH is tetragonal with space group P4₁ 2₁ 2. The lattice parameters of KMNSH crystal agree well with the reported value of Vanitha et al. [13]. The powder XRD pattern of the grown crystals is shown in Figures 2(a) and 2(b), respectively.

Table 1: Lattice parameters of NSH and KMNSH crystals.

Parameter
NSH crystal
KMNSH crystal

Crystal system
Tetragonal
Monoclinic

Space group ()
P4₁ 2₁ 2,
P₁2₁/c,

a (A°)
6.6787
6.137

b (A°)
6.6787
12.190

c (A°)
18.2990
9.005

90°
90°

90°
105°

90°
90°

(a)

(b)

Figure 2: (a) Powder X-diffraction of NSH crystal and (b) powder X-diffraction of KMNSH crystal.

3.2. UV-Vis Spectroscopy

The UV-Visible transmittance spectrum of the grown crystal was carried out using UV-1700 series UV-Vis spectrophotometer in the wavelength range from 200 nm to 800 nm. The UV-Visible spectra of NSH and KMNSH crystals are shown in Figures 3(a) and 3(b), respectively. In general majority of the crystals show continual optical transmission from UV to near IR wavelength range. Only very few crystals show discontinuity. For both NSH and KMNSH crystal transmission efficiency is observed in a small narrow range. The discontinuous spectral characteristics can be due to the absorption of hydrated transition metal ions Ni (H₂O)₆. The absorption spectra of NSH and KMNSH show lower cutoff wavelength around 228 nm and 226 nm, respectively. Similar result has been reported for thiourea potassium magnesium sulphate crystal [14] also. Using the formula , optical band gap energy values were found as 3.405 eV and 3.435 eV for NSH and KMNSH crystals, respectively.

(a)

(b)

Figure 3: (a) UV transmittance spectrum for NSH crystal and (b) UV transmittance spectrum for KMNSH crystal.

3.3. FTIR Spectroscopy

The FTIR spectroscopy studies are used to analyze qualitatively the presence of functional groups in the synthesized crystal. The spectrum was recorded in the wavelength range 400–4000 cm⁻¹. The stretching vibration of the water molecule is observed for KMNSH at 3162 cm⁻¹. The medium broadband noticed around 1581 cm⁻¹ is assigned to the vibrational mode of water molecules. The band observed at 763 cm⁻¹ is assigned to liberational mode of water molecules. In general free ion has 4 fundamental vibrations, namely, a nondegenerate mode at 987 cm⁻¹ and a doubly degenerated mode and a triply degenerated vibration at 1149 cm⁻¹ and 632 cm⁻¹, respectively, [15]. FTIR studies also confirm the presence of water molecule and sulphate. The FTIR Spectrum of NSH and KMNSH is shown in Figures 4(a) and 4(b), respectively. The observed frequencies and their assignments are listed in Table 2.

Table 2: Assignment of vibrational frequencies in the FTIR spectra of NSH and KMNSH crystal.

NSH crystal
KMNSH crystal
Assignment

3162
OH stretching, water trace

2245
2229
Ni–S stretching

1627

O–H symmetric stretching

1581
H₂O stretching

1149
1141
SO₄ asymmetric stretching

1087
SO₄ deformation

987
979
O–H bends

763
763
O–H op bending

632
632
Deformation of asymmetric SO₄

462
462
Deformation of strong SO₄

(a)

(b)

Figure 4: (a) FTIR spectrum for NSH crystal and (b) FTIR spectrum for KMNSH crystal.

3.4. TGA/DTA

The decomposition, phase transition, melting point, and weight loss of the grown crystal were determined by thermogravimetric analysis (TGA). The thermogram of NSH and KMNSH was recorded between 50°C and 400°C, using Perkin Elmer TGA\DTA instrument at a heating rate of 10°C/min in the nitrogen atmosphere. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) of the crystal were carried out to understand the thermal stability of the crystal because it is an important factor for crystals that are to be used as Ultraviolet light filter. The thermogram of the NSH and KMNSH indicates a major weight loss at temperatures 76°C and 94°C as shown in Figures 5(a) and 5(b), respectively. It may be due to the expulsion of physically adsorbed water molecules. The grown potassium magnesium nickel sulphate hexahydrate crystals have higher thermal stability up to 94°C and hence are used in missile approach warning systems and as sensors in spaceships. The dehydration temperature of the potassium magnesium nickel sulphate hexahydrate (KMNSH) is more than pure nickel sulphate hexahydrate by 18°C. Youping He et al. [16] have also observed dehydration temperature of potassium nickel sulphate hexahydrate (KNSH) crystal to be higher than that of nickel sulphate hexahydrate (NSH) by 24°C. DTA curves of both pure NSH and KMNSH crystal show an endothermic dip at 107°C and 136°C, respectively. This endothermic dip represents the decomposition of crystals.

(a)

(b)

Figure 5: (a) TGA/DTA analysis of NSH crystal and (b) TGA/DTA analysis of KMNSH crystal.

4. Conclusion

Good quality single crystals of NSH and KMNSH have been grown by slow evaporation solution growth technique. The crystalline nature of the grown crystals was verified by powder X-ray diffraction analysis. The crystal system of NSH and KMNSH is tetragonal and monoclinic, respectively. The FTIR analysis confirmed the presence of water molecules and sulphate. The UV-Visible absorption spectra of the NSH and KMNSH crystals show lower cutoff wavelength around 226 nm and 228 nm, respectively. Thermogravimetric analysis reveals that both grown crystals remain thermally stable up to 76°C and 94°C, respectively. From TGA studies, it is confirmed that there are six water molecules of crystallization. Hence, the grown KMNSH crystal is a potential material for Ultraviolet light filter.

Conflict of Interests

The authors declare that there is no conflict of interests regarding the publication of this paper.

References

N. B. Singh, W. D. Partlow, S. Strauch, A. M. Stewart, J. F. Jackovitz, and D. W. Coffey, “Crystals for ultraviolet light filters,” U. S. Patent 5788765, 1998.

Y. He, J. Chen, G. Su, X. Zhuang, G. Lee, and R. Jiang, “Growth of potassium nickel sulfate hexahydrate (KNSH) crystal and its characterization,” Journal of Crystal Growth, vol. 233, no. 4, pp. 809–812, 2001.

E. B. Rudneva, V. L. Mamomenova, L. F. Malakhova, A. É. Voloshin, and T. N. Smirnova, “Cs₂Ni(SO₄)₂ · 6H₂O (CNSH) crystal: growth and some properties,” Crystallography Reports, vol. 51, no. 2, pp. 344–347, 2006.

G. Su, X. Zhuang, Y. He et al., “A new single crystal of iron nickel sulfate twelvehydrate (FNSH) used as optical bandpass filters,” Journal of Crystal Growth, vol. 243, no. 2, pp. 238–242, 2002.

X. Wang, X. Zhuang, G. Su, and Y. He, “A new ultraviolet filter: Rb₂Ni (SO₄)₂· 6H₂O (RNSH) single crystal,” Optical Materials, vol. 31, no. 2, pp. 233–236, 2008.

G. Su, X. Zhuang, Y. He, and G. Zheng, “A new crystal of ammonium cobalt nickel sulfate hexahydrate for UV light band-pass filter,” Optical Materials, vol. 30, no. 6, pp. 916–919, 2008.

S. Radhika, C. M. Padma, S. Ramalingom, and T. Chithambara Thanu, “Growth, optical, thermal, mechanical and dielectric studies of potassium sulphate crystals doped with urea,” Archives of Physics Research, vol. 4, no. 1, pp. 49–59, 2013.

S. Bin Anooz, R. Bertram, and D. Klimm, “The solid state phase transformation of potassium sulfate,” Solid State Communications, vol. 141, no. 9, pp. 497–501, 2007.

X. X. Zhang, G. B. Su, Y. P. He, and G. Z. Zheng, “Growth and characterisation of potassium cobalt nickel sulfate hexahydrate for UV light filters,” Crystal Research and Technology, vol. 41, no. 10, pp. 1031–1035, 2006.

I. Polovynko, S. Rykhlyuk, I. Karbovnyk, et al., “A new method of growing mixed crystals and their spectral investigation,” Journal of Crystal Growth, vol. 311, no. 23-24, pp. 4704–4707, 2009.

V. Krishnakumar, C. Ramachandraraja, and R. S. Sundararajan, “Crystal growth and vibrational spectroscopic studies of the semiorganic non-linear optical crystal—bisthiourea magnesium sulphate,” Spectrochimica Acta—Part A: Molecular and Biomolecular Spectroscopy, vol. 68, no. 1, pp. 113–116, 2007.

S. Karan and S. P. S. Gupta, “Vickers microhardness studies on solution-grown single crystals of magnesium sulphate hepta-hydrate,” Materials Science and Engineering A, vol. 398, no. 1-2, pp. 198–203, 2005.

D. Vanitha, S. Asath Bahadur, and Athimoolam, “Crystal growth and characterization of potassium magnesium nickel sulphate hexahydrate as UV filter,” Archives of Applied Science Research, vol. 4, no. 6, pp. 2378–2381, 2012.

A. Ruby and A. C. Raj, “Growth and characterization of a new metal-organic nonlinear optical thiourea potassium magnesium sulphate single crystals,” Archives of Physics Research, vol. 3, no. 2, pp. 130–137, 2012.

G. Sivanesan, P. Kolandaivel, and S. Selvasekarapaandian, “Laser Raman and FT-IR studies of pure and Zn-doped TGS,” Materials Chemistry and Physics, vol. 34, no. 1, pp. 73–77, 1993.

Y. He, J. Chen, G. Su, X. Zhuang, G. Lee, and R. Jiang, “Growth of potassium nickel sulfate hexahydrate (KNSH) crystal and its characterization,” Journal of Crystal Growth, vol. 233, no. 4, pp. 809–812, 2001.