Optik 125 (2014) 4402–4404
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Synthesis, growth, optical properties of a new metalic crystal S. Dheivamalar a,∗ , G. Anuradha b , V. Silambarasan c a
Department of Physics, Government Arts College for Women, Pudukottai, Tamil Nadu, India Department of Physics, Kunthavai Naachiyar Government Arts College (W), Thanjavur, Tamil Nadu, India c CAS in Crystallography & Biophysics, University of Madras, Guindy Campus, Chennai, 600 025, India b
a r t i c l e
i n f o
Article history: Received 11 August 2013 Accepted 20 February 2014 Keywords: Ptc Xrd Ftir Impedence Microhardness
a b s t r a c t The present fascinating field of research is synthesize, grow, and characterize NLO crystals. Optically good quality single crystals of Potassium Thiourea Carbonate (PTC) crystals have been grown by a slow evaporation method. The grown crystals were characterized by powder X-ray diffraction (XRD), FTIR, UV–vis, micro hardness, impedence analysis. FTIR studies confirm the functional groups present in the grown crystal. The UV–vis spectrum showed the transmitting ability of the crystals in the visible region. Vickers micro hardness is showed the hardness of the material. The impedence of the crystal for various frequencies is also reported. © 2014 Published by Elsevier GmbH.
1. Introduction Material with large second order optical non-linearities find wide applications in the field of laser technology, laser communication, data storage technology and opto electronic technologies [1–3]. Single crystals of the inorganic complex of thiourea have evoked much interest in the last few years due to their non-linear optical properties [4–7]. Thiourea molecules are an interesting inorganic matrix modifier due to its large dipole moment and its ability to form and extensive network of hydrogen bond [8]. The centrosymmetric thiourea molecule, when combine with inorganic salt yield noncentrosymmetric complexes, which has the non-linear optical properties [9]. Hence, in several years, search is focused on new types NLO materials which combined the advantages of organic and inorganic salts called semiorganic materials. Two types of semiorganic material include organic and inorganic salts and metals organic co-ordination complex [10–15]. The nonlinear optical properties of some of the complexes of thiourea such as bis (thiourea) cadmium chloride (BTCC), bis (thiourea) zinc chloride (BTZC), tris(thiourea) zinc sulphate (ZTS), tris (thiourea) cadmium sulphate (CTS), potassium thiourea bromide have gained significant attention in the last few years [16]. Because both organic components in it contribute specifically to the process of second harmonic generation. In the present study, thiourea is combined
∗ Corresponding author. E-mail addresses:
[email protected] (S. Dheivamalar),
[email protected] (V. Silambarasan). http://dx.doi.org/10.1016/j.ijleo.2014.02.040 0030-4026/© 2014 Published by Elsevier GmbH.
with potassium carbonate to form a new semi-organic non linear optical material. In this paper, we report the growth of single crystals of Potassium Thiourea Carbonate (PTC) by slow evaporation method and characterization by powder X-ray diffraction (XRD), Fourier transform infrared (FTIR) studies, UV studies, microhardness studies and impedence.
2. Experimental 2.1. Synthesis and crystal growth Raw materials for the growth of Potassium Thiourea Carbonate (PTC) was synthesized by mixing aqueous solution of Potassium Carbonate and Thiourea in the 1:1. Since thiourea has the coordinating capacity to form different phases of metal thiourea complexes, the mixture of the reactants had to be stirred well to avoid coprecipitation of multiple phases. The product was purified by repeated crystallization before it is used for the growth of PTC crystals. The solvent evaporation technique was used to grow single crystals of PTC in aqueous solution. Crystals of PTC, which are optically transparent and free from macro-defects obtained by the self nucleation of the saturated solution, are used as seed crystals. subsequently, single crystals of PTC were grown using these seed crystals from saturated aqueous solution of PTC by slow evaporation at room temperature. Colourless perfect crystals were obtained. The crystals were optically transparent is shown in Fig. 1.
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4403
Table 1 Assignments of IR bands (cm−1 ).
Fig. 1. Photograph of PTC crystal.
3. Characterization The grown crystals have been analyzed by different characterization techniques. Powder X-ray diffraction pattern was recorded using the RICHE SEIFERT SH-37/80 diffractometer. The FTIR spectrum was recorded using BRUKER IFS-66 V FT-IR spectrometer with KBr pellet technique for the range 4000–400 cm−1 . The optical properties of the crystals were examined between 200 and 1200 nm LAMBDA-35 UV-Vis spectrometer. Vickers microhardness measurement studies where carried out using a using a MITUTOYO MODEL HM 112 hardness tester. Microhardness testing is one of the best methods of understanding the mechanical properties of material. 3.1. Powder X-ray diffraction Powder X-ray diffraction pattern was recorded using the RICHE SEIFERT SH-37/80 diffractometer. The purified samples of the grown crystals have been crushed to a uniform fine powder and subjected to a powder X-ray diffraction. The k˛ radiations ˚ from a copper target were used. The specimen ( = 1.540598 A) was scanned in the reflectionmode in the 2 range 10–70◦ . It was found that the intense peak at 2 = 25◦ . The sharp peaks found in spectra shows good crystallinity of the grown crystals. The well defined Bragg’s peaks at specific 2 angles show the crystallinity. The corresponding XRD data are shown in Fig. 2. 3.2. Vibrational analysis The vibrational analysis of the grown crystal was done using FTIR spectrum. The FTIR spectrum was recorded in the range of 400–4000 cm−1 using BRUKER IFS-66 V FT-IR spectrometer and is shown in Fig. 2. A number of reports are available on the absorption studies of thiourea [17,18]. Thiourea exhibits characteristic peaks at 1618, 1471, 1412, 1087 and at 730 cm−1 . The 1618 cm−1 is due to the deformation of NH2 and that at 1087 is due to the rocking of NH2 . The strong band at1471 cm−1 and those at 1412 cm−1
Thiourea
PTC
Assignments
730 1087 1412 1471 3167 3280 3376
724.70 1090.97 1386.47 1465.14 3159.84 3253.93 3361.50
␦(C S) (NH2 ) s(C S) (N C N) s(NH2 ) s(NH2 ) s(NH2 )
and 730 cm−1 are attributed to asymmetric stretching of CN, and symmetric stretching of CS, respectively. The standard IR band frequencies of pure thiourea and that obtained for PTC crystal are compared in Table 1, along with their assignments. Thiourea could form metal complexes by coordinate bonds through sulphur or nitrogen. If the bonding is through sulphur, there will be a decrease in the CS stretching frequency and an increase in the CN stretching frequency. The reverse happens if it is through nitrogen. The observations suggest that the complex formation was established through sulphur–metal bonds. In the higher wave number region, 3100 –3500 cm−1 , there are several bonds, which are characteristics of NH2 stretching vibrations of numerous hydrogen bonds crystal structure and is shown in Fig. 3. 3.3. UV–vis spectral analysis UV–vis spectral analysis has been measured using LAMBDA-35 UV-Vis spectrometer in the wavelength range of 200–1200 nm. The UV spectral studies were very important for any NLO materials because NLO materials must have a wide transparency window for optical applications. The UV–vis spectrum gives limited information about the structure of the molecule because the absorption of UV and visible light involves promotion of the electron in and orbital from the ground state to higher energy states. The UV cut-off wavelength of PTC was 250 nm. The recorded optical absorption spectrum was shown in Fig. 4. There was no absorption of light in the 350–1000 nm. The transmittance windows in the visible region and IR region enabled good optical transmission of the second Harmonic frequencies of Nd:YAG laser. 3.4. Vickers hardness test Vickers microhardness measurement studies were also carried out using a MITUTOYO MODEL HM112 hardness tester. The best general definition that can be given is that hardness is a measure of the resistance deformation. Microhardness indentation test is used to characterize the hardness is non-destructive testing method to determine the mechanical behaviour of the materials. It is a resistance against plastic deformation. By definition the indentation 101.4 100 95 90 85
Intensity in counts
2000
80 %T
75 70 65
1000
60 55 48.8
0 10
20
30
40 2-Theta
Fig. 2. Powder XRD of PTC crystals.
50
60
3983.2
3600
3200
2800
2400
2000
1800
1600
1400
1200
Wave Number (cm-1)
Fig. 3. FTIR of PTC crystals.
1000
800
600
416.8
4404
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1 M, the crystal shows the minimum impedence at 5 kHz. It is given in Fig. 6. So, in the lower frequency the impedence is high, in higher frequency the impedence is low. The values for various frequencies are shown in Fig. 6.
1.4
1.2
1
4. Conclusion
O.D
0.8
0.6
0.4
0.2
1500 1459 1418 1377 1336 1295 1254 1213 1172 1131 1090 1049 1008 967 926 885 844 803 762 721 680 639 598 557 516 475 434 393 352 311 270
0
Wavelength (nm)
Fig. 4. UV–vis spectrum of PTC crystal. 30
Acknowledgement The authors acknowledge SASTRA University, Thanjavur, for providing lab facility.
25 20
HV
Good optical quality Crystals of potassium Thiourea Carbonate [PTC] were grown by slow evaporation method. The FT-IR spectrum reveals that the various functional groups present in the grown crystal. PTC has a wide transparency window from 350 nm to 1000 nm which highlights their prospects of applications as NLO materials. The Vicker’s hardness was calculated in order to understand the mechanical stability of the grown crystals. The impedence studies shows the resistivity of the grown crystal.
References
15 10 5 0
25
50
100
Load
Fig. 5. Load vs hardness of PTC crystals.
Fig. 6. Impedence of PTC crystals.
hardness is the ratio of the applied load to the surface area generated due to indentation. The hardness number can be evaluated by the knowledge of the load applied and the cross-sectional area of the depth of impression. Smooth surfaces of as-grown PTC crystal were chosen for the investigation. The Vicker’s hardness value is calculated from the formula HV = 1.8544 × (p/d2 ) kg/mm2 . Where p is the applied load in kg and d is the average diagonal length in millimetres of the indented impressions. In the present study, the loads applied 25, 50 and 100 g for each 25 and 50 g radial cracks were obtained for some indentation. Plot of load (p) against Vickers’s hardness is shown in Fig. 5. It was observed that the microhardness number increases with increase of load in the given planes which is in agreement with the normal indentation size effect (ISE) observed for other NLO crystals. 3.5. Impedence studies The impedence studies shows that when the frequency increases the impedence decreases. At particular value of frequency
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