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Synchronized effect of Ca2+ ion doping concentration on structural, UV–vis and second harmonic generation efficiency of zinc thiourea chloride (ZTC) crystal: An interesting comparative study
Accepted Manuscript Title: Synchronized effect of rising Ca2+ ion doping concentration on structural, UV–vis and second harmonic generation efficiency of zinc thiourea chloride crystal: An interesting comparative study Authors: V.G. Pahurkar, Mohd Anis, M.I. Baig, S.P. Ramteke, B. Babu, G.G. Muley PII: DOI: Reference:
S0030-4026(17)30690-3 http://dx.doi.org/doi:10.1016/j.ijleo.2017.06.023 IJLEO 59284
To appear in: Received date: Accepted date:
6-3-2017 6-6-2017
Please cite this article as: {http://dx.doi.org/ 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.
Synchronized effect of rising Ca2+ ion doping concentration on structural, UV-visible and second harmonic generation efficiency of zinc thiourea chloride crystal: An interesting comparative study V.G. Pahurkara, Mohd Anisa*, M.I. Baigb, S.P. Ramtekea, B. Babuc, G.G. Muleya* a
Department of Physics, Sant Gadge Baba Amravati University, Amravati-444602, Maharashtra, India
b
c
Prof Ram Meghe College of Engineering and Management, Amravati-444701, Maharashtra, India
Department of Physics, Sri Ramakrishna Mission Vidyalaya College of Arts and Science, Coimbatore-641020,
Tamilnadu, India Abstract In present investigation attention has been focused to explore the synchronic effect of increasing concentration of metallic impurity Ca2+ on structural, linear and nonlinear optical properties of zinc thiourea chloride (ZTC) crystal. The pure and Ca2+ (1wt%, 3wt%, 5wt%) ion doped ZTC crystals have been grown by slow solvent evaporation technique. The Fourier transform infrared spectral analysis has been employed to confirm the functional groups of grown crystals. The crystalline phase and structural parameters of pure and Ca2+ ion doped ZTC crystal has been comparatively examined by means of powder X-ray diffraction analysis. The influence of Ca2+ ion doping on optical transparency of ZTC crystal has been ascertained in the range of 190-1000 nm by means of UV-visible spectral analysis. The Kurtz-Perry test has been employed to confirm the second order nonlinear optical behavior of grown crystals. The change in value of second harmonic generation (SHG) efficiency of ZTC crystal attributed by each selected concentrations of metal dopant Ca2+ ion has been evaluated. The distinct application of grown crystals for device fabrication has been discussed in light of obtained results. Keywords: Crystal growth; Optical studies; Nonlinear optical materials; X-ray diffraction 1.
Introduction
Nonlinear optics is found to be the frontier and rapidly growing field of research which involves comprehensive study of all nonlinear optical effects desirable for tailoring/designing telecommunication, optoelectronics and photonics devices [1-2]. In current developing scenario of nonlinear optical crystals organometallic complexes has fascinated researchers worldwide [3]. The thiourea metal complexes outstand as promising organometallic Correspondence: Mohd Anis ([email protected]), G.G. Muley ([email protected])
1
materials which seek huge attention owing to large structural diversity and versatile characteristic properties [4]. In the extended family of thiourea metal complex crystals zinc thiourea chloride (ZTC) is found to be a unique and bewildering crystal. The single crystal of ZTC is noncentrosymmetric attributing orthorhombic structure, Pn21a space group and anisotropic behavior. Investigation on ZTC crystal has been attempted by many researcher groups to explore its quantum, optical, electrical and mechanical properties [5-8]. In past few decades it is observed that the target of gaining enhancement in performance of inherent qualities of ZTC crystal has been achieved by doping various organic as well as inorganic additives. The organic additives such as l-arginine, glycine and l-cysteine has shown significant enhancement in optical properties of ZTC crystal [912]. The doping of metallic additives such as potassium, lithium, sodium, magnesium, cadmium, copper, barium and neodymium has shown remarkable effect of different properties of ZTC crystal [13-20]. As metallic additives show strong impetus for enhancing the characteristic features of ZTC crystal therefore, our research group very firstly reports the doping effect of increasing concentration of Ca2+ ion on linear-nonlinear optical properties of ZTC crystal. The effect of different concentration of Ca2+ ion on spectral, structural and optical properties of ZTC crystal has been accomplished by means of Fourier transform infrared, powder X-ray diffraction, UV-visible and Kurtz-Perry SHG efficiency characterization techniques. 2.
Experimental procedure
The ZTC complex was prepared by dissolving the AR grade zinc chloride and thiourea in double distilled water in a stiochiometric ratio of 1:2 respectively. The purity of ZTC crystal complex has been achieved by process of successive recrystallisation. In order to add three different wt% of Ca2+ ion the 1wt%, 3wt% and 5wt% of calcium chloride salt was precisely measured and added to the ZTC crystal complex prepared in three different beakers. These solutions were allowed to stir for four hours on a magnetic stirrer so as to achieve homogeneous mixing of Ca2+ ion in ZTC crystal complex. The respective Ca2+ ion mixed ZTC crystals were filtered in a rinsed beaker and kept for slow evaporation in a constant temperature bath maintained at 35 oC. The pure and Ca2+ (1wt%, 3wt% and 5wt%) ion mixed ZTC single crystals were grown in a period of 22 days is shown in Fig. 1.
2
3.
Results and discussion The qualitative analysis of pure and Ca2+ (1wt%, 3wt% and 5wt%) ion mixed ZTC crystal has been
identified by means of Fourier transform infrared (FTIR) analysis. The FTIR spectrum of grown single crystals has been recorded (Fig. 2) in the range of 600-4000 cm-1 using the JASCO 410 spectrophotometer by KBr pellet technique. The absorption peaks attributed by C=S bond stretching is evident at 715 and 1402 cm-1. The C-N bond stretching vibration is contributed at wavenumber 1024 and 1533 cm-1. The mild absorption peak observed at 1092 cm-1 corresponds to C-C-N bond stretching vibration. The NH2 bending vibration is evident at 1620 cm1
. The C-H symmetric and antisymmetric stretching vibration is attributed at 2856 and 2914 cm-1. The
antisymmetric stretching of NH3+ groups is evident at 3180 cm-1. The absorption peak observed at 3289 cm-1 corresponds to N-H bond stretching vibration. The associated N-H bond stretching vibration in grown crystals is evident in the range of 3400-4000 cm-1 [21]. The powder X-ray diffraction analysis of pure and Ca2+ mixed ZTC crystal has been carried out using the Rigaku Miniflex II X-ray diffractometer. The diffraction patterns of grown crystals have been recorded at a scan rate of 0.02 o/sec within the 2θ range of 10-70o. The addition of dopant facilitates variation in intensity and shift in 2θ position of identified diffraction peaks of host material which evolves as a consequence of variation in excess growth of specific plane and slight change in cell parameters [22-23]. In present analysis the recorded diffraction peaks are shown in Fig. 3. It reveals that the sharpness of diffraction peak is high with 1wt% and 5wt% concentration of Ca2+ while it is lesser for 3wt% doping concentration of Ca2+ ion. The decrease in intensity of diffraction pattern might have been occurred due to structural deformation inculcated by presence of 3wt% of dopant Ca2+ ion in ZTC crystal. The less full width half maxima and the sharpness observed in diffraction peak due to presence of Ca2+ ion (1wt% and 5wt%) confirms that the grown crystal possesses enhanced crystalline quality and lesser grain boundaries [24-26]. As the sharpness of diffraction peak increases with rise in concentration of additive, this confirms Ca2+ ion as potential additive to achieve good quality ZTC crystals with selected doping concentration. The recorded PXRD patterns were indexed using the PowderX software and the evaluated cell parameters are discussed in table 1.
3
The optical spectrum is an imprint of the response of the electronic transitions occurring in specific energy states to the incident optical signal. The optical transmittance of a crystal medium is characteristic feature which is driven by crystal orientation, defect centres (line, voids, inclusion, striations) and optically active functional groups [27-30]. In present analysis the UV-visible transmittance spectrum of pure and Ca2+ ion doped ZTC crystals have been recorded in the range of 200-1000 nm using the spectrophotometer (Black-C-SR Stellar Net). The spectrum shown in Fig. 4a reveals that the optical transmittance of 1wt% and 5wt% Ca2+ ion doped ZTC crystal is significantly higher than pure ZTC crystal. It is observed that the offered percentage transmittance of 2 mm crystal is 48%, 68%, 74% for pure, 1wt% and 5wt% Ca2+ ion doped ZTC. It is noteworthy that the optical transmittance of 3wt% Ca2+ ion doped ZTC crystal is 41% which is marginally lower as compared to ZTC crystal. It can be ascertained that the less concentration of defects resulted the large enhancement in transmittance of 1wt% and 5wt% Ca2+ ion doped ZTC crystal however, the decrease in transmittance observed in case of 3wt% Ca2+ ion doped ZTC crystal might have been attributed due to relatively increased ratio of defects. The crystals with high optical transparency are demanded for designing optical elements for UV-tunable lasers and SHG devices [31-32]. Amongst the studied crystals the 5wt% Ca2+ ion doped ZTC crystal with maximum transmittance holds the potential candidature for device applications. The phenomenon of frequency doubling in grown crystal materials has been investigated using the Kurtz-Perry powder SHG technique [33]. In present analysis the Q-switched mode Nd:YAG laser (1064 nm, 6 ns, 10 Hz) has been used for SHG efficiency test. The good quality pure Ca2+ ion doped ZTC crystals were crushed in micro-granules of even size and sieved in quartz cavity. The samples were irradiated with the Gaussian filtered beam of Nd:YAG laser and the frequency doubling phenomenon was confirmed as we see the bright green light at the output window. The SHG signal was recorded through the optical fiber assisted spectrophotometer interfaced with computer. The recorded SHG output intensity of each sample is shown in Fig. 4b. It is observed that the SHG efficiency of 1wt% and 5wt% of Ca2+ ion doped ZTC crystal is significantly higher than that of ZTC crystal material. It is interesting to note that the 3wt% of Ca2+ ion doped ZTC crystal has low SHG response as compared to ZTC. The decrease in SHG response might have been occurred due to deformation in crystal structure [16, 34] which is evident from PXRD pattern also the optical transparency is 4
minimum amongst the studied crystal. The SHG efficiency of grown crystals has been systematically discussed in table 2. The study thus confirms that the doped ZTC crystals with high SHG response can be utilized for laser frequency conversion and NLO device applications [35-36]. 4.
Conclusion
The pure, 1wt%, 3wt% and 5wt% Ca2+ ion doped ZTC crystals have been grown at room temperature by slow solvent evaporation technique. The functional groups of pure and doped ZTC crystals have been successfully identified by means of FTIR spectrum analysis. The PXRD analysis confirmed the orthorhombic crystal structure and slight change in cell parameters of doped ZTC crystals. The increase in sharpness of intensity in PXRD pattern revealed that the crystalline quality of ZTC increases with rise in concentration of dopant except for 3wt%. The optical transparency investigated in range of 200-1000 nm showed that the transparency of 1wt% and 5wt% Ca2+ ion doped ZTC crystal is higher than pure ZTC crystal. The doping 3wt% of Ca2+ resulted to fall in transmittance of ZTC crystal by 7%. In Kurtz-Perry test the SHG efficiency of 1wt% and 5wt% Ca2+ ion doped ZTC crystal is found to be 1.19 and 1.49 times greater than ZTC crystal respectively. The SHG efficiency of 5wt% Ca2+ ion doped ZTC crystal is highest amongst the studied crystals, which is found to be 1.19 times that of KDP and 1.49 times that of ZTC crystal. The SHG efficiency of 3wt% Ca2+ ion doped ZTC crystal is found to be 0.71 and 0.89 times that of KDP and ZTC respectively. The analysis of crystalline quality, optical transparency and SHG efficiency altogether showed similar effect for respective concentration of dopant confirming the synchronized effect of dopant on independent feature of ZTC crystal studied in present investigation. The studies confirm that the 5wt% Ca2+ ion doped ZTC crystal with excellent crystalline nature, high transmittance and high conversion efficiency is most suitable material for distinct NLO device applications. Acknowledgements Author Mohd Anis is thankful to University Grants Comission, New Delhi, India for awarding the Maulana Azad National Fellowship (F1-17.1/2015-16/MANF-2015-17-MAH-68193). DST-SERB India is acknowledged for sanctioning the grant (SB/EMEB-328/2013). References 5
[1] Yuanzuo Li, Jing Li, Runzhou Su, Jingang Cui Opt. Mater. 36 (2013) 437-443 [2] Zhi-Bin Cai, Li-Fen Liu, Mao Zhou Opt. Mater. 35 (2013) 1481-1486 [3] M.D. Zidan, M.M. Al-Ktaifani, A. Allahhama Opt. Laser Technol. 90 (2017) 174-178 [4] N.R. Rajagopalan, P. Krishnamoorthy, K. Jayamoorthy Opt. Laser Technol. 89 (2017) 6-15 [5] R. Rajasekaran, P.M. Ushasree, R. Jayavel, P. Ramasamy J. Cryst. Growth 229 (2001) 563-567 [6] Sagadevan Suresh Optik 125 (2014) 1223-1226 [7] R. Rajasekaran, R.M. Kumar, R. Jayavel, P. Ramasamy J. Cryst. Growth 252 (2003) 317-327 [8] H. Pir, N. Gunay, D. Avc, Y. Atalay Indian J. Phys. 86 (2012) 1049-1063 [9] Mohd Anis, R.N. Shaikh, M.D. Shirsat, S.S. Hussaini Opt. Laser Technol. 60 (2014) 124-129 [10] M. Anis, G.G. Muley, G. Rabbani, M.D. Shirsat, S.S. Hussaini Mater. Technol. Adv. Perform. Mater. 30 (2015) 129-133 [11] J. Felicita Vimala, J. Thomas Joseph Prakash Elixir Cryst. Growth 56 (2013) 13355-13358 [12] Mohd Anis, S.S. Hussaini, M.D. Shirsat, G.G. Muley Mater. Sci. Poland 34 (2016) 548-554 [13] L. Ruby Nirmala, J. Thomas Joseph Prakash Spectrochem. Acta A 102 (2013) 297-300 [14] K. Muthu, G. Bhagavannarayana, S.P. Meenakshisundaram, S.C. Mojumdar J. Therm. Anal. Calorim. 108 (2012) 927-932 [15] L. Ruby Nirmala, J. Thomas Joseph Prakash Spectrochem. Acta A 110 (2013) 249-254 [16] G.G. Muley, P.S. Ambhore, A.B. Naik, A.B. Gambhire Procedia Technol. 24 (2016) 715-720 [17] S.P. Ramteke, Mohd Anis, M.I. Baig, V.G. Pahurkar, G.G. Muley Optik (2017) http://dx.doi.org/10.1016/j.ijleo.2017.02.096 [18] K. Muthu, G. Bhagavannarayana, V. Meenatchi, S.P. Meenakshisundaram, S.C. Mojumdar J. Therm. Anal. Calorim. 108 (2012) 951-958 [19] S. Sasi, G. Ramesh, R. Robert, S. Arumugam, C. Inmozhi Optik 127 (2016) 759-762 [20] Mohd Anis, G.G. Muley Opt. Laser Technol. 91 (2017) 190-196 [21] B. Stuart, Infrared Spectroscopy: Fundamentals and Applications (JohnWiley and Sons, 2004) 77-78
6
[22] Mohd Anis, G.G. Muley, V.G. Pahurkar, M.I. Baig, S.R. Dagdale Mater. Res. Innov. (2016) http://dx.doi.org/10.1080/14328917.2016.1264848 [23] Mohd Anis, S.S. Hussaini, M.D. Shirsat, R.N. Shaikh, G.G. Muley Mater. Res. Express 3 (2016) 106204106210 [24] G. Bhagavannarayana, S. Parthiban, S. Meenakshisundaram J. Appl. Cryst. 39 (2006) 784-790 [25] M.S. Pandian, K. Boopathi, P. Ramasamy, G. Bhagavannarayana Mater. Res. Bull. 47 (2012) 826-835 [26] Mohd Anis, M.I. Baig, G.G. Muley, S.S. Hussaini, M.D. Shirsat Optik 127 (2016) 12043-12047 [27] Marvin J. Weber, Handbook of Optical Materials, CRC Press, New York, 2003 [28] Mohd Anis, D.A. Hakeem, G.G. Muley Results Phys. 6 (2016) 645-650 [29] M.S. Pandian, N. Pattanaboonmee, P. Ramasamy, P. Manyum J. Cryst. Growth 314 (2011) 207-212 [30] Mohd Anis, G.G. Muley Phys. Scr. 91 (2016) 85801-85808 [31] P. Vivek, P. Murugakoothan Opt Laser Technol. 49 (2013) 288-295 [32] Mohd Anis, G.G. Muley, M.I. Baig, S.S. Hussaini, M.D. Shirsat Mater. Res. Innov. (2016) http://dx.doi.org/10.1080/14328917.2016.1265250 [33] S.K. Kurtz, T.T. Perry J. Appl. Phys. 39 (1968) 3698-3813 [34] Mohd Shkir, V. Ganesh, N. Vijayan, B. Riscob, Anoop Kumar, Devendra Kumar Rana, Mohd Shoeb Khan, Mohd Hasmuddin, M.A. Wahab, R. Ramesh Babu, G. Bhagavannarayana, Spectrochem. Acta A 103 (2013) 199-204 [35] M.I. Baig, Mohd Anis, G.G. Muley Optik 131 (2017) 165-170 [36] N.N. Shejwal, Mohd Anis, S.S. Hussaini, M.D. Shirsat Int. J. Mod. Phys. B 30 (2016) 1650159-1650170 Figure Caption
7
Fig. 1. As grown crystals
Fig. 2. FTIR spectrum of grown crystal
Fig. 3. PXRD pattern of grown crystals
8
Fig. 4. (a) Transmittance spectrum (b) SHG efficiency output
9
Table 1. XRD data Crystal
Lattice parameters (Å)
Cell volume (Å)3
Structure
ZTC
a = 13.061 , b = 12.789, c = 5.846
976.499
Orthorhombic
ZTC-Ca (1wt%)
a = 13.068, b = 12.766, c = 5.835
973.430
Orthorhombic
ZTC-Ca (3wt%)
a = 13.064, b = 12.749, c = 5.829
970.837
Orthorhombic
ZTC-Ca (5wt%)
a = 13.073, b = 12.771, c = 5.891
983.533
Orthorhombic
Table 2. SHG efficiency of grown crystals Crystal
KDP
ZTC
ZTC-Ca (1wt%)
ZTC-Ca (3wt%)
ZTC-Ca (5wt%)
KDP as reference
1
0.8
0.96
0.71
1.19
ZTC as reference
1.24
1
1.19
0.89
1.49
10
S0030-4026(17)30690-3 http://dx.doi.org/doi:10.1016/j.ijleo.2017.06.023 IJLEO 59284
To appear in: Received date: Accepted date:
6-3-2017 6-6-2017
Please cite this article as: {http://dx.doi.org/ 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.
Synchronized effect of rising Ca2+ ion doping concentration on structural, UV-visible and second harmonic generation efficiency of zinc thiourea chloride crystal: An interesting comparative study V.G. Pahurkara, Mohd Anisa*, M.I. Baigb, S.P. Ramtekea, B. Babuc, G.G. Muleya* a
Department of Physics, Sant Gadge Baba Amravati University, Amravati-444602, Maharashtra, India
b
c
Prof Ram Meghe College of Engineering and Management, Amravati-444701, Maharashtra, India
Department of Physics, Sri Ramakrishna Mission Vidyalaya College of Arts and Science, Coimbatore-641020,
Tamilnadu, India Abstract In present investigation attention has been focused to explore the synchronic effect of increasing concentration of metallic impurity Ca2+ on structural, linear and nonlinear optical properties of zinc thiourea chloride (ZTC) crystal. The pure and Ca2+ (1wt%, 3wt%, 5wt%) ion doped ZTC crystals have been grown by slow solvent evaporation technique. The Fourier transform infrared spectral analysis has been employed to confirm the functional groups of grown crystals. The crystalline phase and structural parameters of pure and Ca2+ ion doped ZTC crystal has been comparatively examined by means of powder X-ray diffraction analysis. The influence of Ca2+ ion doping on optical transparency of ZTC crystal has been ascertained in the range of 190-1000 nm by means of UV-visible spectral analysis. The Kurtz-Perry test has been employed to confirm the second order nonlinear optical behavior of grown crystals. The change in value of second harmonic generation (SHG) efficiency of ZTC crystal attributed by each selected concentrations of metal dopant Ca2+ ion has been evaluated. The distinct application of grown crystals for device fabrication has been discussed in light of obtained results. Keywords: Crystal growth; Optical studies; Nonlinear optical materials; X-ray diffraction 1.
Introduction
Nonlinear optics is found to be the frontier and rapidly growing field of research which involves comprehensive study of all nonlinear optical effects desirable for tailoring/designing telecommunication, optoelectronics and photonics devices [1-2]. In current developing scenario of nonlinear optical crystals organometallic complexes has fascinated researchers worldwide [3]. The thiourea metal complexes outstand as promising organometallic Correspondence: Mohd Anis ([email protected]), G.G. Muley ([email protected])
1
materials which seek huge attention owing to large structural diversity and versatile characteristic properties [4]. In the extended family of thiourea metal complex crystals zinc thiourea chloride (ZTC) is found to be a unique and bewildering crystal. The single crystal of ZTC is noncentrosymmetric attributing orthorhombic structure, Pn21a space group and anisotropic behavior. Investigation on ZTC crystal has been attempted by many researcher groups to explore its quantum, optical, electrical and mechanical properties [5-8]. In past few decades it is observed that the target of gaining enhancement in performance of inherent qualities of ZTC crystal has been achieved by doping various organic as well as inorganic additives. The organic additives such as l-arginine, glycine and l-cysteine has shown significant enhancement in optical properties of ZTC crystal [912]. The doping of metallic additives such as potassium, lithium, sodium, magnesium, cadmium, copper, barium and neodymium has shown remarkable effect of different properties of ZTC crystal [13-20]. As metallic additives show strong impetus for enhancing the characteristic features of ZTC crystal therefore, our research group very firstly reports the doping effect of increasing concentration of Ca2+ ion on linear-nonlinear optical properties of ZTC crystal. The effect of different concentration of Ca2+ ion on spectral, structural and optical properties of ZTC crystal has been accomplished by means of Fourier transform infrared, powder X-ray diffraction, UV-visible and Kurtz-Perry SHG efficiency characterization techniques. 2.
Experimental procedure
The ZTC complex was prepared by dissolving the AR grade zinc chloride and thiourea in double distilled water in a stiochiometric ratio of 1:2 respectively. The purity of ZTC crystal complex has been achieved by process of successive recrystallisation. In order to add three different wt% of Ca2+ ion the 1wt%, 3wt% and 5wt% of calcium chloride salt was precisely measured and added to the ZTC crystal complex prepared in three different beakers. These solutions were allowed to stir for four hours on a magnetic stirrer so as to achieve homogeneous mixing of Ca2+ ion in ZTC crystal complex. The respective Ca2+ ion mixed ZTC crystals were filtered in a rinsed beaker and kept for slow evaporation in a constant temperature bath maintained at 35 oC. The pure and Ca2+ (1wt%, 3wt% and 5wt%) ion mixed ZTC single crystals were grown in a period of 22 days is shown in Fig. 1.
2
3.
Results and discussion The qualitative analysis of pure and Ca2+ (1wt%, 3wt% and 5wt%) ion mixed ZTC crystal has been
identified by means of Fourier transform infrared (FTIR) analysis. The FTIR spectrum of grown single crystals has been recorded (Fig. 2) in the range of 600-4000 cm-1 using the JASCO 410 spectrophotometer by KBr pellet technique. The absorption peaks attributed by C=S bond stretching is evident at 715 and 1402 cm-1. The C-N bond stretching vibration is contributed at wavenumber 1024 and 1533 cm-1. The mild absorption peak observed at 1092 cm-1 corresponds to C-C-N bond stretching vibration. The NH2 bending vibration is evident at 1620 cm1
. The C-H symmetric and antisymmetric stretching vibration is attributed at 2856 and 2914 cm-1. The
antisymmetric stretching of NH3+ groups is evident at 3180 cm-1. The absorption peak observed at 3289 cm-1 corresponds to N-H bond stretching vibration. The associated N-H bond stretching vibration in grown crystals is evident in the range of 3400-4000 cm-1 [21]. The powder X-ray diffraction analysis of pure and Ca2+ mixed ZTC crystal has been carried out using the Rigaku Miniflex II X-ray diffractometer. The diffraction patterns of grown crystals have been recorded at a scan rate of 0.02 o/sec within the 2θ range of 10-70o. The addition of dopant facilitates variation in intensity and shift in 2θ position of identified diffraction peaks of host material which evolves as a consequence of variation in excess growth of specific plane and slight change in cell parameters [22-23]. In present analysis the recorded diffraction peaks are shown in Fig. 3. It reveals that the sharpness of diffraction peak is high with 1wt% and 5wt% concentration of Ca2+ while it is lesser for 3wt% doping concentration of Ca2+ ion. The decrease in intensity of diffraction pattern might have been occurred due to structural deformation inculcated by presence of 3wt% of dopant Ca2+ ion in ZTC crystal. The less full width half maxima and the sharpness observed in diffraction peak due to presence of Ca2+ ion (1wt% and 5wt%) confirms that the grown crystal possesses enhanced crystalline quality and lesser grain boundaries [24-26]. As the sharpness of diffraction peak increases with rise in concentration of additive, this confirms Ca2+ ion as potential additive to achieve good quality ZTC crystals with selected doping concentration. The recorded PXRD patterns were indexed using the PowderX software and the evaluated cell parameters are discussed in table 1.
3
The optical spectrum is an imprint of the response of the electronic transitions occurring in specific energy states to the incident optical signal. The optical transmittance of a crystal medium is characteristic feature which is driven by crystal orientation, defect centres (line, voids, inclusion, striations) and optically active functional groups [27-30]. In present analysis the UV-visible transmittance spectrum of pure and Ca2+ ion doped ZTC crystals have been recorded in the range of 200-1000 nm using the spectrophotometer (Black-C-SR Stellar Net). The spectrum shown in Fig. 4a reveals that the optical transmittance of 1wt% and 5wt% Ca2+ ion doped ZTC crystal is significantly higher than pure ZTC crystal. It is observed that the offered percentage transmittance of 2 mm crystal is 48%, 68%, 74% for pure, 1wt% and 5wt% Ca2+ ion doped ZTC. It is noteworthy that the optical transmittance of 3wt% Ca2+ ion doped ZTC crystal is 41% which is marginally lower as compared to ZTC crystal. It can be ascertained that the less concentration of defects resulted the large enhancement in transmittance of 1wt% and 5wt% Ca2+ ion doped ZTC crystal however, the decrease in transmittance observed in case of 3wt% Ca2+ ion doped ZTC crystal might have been attributed due to relatively increased ratio of defects. The crystals with high optical transparency are demanded for designing optical elements for UV-tunable lasers and SHG devices [31-32]. Amongst the studied crystals the 5wt% Ca2+ ion doped ZTC crystal with maximum transmittance holds the potential candidature for device applications. The phenomenon of frequency doubling in grown crystal materials has been investigated using the Kurtz-Perry powder SHG technique [33]. In present analysis the Q-switched mode Nd:YAG laser (1064 nm, 6 ns, 10 Hz) has been used for SHG efficiency test. The good quality pure Ca2+ ion doped ZTC crystals were crushed in micro-granules of even size and sieved in quartz cavity. The samples were irradiated with the Gaussian filtered beam of Nd:YAG laser and the frequency doubling phenomenon was confirmed as we see the bright green light at the output window. The SHG signal was recorded through the optical fiber assisted spectrophotometer interfaced with computer. The recorded SHG output intensity of each sample is shown in Fig. 4b. It is observed that the SHG efficiency of 1wt% and 5wt% of Ca2+ ion doped ZTC crystal is significantly higher than that of ZTC crystal material. It is interesting to note that the 3wt% of Ca2+ ion doped ZTC crystal has low SHG response as compared to ZTC. The decrease in SHG response might have been occurred due to deformation in crystal structure [16, 34] which is evident from PXRD pattern also the optical transparency is 4
minimum amongst the studied crystal. The SHG efficiency of grown crystals has been systematically discussed in table 2. The study thus confirms that the doped ZTC crystals with high SHG response can be utilized for laser frequency conversion and NLO device applications [35-36]. 4.
Conclusion
The pure, 1wt%, 3wt% and 5wt% Ca2+ ion doped ZTC crystals have been grown at room temperature by slow solvent evaporation technique. The functional groups of pure and doped ZTC crystals have been successfully identified by means of FTIR spectrum analysis. The PXRD analysis confirmed the orthorhombic crystal structure and slight change in cell parameters of doped ZTC crystals. The increase in sharpness of intensity in PXRD pattern revealed that the crystalline quality of ZTC increases with rise in concentration of dopant except for 3wt%. The optical transparency investigated in range of 200-1000 nm showed that the transparency of 1wt% and 5wt% Ca2+ ion doped ZTC crystal is higher than pure ZTC crystal. The doping 3wt% of Ca2+ resulted to fall in transmittance of ZTC crystal by 7%. In Kurtz-Perry test the SHG efficiency of 1wt% and 5wt% Ca2+ ion doped ZTC crystal is found to be 1.19 and 1.49 times greater than ZTC crystal respectively. The SHG efficiency of 5wt% Ca2+ ion doped ZTC crystal is highest amongst the studied crystals, which is found to be 1.19 times that of KDP and 1.49 times that of ZTC crystal. The SHG efficiency of 3wt% Ca2+ ion doped ZTC crystal is found to be 0.71 and 0.89 times that of KDP and ZTC respectively. The analysis of crystalline quality, optical transparency and SHG efficiency altogether showed similar effect for respective concentration of dopant confirming the synchronized effect of dopant on independent feature of ZTC crystal studied in present investigation. The studies confirm that the 5wt% Ca2+ ion doped ZTC crystal with excellent crystalline nature, high transmittance and high conversion efficiency is most suitable material for distinct NLO device applications. Acknowledgements Author Mohd Anis is thankful to University Grants Comission, New Delhi, India for awarding the Maulana Azad National Fellowship (F1-17.1/2015-16/MANF-2015-17-MAH-68193). DST-SERB India is acknowledged for sanctioning the grant (SB/EMEB-328/2013). References 5
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Fig. 1. As grown crystals
Fig. 2. FTIR spectrum of grown crystal
Fig. 3. PXRD pattern of grown crystals
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Fig. 4. (a) Transmittance spectrum (b) SHG efficiency output
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Table 1. XRD data Crystal
Lattice parameters (Å)
Cell volume (Å)3
Structure
ZTC
a = 13.061 , b = 12.789, c = 5.846
976.499
Orthorhombic
ZTC-Ca (1wt%)
a = 13.068, b = 12.766, c = 5.835
973.430
Orthorhombic
ZTC-Ca (3wt%)
a = 13.064, b = 12.749, c = 5.829
970.837
Orthorhombic
ZTC-Ca (5wt%)
a = 13.073, b = 12.771, c = 5.891
983.533
Orthorhombic
Table 2. SHG efficiency of grown crystals Crystal
KDP
ZTC
ZTC-Ca (1wt%)
ZTC-Ca (3wt%)
ZTC-Ca (5wt%)
KDP as reference
1
0.8
0.96
0.71
1.19
ZTC as reference
1.24
1
1.19
0.89
1.49
10