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Structural, mechanical, electrical and optical properties of a new lithium boro phthalate NLO crystal synthesized by a slow evaporation method
Optics and Laser Technology xxx (2017) xxx–xxx
Contents lists available at ScienceDirect
Optics and Laser Technology journal homepage: www.elsevier.com/locate/optlastec
Full length article
Structural, mechanical, electrical and optical properties of a new lithium boro phthalate NLO crystal synthesized by a slow evaporation method K. Mohanraj, D. Balasubramanian ⇑, N. Jhansi Raman Research Laboratory, PG & Research Department of Physics, Government Arts College, Tiruvannamalai 606603, Tamilnadu, India
a r t i c l e
i n f o
Article history: Received 1 January 2017 Accepted 5 June 2017 Available online xxxx Keywords: X-ray diffractions Dielectric Microhardness Nonlinear optical materials
a b s t r a c t A new non-linear optical (NLO) single crystal of lithium boro phthalate (LiBP) was grown by slow solvent evaporation technique. The powder sample was subjected to powder X-ray diffraction (PXRD) to find its crystalline nature and the crystal structure of the grown crystal was determined using single crystal Xray (SXRD) diffraction analysis. The Fourier Transform Infrared (FTIR) spectrum was recorded for grown crystal to identify the various functional groups present in the compound. The mechanical property of the LiBP single crystal was studied using Vickers microhardness tester. The dielectric constant and dielectric loss measurements were carried out for the grown crystal at various temperatures. The grown crystal was subjected to UV–Visible Spectral Studies to analyze the linear optical behavior of the grown crystal. The Kurtz-Perry Powder technique was employed to measure the Second Harmonic Generation efficiency of the grown crystal. Ó 2017 Elsevier Ltd. All rights reserved.
1. Introduction In the resent years researcher’s focusing on nonlinear optical (NLO) crystals. Because it’s a potential material for laser oriented application [1], electro-optic switches, frequency conversion [2], color display and photonics included optical information processing [3–6]. Organic crystals have potential applications of semiconductors, superconductors and nonlinear optical devices [7]. Organic crystals have been high NLO response comparing the inorganic materials due to the presence of active p-bonds. Organic nonlinear crystals with large conversion efficiency for a second harmonic generation (SHG) and large transparency window in UV–vis region are required for device applications particularly in optical telecommunications and optical storage device [8]. In the presently researcher’s searching in a novel nonlinear optical materials. At the same time semi-organic novel materials have interesting NLO properties [9–11]. In semi-organic crystals have polarizable organic molecules are bond with an in organic host. So semi-organic crystal have been large optical nonlinearity and a high degree of design chemical flexibility of NLO effects of organic with the physically strong and thermal properties of inorganic materials.
⇑ Corresponding author.
Phthalic acid is a potential material for NLO and electro-optic process. Potassium acid phthalate is an important NLO crystal in the phthalic acid family [12–14]. In the present studies synthesis, crystal growth and characterization of the semi-organic crystal lithium boro phthalate (LiBP) has been reported. 2. Experimental procedure 2.1. Material synthesis Lithium carbonate, Phthalic acid and boric acid purchased in analytical grade reagents (AR) were taken in the 1:1:1equal molar ratio. The calculated amount of materials was taken too dissolved in deionized (18.2 MO/cm) water at constant stirring in room temperature. Lithium boro phthalate (LiBP) was synthesized according to below chemical reaction. The calculated amount of salts added up to saturation stage in 250 ml deionized water at room temperature. The saturation solution was filtered using a filter paper; the filtered solution was transferred in Petri dish. The solution was left dry at room temperature by slow solvent evaporation technique. The synthesized compound purity was improved by repeated recrystallization process. The LiBP crystal was grown period 20–30 days. The optimized crystal growth conditions are shown in Table 1 and LiBP crystal shown in Fig 1.
E-mail address: [email protected] (D. Balasubramanian). http://dx.doi.org/10.1016/j.optlastec.2017.06.001 0030-3992/Ó 2017 Elsevier Ltd. All rights reserved.
Please cite this article in press as: K. Mohanraj et al., Structural, mechanical, electrical and optical properties of a new lithium boro phthalate NLO crystal synthesized by a slow evaporation method, Opt. Laser Technol. (2017), http://dx.doi.org/10.1016/j.optlastec.2017.06.001
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K. Mohanraj et al. / Optics and Laser Technology xxx (2017) xxx–xxx
Table 1 Optimized growth conditions of LiBP crystal. Technique Solvent Lithium carbonate + phthalic acid + Boric acid Temperature Period of growth
Slow solvent evaporation technique Double distilled water 1:1:1 Molar ratio Room temperature 20–30 days
Fig. 2. Powder X-ray diffraction pattern of LiBP crystal.
3.1. Powder X-ray diffraction analysis (PXRD) Rich Seifert diffractometer with Cu Ka (k = 1.5418 Å) radiation technique was used to record the powder X-ray diffraction pattern of LiBP crystal. The LiBP powder sample was crushed to a fine powder and subjected to the scan over the range of 10–80° at a scan rate 2°/min. Fig. 2 shows that plot of Intensity (a.u) vs 2h(deg). The sharp and intense peaks confirmed the good crystalline property of grown LiPB crystal. The peaks are indexed using the program DICVO91 used to index the hkl value. 3.2. Single crystal X-ray diffraction analysis (SXRD)
Fig. 1. As grown crystals of LiBP.
The grown LiBP single crystal was cut to suitable size and mounted on the X-ray goniometer of ENRAF NONIUS CAD-4 single crystal X-ray diffractometer with Cu Ka radiation (k = 1.5418 Å). The crystal was optically centered at the sphere of confection
Phthalic acid þ Lithium carbonate þ boric acid
at room temp
!
lithium boro phthalate
OH CHOOH
OH
O
B
C COOH
LiO LiO HO
COO at room temp
OH
B OHLi
CO2
COOLi
Scheme for the synthesis of LiBP 3. Characterization Single crystal X-ray diffraction studies was reported crystal structure and lattice parameter using ENRAF NONIUS CAD-4 Xray diffractometer with Mo Ka (k = 0.1770 Å) radiation. The powder X-ray diffraction technique reported crystalline nature of material using SIEFRT X-ray diffractometer with Cu Ka (k = 1.5406 Å) radiation. Kurtz powder technique was used to studied SHG efficiency. The FTIR spectrum was recorded in the range 400–4000 cm1 using a Perkin-Elmer spectrometer by KBr pellet technique to analyzed the incorporated of boron into LiBP NLO crystal. The Lambda-35 UV–vis-NIR spectrometer used to record a linear optical property of grown LiBP NLO crystal in the range 200-1100 nm. The Leitz-Wetzlar micro hardness tester used to study the micro hardness property of grown LiBP NLO crystal. The HIOCKI 3532-50 LCR HITESTER used to investigated the dielectric property of grown LiBP crystal.
and twenty-five reflections were collected from different zones of the reciprocal lattice using random search procedure. The parameters obtained are tabulated in Table 2 and LiBP crystal is found to be monoclinic structure with space group C2, which belongs to non- centro symmetric.
3.3. Linear optical analysis (UV–Visible) The linear optical spectra are very important to study the optical character of any optical materials. The good quality single crystal of LiBP of 1.89 mm thickness was subjected linear optical analysis using LAMBDA-35 UV–vis spectrometer. The optical absorption spectrum was recorded in the range 200–900 nm and it is shown in Fig. 3. The spectrum gives two peaks, one intense peak at 275 nm corresponding to p–p⁄ transition and another peak at 224 nm corresponds to n–p⁄ transition (Fig. 5.3) [15]. Hence LiBP
Please cite this article in press as: K. Mohanraj et al., Structural, mechanical, electrical and optical properties of a new lithium boro phthalate NLO crystal synthesized by a slow evaporation method, Opt. Laser Technol. (2017), http://dx.doi.org/10.1016/j.optlastec.2017.06.001
3
K. Mohanraj et al. / Optics and Laser Technology xxx (2017) xxx–xxx Table 2 Cell parameter of LiBP crystal.
Table 3 FTIR assignments of LiBP crystal.
Compound details
Experimental results
Frequency in wave number (cm1)
Assignment of functional groups
Identification code Crystal system Space group Unit cell dimensions
LiBP Monoclinic C2 a = 5.02 Å; a = 90° b = 14.29 Å; b = 93.36° c = 9.59 Å; c = 90° V = 687 A3
3676 3502 & 3374 3078 3005, 2876 & 2647 2522 1775 1667 1583 1398 1266 1066 669 & 792 554 & 420
OAH stretching, free hydroxyl OAH stretching @CAH stretching CAH stretching HAC@O stretching C@O stretching AC@CA stretching CAC stretching (in-ring) CAC stretching CAO stretching BAO asymmetric stretching BAO symmetric stretching Alkali metal ions
Volume
the peaks at 1066 cm1 corresponds to the BAO asymmetric stretching [17]. And 669 cm1 and 702 cm1 correspond to BAO symmetric stretching [17]. A peak at 554 cm1 and 420 cm1 shows the presence of Alkali metals ions [16].
3.5. Micro hardness analysis The microhardness analysis of grown LiBP single crystal was carried out using Vicker’s microhardness tester. The polished LiBP crystal was subjected in the SHIMADZU HMV microhardness tester at room temperature. Several indentations were made for various loads at constant indentation time 10 s. The Vickers micro hardness number was determined using the formula,
Fig. 3. Linear optical spectrum of LiBP crystal.
2
HV ¼ 1:8544ðp=d Þ kg=mm2 where, HV – Vickers microhardness number in kg/mm2. 1.8544 – Constant geometrical factor for diamond pyramid. P – Applied load in g. d – Diagonal length of indentation impression in mm. The plot Hardness number vs Load is shown in the Fig. 5, which reveals that the hardness number increases with the load. This shows that the grown LiBP single crystal is a soft material which is suitable for device fabrication.
Fig. 4. FTIR spectrum of LiBP crystal.
single crystal is applications.
found to
be
suitable for
optoelectronic
3.4. Fourier transforms infrared spectroscopy analysis (FTIR) The FTIR spectrum for grown LiBP single crystal was recorded using BRUKKER IFS 66V spectrometer by KBr pellet technique at the range of 400–4000 cm1. The obtained infrared spectrum is shown in Fig. 4. From the spectrum, several functional groups present the grown crystal have been identified and the assignments are listed in the Table 3. Peaks at 2522 cm1 and 1775 cm1 correspond to HAC@O stretching respectively confirms the presence of carboxylic acid [16]. The presence of Boron has been endorsed by
Fig. 5. Hardness number (HV) vs load (P) of LiBP crystal.
Please cite this article in press as: K. Mohanraj et al., Structural, mechanical, electrical and optical properties of a new lithium boro phthalate NLO crystal synthesized by a slow evaporation method, Opt. Laser Technol. (2017), http://dx.doi.org/10.1016/j.optlastec.2017.06.001
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K. Mohanraj et al. / Optics and Laser Technology xxx (2017) xxx–xxx
2.5
3.6. Dielectric analysis
er ¼
0
40 C 0 45 C 0 50 C 0 55 C 0 60 C
2.0
Dielectric loss ( tan )
The dielectric study on LiBP single crystal was carried out on [011] face using the instrument, HIOCKI 3532-50 LCR HITESTER. A sample of dimension 0.5 0.5 0.3 cm3 was used for this experiment. The metallic contacts on the smooth surfaces on either side of the sample were sputtered and leads were bonded with silver epoxy to the plates. Thus a parallel plate capacitor with the dielectric of LiBP sample was formed. The capacitance of the sample was measured by varying the frequency from 100 Hz to 5 MHz at various temperatures 313 K, 318 K, 323 K, 328 K and 338 K. The dielectric constant er was calculated based on capacitance, electrode area and sample thickness using the relation
Cd
1.5
1.0
0.5
0.0
eo A
where C is the capacitance, d is the thickness of the crystal, eo is the permittivity of free space and A is the area of the crystal sample. The variation of dielectric constant and dielectric loss of LiBP as a function of frequency at different temperatures are shown in the Figs. 6 and 7 respectively. From the graph it is inferred that the dielectric constant has higher value in the lower frequency region. With further increase in frequency dielectric constant decreases and becomes more or less independent in the higher frequency range above 1 kHz for all the temperature. The high value of dielectric constant at low frequencies is attributed to the contribution from space charge and orientational polarization and its low value at higher frequency region may be due to the loss of significance of these factors. The decrease in the values of dielectric constant with the frequency takes place when the jumping frequency of electric charge carriers cannot follow the alternation of the ac electric field applied beyond a certain critical frequency. Dielectric constant and dielectric loss decrease with frequency, which is a typical characteristic of a normal dielectric. The lower value of dielectric constant and its independent behavior with respect to temperature is a suitable parameter for the enhancement of SHG coefficients and this assures the quality of the crystal with fewer defects. Dielectric loss versus frequency curve might be attributed to parallel conduction, which is probably due to the porosity and it is observed that at higher frequencies this parameter becomes almost frequency-independent. Since, the dielectric loss of LiBP crystal is found to be less at higher frequencies, the power dissipation in the crystal is relatively low. Thus the LiBP crystal can be
1
2
3
4
5
6
7
Log f Fig. 7. Variation of dielectric loss with log frequency of LiBP.
Table 4 Second Harmonic efficiency LiBP crystal. Sl. No.
Name of the sample
Input power (joule)
Output power (mJ)
1 2
LiBP KDP (Reference)
0.68 0.68
11.6 8.8
effectively employed modulators.
for
the
fabrication
of
electro-optic
3.7. Second Harmonic studies (SHG) The SHG property of LiBP crystal was studied using Q-switched Nd: YAG laser employing Kurtz powder test. The fundamental beam of Nd: YAG laser with 1064 nm wavelength, pulse duration of 35 ps and 10 Hz repetition rate is focused on to the powder sample. A green light of wave length 532 nm with the radiation energy 11.6 mJ was obtained as the output from the grown LiBP single crystal whereas the output radiation emitted from the KDP reference sample was 8.8 mJ. Thus, the SHG efficiency of as grown LiBP crystal is found to be nearly 1.3 times that of KDP. Input and out power of laser light passed and emitted by the LiBP and KDP are show in the Table 4.
1200 0
40 C 0 45 C 0 50 C 0 55 C 0 60 C
1100 1000
Dielectric constant ( r )
900 800
4. Conclusion
700 600 500 400 300 200 100 0 1
2
3
4
5
6
Log f Fig. 6. Variation of dielectric constant with log frequency of LiBP.
7
The lithium boro phthalate (LiBP) compound was synthesized using phthalic acid, Boric acid and Lithium carbonate taken in equi molar ratio and the seed crystals were grown from synthesized compound by slow evaporation technique. Purity of the seed crystals was improved by successive recrystallization process. The Bulk single crystal of LiBP was grown at room temperature by slow evaporation technique with good morphology. Powder X-ray diffraction analysis confirmed the crystalline nature of the grown crystal, and the structure of the grown crystal is found to be monoclinic structure with space group C2. The FTIR spectrum recorded for the grown sample confirms the presence of suitable functional groups in the grown crystal. The linear optical study revealed the good transparency of the grown crystal in wide wavelength range which suits the crystal for various electro optic applications. It is interesting to observe that the NLO efficiency of LiBP is superior to KDP. Microharness test reveals that the LiBP single
Please cite this article in press as: K. Mohanraj et al., Structural, mechanical, electrical and optical properties of a new lithium boro phthalate NLO crystal synthesized by a slow evaporation method, Opt. Laser Technol. (2017), http://dx.doi.org/10.1016/j.optlastec.2017.06.001
K. Mohanraj et al. / Optics and Laser Technology xxx (2017) xxx–xxx
crystal behaves like a soft material, which is suitable for device fabrication. The dielectric studies show that the dielectric constant of the LiBP single crystal remains same at various temperatures, which reveals the good dielectric behavior of the grown crystal. The less value of dielectric loss of higher frequencies proves the good quality of the grown crystal. In view of the good optical properties, better SHG efficiency and moderate mechanical behavior, LiBP crystal would be a suitable material for nonlinear optical device applications. References [1] N. Zaitseva, L. Carman, Prog. Cryst. Growth Charact. 43 (2001) 1–118. [2] J. Badan, R. Hierle, A. Perigaud, J. Zyss, NLO Properties of Organic Molecules and Polymeric Materials, American Chemical Society Symposium Series 233, American Chemical Society, Washington, DC, 1993. [3] N.P. Prasad, Polymer 32 (1991) 1746–1751. [4] B.G. Penn, B.H. Cardelino, C.E. Moore, A.W. Shields, D.O. Frazier, Prog. Cryst. Growth. Charact. 22 (1991) 19–51.
5
[5] B.E.A. Saleh, M.C. Teich, In Fundamental of Photonics, Wiley, New York, 1991. [6] S.R. Marder, S.E. Sohn, G.D. Stucky, Material for Nonlinear Optics, American Chemical Society, Washington, DC, 1991. [7] T. Uma Devi, N. Lawrence, R. Ramesh Babu, K. Ramamurthi, Spectrochim. Acta 71A (2008) 340–343. [8] V. Krishnakumar, R. Nagalakshmi, Spectro chim. Acta 66A (2007) 924–934. [9] Xu Dong, Yuan Duo-rong, Zhang Nan, Hou Wen-bo, Liu Ming-guo, Sun Suoying, Jiang Min-hua, J. Phys. D Appl. Phys. 26 (1993) B230. [10] J. Zaccaro, J. Hartwig, J. Baruchel, A. Ibanez, J. Crystal Growth 204 (1999) 325. [11] J.P. Feve, B. Boulanger, I. Rousseau, G. Marnier, J. Zaccaro, A. Ibanez, IEEE J. Quantum Electron. 35 (1999) 66. [12] A.V. Alex, J. Philip, J. Appl. Phys. 88 (2000) 2349. [13] M.H.J. Hottenhuis, J.G.E. Gardenhers, L.A.M.J. Jetten, P. Bennema, J. Crystal Growth 92 (1988) 171. [14] N. Kejalakshmy, K. Srinivasan, Opt. Mater. 27 (2004) 389. [15] S.R. Thilagavathy, P. Rajesh, P. Ramasamy, K. Ambujam, Spectrochim. Acta Part A Mol. Biomol. Spectrosc. 127 (2014) 248–255. [16] B. Sivakumar, S. Gokul Raj, G. Ramesh Kumar, R. Mohan, J. Crystal. Proc. Technol. 2 (2012) 130–136. [17] V. Chithambaram, S. Jerome Das, R. Arivudai Nambi, S. Krishnan, Opt. Laser Technol. 43 (2011) 1229–1232.
Please cite this article in press as: K. Mohanraj et al., Structural, mechanical, electrical and optical properties of a new lithium boro phthalate NLO crystal synthesized by a slow evaporation method, Opt. Laser Technol. (2017), http://dx.doi.org/10.1016/j.optlastec.2017.06.001
Contents lists available at ScienceDirect
Optics and Laser Technology journal homepage: www.elsevier.com/locate/optlastec
Full length article
Structural, mechanical, electrical and optical properties of a new lithium boro phthalate NLO crystal synthesized by a slow evaporation method K. Mohanraj, D. Balasubramanian ⇑, N. Jhansi Raman Research Laboratory, PG & Research Department of Physics, Government Arts College, Tiruvannamalai 606603, Tamilnadu, India
a r t i c l e
i n f o
Article history: Received 1 January 2017 Accepted 5 June 2017 Available online xxxx Keywords: X-ray diffractions Dielectric Microhardness Nonlinear optical materials
a b s t r a c t A new non-linear optical (NLO) single crystal of lithium boro phthalate (LiBP) was grown by slow solvent evaporation technique. The powder sample was subjected to powder X-ray diffraction (PXRD) to find its crystalline nature and the crystal structure of the grown crystal was determined using single crystal Xray (SXRD) diffraction analysis. The Fourier Transform Infrared (FTIR) spectrum was recorded for grown crystal to identify the various functional groups present in the compound. The mechanical property of the LiBP single crystal was studied using Vickers microhardness tester. The dielectric constant and dielectric loss measurements were carried out for the grown crystal at various temperatures. The grown crystal was subjected to UV–Visible Spectral Studies to analyze the linear optical behavior of the grown crystal. The Kurtz-Perry Powder technique was employed to measure the Second Harmonic Generation efficiency of the grown crystal. Ó 2017 Elsevier Ltd. All rights reserved.
1. Introduction In the resent years researcher’s focusing on nonlinear optical (NLO) crystals. Because it’s a potential material for laser oriented application [1], electro-optic switches, frequency conversion [2], color display and photonics included optical information processing [3–6]. Organic crystals have potential applications of semiconductors, superconductors and nonlinear optical devices [7]. Organic crystals have been high NLO response comparing the inorganic materials due to the presence of active p-bonds. Organic nonlinear crystals with large conversion efficiency for a second harmonic generation (SHG) and large transparency window in UV–vis region are required for device applications particularly in optical telecommunications and optical storage device [8]. In the presently researcher’s searching in a novel nonlinear optical materials. At the same time semi-organic novel materials have interesting NLO properties [9–11]. In semi-organic crystals have polarizable organic molecules are bond with an in organic host. So semi-organic crystal have been large optical nonlinearity and a high degree of design chemical flexibility of NLO effects of organic with the physically strong and thermal properties of inorganic materials.
⇑ Corresponding author.
Phthalic acid is a potential material for NLO and electro-optic process. Potassium acid phthalate is an important NLO crystal in the phthalic acid family [12–14]. In the present studies synthesis, crystal growth and characterization of the semi-organic crystal lithium boro phthalate (LiBP) has been reported. 2. Experimental procedure 2.1. Material synthesis Lithium carbonate, Phthalic acid and boric acid purchased in analytical grade reagents (AR) were taken in the 1:1:1equal molar ratio. The calculated amount of materials was taken too dissolved in deionized (18.2 MO/cm) water at constant stirring in room temperature. Lithium boro phthalate (LiBP) was synthesized according to below chemical reaction. The calculated amount of salts added up to saturation stage in 250 ml deionized water at room temperature. The saturation solution was filtered using a filter paper; the filtered solution was transferred in Petri dish. The solution was left dry at room temperature by slow solvent evaporation technique. The synthesized compound purity was improved by repeated recrystallization process. The LiBP crystal was grown period 20–30 days. The optimized crystal growth conditions are shown in Table 1 and LiBP crystal shown in Fig 1.
E-mail address: [email protected] (D. Balasubramanian). http://dx.doi.org/10.1016/j.optlastec.2017.06.001 0030-3992/Ó 2017 Elsevier Ltd. All rights reserved.
Please cite this article in press as: K. Mohanraj et al., Structural, mechanical, electrical and optical properties of a new lithium boro phthalate NLO crystal synthesized by a slow evaporation method, Opt. Laser Technol. (2017), http://dx.doi.org/10.1016/j.optlastec.2017.06.001
2
K. Mohanraj et al. / Optics and Laser Technology xxx (2017) xxx–xxx
Table 1 Optimized growth conditions of LiBP crystal. Technique Solvent Lithium carbonate + phthalic acid + Boric acid Temperature Period of growth
Slow solvent evaporation technique Double distilled water 1:1:1 Molar ratio Room temperature 20–30 days
Fig. 2. Powder X-ray diffraction pattern of LiBP crystal.
3.1. Powder X-ray diffraction analysis (PXRD) Rich Seifert diffractometer with Cu Ka (k = 1.5418 Å) radiation technique was used to record the powder X-ray diffraction pattern of LiBP crystal. The LiBP powder sample was crushed to a fine powder and subjected to the scan over the range of 10–80° at a scan rate 2°/min. Fig. 2 shows that plot of Intensity (a.u) vs 2h(deg). The sharp and intense peaks confirmed the good crystalline property of grown LiPB crystal. The peaks are indexed using the program DICVO91 used to index the hkl value. 3.2. Single crystal X-ray diffraction analysis (SXRD)
Fig. 1. As grown crystals of LiBP.
The grown LiBP single crystal was cut to suitable size and mounted on the X-ray goniometer of ENRAF NONIUS CAD-4 single crystal X-ray diffractometer with Cu Ka radiation (k = 1.5418 Å). The crystal was optically centered at the sphere of confection
Phthalic acid þ Lithium carbonate þ boric acid
at room temp
!
lithium boro phthalate
OH CHOOH
OH
O
B
C COOH
LiO LiO HO
COO at room temp
OH
B OHLi
CO2
COOLi
Scheme for the synthesis of LiBP 3. Characterization Single crystal X-ray diffraction studies was reported crystal structure and lattice parameter using ENRAF NONIUS CAD-4 Xray diffractometer with Mo Ka (k = 0.1770 Å) radiation. The powder X-ray diffraction technique reported crystalline nature of material using SIEFRT X-ray diffractometer with Cu Ka (k = 1.5406 Å) radiation. Kurtz powder technique was used to studied SHG efficiency. The FTIR spectrum was recorded in the range 400–4000 cm1 using a Perkin-Elmer spectrometer by KBr pellet technique to analyzed the incorporated of boron into LiBP NLO crystal. The Lambda-35 UV–vis-NIR spectrometer used to record a linear optical property of grown LiBP NLO crystal in the range 200-1100 nm. The Leitz-Wetzlar micro hardness tester used to study the micro hardness property of grown LiBP NLO crystal. The HIOCKI 3532-50 LCR HITESTER used to investigated the dielectric property of grown LiBP crystal.
and twenty-five reflections were collected from different zones of the reciprocal lattice using random search procedure. The parameters obtained are tabulated in Table 2 and LiBP crystal is found to be monoclinic structure with space group C2, which belongs to non- centro symmetric.
3.3. Linear optical analysis (UV–Visible) The linear optical spectra are very important to study the optical character of any optical materials. The good quality single crystal of LiBP of 1.89 mm thickness was subjected linear optical analysis using LAMBDA-35 UV–vis spectrometer. The optical absorption spectrum was recorded in the range 200–900 nm and it is shown in Fig. 3. The spectrum gives two peaks, one intense peak at 275 nm corresponding to p–p⁄ transition and another peak at 224 nm corresponds to n–p⁄ transition (Fig. 5.3) [15]. Hence LiBP
Please cite this article in press as: K. Mohanraj et al., Structural, mechanical, electrical and optical properties of a new lithium boro phthalate NLO crystal synthesized by a slow evaporation method, Opt. Laser Technol. (2017), http://dx.doi.org/10.1016/j.optlastec.2017.06.001
3
K. Mohanraj et al. / Optics and Laser Technology xxx (2017) xxx–xxx Table 2 Cell parameter of LiBP crystal.
Table 3 FTIR assignments of LiBP crystal.
Compound details
Experimental results
Frequency in wave number (cm1)
Assignment of functional groups
Identification code Crystal system Space group Unit cell dimensions
LiBP Monoclinic C2 a = 5.02 Å; a = 90° b = 14.29 Å; b = 93.36° c = 9.59 Å; c = 90° V = 687 A3
3676 3502 & 3374 3078 3005, 2876 & 2647 2522 1775 1667 1583 1398 1266 1066 669 & 792 554 & 420
OAH stretching, free hydroxyl OAH stretching @CAH stretching CAH stretching HAC@O stretching C@O stretching AC@CA stretching CAC stretching (in-ring) CAC stretching CAO stretching BAO asymmetric stretching BAO symmetric stretching Alkali metal ions
Volume
the peaks at 1066 cm1 corresponds to the BAO asymmetric stretching [17]. And 669 cm1 and 702 cm1 correspond to BAO symmetric stretching [17]. A peak at 554 cm1 and 420 cm1 shows the presence of Alkali metals ions [16].
3.5. Micro hardness analysis The microhardness analysis of grown LiBP single crystal was carried out using Vicker’s microhardness tester. The polished LiBP crystal was subjected in the SHIMADZU HMV microhardness tester at room temperature. Several indentations were made for various loads at constant indentation time 10 s. The Vickers micro hardness number was determined using the formula,
Fig. 3. Linear optical spectrum of LiBP crystal.
2
HV ¼ 1:8544ðp=d Þ kg=mm2 where, HV – Vickers microhardness number in kg/mm2. 1.8544 – Constant geometrical factor for diamond pyramid. P – Applied load in g. d – Diagonal length of indentation impression in mm. The plot Hardness number vs Load is shown in the Fig. 5, which reveals that the hardness number increases with the load. This shows that the grown LiBP single crystal is a soft material which is suitable for device fabrication.
Fig. 4. FTIR spectrum of LiBP crystal.
single crystal is applications.
found to
be
suitable for
optoelectronic
3.4. Fourier transforms infrared spectroscopy analysis (FTIR) The FTIR spectrum for grown LiBP single crystal was recorded using BRUKKER IFS 66V spectrometer by KBr pellet technique at the range of 400–4000 cm1. The obtained infrared spectrum is shown in Fig. 4. From the spectrum, several functional groups present the grown crystal have been identified and the assignments are listed in the Table 3. Peaks at 2522 cm1 and 1775 cm1 correspond to HAC@O stretching respectively confirms the presence of carboxylic acid [16]. The presence of Boron has been endorsed by
Fig. 5. Hardness number (HV) vs load (P) of LiBP crystal.
Please cite this article in press as: K. Mohanraj et al., Structural, mechanical, electrical and optical properties of a new lithium boro phthalate NLO crystal synthesized by a slow evaporation method, Opt. Laser Technol. (2017), http://dx.doi.org/10.1016/j.optlastec.2017.06.001
4
K. Mohanraj et al. / Optics and Laser Technology xxx (2017) xxx–xxx
2.5
3.6. Dielectric analysis
er ¼
0
40 C 0 45 C 0 50 C 0 55 C 0 60 C
2.0
Dielectric loss ( tan )
The dielectric study on LiBP single crystal was carried out on [011] face using the instrument, HIOCKI 3532-50 LCR HITESTER. A sample of dimension 0.5 0.5 0.3 cm3 was used for this experiment. The metallic contacts on the smooth surfaces on either side of the sample were sputtered and leads were bonded with silver epoxy to the plates. Thus a parallel plate capacitor with the dielectric of LiBP sample was formed. The capacitance of the sample was measured by varying the frequency from 100 Hz to 5 MHz at various temperatures 313 K, 318 K, 323 K, 328 K and 338 K. The dielectric constant er was calculated based on capacitance, electrode area and sample thickness using the relation
Cd
1.5
1.0
0.5
0.0
eo A
where C is the capacitance, d is the thickness of the crystal, eo is the permittivity of free space and A is the area of the crystal sample. The variation of dielectric constant and dielectric loss of LiBP as a function of frequency at different temperatures are shown in the Figs. 6 and 7 respectively. From the graph it is inferred that the dielectric constant has higher value in the lower frequency region. With further increase in frequency dielectric constant decreases and becomes more or less independent in the higher frequency range above 1 kHz for all the temperature. The high value of dielectric constant at low frequencies is attributed to the contribution from space charge and orientational polarization and its low value at higher frequency region may be due to the loss of significance of these factors. The decrease in the values of dielectric constant with the frequency takes place when the jumping frequency of electric charge carriers cannot follow the alternation of the ac electric field applied beyond a certain critical frequency. Dielectric constant and dielectric loss decrease with frequency, which is a typical characteristic of a normal dielectric. The lower value of dielectric constant and its independent behavior with respect to temperature is a suitable parameter for the enhancement of SHG coefficients and this assures the quality of the crystal with fewer defects. Dielectric loss versus frequency curve might be attributed to parallel conduction, which is probably due to the porosity and it is observed that at higher frequencies this parameter becomes almost frequency-independent. Since, the dielectric loss of LiBP crystal is found to be less at higher frequencies, the power dissipation in the crystal is relatively low. Thus the LiBP crystal can be
1
2
3
4
5
6
7
Log f Fig. 7. Variation of dielectric loss with log frequency of LiBP.
Table 4 Second Harmonic efficiency LiBP crystal. Sl. No.
Name of the sample
Input power (joule)
Output power (mJ)
1 2
LiBP KDP (Reference)
0.68 0.68
11.6 8.8
effectively employed modulators.
for
the
fabrication
of
electro-optic
3.7. Second Harmonic studies (SHG) The SHG property of LiBP crystal was studied using Q-switched Nd: YAG laser employing Kurtz powder test. The fundamental beam of Nd: YAG laser with 1064 nm wavelength, pulse duration of 35 ps and 10 Hz repetition rate is focused on to the powder sample. A green light of wave length 532 nm with the radiation energy 11.6 mJ was obtained as the output from the grown LiBP single crystal whereas the output radiation emitted from the KDP reference sample was 8.8 mJ. Thus, the SHG efficiency of as grown LiBP crystal is found to be nearly 1.3 times that of KDP. Input and out power of laser light passed and emitted by the LiBP and KDP are show in the Table 4.
1200 0
40 C 0 45 C 0 50 C 0 55 C 0 60 C
1100 1000
Dielectric constant ( r )
900 800
4. Conclusion
700 600 500 400 300 200 100 0 1
2
3
4
5
6
Log f Fig. 6. Variation of dielectric constant with log frequency of LiBP.
7
The lithium boro phthalate (LiBP) compound was synthesized using phthalic acid, Boric acid and Lithium carbonate taken in equi molar ratio and the seed crystals were grown from synthesized compound by slow evaporation technique. Purity of the seed crystals was improved by successive recrystallization process. The Bulk single crystal of LiBP was grown at room temperature by slow evaporation technique with good morphology. Powder X-ray diffraction analysis confirmed the crystalline nature of the grown crystal, and the structure of the grown crystal is found to be monoclinic structure with space group C2. The FTIR spectrum recorded for the grown sample confirms the presence of suitable functional groups in the grown crystal. The linear optical study revealed the good transparency of the grown crystal in wide wavelength range which suits the crystal for various electro optic applications. It is interesting to observe that the NLO efficiency of LiBP is superior to KDP. Microharness test reveals that the LiBP single
Please cite this article in press as: K. Mohanraj et al., Structural, mechanical, electrical and optical properties of a new lithium boro phthalate NLO crystal synthesized by a slow evaporation method, Opt. Laser Technol. (2017), http://dx.doi.org/10.1016/j.optlastec.2017.06.001
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crystal behaves like a soft material, which is suitable for device fabrication. The dielectric studies show that the dielectric constant of the LiBP single crystal remains same at various temperatures, which reveals the good dielectric behavior of the grown crystal. The less value of dielectric loss of higher frequencies proves the good quality of the grown crystal. In view of the good optical properties, better SHG efficiency and moderate mechanical behavior, LiBP crystal would be a suitable material for nonlinear optical device applications. References [1] N. Zaitseva, L. Carman, Prog. Cryst. Growth Charact. 43 (2001) 1–118. [2] J. Badan, R. Hierle, A. Perigaud, J. Zyss, NLO Properties of Organic Molecules and Polymeric Materials, American Chemical Society Symposium Series 233, American Chemical Society, Washington, DC, 1993. [3] N.P. Prasad, Polymer 32 (1991) 1746–1751. [4] B.G. Penn, B.H. Cardelino, C.E. Moore, A.W. Shields, D.O. Frazier, Prog. Cryst. Growth. Charact. 22 (1991) 19–51.
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Please cite this article in press as: K. Mohanraj et al., Structural, mechanical, electrical and optical properties of a new lithium boro phthalate NLO crystal synthesized by a slow evaporation method, Opt. Laser Technol. (2017), http://dx.doi.org/10.1016/j.optlastec.2017.06.001