# Growth and Characterization of Unidirectional Grown Imidazolium L-Tartrate (IMLT) Single Crystal by SR Method

V Thayanithi, P Praveen Kumar

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V Thayanithi, P Praveen Kumar. Growth and Characterization of Unidirectional Grown Imidazolium L-Tartrate (IMLT) Single Crystal by SR Method. Mechanics, Materials Science & Engineering MMSE Journal. Open Access, 2017, 9, 10.2412/mmse.13.44.508. [https://hal.science/hal-01503643](https://hal.science/hal-01503643)

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# Growth and Characterization of Unidirectional Grown Imidazolium L-Tartrate (IMLT) Single Crystal by SR Method

V. Thayanithi<fnref n="1" />, P. Praveen Kumar<fnref n="1" />,ᵃ

<figure><img src="image_2.png" /></figure>

DOI 10.2412/mmse.13.44.508 provided by [Seo4U.link](https://link.springer.com/10.2412/mmse.13.44.508)

**Keywords:** Slow evaporation, SR method, Single XRD, Photoluminescence, Nonlinear optics.

**ABSTRACT.** The second order non-linear optical material Imidazolium L-Tartrate (IMLT) seed crystal was successfully grown by slow evaporation method. <0 0 1> plane unidirectional crystal was successfully grown by Sankaranarayanan and Ramasamy (SR) method. The growth of conventional and SR grown crystals were optimized. Cell parameter, space group and morphology of the grown conventional method crystal were found by single XRD. Transparency of the grown IMLT crystals by conventional and SR method were compared by UV-Vis-NIR spectroscopy. Emission spectrum of the grown IMLT crystals were analysed by Photoluminescence. Dielectric constant and Dielectric loss of the grown crystals were analysed. Mechanical strength of the grown IMLT crystals was determined by Vickers hardness test.

**Introduction.** Chiral organic compounds with high order nonlinear susceptibility ($\chi^{(n)}$) are fast response than inorganic compounds in optical application such as optical communication, optical data storage, terahertz generation. In recent years, many researchers give more attention on the organic compounds because organic compounds are crystallizing with hydrogen bonds, large dipole moment, weak van der Waals force, eccentric crystal structure [1-3]. The aromatic heterocyclic organic compound of imidazole react with organic and inorganic acid and its forms hydrogen bond and delocalized $\pi$-electron system, which enhance the molecular hyper-polarizability is potentially effective strategy for crystallizing nonlinear optical materials [4-6]. It is difficult to grow specific oriented bulk size crystal without defects from solution by slow evaporation method for device application. In this point of view Sankaranarayanan and Ramasamy (SR) method has been applied to grow unidirectional crystal from solution [7, 8]. In this present investigation, Imidazolium tartrate was successfully grown unidirectional by SR method. Single XRD conformed crystalline nature. Grown crystal was subjected to UV-Vis-NIR spectroscopy, photoluminescence, Dielectric and Mechanical strength.

**Experimental procedure.** Title of the compound imidazolium tartrate was synthesized by dissolving of Imidazole and L-Tartaric acid equimolar ratio in de-ionized water and the reaction scheme of crystal is shown in Fig 1. The mixed solution was stirred well upto 6 hours. After saturation was attained, the solution was filtered into beaker and covered polythene paper with few holes and retained at dust free place. Crystals were obtained from mother solution within a week by slow evaporation method. Repeated recrystallization was take place to improve crystal perfection. Good transparent crystal was selected and dipped into beaker with mother solution. After 20 days of time period, 15 × 10 × 3 mm³ dimension crystal was obtained from solution. The photograph of the grown crystal by conventional method is shown in Fig 2a.

Growth setup of SR method [7] was constructed. C-axis < 0 0 1> plane was selected, based on the morphology of the conventional grown crystal. The selected crystal was placed in bottom of the

<footnote n="1">1 – Department of Physics, Presidency College, Chennai, India</footnote>

<footnote>a – ppkpresidency@gmail.com</footnote>
ampoule and <0 0 1> plane was oriented towards the saturated solution. Evaporation of the solvent take place at top portion by ring heater, seed crystal was initiated to crystallize. Temperature of top portion was maintained at 315 K. After 30 days of period, IMLT crystal with 28 mm of length and 15 mm of diameter was obtained. The photograph of the grown by SR method crystal is shown in Fig. 2b.

<figure><img src="image_3.png" /><figcaption>Fig. 1. Reaction scheme of the grown IMLT crystal.</figcaption></figure>

**Result and Discussion**

The grown IMLT crystal was subjected to single crystal XRD by using ENRAF NONIUS CAD4 diffractometer. The grown IMLT crystal resides to monoclinic crystal system with noncentrosymmetric space group P2₁. Cell parameters values of grown IMLT crystal are a = 7.55 Å, b = 6.93 Å, c = 8.97 Å, β = 102.05 and volume V = 469.32 Å³, which are in good agreement with reported values [9]. Morphology of the grown crystal was identified by X-ray goniometry and it was drawn by using Winxmorph software. Morphology of the grown crystal shows that it is in bar shape. <0 0 1> plane is dominant and major growth direction along with c-axis of the grown IMLT crystal. Morphology of the grown IMLT crystal is shown in Fig. 2c.

**Single X-ray Diffraction.**

<figure><img src="image_4.png" /><figcaption>Fig. 2. The photograph of grown crystal (a) conventional method (b) SR method (c) Morphology of the grown crystal.</figcaption></figure>

**UV-Vis NIR analysis.** Linear optical properties of the grown IMLT crystals transmittance were examined by UV-Vis NIR spectrum, recorded using Shimadzu spectrometer in range 200 nm to 800 nm. The lower cut of wavelength of grown IMLT crystal absorbed at 235 nm. The transmittance percentage of the grown IMLT of SR method and conventional crystals has 49 % and 33 % respectively in visible region. The transmittance percentage of the grown SR method crystal is
increased 16% than conventional method. The recorded transmittance spectra of the grown IMLT crystals were shown in Fig 3.

**Photoluminescence spectroscopy.** Photoluminescence emission spectrum was recorded for the conventional and SR grown crystals using Bruker S4 pioneer in the range 300 – 800 nm. The emission wavelength of the grown IMLT crystals observed at 535 nm and it corresponds to emission region. The emission spectra of the grown IMLT crystals are shown in Fig 4.

<figure><img src="image_5.png" /><figcaption>Fig. 3. Transmittance spectra of the grown IMLT crystals.</figcaption></figure>

<figure><img src="image_6.png" /><figcaption>Fig. 4. Emission spectra of the grown IMLT crystals.</figcaption></figure>

**Dielectric studies.** Dielectric constant ($ε_r$) and Dielectric loss (tan δ) of the grown IMLT crystals were studied by using Agilent 4284-A LCR meter. The cut polished of the grown IMLT crystals of SR method and conventional method were mounted in sample holder and the dielectric measurements were carried out in the frequency range 100 Hz – 5 MHz at room temperature. The dielectric constant of the grown IMLT crystals by SR method and conventional method is decreases with increasing frequency [10] and it is shown in Fig. 5, a. The dielectric constant of the grown IMLT crystal by SR method has higher value compared than conventional crystal. The dielectric constant of the grown crystals is due to the contribution of dipolar, ionic, electronic and space charge polarization and it depend, on the frequency. The dielectric loss of the grown IMLT of SR method and conventional crystals are shown in Fig. 5, b. The dielectric loss of the grown IMLT of SR method crystal is lesser than conventional method, due to lesser defects in crystalline nature [11].

<figure><img src="image_7.png" /><figcaption>Fig. 5. (a) Dielectric constant versus log (f), (b) Dielectric loss versus log (f).</figcaption></figure>
**Microhardness studies.** Vicker's microhardness test determines the mechanical strength of the grown IMLT crystal by SR method and conventional method and it is taken by Leitz-wetzler hardness tester with diamond indenter. The load P indentation is range from 10 g to 100 g. The microhardness value was calculated using this formula

$$H_v = (1.8544) P / d^2 \text{ Kg/mm}^2$$

where $H_v$ (Kg/mm²) is Vickers hardness number;

$P$ (g) is applied load;

$d$ (µm) is average diagonal length of the indentation mark.

The hardness value of the grown IMLT of SR method and conventional crystal is decreases with increasing load. The hardness value of the grown IMLT crystal by SR method is higher than the conventional crystal and it is shown in Fig 6. The work hardening coefficient $n$ (Meyer's index) was calculated [11]. The calculated hardness coefficient ($n$) values of the grown IMLT of SR method crystal and conventional crystal are 1.85 and 1.96 respectively. From this hardness coefficient values of IMLT crystals are in soft category and SR grown crystal have higher hardness compare than conventional crystal.

<figure><img src="image_8.png" /><figcaption>Fig. 6. Vicker's hardness analysis for the grown IMLT crystal.</figcaption></figure>

**Summary.** Optically good quality crystal of noncentrosymmetric Imidazolium Tartrate crystal has been successfully grown using conventional and SR method. The grown crystal belongs to the monoclinic system with noncentrosymmetric space group $P2_1$. The optical transmittance of the grown IMLT crystal by SR method is increased 16% than conventional method and lower cut of wavelength found to be 235 nm. The emission wavelength of the grown IMLT crystals observed at 535 nm and they are in green emission region. The grown IMLT crystal by SR method has high dielectric constant with low dielectric loss compared than the conventional method crystal. The hardness value ($H_v$) of the grown IMLT crystal by SR method has high compared than conventional crystal. It is concluded that the grown IMLT crystal by SR method is good promising NLO material compared than conventional method.

## Acknowledgements

The authors acknowledge the SAIF IIT, Madras for characterization studies.
References

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Cite the paper

V. Thayanithi, P. Praveen Kumar (2017). *Growth and Characterization of Unidirectional Grown Imidazolium L-Tartrate (IMLT) Single Crystal by SR Method*. Mechanics, Materials Science & Engineering, Vol 9. DOI: 10.2412/mmse.13.44.508