Studies on growth and characterization of a novel nonlinear optical and ferroelectric material – N,N-dimethylurea picrate single crystal

Journal of Crystal Growth 393 (2014) 7–12

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Journal of Crystal Growth journal homepage: www.elsevier.com/locate/jcrysgro

Studies on growth and characterization of a novel nonlinear optical and ferroelectric material – N,N-dimethylurea picrate single crystal A. Shanthi a,∗, C. Krishnan b, P. Selvarajan c a

Department of Physics, Rani Anna Govt. College, Tirunelveli, Tamilnadu, India Department of Physics, Arignar Anna College, Aralvoimoli, Tamilnadu, India c Department of Physics, Aditanar College of Arts and Science, Tiruchendur, Tamilnadu, India b

art ic l e i nf o

a b s t r a c t

Available online 22 December 2013

A novel organic nonlinear optical (NLO) material viz. N,N-dimethylurea picrate (NNDMP) was grown by the slow evaporation technique using N,N-dimethyl formamide as a solvent. The solubility of the grown sample has been estimated for various temperatures. The XRD study reveals that the grown crystal crystallizes in the monoclinic crystal system and the corresponding lattice parameters were determined. The relative second harmonic generation (SHG) efficiency of the NNDMP was found to be 1.045 times that of KDP by Kurtz–Perry powder technique. FTIR and FT-Raman spectral analyses explain the various functional groups present in the sample. The optical spectral analysis of the grown crystal has been performed by UV–vis–NIR spectroscopy and the band gap energy was found out. The thermogravimetric analysis and differential thermal analysis (TG/DTA) reveal that the NNDMP crystal is stable at up to 172 1C. A prominent first-order ferroelectric to paraelectric phase transition at 323 K has been observed and activation energy was determined for the AC conduction process in the sample. & 2013 Elsevier B.V. All rights reserved.

Keywords: A1. X-ray diffraction A2. Growth from solutions B1. Organic compound B2. Ferroelectric materials B3. Nonlinear optical

1. Introduction Many new organic crystals have been found based on the predictive molecular engineering approach and have been shown to have potential applications in nonlinear optics and these materials find wide application in telecommunication, frequency mixing, optical parametric oscillation, optical bi-stability, optical image processing and under water communication etc. [1–2]. The advantage of the organic materials is that they offer high degree of synthetic flexibility to tailor their optical properties through structural modification and exhibit very high laser damage threshold [3]. One of the ways in which an organic molecule can have a large optical nonlinearity is by possessing a conjugated system of one of the bonds which gives rise to a strong π-electron delocalization. The delocalization of the π-electrons can be further enhanced by the addition of donor and accepter groups at the opposite ends of the conjugated system. The strong charge transfer between such groups operating across the entire extended system markedly adds to the optical nonlinearity of the structure [4]. In order to achieve good macroscopic nonlinear response in organic crystals, one requires an increase in the number of π-electrons and π-delocalization length, so as to lead to high molecular hyperpolarizability and also proper orientation of the molecule in the solid

n

Corresponding author. Tel.: þ 91 9442451124. E-mail address: [email protected] (A. Shanthi).

0022-0248/$ - see front matter & 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jcrysgro.2013.12.011

state structure to facilitate high-frequency conversion efficiency. Ferroelectric materials exhibit highly electromechanical coupling with the ability of polarization in response to an external electric field or mechanical load [5]. The ferroelectric crystal is a phasetransforming material and there exists a critical temperature, called the Curie temperature (Tc). Below the Curie temperature, ferroelectric and pyroelectric polar materials possess a spontaneous polarization or electric dipole moment but above Tc, they are paraelectric with nonpolar structures. Ferroelectric crystals have attracted attention for application in various actuator and sensor applications due to high frequency response and electrooptic properties for device fabrication [6,7]. N,N-dimethylurea picrate crystal is observed to be nonlinear optical and ferroelectric material and it is one of the organic crystals that have enhanced optical properties compared with urea [8]. Picric acid is a well-established nonlinear optical material, which crystallizes in a non-centrosymmetric space group Pca21 [9]. The crystal structures of a large number of picrate salts and picric acid complexes have been studied to understand the conformational features and charge transfer processes [10,11]. Picric acid forms crystalline picrate salt with various organic molecules by virtue of its acidic nature and forms salts through specific electrostatic or hydrogen bonding interactions. Several authors were reported stable picrate compounds with various organic molecules such as L-asparagine [12], 8-hydroxyquinoline [13], L-proline [14] and Glycine Picrate [15] due to the presence of active π- and ionic bonds. Vivek et al. [16] have reported the growth and anisotropic studies

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A. Shanthi et al. / Journal of Crystal Growth 393 (2014) 7–12

of nonlinear optical single crystal Imidazole–Imidazolium picrate (IIP). The SHG efficiency of IIP crystal is 3.6 times that of KDP. Anandha babu et al. [17] have discussed the synthesis, structure and physical properties of 1,3-Dimethylurea dimethyl ammonium picrate (DMUP) and the crystal structure belongs to the orthorhombic with space group Cmc21. The present investigation deals with the growth of N,N-dimethylurea picrate (NNDMP) single crystals grown using N,N-dimethylformamide as the solvent by slow solvent evaporation technique at room temperature (30 1C). The grown crystals were characterized by X-ray diffraction, FTIR, FT-Raman, UV–vis–NIR spectroscopy, TG/DTA and DSC analysis, dielectric and SHG analysis and the results are discussed and reported for the first time. 2. Solubility and crystal growth The title compound was synthesized by taking precursor chemicals like GR grade N,N-dimethylurea and picric acid in the molar ratio of 2:1 by the solution method. Calculated amounts of the chemicals were dissolved in N,N-dimethyl formamide solvent and N,N-dimethylurea picrate (NNDMP) salt was synthesized and it was re-crystallized twice. The solubility study of the title compound in N,N-dimethyl formamide solution was performed using a hot-plate magnetic stirrer and a digital thermometer by the gravimetric method [18]. The re-crystallized salt of NNDMP was added step by step to 25 ml of N,N-dimethyl formamide solution in an air tight container kept on the hot-plate magnetic stirrer. Addition of the salt and stirring were continued till a small precipitate was formed. This gave the conformation of the supersaturated condition of the solution. Then 10 ml of the clear supernatant liquid was withdrawn by means of a pipette and the same was poured into a clean, dry and weighed empty Petri dish. The solution was warmed up at 45 1C till the solvent was evaporated out. The amount of salt present in the 10 ml of the solution was measured by subtracting the weight of the empty Petri dish. From this, the quantity of NNDMP salt (in gram) dissolved in 100 ml of N,N-dimethyl formamide solution was determined. The same procedure was followed to find out the solubility of NNDMP sample for various temperatures. The solubility curve of NNDMP is shown in Fig. 1. From the curve, it is observed that the solubility of NNDMP sample in N,N-Dimethyl formmaide solvent linearly increases with temperature, exhibiting a high solubility gradient and positive temperature coefficient. This shows the slow evaporation technique is the appropriate method and the solvent is suitable for the growth of NNDMP

crystal. It is to be mentioned here that the title compound is not soluble in water and hence water is not used as the solvent in this work. For the growth process of N,N-dimethylurea picrate (NNDMP) single crystals, slow solvent evaporation technique was adopted. Using the re-crystallized salt of NNDMP and N,N-dimethylformamide solvent, the saturated solution was prepared in accordance with the solubility data at room temperature and stirred continuously about 2 h to ensure homogeneous concentration throughout the volume of the solution. Then the solution was filtered by a high quality 4 μm Whatmann filter paper to remove extraneous solid colloidal particles and the clear filtrate was kept in a controlled evaporation condition using a constant temperature bath (CTB). The seed crystals of NNDMP were obtained by spontaneous nucleation. To grow bigsized single crystals, the bottom seed growth method was used. Good quality of stable, non-hygroscopic and yellow colored crystals of size 14  4  3 mm3 were harvested in 45–50 days. Photograph of NNDMP crystals are shown in Fig. 2.

3. Characterization techniques The grown NNDMP crystals were subjected to single crystal Xray diffraction method to estimate the lattice parameters by employing ENRAF NONIUS CAD4-F X-ray diffractometer. To identify the diffraction planes, the powder X-ray diffraction pattern of the powdered sample of NNDMP was recorded using a X0 Pert Pro Powder X-ray diffractometer with CuKα radiation(λ¼ 1.54056 Å). The sample was scanned over the required range for 2θ and relative intensity values. A Perkin Elmer FTIR spectrometer was used for IR spectral measurements. The sample was prepared by the KBr pellet technique and the spectrum was recorded in the range of 4000–400 cm  1. Raman spectrum was recorded using a Bruker RFS27 FT-Raman spectrometer in the range of 4000– 50 cm  1. The optical transmissioin spectrum of NNDMP crystal was recorded using a UV–vis–NIR spectrophotometer (Lamda 35 model) from 200 to 1100 nm. The NLO conversion efficiency of grown crystal was measured by Kurtz and Perry Powder SHG Test using a Q-switched mode locked Nd: YAG laser with the first harmonic output at 1064 nm with 6 ns pulse width. The transmitted fundamental wave was passed over a monochromater which separates 532 nm (second harmonic signal) from 1064 nm and passed through BG-34 filter to remove the residual 1064 nm light. The capacitance (Ccry) and dielectric loss (tan δ) were measured using the conventional parallel plate capacitor method with frequency range (50 Hz–1 MHz) using LCR meter (agilent

112 110

solubility (g /100 ml)

108 106 104 102 100 98 96 94 92 90 30

32

34

36

38

40

42

44

46

Temperature ( C) Fig. 1. Solubility curve of NNDMP crystal.

Fig. 2. Photograph of NNDMP crystals.

4.2. Fourier transform infrared and FT-Raman spectral analysis The recorded FTIR and FT-Raman spectra are presented in the Fig. 4. The formation of charge transfer complex by the reaction between N,N-dimethylurea and picric acid is strongly evident by the presence of the main characteristic of infrared bands of the donor and accepter species in the crystal. The high wave number region of 120

16000

1163 1077 821

40 20 509 333

1830

1271 1163

FT- Raman

1603

2462

2

0

101

30

105

20

213 -4 0 3

-1 2 1

200

10 2 112 020

6000

-1 0 1

Intensity (counts)

8000

2000

500

0

Fig. 4. FTIR and FT-Raman spectra of NNDMP crystal.

the IR spectrum, the sharp peak at 3334 and the shoulder band 3196 cm  1 is due to the N–H asymmetric and symmetric stretching vibrations of NH3 þ group respectively [24]. This analog is not observed in the Raman spectrum. The band at 3044 cm  1 observed in IR and Raman spectra corresponding N–H symmetric vibration. The medium band observed in IR band at 2939 cm  1 and 2974 cm  1 in Raman spectrum is assigned to the C–H asymmetric stretching mode. The wide band observed at 1558 cm  1 and medium band in Raman spectra at 1561 cm  1 can be correlated to the combination of NO2 asymmetric stretching and NH3 þ symmetric deformation. The asymmetric and symmetric deformation mode of methyl groups appears at very wide band at 1441 and 1368 cm  1 in the IR and 1367 cm  1 band in the Raman spectrum. The aromatic CQH plane bending mode of vibration appears at 1163 and 1077 cm  1 bands in the IR spectrum and the corresponding weak bands at 1164 and 1078 cm  1 in the Raman spectrum [25]. The medium band at 1487 cm  1 in the IR spectrum and weak band in the Raman at 1491 cm  1 is most probably due to the CH2 asymmetric deformation mode. The very sharp band in IR and weak band in Raman observed at 916 cm  1 owe to the C–NO2 stretching vibration [26]. The mode of vibration such as wagging (out of plane), scissoring and rocking (in plane) of NO2 usually occur at wave numbers below 900 cm  1. The external modes which are due to translator and rotatory motion of molecules in the crystalline lattice have been appeared in Raman spectra below 200 cm  1. The other skeletal mode of vibrations C–N, C–C and C–O have been identified and assigned in Table 1 [27,28].

4.3.1. Differential scanning calorimetric (DSC) study Differential scanning calorimetry (DSC) was used to find out the melting and decomposition point of the sample and to detect the presence of crystalline phase. The recorded DSC spectrum of NNDMP crystal is shown in Fig. 5. It is observed that both endothermic and exothermic peaks are around at 126 1C and 265 1C respectively. The sharp endothermic peak is assigned to the melting point of the substance and the decomposition of the sample starts from 172 1C. The exothermic peak at 265 1C may be due to liberation of some gaseous molecules. The sharpness of the peak shows good degree of crystallinity of the sample [29].

12000

4000

-20 4000 3500 3000 2500 2000 1500 1000 Wavenumber (cm-1)

4.3. Thermal analysis

14000

10000

80 60

0

Single crystal X-ray diffractometric analysis reveals that NNDMP crystal belongs to the monoclinic system which is recognized as noncentrosymmetric and thus satisfying one of the basic and essential requirements of for the SHG activity of the crystal. The lattice parameter values are a¼11.097(8) Å, b¼6.825 (2) Å, c¼11.128 (6) Å, α¼γ¼90.00 (0) Å, β¼100.03 (6) Å and volume¼ 830.0 (1) Å3. Artali et al. reported 1,3-dimethylurea picrate in the molecular ratio of 1:1 belongs to triclinic crystal system [19]. The NNDMP crystals were found to be elongated along crystallographic c-direction due to comparatively higher growth rate along this direction and same type of morphology was observed in the polar crystals such as MMONS [20], m-NA [21] and DMU [22]. The growth is inhibited along one of the directions of the polar axis by additives or solvent molecules. Such a unidirectional growth is observed in NNDMP crystal and NNDMP is also a polar crystal. The powder XRD study was also carried out to check the correctness of the data and to identify the diffraction planes of the grown crystal. Powder XRD pattern of NNDMP is given in Fig. 3 and the sharp Bragg peaks of powder XRD pattern were indexed using the TREOR software package following the procedure of Lipson and Steeple [23]. Specific well-defined peaks at 2θ values indicate high crystallinity of the grown crystal and h k l planes satisfy the general reflection conditions of space group observed from the structure determination of the NNDMP crystal.

100

% Transmittance

541 507

910 710

3334

4

3044

4.1. X-ray diffraction studies

(FT- IR )

2879

4. Results and discussion

6 Raman intensity (arb. units)

4284A) at various temperature ranging from 306 to 343 K. The DSC study was performed using Perkin Elmer differential scanning calorimeter. The sample weight of 4.2 mg was placed in an aluminum pan with heating rate of 10 1C min  1 in the range of 30–445 1C. The thermogravimetric analysis and differential thermal analysis (TG/DTA) curves were recorded by employing using Perkin Elmer thermal analyzer in nitrogen atmosphere at a heating rate of 10 1C/min. and the temperature from 40 1C to 750 1C.

9

1302

A. Shanthi et al. / Journal of Crystal Growth 393 (2014) 7–12

0 -2000 10

40

50

2

degrees)

60

70

80

Fig. 3. Powder X-ray diffraction pattern of NNDMP crystal.

90

4.3.2. TG/DTA analysis The thermogravimetric analysis and differential thermal analysis (TG/DTA) of NNDMP crystal are displayed in Fig. 6. From the

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A. Shanthi et al. / Journal of Crystal Growth 393 (2014) 7–12

Table 1 FTIR and FT-Raman bands and their assignments for NNDMP crystal. FTIR (cm  1)

FT-Raman (cm  1)

3334 and 3196 3044 2939 1558

3044 2974 1561

1487 1441 and 1368

1491 1367

1163 and 1077 916 – 786 744 710 678 541 524 507

1164 and 1078 916 821 786 – – – – – 509

Assignments NH3 þ asymmetric stretching NH3 þ symmetric stretching C–H asymmetric Stretching NO2 asymmetric and NH3 þ symmetric deformation CH2 asymmetric deformation Asymmetric and symmetric deformation mode of methyl group Aromatic CQH plane bending C–NO2 stretching C–H bending mode NO2 deformation Aromatic CQH out of plane bending N–H bending C–H out of plane deformation C–C deformation NO2 scissoring C–O bending

256 °C -5

Heat Flow end down (mW)

DSC 0 5 10 15 20 25 30 35 40

There is a little weight loss between 414 and 750 1C observed and this is due to decomposition of the residue that is left over after the major weight loss. The absence of weight loss around 100 1C conforms that there is no crystallization of water in the molecular structure. The TG study of the NNDMP crystal shows that the crystal is stable up 172 1C and it could be used for device fabrication. From the DTA curve, it is observed that an endothermic peak at 126 1C is attributed to the melting point of NNDMP crystal and it is observed to be in good agreement with the endothermic peak in DSC curve. This is followed by an exothermic peak at 258 1C which coincides with decomposition observed in TG curve. 4.4. Second harmonic generation test Second harmonic generation (SHG) is also called a frequency doubling in nonlinear optics, in which photons interacting with a nonlinear material are effectively combined to form new photons with twice the energy, and therefore twice the frequency of the initial photons. The study of NLO efficiency has been carried out by modified experimental set up of Kurtz and Perry [30]. The crystal was ground into a homogenous powder and densely packed between two transparent glass micro capillary tubes. An intensity of Nd: YAG laser (λ ¼1064 nm) with a pulse duration 6 ns was through the powdered sample. A standard KDP crystal was used as a reference material and tested under identical experimental condition. The SHG behavior was confirmed from the output of the laser beam having the green light emission. The second harmonic emission of 9.2 mJ for NNDMP crystal obtained for an input energy of 0.68 J. Thus the relative measured output from the specimen with respect to KDP crystal (8.8 mJ) shows that relative SHG efficiency of the NNDMP crystal is 1.045 times that of the KDP crystal. This strongly suggests that the grown crystal is a potential candidate for SHG application and it could be a better alternative for KDP in frequency doubling.

126 °C

4.5. Optical property 100

200

300

400

Temperature ( °C ) Fig. 5. DSC thermogram of NNDMP crystal. 9 -120

7

-100

Weight (mg)

DTA 6

-80

254 C

5

-60

4

-40

3

-20

2

0 20

1 125 C

100

200

Heat flow endo down (mW)

-140

TGA

8

40 300

400

500

600

700

Temperature (°C °C) Fig. 6. TGA/DTA thermal curves for NNDMP crystal.

TG curve, it is clear that there is no weight loss between the room temperature to 172 1C and it shows that the title compound is stable up to 172 1C. The first stage of decomposition commences at 172 1C and end at 274 1C. The next weight loss occurs between 274 and 414 1C and shows that the decomposition is almost complete.

The transmittance range and cut-off wavelength of single crystals are important factors for optical applications. Hence the study of the transmission of UV–visible range through the NLO material is necessary. It gives more information about the band structure, types of optical transition and quality of the material etc. The recorded UV–vis-transmission spectrum of NNDMP crystal is presented in the Fig. 7. Optically polished single crystal of 1.5 mm thickness was used for this study. The transmission spectrum for NNDMP sample indicates that the crystal has minimum absorbance in the region from 440 to 1100 nm without any sharp absorption peaks, revealing the absence of any impurity in the grown crystal. It is evident from the transmission spectrum of NNDMP crystal that it possesses good transperency in the visible and near UV region. It shows nearly 75% transparency and it can be used for optical application including the second harmonic generation of Nd: YAG laser of fundamental wavelength λ¼ 1064 nm. The crystal has its lower cut-off wavelength closer to 440 nm and it is leading to electronic excitation from the valence band to conduction band, can be used to determine nature and value of optical band gap. The high value of absorption edge is due to the charge transfer taking place between the phenolic group of picric acid and amino group of N, N-dimethylurea and this also leads the coloration in the grown material. The measured transmittance (T) is used to calculate the absorption coefficient (α) using the following relation [31]: α¼

2:303 log ð1=TÞ d

A. Shanthi et al. / Journal of Crystal Growth 393 (2014) 7–12

90

100 kHZ 400 kHZ 600 kHZ 1MHz

150

80

Dielectric constant (εr)

140

70 % Transmittance

11

60 50 40 30 20

130 120 110 100 90 80

10

70

0 200

400

600 800 Wavelength (nm)

1000

1200

Fig. 7. Transmission spectrum for NNDMP crystal.

305

310

315

320 325 330 Temperature (K)

335

340

345

Fig. 9. Variation of dielectric constant with temperature at different frequencies for NNDMP crystal.

60 0.09

--

50

0.08

40

0.07

Dielectric loss (tan )

( hv)2 (eV mm-2)

Eg = 2.73 eV

30

20

10

100kHz) 400kHz 600kHz 1MHz

0.06 0.05 0.04 0.03 0.02

0

1

2

3

4

5

6

7

hv (eV) 2

Fig. 8. Plot of (αhν) versus photon energy for NNDMP crystal.

where T is the transmittance and d is the thickness of the crystal in mm. The optical band gap energy (Eg) can be evaluated from the transmission spectra [32]. Optical absorption coefficient (α) near the absorption edge is given by the following relation: qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi αhν ¼ A ðhν  Eg Þ where Eg is the optical band gap energy of the crystal, h is the Planck0 s constant, ν is the frequency of the incident photon and A is a constant. The Tauc0 s graph [33] plotted between variation of (αhυ)2 with the photon energy (hυ) is shown in Fig. 8 and the band gap energy is calculated by extrapolation of linear part. The band gap energy is found to be 2.73 eV. 4.6. Dielectric study The dielectric constant and dielectric loss factor (tan δ) were measured using the conventional parallel plate capacitor method [34–36]. The defect-free and good quality sample was selected for this study. Opposite faces of the sample crystal was coated with good quality graphite to obtain good ohmic contact. The plots between dielectric constant (εr) and temperature (T) for various frequencies are drawn and shown in Fig. 9. From the graph it is observed that the dielectric constant (εr) increases with increase of temperature and it reaches maximum at 323 K and then gradually decreases with the increase of temperature. This indicates that the

0.01 305

310

315

320

325

330

335

340

345

Temperature (K) Fig. 10. Variation of dielectric loss with temperature at different frequencies for NNDMP crystal.

grown crystal begins to undergo phase transition from ferroelectric to paraelectric at 323 K. Similar results have been reported earlier for various samples like zinc tris (thiourea) sulfate [37] and Strontium tartrate trihydrate [38] which exhibit ferroelectric properties. Thus, it is inferred that the grown crystal of NNDMP is a ferroelectric material. The dielectric loss (tan δ) was also studied as a function of temperature at various frequencies and is shown in Fig. 10. The low value of dielectric loss suggests that the grown crystal is of moderately good quality and it can be used for the applications towards photonic and electro-optic devices. The electrical conduction in dielectrics is mainly due to defects controlled process in low temperature region and the presence of impurities and vacancies predominantly determines conducting process in this region. AC conductivity was determined for the sample using the relation rac ¼ ωεrεo tan δ where εo is the permittivity of the free space and ω is the angular frequency. Using the data of conductivity, the activation energy was calculated. The activation energy of a substance is the minimum energy required for the charged species in the compound to activate while an AC voltage is applied. The general relation proposed by Arrhenius for the temperature variation of conductivity is given by rac ¼ roexp ( Eac/kT) where k is the Boltzmann0 s constant, Eac is the activation energy, T is the absolute temperature and so is a constant which

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A. Shanthi et al. / Journal of Crystal Growth 393 (2014) 7–12

M.K. University (Madurai), Crescent Engineering College, Chennai and IIT Madras. The authors are also grateful to the management of S.T. Hindu College, Nagercoil, Aditanar College, Tiruchendur and the staff members of Rani Anna Government College, Tirunelveli.

-11.4 -11.5

Eac = 0.021 eV -11.6

In (

ac

)

-11.7 -11.8

References

-11.9 -12.0 -12.1 -12.2 -12.3 3.14

3.16

3.18

3.20

3.22

3.24

3.26

3.28

-1

1000 / T (K ) Fig. 11. Plot of ln sac versus 1000/T at frequency of 1000 Hz for NNDMP crystal.

depends upon the type of the sample. The above equation may be re-written as ln rac ¼ ln ro  (Eac/kT). A plot of (ln rac) versus 1/T is drawn for frequency of 1000 Hz and it is shown in Fig. 11 which gives Eac/k as the slope. The activation energy was estimated from the slope of the plot and its value is found to be 0.021 eV. 5. Conclusions High quality single crystals of NNDMP with good optical grade were conveniently grown by the slow solvent evaporation technique. The solubility of the NNDMP sample was estimated at different temperatures. The X-ray diffraction studies confirm the monoclinic structure and crystallinity of the grown crystal. The presence of the fundamental functional groups has been established by FTIR and FT-Raman studies. Optical study shows the NNDMP crystal has wide transparency window from 440 to 1100 nm, which highlights its prospects of application as an NLO material. Thermal studies such as TG/DTA and DSC reveal the three stages of weight loss occurring in the sample and it further proves that NNDMP crystal is thermally stable up to 172 1C. The powder SHG effective nonlinearity of NNDMP material is 1.045 times as that of the KDP. Dielectric study reveals NNDMP crystal has a phase transition from ferroelectric to paraelectric at 323 K temperature. It is evident that crystal exhibits ferroelectric property and it attracts much attention due to its applications in dielectric capacitors, actuators etc. The NLO property of NNDMP material value is closely related to KDP and it has a higher ferroelectric transition temperature compared to KDP and it is the advantage of the title compound. It is to be mentioned here that other ferroelectric characterization studies of the grown crystal are in progress. Acknowledgment The authors are thankful to staff members for the supportive work from various research centers of St. Joseph College (Trichy),

[1] K Ambujam, K Rajarajan, S. Selvakumar, J. Madhavan, Gulam Mohamed, P. Sagayaraj, Opt. Mater 29 (2007) 657–662. [2] K. Meera, R Muralidharan, R. Dhanasekaran, P Prapun Manyum, Ramasamy, J. Cryst. Growth 263 (2004) 510–516. [3] C. Justin Raj, S. Dinakaran, S. Krishnan, B. Miltonboaz, R. Robert, S. Jerome Das, Opt. Commun. 281 (2008) 2285–2290. [4] G. Anadha Babu, A.S Sreedhar, S. Venugopal Rao, P. Ramasamy, J. Cryst. Growth 311 (2009) 3461–3465. [5] K. Ravichandran Bhattacharya, Acta Mater. 51 (2003) 5941–5960. [6] K. Uchino, Acta Mater. 46 (1998) 3745–3753. [7] Sachio Horiuchi, Reiji Kumai, Yoshinori Tokura, J. Am. Chem. Soc. 127 (2005) 5010–5011. [8] M. Zha, M Ardoino, G. Zuccalli, C. Paorici, C Razzetti, Synth. Metals 83 (1996) 209–211. [9] Li Xiao-Hong, Zhang Xian-Zhou, Comput. Theor. Chem. 963 (2011) 27–34. [10] H. Nagata, Y. In, M. Doi, T. Ishida, A. Wakahara, Acta Cryst. E B51 (1995) 1051–1058. [11] G. Smith, U.D. Wermuth, P.C. Hearly, Acta Cryst. E 60 (2004) O1800–O1803. [12] P Srinivasan, T. Kanagasekaran, R. Gopalakrishnan, G Bhagavannarayana, P. Ramasamy, Cryst. Growth Des. 6 (2006) 1663–1670. [13] V. Krishna Kumar, R Nagalakshmi, Spectrochim. Acta Part A 66 (2007) 924–934. [14] T. Uma Devi, N Lawerence, Ramesh Babu, K. Ramamurthi, J. Cryst. Growth 310 (2008) 116–123. [15] K. Anitha, B. Sridhar, R.K. Rajaram, Acta Cryst. E 60 (2004) 1530–1532. [16] P. Vivek, P. Murugakoothan, Opt. Laser Technol. 49 (2013) 288–295. [17] G. Anadha Babu, A. Chandra Mohan, P. Ramasamy, G. Bhagavannarayana, Babu Varghese, Mater. Res. Bull. 46 (2011) 464–468. [18] P Selvarajan, J. Glorium, Arul Raj, S. Perumal, J. Cryst. Growth 31 (2009) 3835–3840. [19] R. Artali, G. Bombieri, C.C. Carvalho, Cryst. Mater. 217 (2011) 88–90. [20] H.K. Honk, J.W. Park, K.S. Lee, C.S. Yoon, J. Cryst. Growth 277 (2005) 509–517. [21] G. Ryu, C.S Yoon, J. Cryst. Growth 191 (1998) 492–500. [22] J. Perez-Folch, J.A. Subirana, J. Aymami., J. Chem. Crystallogr. 27 (1997) 367–369. [23] H. Lipson, H. Steeple, Interpretation of X-ray Powder Diffraction Patterns, fifth ed., Macmillan, New York, 1970. [24] N Sudarsana., B. Keerthana, R Nagalakshmi, V. Krishna Kumar, L.Guru Prasad, Mater. Chem. Phys. 134 (2012) 736–746. [25] G. Anadha Babu, A.S. Sreedhar, S. Venugopal Rao, P. Ramasamy, J. Cryst. Growth 312 (2010) 1957–1962. [26] Robert M. Silverstein, Francis X. Webster, David J. Kiemle, Spectrometric Identification of Organic Compounds, 7th ed., Wiley & Sons, INC., 2005. [27] M. Briget Mary, V. Sasirekha, V. Ramakrishna, Spectrochim. Acta Part A 65 (2006) 955–963. [28] T Danabal, G Amirthaganesan, M Dhanapandi, Samar K Das, J. Chem. Sci. 124 (2012) 951–961. [29] A.S.H. Hameed, G. Ravi, P. Dhanasekaran, P. Ramasamy, J. Cryst. Growth 212 (2000) 227–232. [30] S.K. Kurtz, T.T Perry, J. Appl. Phys. 39 (1968) 3798–3814. [31] T. Arumanayagam, P. Murugakoothan, Mater. Lett. 65 (2011) 2748–2750. [32] A Ashour, N El-Kadry, SA. Mahmud, Thin Solid Films 269 (1995) 117–120. [33] J Tauc, R Grigorovici, A. Vancu, Phys. Status Solidi 15 (1966) 627–637. [34] P. Selvarajan, B.N. Das, H.B. Gon, K.V. Rao, J. Mater. Sci. 29 (1994) 4061–4064. [35] A.S.J. Lucia Rose, P. Selvarajan, S. Perumal, Spectrochim. Acta Part A 81 (2011) 270–275. [36] V.N. Praveen, C.K Mahadevan, Indian J. Phys. 79 (2005) 639–642. [37] S Moitra, S. Bhattacharya, T Kar, A Ghosh, Physica B 403 (2008) 3244–3247. [38] S.K. Arora, Vipul Patel, Brijesh Amin, Anjana Kothari, Bull. Mater. Sci. 27 (2004) 141–147.