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Influence of additives on thermal and dielectric properties oftechnologically important DAST single crystalsTo cite this article before publication: M. Manivannan et al 2019 Mater. Res. Express in press https://doi.org/10.1088/2053-1591/ab22f6

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1

Influence of additives on thermal and dielectric properties of technologically important

DAST single crystals

M Manivannan, S A Martin Britto Dhas and M Jose *

* Department of Physics, Sacred Heart College (Autonomous), Tirupattur–635601,

Tamilnadu, India

*Corresponding author mail id: [email protected], Alternate mail: [email protected]

Abstract

An efficient nonlinear optical terahertz emitting pure, EDTA and DTPA doped DAST

crystals were grown from saturated methanol solution employing controlled slow evaporation

technique. Crystallinity and chemical composition of the grown crystals were identified by

powder X–ray diffraction analysis. The photoacoustic spectroscopic results revealed that the

DTPA added DAST crystal show better thermal diffusivity, effusivity and conductivity than

that of pure and EDTA doped crystal. Dielectric properties of the pure and additives added

DAST crystals were studied in the broad range of frequencies from 1 Hz to 1 MHz at various

temperatures from 50–200 °C. The permittivity and dielectric loss were found to be strongly

dependent on additives, temperature and frequency of the applied electric field. Nyquist plot

suggests that the grain boundary effect is involved in the material and shows non–Debye type

of relaxation phenomena.

Key Words: crystal growth, powder X–ray diffraction study, photoacoustic analysis,

dielectric analysis, electric modulus

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1. Introduction

Nonlinear optics (NLO) is one of the interesting areas of research due to its massive

applications in the field of photonics, switching of optical signals and high speed data

transmission. Photonics covers a swiftly increasing range of novel materials, techniques and

optical components, including bar code laser scanners, solid state laser, information storage,

optical fiber communication and compact disc players [1]. This reminds a necessity for new

NLO materials with splendid optical and mechanical properties. For a strong second order

NLO property, the material should possess a high molecular hyperpolarizability, good

transparency, high thermal stability and have to crystallize in a non–centrosymmetric

structure. Hence, the hyperpolarizability is the foundation for a powerful second harmonic

generation [2]. This can be improved by the quantity of delocalized π– electron arrangement

with influential donor and acceptor. During the past two decades, the search for efficient

NLO materials was the focus of research activity throughout the world for the optoelectronic

applications such as optical communications, data storage and high speed signal processing.

[3]. In general, inorganic materials are broadly used for these applications due to their huge

melting point, mechanical strength and degree of chemical inertness. On the other hand,

organic materials show a better NLO response than few well known inorganic materials,

however, the difficulty is growing them in bulk size with good transparency and large

mechanically stable single crystal.

4–N, N–Dimethylamino–4–N–methyl stilbazolium tosylate (DAST) is one of the

commercially important organic NLO crystals which exhibit low permittivity, large electro–

optical coefficient and large second–order nonlinear optical coefficients. Moreover, it

exhibits excellent Terahertz (THz) generation as well as detection as compared with currently

existing bulk organic crystals. Among several methods, Photoconductive (PC) switching and

optical rectification (OR) have been widely applied to emit pico–second THz pulses [4–6].

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THz radiation has various exceptional features such as low photon energy, good

penetrability, and excellent capability for spectral analysis. Hence, it is widely used in many

fields such as THz absorption spectroscopy or spectroscopic imaging, optical parametric

oscillator in infrared (IR), wavelength conversion, sub–millimetre wave generation, non–

destructive inspection, security check, biology research, gas sensing, and cancer diagnosis so

on [7, 8]. The THz conversion efficiency of DAST crystal is 42 times higher than the

benchmark materials like GaAs and InP crystals, while, the generation of THz electric field is

185 and 50 times greater than LiTaO3 and LiNbO3 crystals respectively. In addition, DAST

exhibits larger second order nonlinear coupling coefficient compared to the well known

standard inorganic materials like CdTe, GaSe and ZnTe crystals [9–12]. Recently, novel

binary composite films of DAST–CNT and DAST graphene have been designed and

synthesized which demonstrates significantly improved optical and electrical properties as

compared to DAST film which substantiate the possibility of DAST for novel applications

such as in bolometric materials for uncooled IR or THz detectors [13, 14].

In addition, the growth of good quality bulk DAST crystal is still a big challenge due

to the uncontrollable occurrence of multi-nucleation during the growth process. Furthermore,

this crystal has two major difficulties such as controlling the location and growth direction of

nucleation. Also, DAST crystals generally tend to stick to the bottom of the growth vessel,

leading to poor crystalline perfection and tend to coagulate together and form poly–crystals.

However, the quality of the crystal can be enhanced to a large extent by the

understanding of its nucleation processes. Additives or dopants play a major role in

controlling the nucleation, rate of growth, nucleation kinetics, quality and properties of the

crystals, by controlling the cluster formation by capturing the metallic ions and enhancing the

metastable zone width. Among the number of growth agents, Ethylene Diamine Tetraacetic

Acid (EDTA) and Dimethylene Triamine Pentaacetic Acid (DTPA) could be useful to


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enhance the metastable zone width and improve the growth of crystal depending on the

concentration of additives, pH, temperature and super saturation of the solution [15]. EDTA

is a good growth agent, containing large number of nitrogen atoms with small chain

carboxylic group and it forms ionized complexes with the metal ion in the growth solution

and controls the chemical interaction [16–17]. DTPA can easily bind with a number of metal

atoms and has five acetate moieties which make strong bond with the material to form more

stable than other growth agents [16].

This paper reports, the growth of large size DAST crystal using different additives

from methanol solution by slow solvent evaporation technique. The grown pure and additives

added DAST crystals were identified by single crystal x-ray diffraction and powder x–ray

diffraction investigation. The absences of additional peaks confirm that the fundamental

structure of the DAST crystal was not affected by additives. Photoacoustic spectroscopic

analysis demonstrated the thermo–physical property such as thermal diffusivity, thermal

effusivity and thermal conductivity of the crystals. The dielectric behaviour of pure and

additives added DAST crystals were examined throughout the frequencies from 1 Hz to 1

MHz for various temperatures between 50–200 °C. The permittivity and dielectric loss

reveals the influence of additives in the grown crystals. The conductivity at different

frequencies and temperatures are interpreted from the Arrhenius plot and the variation in

activation energy with respect to frequency is tabulated in Table 2.

2. Experiment

2.1 Preparation and growth of DAST

DAST salt is synthesized by condensation technique and the resulting DAST raw

material is further purified by repeated recrystallization process [18]. Saturated solution of

DAST is prepared at ambient temperature without addition of additives and kept for

nucleation. Simultaneously, a required amount of additives EDTA (0.001M) and DTPA


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(0.001M) was added separately and stirred well with the DAST solution. The solutions are

filtered and located in a vibration free position for the further growth. After number of trials,

plate–like single crystals of pure and additives added DAST crystals are obtained in 1 mm

thickness with different crystallographic faces after the growth period of 20 days at ambient

temperature. The photographs of grown pure, EDTA and DTPA added DAST crystals are

shown in Fig.1 (a–c). It is found that the additives added DAST crystals have grown better

size compared with pure DAST. The growth rate of (110) facet is found to be large compared

with the other facets.

3. Results and Discussions

3.1 X–ray diffraction analysis

Structural parameters of the pure and doped DAST crystals were analyzed by single

X–ray diffraction (SXRD) analyses. SXRD result reveals that the pure and doped DAST

crystals belong to monoclinic crystal system with non–centrosymmetric space group of Cc

and point group m. The grown pure and additives added DAST crystals are characterized by

powder X–ray diffraction technique using a Rich Seifert powder X–ray diffractometer with

CuKα radiations (λ = 1.5408 Å) and the 2θ range is analyzed from 10° to 50 ̊. The recorded

powder XRD spectra are shown in Fig.2 and the prominent peaks are indexed with the

corresponding (h k l) values. As can be seen in the spectra no additional phases are seen when

the additives are doped. However, in the spectra for EDTA and DTPA added DAST crystals,

Fig.1 (a–c) photographs of grown pure, DTPA and EDTA added DAST crystals

c)

1 cm

b)

1 cm 1 cm

a)


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a small variation in the intensity of the peak are observed. The lattice parameters are

calculated using 2θ values and they are listed in the Table 1. The obtained and calculated

lattice parameters of pure DAST crystal and additives added DAST crystals are more reliable

with the reported values [4, 9]. The obtained XRD results validate that the existence of

additives has not transformed the fundamental structure of the DAST crystal.

Fig. 2 Powder XRD pattern of pure, DTPA and EDTA added DAST crystals.

Table 1 Lattice parameters of pure, DTPA and EDTA added DAST crystals

Crystals

Lattice Parameters (Å)

a b c

SXRD PXRD SXRD PXRD SXRD PXRD

Pure DAST 10.341(12) 10.339 11.301(13) 11.321 17.845(20) 17.831

EDTA+DAST 10.397(12) 10.397 11.319(12) 11.408 17.893(20) 17.957

DTPA +DAST 10.366(13) 10.357 11.232(12) 11.421 17.892(12) 17.867


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3.2 Photoacoustic spectroscopy (PAS)

Thermal properties like thermal diffusivity, conductivity and effusivity play important

role in the process of heat transfer in nature [19]. The variation in the thermal parameter of

the materials is depends on the initial temperature, moisture content, and bulk density [20].

Among standard transient techniques, photo–thermal and laser flash method are most

accepted methods for the evaluation of thermal diffusivity of solids. Thermal diffusivity is a

good way to transfer the thermal energy and it defines as the rate of heat transfer from hot

region to cold region. Any temperature variation in the crystal system makes a transfer of

heat from higher temperature region to that of lower until the crystal reach its thermal

equilibrium state. The heat variation within the crystal creates a variable temperature profiles

with respect to time, which have significantly effect on the quality of the output. The crystal

with large thermal diffusivity will achieve thermal equilibrium very faster than the crystal

with low thermal diffusivity. Since, the crystals with high thermal diffusivity carry the

temperature rapidly through the crystal from a high temperature region to lower temperature

region, which prevents the crystal from thermal damages. This kind of crystals are widely

used in mobile phones, LED panels, laptop, tablet PCs and high–power LEDs [21].

In the present study, plate like and polished crystals along (001) plane with uniform

thickness of 1mm are placed in the sample holder and the photoacoustic signal was measured

for various chopping frequencies from 10 Hz to 120 Hz. The plot of normalized PA signal

amplitude with the square root of the chopping frequency (Fig. 3) reveals that the PA signal

is decayed exponentially with respect to the chopping frequency indicating that the chopping

frequency influences PA signal. From this plot the thermal diffusivity was derived by curve

fitting method by adopting Barros Mela and Fariea [22].

The thermal conductivity and effusivity of the grown crystals are obtained using curve

fit method and the following empirical equations [22–23].


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pck = ........... (N m–1 K–1)

pce = ............... (J m–3 K–1)

Where, k, e, α, ρ and cp are the thermal conductivity, effusivity, diffusivity, density

and the specific heat capacity of the crystals respectively. The differential scanning

calorimetric (DSC) analysis was performed for the pure and additives added DAST crystals

and the specific heat capacities at 30 °C are calculated. The calculated thermal diffusivity,

effusivity and conductivity of pure and additives added DAST crystal are shown in and Fig. 4

for comparison. It demonstrates that the DTPA added DAST crystal has high thermal

diffusivity, conductivity and effusivity compared to the pure and other additives added DAST

crystals, With the addition of EDTA with DAST crystal, the thermal diffusivity, conductivity

and effusivity showed lower values and this may be probably due to decrease in lattice

vibration or decrease in the free electrons in the crystals [19].

Fig. 3 The chopping frequency verses the normalized PA signal amplitude.


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Fig. 4 Comparison of thermal parameters of pure and additives added DAST crystal

3.3 Dielectric Studies

The dielectric behaviour of a solid in bulk form is extremely sensitive to the

involvement of neighbouring electric field in the sample [24]. The dielectric investigation is a

significant characteristic that can be performed to fetch information about the structural

changes, transport mechanism and defect behaviour [25] of the grown crystals based on the

electrical behaviour of the material as a function of temperature and frequency. The dielectric

parameters normally depend on the temperature, frequency, density as well as other aspects

such as material composition and structure.

For electrical characterization, defect free flat (001) facet crystals of pure, EDTA and

DTPA added DAST crystals are coated with silver paste on both faces for good electrical

contact and placed in between the two electrodes, which react as a parallel plate capacitor.

The temperature dependence of the dielectric response of the crystals is examined by

programmable furnace with PSM 1735 LCR meter as a function of frequency. The

permittivity of the crystal is calculated from the standard equation,


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A

Ct

o =

where, ε, C, εo, t, and A are the permittivity, capacitance, permittivity of free space

(8.854×10–12 Fm–1), thickness and area of the samples respectively. The relative permittivity

(ε) measured for different temperatures (50–200 °C) (Fig. 5(a–d)) decreases with increase in

frequency at all the temperatures for both pure and substituted DAST crystals. The

permittivity tends to decrease upto 10 KHz due to the inadequate dipolar orientation and

generation of space charge polarization along the applied field direction, which reveals the

quality of pure and doped DAST crystals with lesser number of defects [26]. Moreover,

dispersive behaviour observed for pure and substituted DAST crystals at lower frequency

seem to exhibit similar trend which can be attributed to the formation of charge polarization

between the interfacial electrodes and the samples. Conversely, permittivity becomes static

above 10 KHz, the space charge becomes inactive as the contribution of polarization filters

off by reducing net polarization [27]. However, the permittivity attained constant values and

merged at higher frequencies for all the temperatures for both the additives due to the

suppression of the dipolar relaxation process with increasing temperatures. The permittivity

of EDTA and DTPA doped DAST crystals shows higher permittivity than the pure one.

Moreover, it is noticed that permittivity increased with increasing temperature in the entire

frequency range of pure and doped DAST crystals which may be due to the randomizing

effect of temperature. Hence, crystal with low permittivity could be an appropriate material

for microelectronic, electro–optic, and photonic device applications [28].


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Fig. 5 (a–h) Variation of permittivity and loss of pure and additives added DAST for

different temperature (50–200 °C)


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Fig. 5 (e–h) represents the dielectric loss of pure and additives added DAST crystals

for different temperatures. The dielectric loss of pure and additives added DAST crystals was

found to be maximum at lower frequencies and it gradually decreases as the frequency is

increased and then reached constant values at higher frequencies. Further, the dielectric loss

increases with increasing temperature in the complete range of frequency. The change in loss

with temperature suggests the grown crystals have thermally activated process. In general, as

the temperature is increased, the mobility of majority charge carriers in the crystal may

increase due to the creation of disordered structure and imperfections in the crystals which

lead to increase in permittivity and loss. The reverse trend is attributed to the increase in

crystallinity of the crystals with increase of temperature [29].

The cole–cole plot of pure and additives added DAST crystals (Fig. 6 (a–d)) shows

single semicircular arcs throughout the full range of frequencies and temperatures, which is

mainly due to the existence of grain edges in the crystals [26]. The diameters of the semi

circular arcs are correlated with the capacitive and recombination resistance of the crystals,

respectively. The change in the radius of the observed semicircular arc with respect to

additives and temperature suggest the non–Debye type of behaviour in the grown crystals

[30]. The shift in the centre maxima of the arc in the direction of origin of the complex plane

of the pure and additives added DAST crystals is attributed to the charge transfer resistance

between the photoanode and electrolytic interface with increase in temperature [31].

However, the incomplete semicircular arc appearing in the plots of pure and DTPA added

crystals might be due to the less influenced charge transfer resistance due to the presence of

larger ionic conduction. The decrease of radius of semicircular arc of EDTA doped DAST

crystal with an increase in temperature reveals the decrease in electrical resistivity and

consequently, increase in conductivity proving negative temperature coefficient of the

resistance type behaviour of all the crystals.


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Fig. 6 (a–d) cole–cole plot of pure and additives added DAST for various temperatures

(50–200 °C)

To understand the electrical behaviour of the crystal, it is necessity to develop the

equivalent circuit model that provides a representation of the electrical process which occurs

in the crystal. Each semicircular arc can be attributed to a parallel arrangement of resistance

Fig. 6 (e) Equivalent circuit for the pure DAST crystal (f) equivalent circuit for the

EDTA and DTPA added DAST crystals

e) f)


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and capacitance. The equivalent circuit and the LCR magnitudes are evaluated using Z–view

impedance analysis software and it consist of RC parallel circuit as shown in Fig. 6 (e, f).

The change in the real and imaginary parts of impedance (Z′ & Z′′) with respect to the

entire frequency range at different temperature (Fig.7 (a–h)) shows that the scale of Z′ and Z′′

is large at low frequency range and it decreases gradually as the frequency increases and all

the curves are merged together in the higher frequency range for pure and additives added

DAST crystals, which is due to the inactive interfacial space charge polarization [32]. The

decreasing trend of Z′ and Z′′ with respect to increase in frequency reveals that relaxation in

the crystal is temperature dependent [33]. The peak shifting in the spectra is directly related

to the change in relaxation time constant. At low frequency, the magnitude of Z′ decreases

with increase in temperature in all the pure and additives added DAST crystals. The observed

asymmetric nature of peaks is an indication of the electrical relaxation in the crystal.

Furthermore, the appearance of relaxation peaks for all the temperatures is a clear indication

of electrical relaxation process involved in the crystals. In common, the frequency at which

Z′′ value reaches a maximum is referred as the relaxation frequency of the grown crystals.

Besides, the broadening of peaks and peaks shift in the direction of higher frequencies region

with increase in temperature confirms the temperature dependent relaxation process involved

in the pure and doped DAST crystals [34]. The emergence of relaxation process in the

crystals is due to the creation of defects and vacancies at higher temperatures [35].


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Fig. 7 (a–h) Variation of Z′ and Z′′ for pure and additives added DAST for different

temperatures (50–200 °C)


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3.3.1 Electric Modulus Analysis:

The electric modulus analysis provides understandable initiative on charge convey

processes such as mechanism of ion dynamics and conductivity relaxation with respect to

frequency and temperature [36]. The advantage of applying the electric modulus spectra is to

separate the grain boundary conduction and electric polarization procedures [37]. The electric

modulus is calculated using the relations,

]"[' 0 Zt

fAM

=

]'[" 0 Zt

fAM

=

where, M′, M′′, f, Z′, and Z′′ are the real, imaginary part of electric modulus, frequency, real

and imaginary part of impedance respectively.

Fig.8 (a–h) represents the real (M’) and imaginary (M”) part of electrical modulus

plotted against applied frequency for different temperatures of pure and EDTA and DTPA

doped DAST crystals. The real part of electric modulus (M′) approaches very low values at

low frequencies due to the negligible electrode polarization while it dispersed in the mid

frequency region due to the mobility of charge carriers contributing for the conduction and

frequency independent electrical conduction is observed in the higher frequencies region

[38]. The magnitude of M′ decreases for the additives added DAST crystals compared to the

pure one, which may be attributed to a deficiency of restoring energy ruling the mobility of

the charge carrier due to the applied electric field [39]. The change in imaginary part of

electric modulus (M′′) as a function of various temperatures (Fig.8 (e–h)) explains the

mechanism of the conductivity relaxation, electrical transport and ion dynamics as a function

of temperature and frequency [40].


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Fig. 8 (a–h) Variation of M′ and M′′ for pure and additives added DAST for different



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The imaginary part of electric modulus with the variation of frequency shows a single

symmetric peak. The observed relaxation peak represents the large grain behavior of the pure

and additives added grown crystals [41]. Further, the shifting of relaxation peaks reveals the

spread of relaxation time and temperature dependent relaxation of pure and doped DAST

crystals. The emergence of relaxation peaks at lower, middle and higher region of frequencies

is due to the contribution of capacitance to the grain boundary, mobile charges and grain

phase properties, respectively. The broad nature of the peaks could be the effect of the

distribution of relaxation time due to non–Debye nature of the crystals [42]. The EDTA

influenced DAST crystal shows a peak shift in the direction of higher frequency with increase

in temperature, which may be attributed to the transitional mobility of charge carriers.

Fig 9 (a–d) Modulus cole–cole plot of pure and additives added DAST for different


Fig. 9 (a–d) shows the complex electrical modulus plot of pure and additives added

DAST crystals at different temperatures. A single semicircle arc could be observed for all the


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additives for various temperatures with small shifts occurred towards higher M′ values. This

may be due to the decrease in modulus grain boundary resistance with the increase of

temperature. The obtained single semi circular arc for a specific temperature implies the

single phase behaviour of the crystals [35, 43]. It is also noticed that the arc of the M′ moves

towards the higher values due to the increase in capacitance value.

3.3.2 Electrical Conductivity of DAST

The electrical conductivity of pure and additives added DAST crystal at various

temperatures is shown in Fig. 10 (a–d). The electrical conductivity (σ) is calculated using the

relation RAl /= ... ohm−1m−1. Where, R, l and A are the resistance, thickness and area of

the crystal respectively. The conductivity graph reveals three dissimilar regions. At low

frequencies, the frequency dependent response of conductivity is observed upto 1 KHz. In the

middle frequencies (1 KHz–190 KHz), it is observed that the conductivity plot for all the

temperatures decreases then increases, while the higher frequency region (190 KHz–1MHz)

displayed a sudden decrease of conductivity with temperatures which may be due to the

presence of hopping conduction behaviour of the crystals [44]. The decrease of conductivity

with temperature reveals the presence of negative activation energy [45]. From Fig.10 (a–d),

it is noticed that the conductivity of EDTA added DAST increases with increase in

temperatures which is due to the mobility of charge carriers and thermally induced vacancies

with increasing temperatures [46]. The conductivity of pure and DTPA added DAST crystals

decreases with increase in temperature which may be due to the impurity ions and vacancies

of trapped charges. The nature of change in the conductivity throughout large temperature

range confirms the thermally activated characteristics of the material. As well as the

temperature dependent conductivity changes is also detected

The Arrhenius plot is plotted with the logarithm of dc conductivity versus the inverse

temperature 1000/T at various frequencies, such as 50 Hz, 100 Hz, 10 KHz, and 100 KHz.


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The variation over different temperature range confirms the presence of thermally activated

transport behaviour of the crystals, which obeys the Arrhenius equation. It could be explained

in accordance with the equation [45]

=

kT

Eo exp

where, ΔE is the activation energy for electron transfer, σo is the pre–exponential factor and k

is the Boltzmann constant. The dc conductivity of the pure and additives added DAST

crystals shows a linear variation with additives and temperature (Fig.11 (a–d)) and the slope

of the linear line is equal to (ΔE/k), from which the activation energy of the crystals is

calculated.

Fig 10 (a–d) Variation of the conductivity of pure and additives added DAST crystals for

different temperature (50–200 °C)


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Fig. 11 (a–d) Arrhenius plot at different temperatures and frequencies for pure and additives

added DAST crystals.

The overall trend of activation energy at different frequencies by the static electric

field of pure and additives influenced DAST crystal is shown in Table 2. It is in vicinity that

the contribution of charged polarons in mobilizing the charge carriers for pure DAST crystal

is less at lower frequency region, later increases linearly upto the threshold frequency

(10 KHz) and suddenly drops to the initial state. This phenomenon is due to the dynamical

reorientation of polarons at active frequency region between 50 Hz–10 KHz. A quick fall at

100 KHz may be due the acceleration of electrons in polarizing the neighbouring atomic sites

are less mobilized.


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Table 2 Activation energy of pure and additives influenced DAST crystals at different

frequencies

Crystals Activation Energy Ea (eV)

50 Hz 100 Hz 10 KHz 100 KHz

Pure DAST 0.17 0.23 0.42 0.17

DAST+ EDTA 0.36 0.38 0.45 0.24

DAST+ DTPA 0.31 0.38 0.52 0.29

4. Conclusion

Good quality single crystals of DAST are successfully grown in the presence of

EDTA and DTPA by slow evaporation technique at ambient temperature. The structure of the

grown crystals and crystalline nature are confirmed by powder X–ray diffraction spectra.

Photoacoustic spectroscopy analysis reveals that the thermal diffusivity, thermal effusivity

and thermal conductivity of DTPA added DAST crystal has good results than others. The

dielectric behaviour of pure and additives added crystals demonstrate that the grown crystals

have low permittivity and dielectric loss at higher frequencies, which enhanced the optical

quality with minimum defects. The peak in the dielectric loss spectrum confirms the

occurrence of dielectric relaxation in the crystals. The electric modulus of the pure and

additives added crystals shows a non–Debye category of relaxation. The activation energy of

the grown pure and additives added DAST crystals were found to be increasing with

increasing frequency, which reveals the conductivity is a thermally activated process.

Acknowledgements

The authors acknowledge Department of Atomic Energy–Board of Research in

Nuclear Sciences (DAE–BRNS), Government of India for providing financial assistance to

execute this research work (Sanction Number: 34/14/54/2014–BRNS).


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Reference:

[1] K.Jagannathan, P.Umarani, V.Ratchagar, V.Ramesh and S. Kalainathan, 2016 Growth

and characterization of novel organic 3–hydroxy benzaldehyde–N–methyl

4-stilbazolium tosylate crystals for NLO applications, Spectrochim. Acta, Part A,

153, 735–740.

[2] B. Zhao, W. Q. Lu, Z.–H. Zhou and Y. Wu 2000 The important role of the bromo

group in improving the properties of organic nonlinear optical materials, J. Mater.

Chem. 10, 1513–1517.

[3] K. Sugandhi, S. Dinakaran, M. Jose, R. Uthrakumar, V. Joseph, A. Jeya Rejendran,

G. Bhagvannarayana and S. Jerome Das 2010 Crystalline perfection, spectroscopic

investigations and transport properties of trisglycine zinc chloride NLO single crystal,

Physica B, 405, 3929–3935.

[4] M. Manivannan, S.A. Martin Britto Dhas and M. Jose 2017 Ferroelectric behavior of

organic terahertz radiating DAST crystal, J Inorg Organomet Polym. 27, 1870–1877.

[5] H R Zangeneh, and M A F Jahromi 2014 Design and analysis of a metallic waveguide

with a DAST cap for continuously phase-matched terahertz difference frequency

generation, Optik. 125 (13), 3098–3101.

[6] S. Brahadeeswaran, Y. Takahashi, M. Yoshimura, M. Tani, S. Okada, S. Nashima, Y.

Mori, M. Hangyo, H. Ito and T. Sasak 2013 Growth of ultrathin and highly efficient

organic nonlinear optical crystal 4′-dimethylamino-N-methyl-4-stilbazolium p-

chlorobenzenesulfonate for enhanced terahertz efficiency at higher frequencies, Cryst.

Growth Des. 13, 415–421.

[7] A Schneider, M Neis, M Stillhart, B Ruiz, R U. A. Khan and P Günter 2006

Generation of terahertz pulses through optical rectification in organic DAST crystals:

theory and experiment, J. Opt. Soc. Am. B 23, 1822–1835.


123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960 A

ccep

ted

Man

uscr

ipt

http://www.sciencedirect.com/science/journal/13861425/153/supp/Chttp://www.sciencedirect.com/science/journal/00304026http://www.sciencedirect.com/science/journal/00304026/125/13

24

[8] S Sohma, H Takahashi, T Taniuchi and H Ito 1999 Organic nonlinear optical crystal

DAST growth and its device applications, Chem. Phys. 245, 359–364.

[9] X.C. Zhang, X. F. Ma, Y. Jin, T.M. Lu, E. P. Boden, P. D. Phelps, K. R. Stewart and

C. P. Yakymyshyn 1992 Terahertz optical rectification from a nonlinear organic

crystal, Appl. Phys. Lett. 61, 3080–3082.

[10] Y Takahashi, S Onzuka, S Brahadeeswaran, M Yoshimura, Y Mori and T Sasaki

2007 Suppression of narrow-line defects in organic 4-dimethylamino-N-methyl-4-

stilbazolium tosylate crystals through uninterrupted solution stirring during growth

process, Jpn. J. Appl. Phys. 46, 324–327.

[11] S R. Marder, J W. Perry and W P. Schaefer 1992 4-N-methylstilbazolium toluene-p-

sulfonate salts with large second-order optical non-linearities, J. Mater. Chem. 2, 985–

986.

[12] K. S. Rao, M. Venkatesh, K. Thirupugalmani, S. Brahadeeswaran and A.K.

Chaudhary 2014 Optical parametric amplifier based efficient terahertz generation in

DAST crystal using optical rectification, Opt. Photo. 1–3.

[13] X. Xu, Z. Sun, K. Fan, Y. Jiang, R. Huang, Y. Wen, Q. He and T. Ao 2015

Conversion of 4-N, N-dimethylamino-4′-N′-methylstilbazolium tosylate (DAST) from

a simple optical material to a versatile optoelectronic, Material, Sci. Rep. 5, 1–13.

[14] X Xu, L Huang, K Fan, Y Jiang, Z Sun, Q He, T Ao, R Huang, Y Wen and C Ma

2014 Electrical and optical properties of 4-N,N-dimethylamino-4’-N’-methyl-

stilbazolium tosylate (DAST) modified by carbon nanotubes, J. Mater. Chem. C 2,

2394–2403.

[15] P.V. Dhanaraj, N.P. Rajesh, C.K. Mahadevan and G. Bhagavannarayan 2009

Nucleation studies and characterization of potassium thiocyanate added KDP

crystals grown by seed rotation technique, Physica B, 404, 2503–2508.


123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960 A

ccep

ted

Man

uscr

ipt

25

[16] A.S. Haja Hameed, S. Rohani, W.C. Yu, C.Y. Tai and C.W. Lan 2007 Growth and

characterization of a new chelating agent added 4-dimethylamino-N-methyl-4-

stilbazolium tosylate (DAST) single crystals, Mater. Chem. Phys. 102, 60–66.

[17] B Liu, Y Yang, Y Zhang, X Lv, L Wei and X Wang 2015 Effects of EDTA additives

on optical properties of rapidly grown KDP single crystals, J Mater Sci: Mater

Electron, 26, 8097–8102.

[18] M. Manivannan, S. A. Martin Britto Dhas and M. Jose 2016 Photoacoustic and

dielectric spectroscopic studies of 4-dimethylamino-nmethyl-4-stilbazolium tosylate

single crystal: An efficient terahertz emitter, J. Cryst. Growth 455, 161–176.

[19] E. Marin 2007 The role of thermal properties in periodic time-varying phenomena,

Eur J. Phys. 28, 429–445.

[20] A. Opoku, L.G. Tabil, B. Crerar and M.D. Shaw 2006 Thermal conductivity and

thermal diffusivity of timothy hay, Can. Biosyst. Eng. 48, 1–7.

[21] J Zhong, D Liu, Z Li and X Sun 2012 High thermal conductivity materials and their

application on the electronic products, IEEE, 978–1–4673–0668–3/12

[22] W. L. Barros Melo and R.M. Faria 1995 Photoacoustic procedure for measuring

thermal parameters of transparent solids, Appl. Phys. Lett. 67, 3892–3894.

[23] A. Mandelis 1991 Photothermal applications to the thermal analysis of Solids, J.

Therm. Anal.37, 1065–1101.

[24] G Dominiak–Dzik, W R Romanowski, R Lisiecki, P Solarz, B Macalik, M Berkowski

and V Domukhovski 2010 The czochralski growth of (Lu1-xGdx)2SiO5:by Single

crystals: structural, optical, and dielectric characterization, Cryst. Growth Des. 10,

3522–3530.


123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960 A

ccep

ted

Man

uscr

ipt

26

[25] Y Cherifi, A Chaouchi, Y Lorgoilloux, M Rguiti, A Kadri and C Courtois 2016

Electrical, dielectric and photocatalytic properties of Fe-doped ZnO nanomaterials

synthesized by sol gel method, Process. Appl Ceram. 10, 125–135.

[26] P Khatri, B Behera and R.N.P. Choudhary 2009 Structural and impedance properties

of Ca3Nb2O8 ceramics, J. Phys. Chem. Solids, 70, 385–389.

[27] B. Behera, P. Nayak and R.N.P. Choudhary 2008 Structural and impedance properties

of KBa2V5O15 ceramics, Mater. Res. Bull. 43, 401–410.

[28] B. Babu, J. Chandrasekaran, B. Mohanbabu, Y Matsushita and M. Saravanakumar

2016 Growth, physicochemical and quantum chemical investigations on 2-amino 5-

chloropyridinium 4-carboxybutanoate–an organic crystal for biological and

optoelectronic device applications, RSC Adv. 6, 110884–110897.

[29] A.Eroglu, A.Tataroglu and S.Altındal 2012 On the temperature dependent dielectric

properties, conductivity and resistivity of MIS structures at 1 MHz, Microelectron.

Eng. 91,154–158.

[30] M. Thambidurai, N. Muthukumarasamy, D Velauthapillai, S. Agilan and

R. Balasundaraprabhu 2012 Impedance spectroscopy and dielectric properties of

cobalt doped CdS nanoparticles, Powder Technol. 217, 1–6.

[31] Y.D. Kolekar, L.J. Sanchez and C.V. Ramana 2014 Dielectric relaxations and

alternating current conductivity in manganese substituted cobalt ferrite, J. Appl. Phys.

115, 144106–144111.

[32] G. Murugesan, R. Nithya, S. Kalainathan and S Hussain 2015 High temperature

dielectric relaxation anamolies in Ca0.9Nd0.1Ti0.9Al0.1O3-δ single crystals, RSC Adv. 5,

78414–78421.


123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960 A

ccep

ted

Man

uscr

ipt

https://www.sciencedirect.com/science/article/pii/S0167931711006757https://www.sciencedirect.com/science/article/pii/S0167931711006757

27

[33] A K. Roy, K Prasad and A Prasad 2013 Piezoelectric, impedance, electric modulus

and AC conductivity studies on (Bi0.5Na0.5)0.95Ba0.05TiO3 ceramic, Proces. Appl.

Ceram. 7, 81–91.

[34] A Mishra, S.N. Choudhary, K. Prasad and P.Choudhary 2011 Complex impedance

spectroscopic studies of Ba(Pr1/2Ta1/2)O3 ceramic, Physica B 406, 3279–3284.

[35] L Singh, l W Kim, B C Sin, A.Ullah, S K Woo and Y Lee 2015 Study of dielectric,

AC-impedance, modulus properties of 0.5Bi0.5Na0.5TiO3.0.5CaCu3Ti4O12 nano-

composite synthesized by a modified solid state method, Mater. Sci. Semi cond.

Process. 31, 386–398.

[36] N Tugluoglu, S Karadeniz and B Baris 2014 Electrical modulus and dielectric

spectroscopy behavior of spin coated perylene-monoimide semiconductor films,

Mater. Sci. Semicond. Process. 27, 891–898.

[37] S Mahajan, D Haridas, S.T. Ali, N.R. Munirathnam , K. Sreenivas, O.P. Thakur and C

Prakash 2014 Investigation of conduction and relaxation phenomena in BaZrxTi1-xO3

(x=0.05) by impedance spectroscopy, Physica B 451, 114–119.

[38] A. Sakthisabarimoorthi, S.A. Martin Britto Dhas, R. Robert and M. Jose 2018

Influence of Erbium doping on the electrical behaviour of CaCu3Ti4O12 ceramics

probed by impedance spectroscopy analysis, Mater. Res. Bull. 106, 81–92.

[39] S Brahma, R.N.P. Choudhary, Awalendra and K. Thakur 2005 AC impedance

analysis of LaLiMo2O8 electroceramics, Physica B 355, 188–201.

[40] B Behera, P. Nayak and R.N.P. Choudhary 2009 Structural, dielectric and impedance

properties of NaCa2V5O15 ceramics, Curr. Appl. Phys. 9, 201–205.

[41] H Mahamoud, B.Louati, F. Hlel and K. Guidara 2011 Impedance and modulus

analysis of the (Na0.6Ag0.4)2PbP2O7 compound J. Alloys Compd. 509, 6083–6089.


123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960 A

ccep

ted

Man

uscr

ipt

https://www.sciencedirect.com/science/article/pii/S0025540818301326https://www.sciencedirect.com/science/article/pii/S0025540818301326

28

[42] B Behera, P. Nayak and R.N.P. Choudhary 2007 Study of complex impedance

spectroscopic properties of LiBa2Nb5O15, ceramics, Mater. Chem. Phy. 106, 193–197.

[43] M. Prabu and S. Selvasekarapandian 2012 Dielectric and modulus studies of LiNiPO4,

Mater. Chem. Phys. 134, 366–370.

[44] S.S. Pawar, K P.Shinde, A.G.Bhosale and S. H. Pawar 2013 Studies on Electric and

Dielectric Properties of Porous Sm0.5Sr0.5CoO3−𝛿, J. Mater. 987328, 1–7.

[45] F. Yakuphanoglu, Y. Aydogdu, U. Schatzschneider and E. Rentschler 2003 DC and

AC conductivity and dielectric properties of the metalradical compound: Aqua[bis(2-

dimethylaminomethyl-4-NITphenolato)]copper(II), Solid State Commun. 128, 63–67

[46] R.Ananda kumari and R. chandramani 2005 Electrical conductivity and dielectric

measurements in Au+ doped/undoped KDP crystals with KCl and NaCl as Additives,

Indian J Pure Ap. Phy. 43, 125–128.


123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960 A

ccep

ted

Man

uscr

ipt

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