ABSTRACT fusion recations. In second order nonlinear optical materials

 

ABSTRACT

A semi organic nonlinear optical
crystal of Bis thiourea Zinc acetate (BTZA) has grown by slow evaporation
technique. The raw material for the growth of BTZA was synthesized by 1:2 molar
ratio in de-ionized water. The crystal system and lattice parameters determined
from X-ray diffraction. Fourier transform infrared studies confirm the various
functional group present in the grown crystal. The
UV-Visible spectrum absorbance and transmittance was recorded in the wavelength
range of 190–1100 nm. The absorption reveals that the lower cutoff wavelength
is 230nm. The
thermal behavior of the grown crystal and noncentrosymmetric space group. The
dielectric constant and dielectric loss has been studied and various
temperatures and the result were discussed. The SEM analysis was the surface
morphology of BTZA single crystal analysed.

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Key Word: BTZA, FTIR,
UV-Visible, Vicker’s hardness test, Powder XRD, TG-DTA analysis.   

Introduction

            Now a days nonlinear optical
materials have various area of telecommunications and optical storage devices.
The NLO crystals have been found to perform many applications in optical
communications, optical information processing, optical computing high density
data storage and laser fusion recations. In second order nonlinear optical
materials have recently attracted of their potential applications in emerging
optoelectronic devices. The inorganic NLO materials like KDP, ADP, L-arginine
and L-arginine phosphate, Bisthiourea Zinc acetate, L-histidinium
tetrafluroborate, L-histidinium tetrafluroborate have gained significant
attention in the last few years. In the present work the title compound was
successfully synthesized by Bisthiourea Zinc acetate in equimolar ratio. The
single crystal has been grown by slow evaporation solution growth technique
using water as the solvent. The number of studies are available on the
structural/ crystalline perfection. Mechanical and optical behavior of the
present compound. In view of NLO applications these studies were carried by
XRD, Vickers microhardness and photoluminous (PL). the grown crystals are
PXRD,FTIR,UV-Visible, refractive index, and SHG measurements and electrical
studies were discussed. These studies show high efficiency in NLO single
crystals.

Experiment

Crystal
growth

            BTZA single crystals were
synthesized using thiourea and Zinc acetate in deionized water by
stoichiometric ratio 1:2 of the chemical recation.

2CS(NH2)2 + Zn(CH3COO)2
               ZnCS(NH2)2 (CH3COO)2

The solution was
stirred using magnetic stirrer and the mixture was heated upto 50°C to
decomposition of the solute molecules. The thiourea coordinating from different
phases of metal-thiourea complexes, purity of synthesized salt was improved by
recrystallization process. The single crystal pure of BTZA was harvested in a
period of 30 to 40 days of grown crystal.

  Fig.1: The
Photograph of BTZA Single crystal

Characterization 

Single
Crystal X-Ray diffraction Analysis

The single crystal
X-Ray diffraction has been using Bruker D8 venture diffractometer. The unit
cell parameters in determined by APEX2 program. The single crystal diffraction
analysis of pure BTZA single crystal reveal that the compound crystallizes in
monoclinic system. The lattice parameters for pure BTZA are a=7.17 Å, b=17.80 Å,
c=11.23 Å and ?=?=90?, ?=103.21? and cell volume V=1396Å3
respectively.

Powder
X-Ray Diffraction Analysis

                     

Fig 2. Powder X-ray diffraction pattern of pure BTZA
crystal

The sample of the
grown crystal was subjected to powder X-ray diffraction analysis using analytical.
Xpert PRO powder X-ray diffractrometer employing CuK? radiation (?=1.5405Å).
the XRD pattern of pure BTZA crystal shown in figure.2. the observed peaks in
spectrum indicated the resemblance of grown crystal to monoclinic structure.
The evaluated cell parameters are a=14.431 Å, b=5.340 Å, c=10.981 Å. and ?=?=90?, ?=103.37?
respectively.

FTIR
Analysis

Fig 3. FTIR Analysis of
BTZA Single Crystal

The infrared
spectroscopy used to identify the functional groups of the samples FTIR spectra
of pure BTZA single crystals were recorded in the KBr pellet technique. The
frequency region from 400-4000 cm-1 ranges using perkin elmer
spectrometer. The FTIR spectra comparision of the grown crystals is shown in
the table1 & figure 2. The FTIR spectrum of pure BTZA with the spectra of
thiourea a shift in the peak was observed, the confirmed metal coordination
with thiourea. The N-H vibration bands in the high frequency range from
3000-3400cm-1. It indicates that the bonding is between sulphur and
zinc atoms, the peaks at 2751cm-1 for pure BTZA and the band 1644cm-1
which are assigned C=N stretching vibration. The appearance of peak 1406 and
1043cm-1 for pure BTZA single crystals. In absorption of pure C-S
and C-N strectching frequency of complex formation. In pure BTZA single
crystals of symmetric and asymmetric vibrations at 932 and 775cm-1
respectively. The FTIR studies shows that in the spectra BTZA is a frequency
band in the lower frequency band in the lower frequency region of BTZA single
crystals.

Table 1

FTIR data of Pure BTZA single
crystal

Pure
BTZA Wavenumber    (cm-1)

Assignment

3375

N-H Stretching

2751

C-H Stretching

1644

C-N Stretching

1406

Asymmetric
C=S Stretching

1043

C-N Stretching

932

C-O-H
Bending

775

Symmetric
C=S Stretching

 

 

 UV-Visible analysis

The
UV-Vis spectrum of pure BTZA single crystal was recorded in the range of
200-1100nm. The instrument used was LAMBDA-35 UV-Vis spectrophotometer. The
optical study for SHG, the material is good transparent in the wavelength
region for NLO material. The transmittance is found to be maximum in the
visible near infrared region. In pure BTZA single crystal is found to be 80% transmittance
wavelength. The lower cutoff frequency was at 270nm in pure BTZA single
crystals for the opto electronic applications.

Fig 4. UV-Visible transmittance of
BTZA Crystal

Microhardness
measurement

Vickers microhardness
test is used to hardness of the material. The hardness number has to be
evaluated of the load applied and the cross-sectional area of the depth of the
impression. The Smooth surfaces of a grown pure BTZA crystals. The Vickers
hardness value is calculated from the formula:

Hv = 1.8544*(p/d2)
kg/mm2

Where p is the applied
load in kg and d is the average diagonal length in millimeters of the
impressions in the present study. The Vickers hardness was measured using
Leitz-Wetzler hardness tester in different load is shown in fig.4. it is
observed that the microhardness increases with the increase of load at lower
values to the work hardness of the surface layers. At higher loads 100g the
microhardness shows a tendency to surface.

Fig.5. Hardness Vs load
graph of pure BTZA crystal

EDAX
Analysis

     Fig 6. EDAX spectrum of pure BTZA crystal

Energy
dispersive X-ray analysis for characterizating the elements was present in the
grown crystal. EDAX  analysis carried out
using JEOL-6360 scanning electron microscope. The recorded sepectrum is shown
fig.5. The presence of carbon, nitrogen, nickel, oxygen, slphur and zinc
elements show incorporation of Pure BTZA grown crystal.

Thermal Analysis

TGA/DSC

Fig.7
Thermal analysis of TGA/DSC pure BTZA crystal

The thermal stability
and physicochemical changes of BTZA single crystal were studied by thermo
gravimetric analysis and differential scanning calorimetric analysis. The curve
of BTZA shown in fig.7. TGA/DSC. The thermal decomposition starts at 199.2?C
the acetate complexes with inorganic ligends the decomposition of thiourea
molecules and the decomposition of the Zinc acetate and metal oxides. The
thermal decomposition of BTZA is exothermic peak at 200?C in the DSC analysis
shows the melting point of the complex on compared to other thiourea based
complex 250?C and the allythiourea metal halides to be thermal stability of the
BTZA good quality in single crystal.

 

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