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Dive into the research topics where G. Ramasamy is active.

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Featured researches published by G. Ramasamy.


CrystEngComm | 2010

Rare earth cerium doping effects in nonlinear optical materials: potassium hydrogen phthalate (KHP) and tris(thiourea)zinc(II) sulfate (ZTS)

L. Kasthuri; G. Bhagavannarayana; S. Parthiban; G. Ramasamy; K. Muthu; Subbiah Meenakshisundaram

The influence of Ce(IV) doping on ZTS and KHP crystals over a concentration range from 1 to 10 mol% in the solution during crystallization, which leads to a true concentration range from few ppm to few tens of ppm in the crystals has been investigated. The XRD and FT-IR analyses indicate that the crystal undergoes considerable stress as a result of doping. Incorporation of the Ce(IV) dopant into the crystal lattice was well confirmed by energy dispersive X-ray spectroscopy (EDS) and quantified by inductively coupled plasma (ICP) technique. The high-resolution X-ray diffraction (HRXRD) studies reveal that Ce doping in KHP leads to degradation of crystal quality whereas ZTS can accommodate Ce predominantly at the substitutional sites without any degradation of crystalline perfection. The second harmonic generation (SHG) efficiency is not influenced by Ce doping in the KHP crystals while in ZTS crystals, it is enhanced to a considerable extent correlated with moderately improved crystalline perfection.


Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy | 2011

Growth and characterization of Fe3+-doped bis(thiourea)zinc(II) chloride crystals.

K. Nithya; B. Karthikeyan; G. Ramasamy; K. Muthu; Subbiah Meenakshisundaram

Fe3+-doping at ∼10 mol% in aqueous medium during crystal growth by slow evaporation solution method in bis(thiourea)zinc(II) chloride (BTZC) leads to form a new compound C2H8Cl2N4S2Zn0.93Fe0.07 (BTZCF) which crystallizes in orthorhombic structure with centrosymmetric space group Pnma though the parent compound BTZC crystallizes in noncentrosymmetric structure with space group Pn2(1)a. The interesting feature observed in this new crystal is that though it crystallizes in centrosymmetric structure, it exhibits positive SHG result (weak signal), quite likely due to possible surface effects or internal stress. The calculated first-order hyperpolarizability is 1.457×10(-30) esu which is ∼5.5 times that of urea. Fe3+-doping enhances the transmittance to a significant extent. Comparison of the thermal analysis results by DSC reveals the incorporation of dopant into the crystalline matrix. The high resolution XRD studies reveal that the crystalline quality is improved considerably when the doping level is reached to ∼10 mol%.


RSC Advances | 2015

Synthesis, growth, structure and characterization of potassium lithium hydrogen phthalate mixed crystals

J. Vijila Manonmoni; G. Ramasamy; A. Aditya Prasad; Subbiah Meenakshisundaram; M. Amutha

Mixed crystals of lithium-incorporated potassium hydrogen phthalate were grown by the slow evaporation solution growth technique from an aqueous solution containing equimolar quantities of potassium hydrogen phthalate (KHP) and lithium carbonate. The crystal composition, C16H16KLiO11 (PLHP), as determined by single-crystal XRD analysis reveals the coexistence of potassium and lithium in the mixed crystal, further supported by energy dispersive X-ray spectroscopy and atomic absorption spectroscopy. It belongs to the monoclinic system with the space group P21 and the cell parameters a = 9.4866(3) A, b = 6.769(2) A, c = 15.3967(5) A, α = γ = 90°, β = 105.730°(3), V = 951.67(5) A3 and. Z = 2. The relative second harmonic generation (SHG) efficiency measurements reveal that PLHP has an efficiency comparable to that of KHP. The grown crystals were further characterized by single-crystal XRD, FT-IR, SEM/EDS, TGA/DTA, CHN and UV-visible spectral analysis. Hirshfeld surfaces, derived using single crystal X-ray diffraction data, reveal that the close contacts are associated with strong interactions. Fingerprint plots were used to locate and analyze the percentage of hydrogen bonding interactions.


Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy | 2014

Growth, structure and spectral studies of a novel mixed crystal potassium zinc manganese sulphate.

J. Vijila Manonmoni; G. Bhagavannarayana; G. Ramasamy; Subbiah Meenakshisundaram; M. Amutha

Mixed crystals of K2Zn0.84 Mn0.16(SO4)2·6H2O were grown from an equimolar aqueous solution of Tuttons salt, K2 Zn(SO4)2·6H2O and MnSO4 by slow evaporation solution growth technique. The crystal composition as determined by single crystal XRD analysis reveals the co-existence of zinc and manganese in the mixed crystal. The surface morphological changes are observed by scanning electron microscopy. Small variations in cell parameter values, slight shifts in characteristic vibrational patterns in FT-IR and reduction in intensities observed in XRD confirm the crystal stress as a result of formation of mixed crystal. High resolution XRD diffraction estimates the crystalline perfection of the mixed crystal with predominantly vacancy type of defects. It belongs to P21/c space group with cell parameter values, a=6.1530 Å, b=12.2230 Å, c=9.0430 Å, α=β=ν=90°, V=657.56 Å(3), Z=4. High transmittance in the visible region is observed.


CrystEngComm | 2012

The concentration effects of s-, p-, d- and f-block element doping on the growth, crystalline perfection and properties of KDP crystals

G. Ramasamy; G. Bhagavannarayana; Subbiah Meenakshisundaram

The effect of dopants (over a wide concentration range from 0.5 to 10 mol%), namely s-, p-, d- and f-block elements (Mg, Sb, Pd and La) on the growth process, crystalline perfection, external morphology, vibrational patterns, XRD profile and second order nonlinear optical (NLO) properties of potassium dihydrogen phosphate (KH2PO4, KDP) crystals grown by the slow evaporation solution growth technique has been systematically investigated. Incorporation of the dopants into the crystalline matrix even at low concentrations was well confirmed by the inductively coupled plasma (ICP) technique. The change in intensity patterns in XRD profiles of doping specimens reveals lattice distortion, further supported by slight shifts in characteristic vibrational frequencies in FT-IR. The scanning electron microscope (SEM) micrographs exhibit the effectiveness of the impurity in varying the surface morphology. The high-resolution X-ray diffraction (HRXRD) studies used to evaluate the crystalline perfection reveal many interesting features on the ability of accommodating the dopants by the crystalline matrix. It appears that the crystalline perfection depends mostly on the concentration of the dopant. Multi-peaks appear for highly doped specimens indicating the inhomogeneous accommodation. The second harmonic generation (SHG) efficiency is enhanced considerably when the concentration of the dopant is low while depressed activity is observed with poor crystalline perfection at high concentrations irrespective of the nature of the dopants.


Journal of Crystal Growth | 2012

Crystal growth, structure, crystalline perfection and characterization of zinc magnesium ammonium sulfate hexahydrate mixed crystals ZnxMg(1−x)(NH4)2(SO4)2·6H2O

G. Ramasamy; G. Bhagavannarayana; G. Madhurambal; Subbiah Meenakshisundaram


Optik | 2014

Studies on amino acid picrates: Crystal growth, structure and characterization of a new nonlinear optical material l-isoleucinium picrate

G. Ramasamy; Subbiah Meenakshisundaram


Journal of Crystal Growth | 2013

Synthesis and crystal structure of potassium hydrogen phthalate mixed crystal K0.78Na1.22[C6H4(COO)2]·H2O

G. Ramasamy; Subbiah Meenakshisundaram


Journal of Crystal Growth | 2012

Synthesis, characterization, crystal structure and NLO properties of a new mixed crystal potassium sodium ammonium dihydrogenphosphate K0.23Na0.23(NH4)0.54H2PO4

G. Ramasamy; Subbiah Meenakshisundaram


Optik | 2014

Optical, thermal and mechanical characterization of Al(III)/Sb(III)-doped tris(thiourea)zinc(II) sulphate crystals

K. Meena; G. Ramasamy; M. Rajasekar; K. Muthu; Sp. Meenakshisundaram

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G. Bhagavannarayana

National Physical Laboratory

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K. Muthu

Annamalai University

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K. Meena

Annamalai University

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