• P Ramasamy

      Articles written in Bulletin of Materials Science

    • Single-crystal neutron diffraction study of ferroelectric Ba0·92Ca0·08TiO3

      H Rajagopal P U M Sastry A Sequeira P Ramasamy

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      Crystal structure of BaTiO3 doped with 8% Ca2+ is refined using single-crystal neutron diffraction data and it is shown that the doped Ca2+ ion substitutes only at the Ba sites. The refined cell (P4 mm) parameters area=b=3·982(3) Å,c=4·003(3) Å with a finalR value of 0·02 (onF). Existence of multiple domains in the crystal is ruled out based on refinement with multidomain model.

    • Investigations on nucleation thermodynamical parameters of NdBa2Cu3O7-δ (Nd123) crystallization by high temperature solution growth

      D P Paul R Jayavel C Subramanian P Ramasamy

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      Investigations on nucleation thermodynamical parameters are very essential for the successful growth of good quality single crystals from high temperature solution. A theoretical estimation of the nucleation thermodynamical parameters like interfacial energy between the solid Nd123 and its flux BaO-CuO, metastable zone-width, Gibbs free energy, critical energy barrier for nucleation and critical nucleation radius have been calculated from the knowledge of solubility data and by applying the classical nucleation theory. Results are discussed to understand the growth kinetics of Nd123 crystals.

    • Growth and characterization of propyl-para-hydroxybenzoate single crystals

      N Karunagaran P Ramasamy R Perumal Ramasamy

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      Single crystals of propyl-𝑝-hydroxybenzoate have been grown by slow evaporation solution technique. The structure of the compound was confirmed by FT–IR, FT–Raman spectroscopy and single crystal X-ray diffraction studies. The crystalline perfection of the grown single crystals has been analysed by high resolution X-ray diffraction measurements. Optical properties of the grown single crystals were studied by UV–Vis NIR spectrum. The luminescence behaviour of the single crystal has been analysed by photoluminescence analysis and found maximum luminescence in the lower wavelength region. A simple interferometric technique was used for measuring birefringence of the crystal. The laser damage threshold of the crystal is 1.3 GW/cm2. The mechanical strength of the grown crystal is measured using Vickers microhardness tester. The dielectric properties have been investigated.

    • Growth of 2-amino-5-chlorobenzophenone single crystal by Microtube Czochralski method and its characterization

      R Govindaraj M Magesh P Ramasamy

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      Organic single crystals of 2-amino-5-chlorobenzophenone (2A5CB) were grown by Microtube Czochralski method using Microtube as a seed. The grown crystals were characterized by single crystal and powder X-ray diffraction. The functional groups of the grown crystal were found using Fourier transform infrared spectroscopy. The cutoff wavelength of 2A5CB has been identified using UV–vis–NIR studies. Thermogravimetric/differential thermal analysis (TG/DTA) has been carried out to find the thermal behaviour. 2A5CB was found to be thermally stable up to 125°C. Powder second harmonic generation (SHG) was investigated to explore its nonlinear optical (NLO) properties. The mechanical stability of 2A5CB is studied by using Vickers hardness testing.

    • Sol-gel synthesized mesoporous anatase titanium dioxide nanoparticles for dye sensitized solar cell (DSSC) applications

      R Govindaraj M Senthil Pandian P Ramasamy Sumita Mukhopadhyay

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      Hierarchically structured titanium dioxide nanoparticles were successfully synthesized by the sol-gel method. The synthesized nanoparticles were subjected to powder X-ray diffraction, UV-Vis DRS spectroscopy, Brunauer–Emmett–Teller method, Barrett–Joyner–Halenda analysis, field emission scanning electron microscopy, high-resolution transmission electron microscopy and energy-dispersive X-ray analysis. The powder X-ray diffraction pattern shows that the obtained particles are of anatase phase with good crystallite nature. The nitrogen adsorption and desorption isotherms show that the prepared material has surface area of 31.71 m2 g-1 and the pore size distribution analysis shows the average pore diameters of mesoporous TiO2 nanostructures to be 7.1 and 9.3 nm. The UV–Vis DRS spectrum shows that the TiO2 nanoparticles are having absorption in the ultraviolet region. The optical band gap of the nanoparticles is 3.2 eV. The morphological studies show the morphology of the particles as spherical in shape. The elemental compositions of TiO2 nanoparticles were confirmed by energy-dispersive X-ray spectrum analysis. The conversion efficiency of the solar cell was 3.415% with open-circuit voltage (𝑉oc), short-circuit current (𝐽sc) and fill factor (FF) of 0.607 V, 13.206 mA cm-2 and 42.56%, respectively.

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    • Dr Shanti Swarup Bhatnagar for Science and Technology

      Posted on October 12, 2020

      Prof. Subi Jacob George — Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bengaluru
      Chemical Sciences 2020

      Prof. Surajit Dhara — School of Physics, University of Hyderabad, Hyderabad
      Physical Sciences 2020

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      Posted on July 25, 2019

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