Journal Articles

Permanent URI for this collectionhttps://idr.nitk.ac.in/handle/123456789/19884

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Author: search.filters.author.Kumari, K.Subject: search.filters.subject.Optical properties

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    Phase analysis, FTIR/Raman, and optical properties of Fe3BO6 nanocrystallites prepared by glass route at moderate temperature in ambient air
    (Elsevier B.V., 2018) Kumari, K.
    In this paper, a facile synthesis method is explored from a supercooled liquid Fe2O3–B2O3 precursor using microwave furnace in order to obtain a single phase Fe3BO6 compound. Study includes X-ray diffraction (XRD), Field emission scanning electron microscope (FESEM), high resolution transmission electron microscopy (HRTEM) images, FTIR/Raman and optical property of sample. The crystal structure and size of the Fe3BO6 crystallites have been characterized in terms of XRD pattern in correlation to the FESEM/HRTEM images. A single phase compound Fe3BO6 of an orthorhombic crystal structure with Pnma space group and average crystallites size D = 49 nm is analyzed from the XRD pattern. IR and Raman bands in the oxygen polygons confer the results of forming Fe3BO6 with a bonded surface layer. UV–visible absorption spectrum over a spectral range 200–800 nm of wavelengths reveals two high-energy bands 222 and 277 nm possibly represent a ligand to metal charge transfer transition while one broad and relatively weak band appears in the visible region at 400 nm ascribed to a ligand field transition 6A1 ? 4T1 of the 3 d5 electrons in the Fe3+ ions occupied. This compound also endures good optical properties in the visible and ultraviolet regions that can be combined to magnetic and other properties useful for developing multifunctional features for possible applications. © 2018
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    Thermal stability and spectroscopic properties of Fe 3 BO 6 of small crystallites with a bonded carbon surface layer
    (Elsevier Ltd, 2019) Kumari, K.
    A well-known canted antiferromagnetic Fe 3 BO 6 with functionalized properties is an important material useful for light energy carrier, electrodes, gas sensors, and biological probes. In this investigation, a facile synthesis is explored in order to obtain Fe 3 BO 6 of small crystallites in a specific shape of nanoplates by self-combustion method. To access (i) whether Fe 3 BO 6 is formed at the as-prepared stage and (ii) how it stands stable with a residual carbon surface layer, thermal gravimetric (TG) analysis has been carried out by heating 10–20 mg powder (as-prepared) at a typical 10 K/min heating rate over 300–1100 K under air or argon atmosphere. The electronic absorption, infrared (IR) and Raman spectra studied for the Fe 3 BO 6 sample in this investigation elucidate how the density of states of the phonons and valence electrons confine in small crystallites. IR and Raman bands in the oxygen polygons also confer the results of forming Fe 3 BO 6 with a bonded surface carbon layer. A stable bonded surface layer supports thermal stability of small crystallites and it affects other useful functional properties. © 2018 Elsevier B.V.
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    Fabrication of Ag/PDMS-TiO2 flexible piezoresistive pressure sensor
    (Elsevier B.V., 2020) Kumari, K.; Rameshan, R.; ArunKumar, D.S.; Meti, S.; Rahman, M.R.
    In this study, TiO2 nanorods are grown on a flexible Polydimethylsiloxane (PDMS) substrate using the hydrothermal technique. The morphological, structural, compositional, optical properties and pressure sensing are investigated in detail by FESEM, XRD, EDX, UV–visible spectrophotometer, and piezoelectric studies. XRD demonstrates the pure rutile phase with a tetragonal structure is formed from deposited TiO2 thin film. FESEM images confirm the TiO2 nanorods with average dimensions length ~620 nm and diameter ~97 nm whereas the optical spectrum shows the strong light absorption in the UV region with bandgap 3.54 eV. The voltage is measured as a response to the applied mechanical load and the sensitivity of the pressure sensor is obtained as 2.56 × 10?5 V/N. The flexible pressure sensors (Ag/PDMS-TiO2) senses over a large pressure range and shows a linear response because of the adjustments in the volume of dielectric that makes the pressure inside the dielectric cavity to vary. © 2020 Elsevier B.V.