Browsing by Author "Chattopadhyay, K.K."

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    PublicationArticle
    Sol-gel-derived ZnO:Mn nanocrystals: Study of structural, Raman, and optical properties
    (2012) Kumar, Shiv; Chatterjee, Sandip; Chattopadhyay, K.K.; Ghosh, Anup K.
    Structural, Raman, and optical properties of sol-gel derived Zn 1-xMn xO (0≤x ≤ 0.06) nanoparticles have been investigated. The crystallite structure, morphology, and size estimation have been performed by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). To study the crystalline quality, structural disorder and defects in the host lattice, we have employed Raman Spectroscopy. The wurtzite structure and formation of tetrahedral coordination of the oxygen ions surrounding the zinc ions has been confirmed by FTIR analysis. Optical properties have been studied by UV-vis and PL spectroscopy. UV-vis measurements show that the band gap is increased with increasing Mn concentration. This may be attributed to the orbital hybridizations that are prevailed throughout the whole range of Mn doping. Variation of resistivity with temperature shows that thermally activated conduction (Arrhenius) mechanism is valid in the high-temperature region (T > 250 K), whereas Mott's variable-range hopping (VRH) mechanism is valid in low-temperature region (T < 250 K). Variation of the activation energy estimated from the resistivity measurement (Arrhenius law) qualitatively follows the variation of the optical band gap. © 2012 American Chemical Society.
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    PublicationArticle
    Structural and magnetic properties of quasi-one-dimensional doped LiCuVO4
    (2013) Kumar, Abhishek; Kumari, Poonam; Das, A.; Dwivedi, G.D.; Shahi, P.; Shukla, K.K.; Ghosh, A.K.; Nigam, A.K.; Chattopadhyay, K.K.; Chatterjee, Sandip
    The Neutron diffraction, X-ray photoemission and Magnetic properties of Zn, Co and Mn-doped LiCuVO4 were investigated. Both with Zn and Co doping the antiferromagnetic correlation increase. On the other hand Mn-doping induces the short range ferromagnetic ordering. Neutron diffraction study does not show any phase transition down to 5 K i.e., there is no indication of long range magnetic ordering. Neutron diffraction study also indicates that with Zn, Co and Mn doping the V-O lengths are changed. Maximum change in the V-O distances is observed for Mn-doped sample. On the other hand, X-ray photoemission spectroscopic data indicates Mn doping converts some Cu 2+ ions into Cu3+ ions. © 2013 Published by Elsevier Inc.
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    PublicationConference paper
    Structural and optical properties of sol-gel derived Zn1-xMnxO nanoparticles
    (2012) Ghosh, Anup K.; Kumar, Shiv; Chatterjee, S.; Chattopadhyay, K.K.
    Mn-doped ZnO i.e. Zn1-xMnxO (0≤x≤0.06) nanoparticles have been synthesized via sol-gel route. Effects of Mn-ion doping on the structural and optical properties have been investigated. The crystallite structure and quality, morphology and size estimation have been performed by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and FTIR analysis. To study optical properties UV-Vis spectroscopy has been employed. UV-Vis measurements show that the band gap is increased with increasing of Mn-concentrations. This may be attributed to the orbitals hybridization which is prevailed throughout the range of Mn-doping. © 2012 American Institute of Physics.