School Of Basic And Applied Sciences

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    Structural, electrical properties and dielectric relaxations in Na+-ion-conducting solid polymer electrolyte
    (Institute of Physics Publishing, 2018) Arya, A.; Sharma, A.L.
    In this paper, we have studied the structural, microstructural, electrical, dielectric properties and ion dynamics of a sodium-ion-conducting solid polymer electrolyte film comprising PEO8-NaPF6+ x wt. % succinonitrile. The structural and surface morphology properties have been investigated, respectively using x-ray diffraction and field emission scanning electron microscopy. The complex formation was examined using Fourier transform infrared spectroscopy, and the fraction of free anions/ion pairs obtained via deconvolution. The complex dielectric permittivity and loss tangent has been analyzed across the whole frequency window, and enables us to estimate the DC conductivity, dielectric strength, double layer capacitance and relaxation time. The presence of relaxing dipoles was determined by the addition of succinonitrile (wt./wt.) and the peak shift towards high frequency indicates the decrease of relaxation time. Further, relations among various relaxation times () have been elucidated. The complex conductivity has been examined across the whole frequency window; it obeys the Universal Power Law, and displays strong dependency on succinonitrile content. The sigma representation () was introduced in order to explore the ion dynamics by highlighting the dispersion region in the Cole-Cole plot () in the lower frequency window; increase in the semicircle radius indicates a decrease of relaxation time. This observation is accompanied by enhancement in ionic conductivity and faster ion transport. A convincing, logical scheme to justify the experimental data has been proposed. ? 2018 IOP Publishing Ltd.
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    Structural, microstructural and electrochemical properties of dispersed-type polymer nanocomposite films
    (Institute of Physics Publishing, 2018) Arya, A.; Sharma, A.L.
    Free-standing solid polymer nanocomposite (PEO-PVC) + LiPF6-TiO2 films have been prepared through a standard solution-cast technique. The improvement in structural, microstructural and electrochemical properties has been observed on the dispersion of nanofiller in polymer salt complex. X-ray diffraction studies clearly reflect the formation of complex formation, as no corresponding salt peak appeared in the diffractograms. The Fourier transform infrared analysis suggested clear and convincing evidence of polymer-ion, ion-ion and polymer-ion-nanofiller interaction. The highest ionic conductivity of the prepared solid polymer electrolyte (SPE) films is ?5 10-5 S cm-1 for 7 wt.% TiO2. The linear sweep voltammetry provides the electrochemical stability window of the prepared SPE films, about ?3.5 V. The ion transference number has been estimated, t ion = 0.99 through the DC polarization technique. Dielectric spectroscopic studies were performed to understand the ion transport process in polymer electrolytes. All solid polymer electrolytes possess good thermal stability up to 300 ?C. Differential scanning calorimetry analysis confirms the decrease of the melting temperature and signal of glass transition temperature with the addition of nanofiller, which indicates the decrease of crystallinity of the polymer matrix. An absolute correlation between diffusion coefficient (D), ion mobility (?), number density (n), double-layer capacitance (C dl), glass transition temperature, melting temperature (T m), free ion area (%) and conductivity (?) has been observed. A convincing model to study the role of nanofiller in a polymer salt complex has been proposed, which supports the experimental findings. The prepared polymer electrolyte system with significant ionic conductivity, high ionic transference number, and good thermal and voltage stability could be suggested as a potential candidate as electrolyte cum separator for the fabrication of a rechargeable lithium-ion battery system. ? 2018 IOP Publishing Ltd.
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    Evaluation of aluminium doped lanthanum ferrite based electrodes for supercapacitor design
    (Elsevier, 2014) Rai, Atma; Sharma, A. L.; Thakur, Awalendra K.; Thakur, A.K.
    We report Al doped ferrites La1 - xAlxFeO 3(x = 0, 0.3) as an electrode material for supercapacitor design. The La1 - xAlxFeO3 has been synthesized via chemical route. Structural and microstructural evolution has been carried out by X-ray diffraction (XRD) analysis and field emission scanning electron microscopy (FESEM) respectively. The electrode property of La 1 - xAlxFeO3 has been evaluated by using three electrode systems, glassy carbon (working), Pt (counter) and Ag/AgCl (reference electrode) with H2SO4 as the electrolyte. The Al doped ferrites show better cycle life (~ 250) and columbic efficiency (?) (~ 96%) in comparison to un-doped lanthanum ferrite sample. An increase in specific capacitance (~ 1.5 times) has also been observed in Al doped lanthanum ferrite in comparison to lanthanum ferrite. The maximum specific capacitance for Al doped lanthanum ferrite is ~ 260 F/g as compared to lanthanum ferrite ~ 200 F/g. The improved specific capacitance, columbic efficiency and cycle life of Al doped ferrites may be related to a relative decrease in equivalent series resistance (95 ? for LFO to 55 ? LAFO) and lower M.W. of Al doped lanthanum ferrite. ? 2013 Elsevier B.V.