• S V Bhat

      Articles written in Bulletin of Materials Science

    • Morphology and conductivity studies of a new solid polymer electrolyte: (PEG)𝑥LiClO4

      Th Joykumar Singh S V Bhat

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      A new solid polymer electrolyte, (PEG)𝑥LiClO4, consisting of poly(ethylene)glycol of molecular weight 2000 and LiClO4 was prepared and characterized using XRD, IR, SEM, DSC, NMR and impedance spectroscopy techniques. XRD and IR results show the formation of the polymer–salt complex. The samples with higher salt concentration are softer, less opaque and less smooth compared to the low salt concentration samples. DSC studies show an increase in the glass transition temperature and a decrease in the degree of crystallinity with increase in the salt concentration. Melting temperature of SPEs is lower than the pure PEG 2000. Room temperature 1H and 7Li NMR studies were also carried out for the (PEG)𝑥iClO4 system. The 1H linewidth decreases as salt concentration increases in a similar way to the decrease in the crystalline fraction and reaches a minimum at around 𝑥 = 46 and then increases. 7Li linewidth was found to decrease first and then to slightly increase after reaching a minimum at 𝑥 = 46 signifying the highest mobility of Li ions for this composition. Room temperature conductivity first increases with salt concentration and reaches a maximum value (𝜎 = 7.3 × 10-7 S/cm) at 𝑥 = 46 and subsequently decreases. The temperature dependence of the conductivity can be fitted to the Arrhenius and the VTF equations in different temperature ranges. The ionic conductivity reaches a high value of ∼ 10-4 S/cm close to the melting temperature.

    • Study of effect of composition, irradiation and quenching on ionic conductivity in (PEG)𝑥 : NH4NO3 solid polymer electrolyte

      R Damle P N Kulkarni S V Bhat

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      We have prepared, characterized and investigated a new PEG-2000 based solid polymer electrolyte (PEG)𝑥: NH4NO3. Ionic conductivity measurements have been made as a function of salt concentration as well as temperature in the range 265–330 K. Selected compositions of the electrolyte are exposed to a beam of 8 MeV electrons and 60Co 𝛾-rays to an accumulated dose of 10 kGy to study the effect on ionic conductivity. The electrolyte samples are also quenched at liquid nitrogen temperature and conductivity measurements are carried out. The ionic conductivity at room temperature exhibits a characteristic peak for the composition, 𝑥 = 46. Electron beam irradiation results in an increase in conductivity for all compositions by a factor of 2–3. Exposure to 𝛾-rays enhances the conductivity by one order of magnitude. Quenching at low temperature has resulted in an increase in conductivity by 1–2 orders of magnitude. The enhancement of conductivity upon irradiation and quenching is interpreted as due to an increase in amorphous region and decrease in crystallinity of the electrolyte. DSC and NMR measurements also support this conclusion.

    • Ba3(P1−𝑥Mn𝑥O4)2 : Blue/green inorganic materials based on tetrahedral Mn(V)

      Sourav Laha Rohit Sharma S V Bhat M L P Reddy J Gopalakrishnan S Natarajan

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      We describe a blue/green inorganic material, Ba3(P1−𝑥Mn𝑥O4)2 (I) based on tetrahedral MnO$^{3-}_{4}$ :3𝑑2 chromophore. The solid solutions (I) which are sky-blue and turquoise-blue for 𝑥 ≤ 0.25 and dark green for 𝑥 ≥ 0.50, are readily synthesized in air from commonly available starting materials, stabilizing the MnO$^{3-}_{4}$ chromophore in an isostructural phosphate host. We suggest that the covalency/ionicity of P–O/Mn–O bonds in the solid solutions tunes the crystal field strength around Mn(V) such that a blue colour results for materials with small values of 𝑥. The material could serve as a nontoxic blue/green inorganic pigment.

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