• Sunil K Paliwal

      Articles written in Bulletin of Materials Science

    • Thermally-stimulated spontaneous currents from metal-iodine doped polyvinyl pyrrolidone-metal system

      P K Khare Sandeep K Jain Sunil K Paliwal

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      A study of the spontaneous response currents from the metal-iodine doped polyvinyl pyrrolidone-metal (MPM) systems, on thermal stimulation at a constant rate, has been made with similar (Al-Al, Ag-Ag and Au-Au) and dissimilar (Al-Cu/Ag/Ni/PbZn) electrode systems. Thermograms of spontaneous current emission of iodine-doped PVP films exhibit two maxima around 90 ± 10°C and 130–160°C in the first heating run, whereas with the second heating run a single peak is found around 140–170°C. The magnitude and direction of current depend on the choice and combination of electrode materials. The position of the current peak in the thermal spectrum shifts with different heating run. A temperature dependence of open-circuit voltage (OCV) is also reported and it was found that OCV varied linearly with the difference in electrode work functions. The active centres of PVP are the carbonyl group of double-bond tertiary nitrogen atom (> N-C=O), and thus the charge transfer complexes are formed with iodine in PVP. The spontaneously-generated current is discussed in terms of weak complex formation with the water molecules and the liberation of different types of charges.

    • Thermally stimulated current and electrical conduction in metal (1)-ethyl cellulose-metal (1)/(2) systems

      P K Khare Ashish Verma Sunil K Paliwal

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      Depolarization current characteristics of solution grown pure ethyl cellulose (EC) films of about 20µm thickness have been studied as a function of electrode materials at constant poling field (5 × 104 V/cm) and poling temperature 40°C. Thermally stimulated current (TSC) thermograms of EC consists of two well resolved peaks (located at 60°C and 140°C) for Al-Al system, which are attributed to the deorientation of strongly attached ethoxy groups of glycosidal units and diffusion of space charges either at electrodes or due to their thermal release at higher temperatures from the defect levels. For dissimilar electrode combinations (Al-Ag/Cu/Au/Sn/Pb), an indication of peak of lower magnitude at around (50–70°C) alongwith a higher temperature peak (140–155°C), have been observed. TSC parameters are found to change with the choice of electrode material. The dependence of dark current at 40°C in metal-ethyl cellulose-metal systems on applied voltage in the range (2·0–5·0) × 104V/cm has also been studied. The results of current-voltage measurement on EC have been interpreted to show that the Schottky-Richardson mechanism is the controlling transport mechanism. Zero field current density extrapolated fromI-E1/2 plots are found to vary with metal work function.

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