Papers by Keyword: DC Conductivity

Abstract: Spinel copper ferrite nanoparticles have wide spread technological applications. Polycrystalline copper ferrite nanoparticles is prepared by sonochemical method. The structural property is investigated by X-ray diffraction study, which reveals cubic spinel structure of copper ferrite NPs with average crystalline size of 20 nm. The temperature variation of DC conductivity of copper ferrite nanoparticles is studied. The conductivity is observed to increase with temperature which implies semiconducting nature of copper ferrite. The Mott study reveals that conduction process is three dimensional in present case. Again, p-n junction formation in the ferrite system is observed from the current voltage (I-V) study. This study further shows that the trap height increases with temperature. Ideality factor with values greater than 1 has been observed in present case.

Abstract: The development of biosensors is essential while determining the inside body assaying and assessing implants in-vivo applications. Researchers are doing remarkable studies in certain areas, but output for receiving, adaptability and circulation of nutrients are also essential. For examining the similar functionality, multi-walled carbon nanotube epoxy-composite with varying filler percentages is examined and compared using electromechanical and morphological assessment. Mechanical investigations like tensile and flexural tests were performed in addition to the hardness of specimens. The DC conductivity test is performed to determine the charge conductivity along with NMR for measuring the signal responses. The surface characterization is performed to determine the morphological properties of specimens. It is observed that the mechanical properties increased and decreased after exceeding the filler composition to addition to 2% of total weight. In comparison, the conductivity and magnetic resonance enhance to a further extent showing proportional to addition of nanofillers, thus making them potential applications for flexible organic bioelectronics products.

Abstract: The phosphate glasses, with composition (60-x)P₂O₅-25ZnO-(15+x)Li₂O where 0.0 ≤ x ≤ 5.0 mol% are prepared by conventional melt quenching method. The amorphous nature of the glass is determined by X-Ray Diffraction (XRD). The physical properties are measured in term of their density and molar volume. Glass density is found to increase from 2.700 to 2.785 g cm^-3 whereas molar volume is found to decrease from 40.735 to 37.488 cm³ mol^-1 with respect to Li₂O content. The DC measurements are done by using four point probes and the activation energies are determined. Arrhenius plot shows straight line behavior as observed that confirmed the conductivity increased with Li₂O content. The activation energy is found to decreases from 0.75 to 0.08 eV as Li₂O content is increased in the temperature range from 310 to 420 K. Measurements of the thermal conductivity using Lee’s disc apparatus have been made. It is observed that the maximum and minimum thermal conductivity are 0.2679 and 0.2168 W m^-1 K^-1 respectively.

Abstract: To ascertain physical mechanism of charge transport in Si/SiO_x structures with Ge nanoclusters the measurements of their DC and AC conductivity, and also the low-frequency measurements were performed. It was revealed that in the temperatures range 110 – 250 K the characteristics measured are governed by the hopping mechanism of charge transport. The model proposed suggests that the charge hopping becomes possible due to the band of localized states inducing in the bandgap of silicon substrate when Ge nanoclusters are introduced. The model was used to estimate some parameters of hopping transport. Also, the analysis of the low-frequency noise measured for Si/SiO_x structures with Ge nanoclusters allowed to ascertain the mechanism of charge hopping resulting in strong temperature dependence of the 1/f noise measured.

Abstract: The temperature dependence of the electrical DC conductivity of fly-ash and illite-based ceramics was measured in the temperature range of 20 – 1050 °C. The measurements were done for illite samples with no fly-ash and fired illite added and illite samples containing 10 wt. %, 20 wt. %, 30 wt. %, and 40 wt. % of fly-ash and 0 wt. %, 10 wt. %, 20 wt. %, and 30 wt. % of fired illite. Addition of fly-ash substantially influences temperature dependences of the DC conductivity and introduces a temperature region with a high conduction activation energy which precedes the dehydroxylation. At the lowest temperatures, the main charge carriers are H⁺ and OH⁻ ions, while at higher temperatures K⁺ and Na⁺ ions also play a role. The phase transformation metaillite -> Al-Si spinel is characterized with a current peak at 940 °C.

Abstract: xNd₂O₃-35LiCl-(30-x)PbO-35ZnO glasses (where x=0.1, 0.2, 0.3, 0.4 and 0.5 mol %) were prepared by melt quenching method and converted to glass ceramics by controlled crystallization processes. Glass and glass ceramic phases were confirmed by XRD. The electrical conductivity of these samples has been carried out as a function of frequencies at different temperature. Ac conductivity data of these glasses has been analyzed using a single power law. The exponents obtained from the power law fits is found to be in the range from 0.2 0.3 in these glass ceramics and shows moderate temperature dependence. The stretched exponent β also is seen to vary slightly with temperature. Scaling behavior also has been carried out using the reduced plots of conductivity and frequency. The time-temperature superposition of data points is found to be satisfactory indicating that the ion transport mechanism decreases with annealing temperature and increase with compositions studied. Activation energy (E_a) has been calculated for all the samples at different temperatures, is found to vary in the range of 0.4eV to 0.5eV.

Abstract: The conducting polymers are vital sources for fabrication of micro electronics chips, GMR sensors, membranes and flexible electrodes. Polyaniline is widely chosen for such products because of its conductivity range. This paper focuses on the studies of dual phase properties of Polyaniline (PANI) - Magnetic Iron Oxide (MIO) composites wherein MIO micro and nanoparticles were incorporated in polyaniline. This type of MIO-Polyaniline composites can enhance both conductive and magnetic property. Polyaniline was synthesized by redox polymerization technique with MIO both in micro and nanosize by in-situ polymerization. The MIO content was maintained at 0.2 to 0.6 gm with respect to 4.6 gm of aniline in polymerization reaction. The composites were characterized by FTIR, UV, XRD, SEM and VSM and conductivity unit. The saturation magnetization of composites was 0.0057 emu/g for 0.6 MIO micro spheres and 1.5507 emu/g for 0.6 MIO nanospheres. The DC conductivity values for pure PANI are 2.06x10^-2 S/cm , 5.13x10^-3 S/cm for PANI-0.6 micro MIO and 1.13x10^-3 S/cm for PANI-0.6 nanoMIO. Micro tubular structure was observed for PANI composite in SEM . It is evident that the electrical properties are altered significantly on tailoring MIO in microtubes and the magnetic property is altered by tuning the composition of MIO from micro to nanorange. These composites will satisfy the properties for applications such as actuators, supercapacitors, EMI shielding, Fuel cells and Sensors. Key words: Polyaniline, Microtubes, Magnetic iron oxide, DC conductivity

Abstract: Co0.6Mg0.4 Fe2O4 samples are prepared by auto-combustion method at various pH values of the solutions (sols). The precursors for the solids are different gels obtained from metal nitrates and citric acid by sol-gel process. The pH is varied by adding ammonia. The gels thus obtained are heated at 2000C and they exhibited self propagating combustion behavior. The residues are heated for one and half hours at 6000C. XRD analysis of the final solids revealed that after combustion the gel is directly transformed into nano sized cobalt magnesium ferrite particles. The samples are sintered at 6000C and higher temperatures. However, the samples sintered at 6000C have shown single phase nano particles. The ferrites formed have shown variation in particle size for varying pH values. FTIR of the samples supported the Octahedral and Tetrahedral site absorption values. The DC conductivity of the above samples has been studied and the results are discussed.

Abstract: Au nanoparticles of average size 3.0 nm have been deposited on SWCNT surfaces following a very lucid wet chemical process. The SWCNT/Au nanohybrid material has been characterized using field emission scanning electron microscopy (FESEM), energy dispersive x-ray analysis (EDAX), X-ray diffraction (XRD) study and Raman spectroscopy. Both optical and electrical characteristics of the hybrid sample have been studied. The PL emission intensity of the nanohybrid structure has been found to decrease on increasing the excitation wavelength in the plasmon absorption region. High temperature DC conductivity has increased appreciably when pristine SWCNT is treated with Au NPs. Such SWCNT- supported gold nanoparticles can serve as efficient catalysts in chemical industry. Also the tendency of gold-based nanoparticles to attach with biological molecules may make them useful in medical diagnostics. Increase in conductivity of SWCNT on decorating with Au NPs can find practical application as conducting filler in polymer composites.

Abstract: Thin films of Sn10Sb20Se70-XTeX (0≤X≤8) composition were deposited using thermal evaporation technique. As-prepared films were amorphous as studied by X-ray diffraction. Surface morphology studies revealed that films have surface roughness ~2 nm and av. grain size ~ 30 nm. Optical band gap Eg calculated from transmittance and reflectance data showed a sharp decrease for initial substitution of Se with Te upto 2 at%. Further substitution upto 4 at%, lead to a small increase in Eg value and thereafter it marginally decreased for further substitution beyond 4at%. The trend of optical band gap variation with tellurium content has been qualitatively explained using band model given by Kastner. The dc-conductivity measurements showed thermally activated conduction with single activation energy for the measured temperature regime and followed Mayer-Neldel rule. The dc-activation energy has nearly half the value as that of optical band gap that revealed the intrinsic nature of semiconductor. The annealing below glass transition Tg led to decrease in optical band gap as well as dc-activation energy that might be related to increase of disorder in material with annealing.