Ashok R. Lamani

Electrical conductivity and microcrystalline parameter in Co-Zn ferrites

Abstract A series of samples of the system Co1−xZnxFe2O4 (for x = 0·0, 0·2, 0·4, 0·6 and 1·0) were prepared by usual ceramic technique. These prepared samples were examined using X-ray powder pattern, which confirms the presence of a spinel structure. The authors have also carried out line profile analysis of individual Bragg reflections observed in these ferrites, which shows variation in the cell parameter. Further electrical conductivity measurements of these ferrites were carried out as a function of temperature. The observed values of the electrical conductivity have been explained on the basis of Verwey’s hopping mechanism. The activation energy was found to decrease with increasing Zn content. In addition, its variations for varying concentrations of Zn in Co are interpreted in terms of microstructural parameters.

Low-Frequency Dependence of Conductivity and Dielectric Properties of Polyaniline/ZnFe2O4 Nanocomposites

Conducting polyaniline/ZnFe2O4 nanocomposites are synthesized by using a simple and inexpensive one-step in-situ polymerization method in the presence of ZnFe2O4 nanoparticles. The structural, morphological and electrical properties of the samples are characterized by x-ray diffraction, Fourier transform infrared spectra and scanning electron microscopy. These results reveal the formation of polyaniline/ZnFe2O4 nanocomposites. The morphology of these samples is studied by scanning electron microscopy. Further, the ac conductivity (σac) of these composites is investigated in the frequency range of 1 kHz–10 MHz. The presence of polarons and bipolarons are responsible for the frequency dependence of ac conductivity in these nanocomposites. The ac conductivity is found to be constant up to 1 MHz and thereafter it increases steeply. The ac conductivity of 0.695 Scm−1 at room temperature is observed as the maxima for the polyaniline with 40wt% of the ZnFe2O4 nanocomposite.

Microwave Dielectric and Magnetic Properties of Co-Zn Ferrites

The dielectric permittivity, loss tangent, in the frequency range 1MHz to 1.8 GHz and hysteresis loop parameters at room temperature were studied on a series of Zn substituted cobalt ferrites with general formula Co1-xZnx Fe2O4 where (x=0.0, 0.2, 0.4, 0.6, 1.0.). The experimental results indicate that the Zn substitution affects all these parameters. The observed dispersion in dielectric permittivity with frequency is in accordance with Maxwell-Wagner model. The high temperature sintering is used to synthesize these materials via solid state reaction route and these samples were characterized by X-ray diffractometer (XRD), vibrating sample magnetometer (VSM). The saturation magnetizations (MS) Hc and Mr of the Particles were measured at room temperature. Here for the smaller dopent concentration Ms increases with increasing in the Zn content this can explained on the basis of increased number of magnetic ions in the spinel lattice, at some point Ms decrease because of the difference between the magnetic moment of Fe2+ and Zn2+, the magnetic moment of the A sub lattice will increases and the moment of the B sub lattice will decrease. The variation of crystalline shape ellipsoid is correlated with variation of dielectric constant.

Study on low temperature DC electrical conductivity of SnO2 nanomaterial synthesized by simple gel combustion method

Nanocrystalline tin oxide (SnO2) material of different particle size was synthesized using gel combustion method by varying oxidizer (HNO3) and keeping fuel as a constant. The prepared samples were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM) and Energy Dispersive Analysis X-ray Spectroscope (EDAX). The effect of oxidizer in the gel combustion method was investigated by inspecting the particle size of nano SnO2 powder. The particle size was found to be increases with the increase of oxidizer from 8 to 12 moles. The X-ray diffraction patterns of the calcined product showed the formation of high purity tetragonal tin (IV) oxide with the particle size in the range of 17 to 31 nm which was calculated by Scherer’s formula. The particles and temperature dependence of direct (DC) electrical conductivity of SnO2 nanomaterial was studied using Keithley source meter. The DC electrical conductivity of SnO2 nanomaterial increases with the temperature from 80 to 300K and decrease with t...