Electrical properties of iron-silica nanocomposites synthesized by electrodeposition

Abstract

Nanometer-sized iron particles with diameters in the range 5.5–11.1 nm were grown within a silica gel by an electrodeposition method. Electron diffraction measurements show that some of the iron particles were oxidized to Fe3O4. dc resistivity measurements over the temperature range 110–300 K show a T−1/4 variation indicating a variable range hopping transport. ac conductivity over the frequency range 100 Hz–2 MHz show an overlapping large polaron tunneling mechanism to be operative. The dielectric modulus spectra as a function of frequency were analyzed on the basis of a stretched exponential relaxation function. The values of the exponent β as extracted from this analysis were in the range 0.38–0.46. The activation energies corresponding to the maximum of the imaginary part of the dielectric modulus were in the range 0.13–0.20 eV. These are ascribed to an electron tunneling mechanism.