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^−¼ 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.