Electrical transport properties of nano crystalline Li–Ni ferrites

Nickel substituted lithium nano ferrites with the chemical composition Li0.5–0.5xNixFe2.5–0.5xO4 (0.0 ≤ x ≤ 1.0) were prepared by Citrate-gel method. The single phase cubic spinel structure of the ferrites was confirmed by X-ray diffraction analysis. Surface morphology and particle size of the samples was studied using Transmission Electron Microscopy (TEM). The TEM micrographs reveal that the particle size of the samples was in the nanometric range confirming the nano crystalline nature. The FTIR spectra shows the two significant absorption bands in the wave number range of 400–600 cm−1 arising due to the inter-atomic vibrations in the tetrahedral and octahedral coordination compounds. The dielectric parameters like dielectric constant (ε′), dielectric loss tangent (tan δ) and AC conductivity (σac) of the samples were measured using LCR meter at room temperature in the frequency range 20 Hz–2 MHz ε′, tan δ and σac of the samples show a normal dielectric behavior of ferrites with frequency which indicates the fact that the dielectric dispersion is due to the hopping of electrons between the Fe2+ and Fe3+ ions. Thermo Electric Power (TEP) studies of Li–Ni ferrites were measured using differential method in the temperature range of 473–873 K. Seebeck coefficient (S) of the prepared ferrites was increased with increasing temperature.