Cation distribution and dielectric properties of nanocrystalline gallium substituted nickel ferrite

Nano crystalline NiFe2-xGaxO4, 0.0 <= x <= 1 ferrite was prepared by citrate method. The structural and micro structural evolutions of the nanophase have been studied using X-ray powder diffraction and the Rietveld method. The refinement result showed that the type of the cationic distribution over the tetrahedral and octahedral sites in the nanocrystalline lattice is partially an inverse spinel. Furthermore, the Mossbauer spectra, measured at 20 K of all the samples show complete magnetic behavior, whereas at room temperature, are combination of ferromagnetic and superparamagnetic components indicating the particle size dependency. The inversion of Ni ions in a sample is affected by the percentage of Ga ions present, consistent with the results of X-ray data analysis. The a.c conductivity was measured in the temperature range 77-493 K and frequency range 50-100 kHz. The dielectric constant increase with increase Ga amount. The a. c conductivity results showed that nanocrystalline Ga doped NiFe2O4 ferrite samples follow the correlated barrier hopping (CBH) model. The activation energy increases from1.2 to 1.8 eV as the amount of Ga increases. (C) 2013 Elsevier B.V. All rights reserved.