The electrical properties of manganese ferrite powders prepared by two different methods

Two powder samples of manganese ferrite (MnFe2O4) with different morphology and particle size 30-40 nm, denoted by A and B have been synthesized by different methods starting from MnCl2 center dot 4H(2)O and FeCl3 center dot 6H(2)O. Sample A was obtained by co-precipitation followed by calcination at 900 degrees C and sample B has been obtained by hydrothermal method. XRD analysis show that calcination leads to the occurrence of other phases than MnFe2O4, therefore the hydrothermal method gives better results. From the temperature dependence of the electrical resistivity, measured over the range 300-483 K, the activation energy, Delta E, of the investigated samples has been evaluated, resulting in 0.43 eV (for sample A) and 0.32 eV (for sample B). The conductivity mechanism in the samples was explained in terms of Mott's variable range hopping (VRH) model. The results showed that the density of states at the Fermi level is constant over the investigated temperature range, being in order of 0.788 x 1017 eV(-1) cm(-3) (for sample A) and 2.05 x 1017 eV(-1) cm(-3) (for sample B). The hopping distance. R and the hopping energy, W (parameters of VRH model) have also been computed. Room temperature values are R=27.08 nm and W=152 meV for sample A and R=21.29 nm and W=120 meV for sample B. (C) 2015 Elsevier B.V. All rights reserved.