Structural and dielectric properties of Cr-doped Ni-Zn nanoferrites

Cr-doped Ni-Zn ferrite nanoparticles having the general formula Ni(0.5)Zn(0.5)CrxFe(2-x)O(4) (x = 0.1, 0.3, 0.5) were prepared by the simplified sol-gel method. The structural and dielectric properties of the samples sintered at 750 +/- 5 degrees C were studied. X-ray diffraction (XRD) patterns confirm the single-phase spinel structure of the prepared samples. The crystallite size calculated from the most intense peak (3 1 1) using the Debye-Scherrer formula was 29-34 nm. Scanning electron microscope images showed that the particle size of the samples lies in the nanometer regime. The dielectric constant (epsilon(r)), dielectric loss tangent (tan delta) and ac electrical conductivity (sigma(ac)) of nanocrystalline Cr-Ni-Zn ferrites were investigated as a function of frequency and Cr concentration. The dependence of epsilon(r), tan delta and sigma(ac) on the frequency of alternating applied electric field is in accordance with the Maxwell-Wagner model. The effect of Cr doping on the dielectric and electric properties was explained on the basis of cations distribution in the crystal structure.