TITLE:
Study of the Dielectric Behaviour of Cr-Doped Zinc Nano Ferrites Synthesized by Sol-Gel Method
AUTHORS:
Mamilla Lakshmi, Katrapally Vijaya Kumar, Krishnan Thyagarajan
KEYWORDS:
Cr-Zn Nano Ferrites, Dielectric Constant, Dissipation Factor, AC Conductivity, Dipole-Dipole Interaction
JOURNAL NAME:
Advances in Materials Physics and Chemistry,
Vol.6 No.6,
June
17,
2016
ABSTRACT: The series of Cr-Zn
nano ferrites having the general composition CrxZnFe2-xO4 (0 ≤ x ≤ 0.5) have been synthesized successfully in the nanocrystalline form
using the sol-gel method. The samples were sintered at 900°C for 3 hours. The effect
of chromium substitution on dielectric properties of Zn-ferrites is reported in
this paper. The analysis of XRD patterns revealed the formation of single phase
cubic spinel structure for all the Cr-Zn ferrite samples. The FTIR spectra show
two strong absorption bands in the range of 400 - 600 cm-1, which corroborate
the spinel structure of the samples. The average grain size was found to be in the
nanometer range and of the order of 43 - 63 nm obtained using TEM images. The lattice
parameter and crystallite size decrease with increase in Cr concentration (x).
The investigation on dielectric constant (ε'),
dissipation factor (D) and ac conductivity
(σac) was carried out at a
fixed frequency 1 kHz and in the frequency range of 100 Hz to 1 MHz at room temperature
using LCR meter. The plots of dielectric constant (ε') versus frequency show the normal dielectric behavior of spinel ferrites.
The value of ac conductivity (σac)
increases with increase in frequency for all the compositions. The appearance of
the peak for each composition in the dissipation factor versus frequency curve suggests
the presence of relaxing dipoles in the Cr-Zn nano ferrite samples. It is also found
that the shifting of the relaxation peak towards lower frequency side with an increase
in chromium content (x) is due to the strengthening of dipole-dipole interactions.
The composition and frequency dependence of the dielectric constant, dielectric
loss and ac-conductivity are explained based on the Koop’s two-layer model, Maxwell-Wagner
polarization process, and Debye relaxation theory.