Abstract:
NiCr0.07
Fe1.93O4
and NiCo0.07
Fe1.93O4
ferrite materials were successfully synthesized by sol-gel
method at the temperature of 750
o
C for 6 hours in air. The structural, the electrical, dielectric
and magnetic properties of both materials are investigated by x-ray powder diffraction (XRD),
scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy,
impedance spectroscopy (IS) and electron spin resonance (ESR) spectroscopy techniques. The
X-ray diffraction patterns of the synthesized samples confirm the formation of spinel structure
with Fd3m space group without any secondary phases or impurities. The crystallite sizes are
calculated from most intense peak using the Scherrer formula. It is found that NiCr0.07
Fe1.93O4
has larger crystal size (48.5nm) than NiCo0.07
Fe1.93O4 (46.3nm). The calculated lattice
parameters are found to be 8.387Å and 8.377Å for NiCr0.07
Fe1.93O4
and NiCo0.07
Fe1.93O4
,
respectively. SEM micrographs of both powder samples are almost dense and have fewer
pores. FT-IR measurements show two fundamental absorption bands, assigned to the vibration
of tetrahedral (A-sites) and octahedral (B-sites). The frequency dependent of the real (Z′) and
imaginary (Z′′) parts of the impedance for both samples measured at room temperature in the
frequency range from 1Hz to 1MHz was investigated in this study. It was observed that the Z′
and Z′′ values are typically higher at low frequency regions. The high value of Z′ and Z′′ at this
frequency region is due to the high polarization caused by space charge. Further, t he frequency
dependence of the electrical and dielectric properties of NiCr0.07
Fe1.93O4 and NiCo0.07
Fe1.93O4
ferrites are studied in the frequency range of 1 Hz to 1MHz. Experimental results show that
the dielectric constant ε′ is found to decrease with increasing frequency. However, the ac
electrical conductivity increases with increasing frequency. From magnetic study; it was
found that both ferrites exhibit broad and symmetrical signals which are due to the presence of
unpaired electrons in the compounds.
