Hexagonal ferrites
materials are metal oxides that exhibit high saturation magnetization, high/low
coercivity, high electrical resistivity, excellent dielectric losses, high
permittivity and permeability 1. Hexa-ferrites are very attractive materials
for technological applications due to their unique electrical and magnetic
properties. Hexagonal ferrites have many applications, such as recording,
magneto-optical devices, and permanent magnets. Its unique magneto-dielectric
property is particularly interesting in microwave and radio frequency applications 3. Dielectric
characteristic is an important property of hexagonal ferrites which depends on
different factors like polarization, sintering temperature and time, frequency,
method of preparation, 5 and kind of charge carrier 6. Composition,
temperature 7 and substituted or
doped
8 badly effect the electrical properties of hexagonal ferrites. So, a little
change in composition, can transform material from insulator to semiconductor
9.

Hexagonal
ferrites are of different types i.e.(SrFe12O19),W(SrM2Fe16O27),
X(Sr2M2Fe28O46,
Y(Sr2M2Fe12O22),
Z(Sr3M2Fe24O41),
U(Sr4M2Fe36O60),
and R(SrM2Fe4O11)
10.
where M = a small 2+ ion such as cobalt, nickel
or zinc.R-type
hexagonal ferrites have hexagonal structure and represented as RR* where R is R
block and R* has the phase shift of 1800 11.

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There
are a lot of methods to synthesize but sol-gel is low cost and easy method.
Therefore, sol-gel technique is used to synthesize the single phase of R-type
hexagonal (SrM2Fe4O11) where ‘M’ is
tetravalent element. The need of using tetravalent element is to maintain the
overall neutrality of the sample.

Maria et al synthesized
strontium-barium X-type hexagonal ferrites with composition SrBaCu2?xNixNdyFe28?yO46
(x = 0, 0.2, 0.4, 0.6,0.8,1 and y=0,0.02,0.04,0.06,0.08,0.1) by sol-gel method.
The XRD analysis reveals
the single phase for all the samples. Doping of Nd-Ni, the trend of dielectric
constant, dielectric loss and AC-conductivity showed decreasing. The Cole-Cole
plots revealed grain boundary contribution. The appearance of single
semi-circle in impedance,the exceptional role of grain boundaries in the
conduction process con?rmed by Cole-Cole graphs. The lower dielectric
parameters of studied nano X-type ferrites propose their possibility for
high-frequency applications i.e. phase shifters, dielectric resonators,etc.

Long et al synthesized
Sr-hexaferrites with series of Sr1-xLaxFe12-xZnxO19
(x=0–0.3) with Bi2O3 chemical by microwave sintering
method at low sintering temperatures. In this work, crystal structure,
magnetic, electrical, and dielectric properties were studied. These properties  indicates that the La3+-Zn2+
ions can partially substitute the Sr2+-Fe3+ ions with
x?0.2 for the low temperature sintered Sr1-xLaxFe12-xZnxO19
(x=0–0.3) hexa-ferrites. The dielectric behavior of the Sr1-xLaxFe12-xZnxO19
(x=0–0.2) ferrites is found to obey the space charge polarization mechanism
from the typical current-voltage (I-V) curves and polarization versus electric
?eld (P-E) loop.

x

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