Summary:The function of temperature. Possible apparatus providing

Summary:The
technique has been used to produce MgGd0.1 Fe1.9 O4
ferrite by developed electrical and dielectric property is conventional ceramic.
The inverse spinel structure of the ferrite is single-phase that is proved by
X-ray analysis. The dc resistivity in evaluation of Magnesium ferrite is raised
through one order of magnitude. The dielectric loss of the model determined at
room temperature is only 3 × 10?3 at 3 MHz. The low wastage of
dielectric and high resistivity could be associated with better compositional
stoichiometry, size and nature of the additives. The deviation in dielectric
properties of the sample as a function of frequency in the range 0.1–20 MHz has
been considered on different temperatures. Furthermore, the electric and
dielectric properties also have been considered as a function of temperature.
Possible apparatus providing toward the results have been conferred exactly in
this paper.

Ø  Introduction:
Spinel
ferrites have been considered extensively because they play a vital role in the
technological applications. Gd–Mg ferrites have emerged as one of the most
important material due to its high dc resistivity and low dielectric losses. It
is very important in many applications to control the dc resistivity of the
spinel ferrites. For this purpose two major possibilities are available,
controlling the sintering temperature and substitution. The dc resistivity of
MgGd0.1Fe1.9O4 ferrite is increased by one
order of magnitude as compared to Mg ferrite. These useful properties of the
spinel ferrites depend upon the choice of the cation along with Fe2+,
Fe3+ ions and their distribution between tetrahedral (A) and
octahedral (B) sites of the spinel lattice, preparation methods, chemical
com-position, and sintering temperature, rate of sintering and nature of the
additives. All the ferrites have high dc resistance. It is used in the
formation of the transformers central parts and chokes. All the ferrites having
extremely low dielectric loss are very helpful for microwave statement. In the
paper, the difference of electric and dielectric properties of the model as a
purpose of frequency at varied temperatures. In addition to this, the effects
of temperature on the electric and dielectric properties were investigated and
reported in the present work.

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Ø  Experimental
details: Mg–Gd ferrite of composition MgGd0.1 Fe1.9
O4 was prepared by using the standard ceramic technique. Logical
grade reagents MgO, Gd2 O3 and Fe2 O3
were weighted in appropriate proportions and mixed thoroughly by wet blending
with de-ionized water in an agate mortar and pestle. The mixed powders were
dried and calcinated at 800 ? C for 3 h to improve the homogeneity
of the constituents. After cooling to room temperature the samples were mixed
with a small quantity of polyvinyl alcohol as a binder and milled. The powders
were compressed into pellets uniaxially under a pressure of 3–8 ton/in.2
in a stainless steel die. The pellets were finally sintered at 1000 ?
C for 3 h and were cool down to room temperature. The single-phase nature of
the prepared samples was checked by X-ray diffraction studies, which were made
by Cu-K radiation of wavelength 1.54 Å using Riga Ku-Denki X-ray diffraction
meter. The surfaces of the pellet were polished and coated with silver paste;
they acted as good contacts and electrodes for measuring the electric and
dielectric properties. The dielectric constant and dielectric loss were
determined by Agilent Technologies 4285A Precision LCR meter at room
temperature in the frequency range from 0.075 to 20 MHz. The dc resistivity of
the samples at different temperatures was measured by using a Keithley Model
2611 in the temperature range 293–473 K.

Ø  Results
and discussion: The X-ray diffraction patterns for the
ferrite powder obtained on calcination at 1000 ? C corresponded to
that of the single-phase inverse spinel structure for the compositions MgGdxFe2?x
O4 (x = 0.00 and 0.1). The diffraction peaks are
quite sharp because of the micrometer size of the crystallite. The particle
size of the sample has been estimated from the broadening of XRD peaks using
the Scherrer equation. The average particle size is about 0.1–1 m at 1000 ?
C. The variation of dc resistivity with temperature. High dc resistivity of ?7
× 108_
cm is obtained at room temperature, and decreases with increase in temperature.
The higher value of dc resistivity is due to Gd3+ content in Mg
ferrite. Gd3+ content doping reduces the iron ion concentration from
2 to 1.9 thereby reduces the number of Fe3+ ions on theoctahedral
sites which play a dominant role in the apparatus of conduction. The inset
shows the variation of dc resistivity of MgFe2O4 (Pure Mg
ferrite) with temperature. The resistivity of the sample decreases with
increase in temperature according to Arrhenious equation. Increasing
temperature leads to decrease in resistivity, which is the normal behavior of
semiconducting materials. Increase in temperature of the sample will help the
trapped charges to be liberated and participate in the conduction process, with
the result of decreasing the resistivity. This decrease in resistivity could be
related to the increase in the drift mobility of the thermally activated
electrons according to the hopping conduction apparatus and not to thermally
creation of the charge carriers. The hopping conduction apparatus between Fe2+
? Fe3++e?1 is the main source of electron hopping
in the process. Activation energy, E was calculated from the slope of
the graph. The value of activation energy for the sample is 0.4497 eV. In
ferrite samples, the activation energy is often associated with the variation
of mobility of charge carriers rather than with their concentration. The charge
carriers are considered as localized at the ions or vacant sites and conduction
occurs via a hopping process. The hopping depends upon the activation energy,
which is associated with the electrical energy barrier experienced by the
electrons during hop-ping. The variation of dielectric constant as purpose of
frequency in the range 0.1_20 MHz at various temperatures. Initially dielectric
constant decreases slowly with frequency up to 1 MHz and becomes almost
constant up to 6 MHz. The increase in dielectric constant above 6 MHz may
indicate the beginning of a possible presence of resonance with peaks occurring
at higher frequencies. The initial decrease in dielectric constant with
frequency up to (1 MHz) can be explained by the phenomenon of dipole
relaxation. The resonance may arise due to the matching of the frequency of
charge transfer between Fe2+ ? Fe3+ ions, and that of the
applied electric field. These changes can also be elaborated on the basis of
space charge polarization model of Wagner and Maxwell. The variation of
dielectric constant with temperature at different frequencies. The dielectric
constant increases with temperature at all frequencies. The hopping of the
charge carriers is thermally activated with the rise in temperature; hence, the
dielectric polarization increases, causing an increase in dielectric constant.
At lower frequencies (100 kHz), the increase in dielectric constant is very
large with an increase in temperature, while at higher frequency range (1–12
MHz), the increase in dielectric constant is small. The dielectric constant of
any materials, in general, is directly related to dielectric polarization. The
higher the polarization, the higher the dielectric constant of the material.
There are four primary apparatus causing polarizations: electronic
polarization, ionic polarization, dipolar polarization and space charges
polarization. Their occurrence depends upon the electric frequency of the
applied field. At low frequencies, space charges polarization and dipolar polarization
are known to play the vital role 19 and
both these polarizations are temperature dependent. At high frequencies, ionic
polarizations are main contributors, and their temperature dependence is
insignificant. The change of dielectric loss with frequency at different
temperatures. The dielectric loss factor decreases initially with increasing
frequency followed by the appearance of a resonance with peaks occurring at
higher frequencies. The initial decrease in dielectric loss (tan ?) with an
increase in frequency is in accordance with the Koop’s phenomenological model.
The resonance may arise due to the matching of hopping frequency with the
frequency of the external electric field. Hudson has shown that, the dielectric
losses in ferrites are reflected in the conductivity measurements where the
materials of high conductivity exhibiting higher losses and vice-versa. The
change of dielectric loss as a function of temperature at different
frequencies. The dielectric loss also shows the same trend as the dielectric
constant curves, and can be explained online similar to those advanced for
explaining dielectric constant. The low values of dielectric constant,
dielectric loss and high value of dc resistivity are due to the Gd3+
ion content in Mg ferrite. This result is explained in view of the hopping
conduction apparatus between Fe2+ ? Fe3+ + e?1,
Gd3+ ions do not participate in conduction and polarization process
but limit the degree of hop-ping by blocking up Fe2+ ? Fe3+
+ e?1 pattern on the octahedral sites. This is due to the
reduction in the concentration of Fe ions inthe system due to the doping of Gd3+
ions in Mg ferrite.

Ø  Conclusions

Single-phase MgGd0.1Fe1.904
ferrite has been synthesized by conventional ceramic method. The particle size
was calculated from the most intense peak (3 1 1) using the Scherrer equation.
The dc resistivity considered shown that ferrite is increased by one order of
magnitude as compared to undoped Magnesium ferrite. High value of dc
resistivity makes this ferrite suitable for the highfrequency applications
where vortex current losses become appreciable. Gd–Mg ferrites may be used in
television yokes and fly back transformers because of their higher resistivity
which eliminates the need for taped insulation between yoke and winding.
Temperature dependent dc resistivity decreases with an increase in temperature
ensuring the normal behavior of semiconducting materials. The value of
dielectric loss in the presently considered ferrite at room temperature is only
0.003 at 3 MHz. Low values of dielectric constant and dielectric losses
exhibited by this ferrite suggest its utility in microwave communications.

 

 

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