Summary:Thetechnique has been used to produce MgGd0.1 Fe1.9 O4ferrite by developed electrical and dielectric property is conventional ceramic.The inverse spinel structure of the ferrite is single-phase that is proved byX-ray analysis. The dc resistivity in evaluation of Magnesium ferrite is raisedthrough one order of magnitude. The dielectric loss of the model determined atroom temperature is only 3 × 10?3 at 3 MHz.
The low wastage ofdielectric and high resistivity could be associated with better compositionalstoichiometry, size and nature of the additives. The deviation in dielectricproperties of the sample as a function of frequency in the range 0.1–20 MHz hasbeen considered on different temperatures. Furthermore, the electric anddielectric properties also have been considered as a function of temperature.
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Possible apparatus providing toward the results have been conferred exactly inthis paper.Ø Introduction:Spinelferrites have been considered extensively because they play a vital role in thetechnological applications. Gd–Mg ferrites have emerged as one of the mostimportant material due to its high dc resistivity and low dielectric losses. Itis very important in many applications to control the dc resistivity of thespinel ferrites. For this purpose two major possibilities are available,controlling the sintering temperature and substitution. The dc resistivity ofMgGd0.1Fe1.9O4 ferrite is increased by oneorder of magnitude as compared to Mg ferrite.
These useful properties of thespinel ferrites depend upon the choice of the cation along with Fe2+,Fe3+ ions and their distribution between tetrahedral (A) andoctahedral (B) sites of the spinel lattice, preparation methods, chemicalcom-position, and sintering temperature, rate of sintering and nature of theadditives. All the ferrites have high dc resistance. It is used in theformation of the transformers central parts and chokes. All the ferrites havingextremely low dielectric loss are very helpful for microwave statement.
In thepaper, the difference of electric and dielectric properties of the model as apurpose of frequency at varied temperatures. In addition to this, the effectsof temperature on the electric and dielectric properties were investigated andreported in the present work.Ø Experimentaldetails: Mg–Gd ferrite of composition MgGd0.1 Fe1.9O4 was prepared by using the standard ceramic technique. Logicalgrade reagents MgO, Gd2 O3 and Fe2 O3were weighted in appropriate proportions and mixed thoroughly by wet blendingwith de-ionized water in an agate mortar and pestle.
The mixed powders weredried and calcinated at 800 ? C for 3 h to improve the homogeneityof the constituents. After cooling to room temperature the samples were mixedwith a small quantity of polyvinyl alcohol as a binder and milled. The powderswere compressed into pellets uniaxially under a pressure of 3–8 ton/in.
2in 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 ofthe prepared samples was checked by X-ray diffraction studies, which were madeby Cu-K radiation of wavelength 1.
54 Å using Riga Ku-Denki X-ray diffractionmeter. The surfaces of the pellet were polished and coated with silver paste;they acted as good contacts and electrodes for measuring the electric anddielectric properties. The dielectric constant and dielectric loss weredetermined by Agilent Technologies 4285A Precision LCR meter at roomtemperature in the frequency range from 0.075 to 20 MHz.
The dc resistivity ofthe samples at different temperatures was measured by using a Keithley Model2611 in the temperature range 293–473 K.Ø Resultsand discussion: The X-ray diffraction patterns for theferrite powder obtained on calcination at 1000 ? C corresponded tothat of the single-phase inverse spinel structure for the compositions MgGdxFe2?xO4 (x = 0.00 and 0.1). The diffraction peaks arequite sharp because of the micrometer size of the crystallite.
The particlesize of the sample has been estimated from the broadening of XRD peaks usingthe 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 Mgferrite. Gd3+ content doping reduces the iron ion concentration from2 to 1.9 thereby reduces the number of Fe3+ ions on theoctahedralsites which play a dominant role in the apparatus of conduction. The insetshows the variation of dc resistivity of MgFe2O4 (Pure Mgferrite) with temperature. The resistivity of the sample decreases withincrease in temperature according to Arrhenious equation. Increasingtemperature leads to decrease in resistivity, which is the normal behavior ofsemiconducting materials.
Increase in temperature of the sample will help thetrapped charges to be liberated and participate in the conduction process, withthe result of decreasing the resistivity. This decrease in resistivity could berelated to the increase in the drift mobility of the thermally activatedelectrons according to the hopping conduction apparatus and not to thermallycreation of the charge carriers. The hopping conduction apparatus between Fe2+? Fe3++e?1 is the main source of electron hoppingin the process. Activation energy, E was calculated from the slope ofthe graph.
The value of activation energy for the sample is 0.4497 eV. Inferrite samples, the activation energy is often associated with the variationof mobility of charge carriers rather than with their concentration. The chargecarriers are considered as localized at the ions or vacant sites and conductionoccurs via a hopping process.
The hopping depends upon the activation energy,which is associated with the electrical energy barrier experienced by theelectrons during hop-ping. The variation of dielectric constant as purpose offrequency in the range 0.1_20 MHz at various temperatures. Initially dielectricconstant decreases slowly with frequency up to 1 MHz and becomes almostconstant up to 6 MHz. The increase in dielectric constant above 6 MHz mayindicate the beginning of a possible presence of resonance with peaks occurringat higher frequencies.
The initial decrease in dielectric constant withfrequency up to (1 MHz) can be explained by the phenomenon of dipolerelaxation. The resonance may arise due to the matching of the frequency ofcharge transfer between Fe2+ ? Fe3+ ions, and that of theapplied electric field. These changes can also be elaborated on the basis ofspace charge polarization model of Wagner and Maxwell.
The variation ofdielectric constant with temperature at different frequencies. The dielectricconstant increases with temperature at all frequencies. The hopping of thecharge carriers is thermally activated with the rise in temperature; hence, thedielectric polarization increases, causing an increase in dielectric constant.At lower frequencies (100 kHz), the increase in dielectric constant is verylarge with an increase in temperature, while at higher frequency range (1–12MHz), the increase in dielectric constant is small.
The dielectric constant ofany materials, in general, is directly related to dielectric polarization. Thehigher the polarization, the higher the dielectric constant of the material.There are four primary apparatus causing polarizations: electronicpolarization, ionic polarization, dipolar polarization and space chargespolarization. Their occurrence depends upon the electric frequency of theapplied field. At low frequencies, space charges polarization and dipolar polarizationare known to play the vital role 19 andboth these polarizations are temperature dependent. At high frequencies, ionicpolarizations are main contributors, and their temperature dependence isinsignificant. The change of dielectric loss with frequency at differenttemperatures.
The dielectric loss factor decreases initially with increasingfrequency followed by the appearance of a resonance with peaks occurring athigher frequencies. The initial decrease in dielectric loss (tan ?) with anincrease in frequency is in accordance with the Koop’s phenomenological model.The resonance may arise due to the matching of hopping frequency with thefrequency of the external electric field. Hudson has shown that, the dielectriclosses in ferrites are reflected in the conductivity measurements where thematerials of high conductivity exhibiting higher losses and vice-versa. Thechange of dielectric loss as a function of temperature at differentfrequencies.
The dielectric loss also shows the same trend as the dielectricconstant curves, and can be explained online similar to those advanced forexplaining 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 hoppingconduction apparatus between Fe2+ ? Fe3+ + e?1,Gd3+ ions do not participate in conduction and polarization processbut limit the degree of hop-ping by blocking up Fe2+ ? Fe3++ e?1 pattern on the octahedral sites. This is due to thereduction in the concentration of Fe ions inthe system due to the doping of Gd3+ions in Mg ferrite.Ø ConclusionsSingle-phase MgGd0.1Fe1.
904ferrite has been synthesized by conventional ceramic method. The particle sizewas 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 ofmagnitude as compared to undoped Magnesium ferrite. High value of dcresistivity makes this ferrite suitable for the highfrequency applicationswhere vortex current losses become appreciable. Gd–Mg ferrites may be used intelevision yokes and fly back transformers because of their higher resistivitywhich eliminates the need for taped insulation between yoke and winding.
Temperature dependent dc resistivity decreases with an increase in temperatureensuring the normal behavior of semiconducting materials. The value ofdielectric loss in the presently considered ferrite at room temperature is only0.003 at 3 MHz. Low values of dielectric constant and dielectric lossesexhibited by this ferrite suggest its utility in microwave communications.