Dielectric and transport properties of Zn substituted Cobalt Ferrite (original) (raw)
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Dielectric and transport properties of Zn-substituted cobalt ferrites
Journal of Bangladesh Academy of Sciences, 2013
Effect of Zn content on the dielectric and transport properties of CoZn x Fe 2-x O 4 (x = 0.0, 0.1, 0.2, 0.3 and 0.4), prepared by standard double sintering ceramic technique, sintered at 1000 o C for 4 hours were investigated. The X-ray diffraction (XRD) pattern of the prepared samples showed single phase inverse-spinel structure without any detectable impurity. Lattice constant of the samples increased with the increasing Zn concentration which follows Vegard's law. The theoretical densities of these samples remained almost constant whereas the bulk density decreased with Zn content up to x = 0.2. But with further increase of Zn content the bulk density increased. The porosity of the prepared samples showed the opposite trend. The dielectric constant (є′) measurement showed the normal dielectric behavior of the prepared ferrite. The DC electrical resistivity of the prepared samples decrease with increasing temperature which indicates the semiconducting behavior of the prepared ferrites. The Zn concentration showed pronounced effect on the resistivity at room temperature. Possible explanation for the observed features of densities, porosity, dielectric constant and resistivity of the studied samples are discussed.
Materials Today: Proceedings, 2017
Zinc doped cobalt ferrite nanoparticles having the basic composition Co1-xZnxFe 2 O 4 (x=0, 0.1, 0.2, 0.3, 0.4, 0.5) were prepared using auto combustion method. The structural, dielectric and a.c conductivity of these samples, which are sintered at 900 0 C were studied. XRD patterns were recorded using X-ray diffractometer. XRD patterns confirm the nanocrystalline nature for the sintered samples. The peaks observed in the XRD spectrum indicated single phase spinel cubic structure for the samples. Surface morphology of the samples has been investigated using Field Emission Scanning Electron Microscope (FESEM). The dielectric constant (ε') and dielectric loss tangent (tan δ) of nanocrystalline cobalt ferrites were investigated as a function of frequency and Zn +2 concentration at room temperature over the frequency range 100 Hz to 1 MHz using Hioki make LCR Hi-Tester 3250. The dependence of ε' and tan δ with the frequency of the alternating applied electric field is in accordance with the Maxwell-Wagner type interfacial polarization. The electrical conductivity (σac) deduced from the measured dielectric data has been thoroughly analyzed and found that the conduction mechanism in the present Co1-xZnxFe 2 O 4 nanoferrites are in conformity with the electron hopping model.
Electrical conductivity and microcrystalline parameter in Co–Zn ferrites
Materials Research Innovations, 2011
A series of samples of the system Co 12x Zn x Fe 2 O 4 (for x50?0, 0?2, 0?4, 0?6 and 1?0) were prepared by usual ceramic technique. These prepared samples were examined using X-ray powder pattern, which confirms the presence of a spinel structure. The authors have also carried out line profile analysis of individual Bragg reflections observed in these ferrites, which shows variation in the cell parameter. Further electrical conductivity measurements of these ferrites were carried out as a function of temperature. The observed values of the electrical conductivity have been explained on the basis of Verwey's hopping mechanism. The activation energy was found to decrease with increasing Zn content. In addition, its variations for varying concentrations of Zn in Co are interpreted in terms of microstructural parameters.
The effect of Mo doping on the structural and dielectric properties of Co-Zn ferrite
Physica B: Condensed Matter, 2017
The effect of Mo doping on the structural and dielectric properties has been investigated in detail for Co-Zn spinel ferrite. Solid state reaction technique has been used to prepare the CZMO. The structural analysis is performed using HRXRD technique which confirms the inverse spinel structure of the material. The frequency and temperature dependence of dielectric constant are studied which reveals that the dielectric dispersion is due to Maxwell-Wagner type polarization in agreement with Koop's phenomenological theory. The contribution of grain and grain boundary at high and low frequency respectively are evident in the dielectric constant. The variation of dielectric loss tangent with both the temperature and frequency has been studied. The room temperature and high frequency dielectric loss is observed to be very small. Also it is revealed that the dielectric loss tangent decreases with Mo substitution.
Dielectric behaviour study of nanocrystalline Co-Zn ferrite
2010
Dielectric properties are studied as a function of electric field frequency for Co 0.5 Zn 0.5 Fe 2 O 4 prepared by wet chemical co-precipitation method. The composition is characterized by X-ray diffraction technique (XRD). XRD study shows formation of singlephase homogeneous compound with cubic structure. The crystal size is calculated from XRD data by using Scherrer equation and is confirmed by SEM, which reveals the formation of nanocrystalline ferrite. Dielectric constant (ε′), complex dielectric constant (ε″) and dielectric loss tangent (tan δ) are measured in the frequency range up to 10KHz, at different temperatures (300K to 900K) and they show dispersion with decrease in frequency and increase in temperature. Thermal variation of ε′, ε″ and tan δ has been studied at four different frequencies 100Hz, 120Hz, 1 KHz, and 10 KHz. The variation of these parameters with frequency is explained qualitatively with the aid of Koops phenomenological theory. The observed results can be explained on the basis of an electron exchange between Fe 2+ and Fe 3+ ions. Improved dielectric properties are with nanocrystallinity of the prepared samples.
Magnetic and dielectric properties of Co–Zn ferrite
Materials Science and Engineering: B, 2013
Nanocrystalline powders of Co substituted Zn ferrite with the chemical formula Co x Zn 1−x Fe 2 O 4 (x = 0, 0.2, 0.4, 0.6, 0.8, 1) were synthesized by sol-gel autocombustion method using tartaric acid as fuel agent. The samples were sintered in static air atmosphere for 7 h at 773 K, 7 h at 973 K and 10 h at 1173 K. The organic phase extinction and the spinel phase formation were monitored by means of Fourier transform infrared spectroscopy. The X-ray diffraction patterns analysis confirmed the spinel single phase accomplishment. Crystallite size, average grains size, lattice parameter and cation distribution were estimated. Magnetic behavior of the as-obtained samples by means of M-H hysteresis measurements was studied at room temperature. Permeability and dielectric permittivity at room temperature versus frequency was the subject of a comparative study for the Co x Zn 1−x Fe 2 O 4 series. In agreement with the proposed cation distribution the sample with Co 0.8 Zn 0.2 Fe 2 O 4 formula exhibits the optimal magnetic and dielectric properties.
Structural and electrical properties of zinc-substituted cobalt ferrite
Journal of Materials Science, 2007
Polycrystalline samples of Co 1-x Zn x Fe 2 O 4 with stoichiometric proportion (x) varying from 0.0 to 1.0 were prepared through the thermal decomposition of their respective oxalates. The samples were calcined at 1000°C for 3 h and characterized using X-ray diffraction (XRD) and Mössbauer spectroscopy techniques. The study of the cation distribution using Mössbauer spectroscopy showed that the ions at the tetrahedral site moved to the octahedral site by the addition of zinc and that the system varied from an inverse to a normal spinel structure. The values of the lattice parameter, X-ray density, oxygen parameter, inversion factor and radii of tetrahedral and octahedral sites were calculated using X-ray diffraction data. The temperature dependence of the conductivity showed a definite kink, except for the ZnFe 2 O 4 sample, which can be attributed to the ferromagnetic-paramagnetic transitions. The calculated activation energy in the paramagnetic region was found to be smaller than that in the ferromagnetic region.
Cobalt-substitution effects on dielectric properties of CuZn ferrites
Ceramics International, 2015
The effects of cobalt oxide addition on the microstructure and electrical properties of CuZn ferrites were investigated. CuZn ferrites with compositions of (CuO) 0.2 (ZnO) 0.8-x (Co 2 O 3) x/2 (Fe 2 O 3) 0.986 ; x = 0 , 0.02, 0.04, 0.08, 0.1 were synthesized using a solid state reaction. It was observed that the addition of cobalt will change the amounts and distribution of Cu 2+ , Cu + , Fe 2+ , and Fe 3+ in the grain and grain boundary. The different amounts and distribution of Cu 2+ , Cu + , Fe 2+ , and Fe 3+ in the bulk and grain boundary for samples added with different amounts of cobalt oxide affected the space polarization and dielectric properties. The dielectric constant increased and reached the maximum as the x value was increased from 0 to 0.04 and then declined with further increasing the x value to 0.1. For the samples with the x value of 0.02, the substitution of Co 3+ may act as a donor and simultaneously produce electrons. Fe 3+ ions in the octahedral sites catch the electrons and then become Fe 2+ ions, which led to the larger dielectric constant at low frequency resulting from the space charge polarization. However, as the x value increased to 0.1, the concentration of Fe 2+ ions decreased, which resulted in a decrease in the amount of space charge in the grains, leading to a decrease in the dielectric constant at low frequency.
Journal of Advanced Dielectrics, 2018
Zinc substituted cobalt ferrite nanoparticles with elemental composition Co[Formula: see text]ZnxFe2O4 ([Formula: see text], 0.2, 0.4, 0.6) were prepared by the sol-gel auto-combustion technique using Co, Fe, Zn nitrate as a precursor where nitrates to citrate was 1:3. The as prepared powder of cobalt zinc ferrite was sintered at 900∘C for 3[Formula: see text]h. Structural, morphological, dielectric and magnetic properties were studied by x-ray diffractometer (XRD), scanning electron microscope (SEM), high precision impedance analyzer and vibrating sample magnetometer (VSM), respectively. The peaks obtained from the XRD confirmed samples having crystallite ([Formula: see text]32–36[Formula: see text]nm) single phase inverse spinel structure without any traceable impurity. Lattice parameters were calculated from XRD and it increases with Zn content. SEM revealed irregularly shaped grains ([Formula: see text]–0.7[Formula: see text][Formula: see text]m) morphology with heterogeneous di...
This work reports the detailed structural characterization of Zn 2+ ion-substituted cobalt ferrite nanoparticles (CFO NPs; Co 1−x Zn x Fe 2 O 4 ; x = 0.00, 0.25, 0.50, and 0.75), prepared using a facile sol-gel method. It correlates structural changes with magnetic and dielectric properties. The as-synthesized samples were investigated by X-ray diffraction (XRD) analysis, BET surface area analyzer, energy-dispersive X-ray (EDX), Fourier transform infrared (FTIR), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM), Mössbauer spectroscopy, and impedance analyzer. The pristine sample (CFO) comprised of NPs with 25 nm size, which decreased up to 11 nm upon the formation of Zn 0.75 Co 0.25 Fe 2 O 4. The N 2 adsorption-desorption isotherm of the prepared Zn 0.5 Co 0.5 Fe 2 O 4 sample confirmed the presence of a mesoporous structure. SEM images revealed that all prepared samples exhibited porous surface with honeycomb-like structures. The cationic distribution was described by Mössbauer spectra. The increment of Zn ions in the prepared samples resulted in sharp reduction of saturation magnetization and remanence values. The normal dielectric dispersion behavior was recorded and can be ascribed to the Maxwell-Wagner type polarization. Besides, the dielectric parameters varied by increasing Zn content in CFO NPs. This may be ascribed to O 2 vacancies and Fe 3+ ions in A-and B-sites. Dielectric studies revealed that, content of Zn ions beyond x = 0.25 was sufficient to reduce both dielectric constant and loss at low frequencies.