Magnetic and dielectric properties of Co–Zn ferrite (original) (raw)
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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.
Ceramics International , 2021
An intensive research has been begun on spinel nano-ferrites owing to their unique and novel size dependent chemical and physical properties. Indium doped cobalt-zinc spinel nano-ferrites, Co 0.9 Zn 0.1 In x Fe 2-x O 4 (x = 0.05, 0.1, 0.15, 0.2, 0.25, 0.3), have been fabricated through solution-combustion (SC) method and characterized for structural, morphological and temperature dependent electric and dielectric behavior. XRD affirmed that all spinel nano-ferrites have single phase. The TEM and EDX micrographs have confirmed morphology and composition of the samples, respectively. The crystallite size has decreased from 23.8 nm to 20.2 nm, while the lattice constant has been seen to enhance from 8.385 Å to 8.426 Å with the replacement of Fe 3+ ions by In 3+ ions. FTIR spectroscopy has been performed to extract the information about the stretching of metal-oxygen bonds as well presence of various functional groups. Moreover, FTIR has confirmed that there is no deviation in the structure of the Co-Zn spinel nano-ferrites with the addition of In 3+ ions. Additionally, there is no significant deviation in the peak positions of respective peaks has been observed except, when composition changes from x = 0.05 to x = 0.10 for peak I and peak II. The resistivity has been observed to decrease with the rise in temperature, which has confirmed the semiconductor character of the prepared spinel nano-ferrites. An enhancement in resistivity has been viewed with the rise in In 3+ ions, while a normal dispersion curve has been observed for the variation of the dielectric constant as a function of frequency. Spinel nano-ferrites show a decrease in the dielectric constant with the increase in frequency as well as indium ion content. The dielectric loss tangent shows minute values suggest the utility of the present spinel nano-ferrites for microwave frequency applications.
Role of Mn2+ ion in the optimization of the structural and dielectric properties of Co–Zn ferrite
Applied Physics A
Mn-substituted Co–Zn ferrite nanomaterials with the general form Co0.8−x Mnx Zn0.2 Fe2O4 (x = 0.0, 0.1, 0.2, and 0.3) were prepared using the coprecipitation method. Based on X-ray diffraction, it can be confirmed that all samples have a single-phase cubic structure with an average crystallite size ranging from 23.46 to 32.66 nm. In addition, the lattice parameter increased from 8.32 to 8.37 Å. In this study, the theoretical density was calculated, and the Fourier-transform infrared spectra of the prepared samples were investigated. Further, the cation distribution of the system was estimated. The proposed cation distribution was confirmed by calculating the theoretical lattice parameter and comparing it with the experimental lattice parameter. We conducted transmission electron microscopy to confirm the obtained particle size. At room temperature, the electrical measurements of the prepared samples were performed using the LCR circuit as a function of frequency up to 5 MHz. In this...
Cobalt ferrite nanoparticles (CoFe 2 O 4) and cobalt zinc ferrites with general formula Co x Zn 1-x Fe 2 O 4 (x = 0.5, 0.6, 0.7) were prepared by sol-gel method at a low temperature with a final pH value of 7. Synthesized spinel ferrites were sintered at various temperatures (220, 400, 600, 800 and 1000 o C). X-ray diffraction (XRD) was used to characterize the sizes of particles and structural properties. The average crystalline size of the prepared ferrite was ranged between 18-49 nm. The FTIR spectra however showed two strong absorption bands ranged between (1037.45-399.26 cm −1), which is a spinel ferrite. The study also focused on several dielectric properties of the samples such as dielectric constant (ε'), dielectric loss tangent (tan δ) and complex dielectric constant (ε''). The variation of dielectric parameters (ε) and tanδ with frequency revealed that the dispersion was due to Maxwell-Wagner. Magnetization measurements showed that the coactivity (H c), saturation magne-tization (M s), remanent magnetization (M r) and squarenessremnance ratio (R = M r /M s) strongly depend on content of zinc.
Temperature Dependent Dielectric Behaviour of Nanocrystalline Co0.5 Mg0.5 Cr0.4 Fe1.6 O4 Ferrite
Macromolecular Symposia, 2017
Chromium substituted Co-Mg ferrite with composition Co 0.5 Mg 0.5 Cr 0.4 Fe 1.6 O 4 has been synthesized by solgel auto combustion method. X-ray diffraction technique confirmed the formation of cubic spinel structure with no additional phase. In order to distinguish the effect of crystallite size-induced broadening and strain-induced broadening of XRD peaks, Williamson and Hall analysis has been performed. Dielectric constant, dielectric loss tangent and ac conductivity have been measured in the frequency range 50 kHz-120 MHz at room temperature. The decrease in dielectric constant with increasing frequency is attributed to Maxwell Wagner model. The variation of dielectric constant and loss tangent with temperature at different frequencies have also been studied. Bragg's angle. The average crystallite size of the nanoparticles as
Chemical synthesis, structural and magnetic properties of nano-structured Co–Zn–Fe–Cr ferrite
Journal of Alloys and Compounds, 2011
Nanoparticles of Co1−xZnxFe2−xCrxO4 (x = 0.0–0.5) ferrites were prepared by chemical co-precipitation technique using metal sulphates. The structural and magnetic properties were investigated by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM), and AC susceptibility measurements. X-ray diffraction patterns indicate that the samples possess single phase cubic spinel structure. The lattice constant initially increases for x ≤ 0.3 and thereafter for x > 0.3 it decreases with increasing x. The saturation magnetization (Ms), magneton number (nB) and coercivity (Hc) decreases with increasing Cr–Zn content x. Curie temperature deduced from AC susceptibility data decreases with increasing x.► Preparation of nanostructured ferrite particles. ► Co-substitution of Zn2+ and Cr3+ in place of Co2+ and Fe3+ ions. ► Structural properties markedly vary with increasing Cr–Zn ions. ► Magnetic properties decrease with increasing Cr–Zn ions.
Journal of Magnetism and Magnetic Materials, 2014
The nanocrystalline Q2 Mg 0.5 Zn 0.5 À x Co x Fe 2 O 4 (x ¼ 0, 0.1, 0.2, 0.3, 0.4 and 0.5) ferrites have been synthesized by sol-gel auto ignition method. Rietveld refinement of X-ray diffraction (XRD) patterns of all concentrations show mixed cubic spinel structure. The lattice Q3 constant values infer decreasing trend from 8.392 to 8.420 Å with the substitution of Co 2 þ. The crystallite size calculated from Scherer formula lies in the range between 28 and 37 nm which confirms the nanocrystalline nature of synthesized samples. In order to study the morphology and phase structure of the synthesized samples, samples were examined by transmission electron microscopy (TEM). Scanning electron microscopy (SEM) confirmed the homogeneous and well defined surface morphology of the synthesized samples. The elemental analysis as obtained from energy dispersive X-ray (EDAX) is in close agreement with the expected composition from the stoichiometry of reactant solutions used. The valence states of the Co 2 þ ions have been confirmed with the help of X-ray photoelectron spectroscopy. Magnetization results obtained from the vibrating sample magnetometer (VSM) confirm that the substitution of Co 2 þ for Zn 2 þ caused an increase in the saturation magnetization and coercivity. The dependence of Mössbauer parameters, viz., line width, isomer shift, quadrupole splitting and hyperfine magnetic field on Co 2 þ substitution have been analyzed. Cation distribution estimated from XRD and Mössbauer spectroscopy are in good agreement with each other. The frequency dependent dielectric properties were studied by measuring dielectric constant (ε 0) and ac conductivity (s ac) at 300 K in the frequency range of 50 Hz-5 MHz. The highest value for ε 0 and s ac is observed for x ¼ 0.5.
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.
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...