Formation Of Spinel Structure Research Articles

Rietveld refined crystal structure, magnetic, dielectric, and electric properties of Zn substituted Ni-Mg ferrites

Sol − gel technique was used to synthesize Ni0.7-xZnxMg0.3Fe2O4 (Ni – Zn – Mg) ferrites with x = 0.1, 0.2, 0.3, 0.4, 0.5. Formation of single phase cubic spinel structure of the synthesized samples was confirmed by employing Rietveld refinement technique. Spherical and inhomogeneous distribution of grains was observed from Transmission Electron Microscopy (TEM) image. The frequency dependent initial permeability (μi), real part of initial permeability (μ′), imaginary part of initial permeability (μ″) was studied for synthesized samples. For zinc content x = 0.2 in Ni – Zn – Mg ferrites μi is observed to be high as compare to other compositions and that attributed to grain size. DC electrical resistivity (ρdc) analysis shows both conducting and semiconducting behavior for all the samples. Room temperature electrical resistivity values were observed to be lower for lower content of zinc and higher for higher content of zinc and that attributed to the hopping mechanisms at octahedral site. The decreasing trend of Curie temperature was observed with increase in zinc content in Ni – Zn – Mg ferrites. Frequency dispersive dielectric properties study of Ni – Zn – Mg ferrites revealed normal dielectric behavior.

Synthesis of Amorphous Nickel-Cobalt Hydroxides for Ni-Zn Batteries.

In this work we developed a hydrothermal method for synthesizing amorphous Ni-Co hydroxide (NC(OH)) and in the subsequent step crystalline NiCo2O4 (NCO) has been produced using water as the solvent. For nickel-zinc batteries, NC(OH) was found to have superior performance to its NCO prepared by two-step process. The thermal stability analysis exhibited the optimum temperature to obtain the NC(OH), and NCO electrode materials. The XRD pattern showed mixed phases containing both Ni and Co hydroxides (during the initial step) and in the subsequent step (calcined) the formation of cubic spinel structure was noticed. For NC(OH), aggregated particles with irregular morphology were observed while clustered nanorod-like shapes were noticed for NCO samples. To be noted, that the nanorod morphology was obtained through a facile approach without employing any structure-directing agent. Both NC(OH) and NCO were employed as cathodes for Ni-Zn battery studies against Zn foil anode with a polyamide-based separator soaked in 6 M KOH saturated with ZnO additive was used as electrolyte. The Ni-Zn cell was fabricated in CR2032 coin cell configuration. The electrochemical studies such as cyclic voltammetry (CV) showed the characteristic redox peaks for NC(OH) sample exhibiting high peak current compared to its NCO counterpart. The NC(OH) had a capacity of 268 mAh g-1 against 120 mAh g-1 for NCO at a current density of 1 Ag-1. The cell was able to retain 85 % of the capacity at the end of 500 cycles and showed remarkable rate capability. The Ni-Zn battery presents energy and power densities of 428.8 Wh Kg-1 and 2.68 kW Kg-1, respectively surpassing the normal values reported for aqueous rechargeable batteries. Owing to the presence of Ni and Co in hydroxide form (reduced crystallinity) the NC(OH) sample showed improved electrochemical activity. This work provides a facile approach and effective strategy for developing bimetallic hydroxides for optimal energy storage performance.

Unveiling the structural, optical, electrical, and ferromagnetic properties of Ca2+ doped mixed spinel ferrites for switching field high-frequency device applications

In this paper, the calcium-doped nickel-zinc nano-ferrites [Ni0.5Zn0.5CaxFe2-xO4; x = 0.00, 0.10, and 0.30] were prepared using the chemical co-precipitation synthesis route and studied for switching field high-frequency device applications. The structural analysis has been completed by analyzing X-ray diffraction (XRD) patterns. The Rietveld refined XRD patterns confirmed the formation of cubic spinel structure of Ca2+ substituted nickel-zinc ferrites. The detection of metal-oxygen bonds present at A and B lattice sites has been unveiled by Fourier transform infrared (FTIR) spectroscopy. The morphological studies obtained through FESEM (Field emission scanning electron microscopy) analysis showed a reduction in the particle size from 70 nm to 53 nm when the concentration of Ca2+ ions in Ni-Zn ferrites was increased. Energy dispersive spectra (EDS) confirmed the presence of elements present in the prepared composition. The structure of a cubic spinel-shaped unit cell has been verified from three active prominent Raman modes (A1g, A2g, and T2g). Diffuse-reflectance spectroscopy (DRS) exhibits the increment in the bandgap values (from 1.55 eV to 1.63 eV) which helps fabricate highly efficient photovoltaic devices. The ferroelectric measurements yielded a rise in polarization values from 1.461 μC/cm2 to 18.228 μC/cm2 for 10 % Ca2+ ion substitution. The tangent loss values declined from 24 to 3 in Ni-Zn ferrites upon substituting Ca2+ ions. The Vibrating sample Magnetometer (VSM) technique found the increment in the saturation magnetization (Ms) values from 34.724 emu/g to 54.662 emu/g on substituting up to 30 % Ca2+ ions in Ni-Zn ferrites. These obtained results support the material in switching field distribution for high-frequency applications. The results exhibited that the prepared samples can be applicable for switching devices, filters, and microwave absorption devices. The results revealed the maximum frequency between 12 and 18 GHz which is useful for Ku band absorption.

Influence of Nd3+ on structural, electrical and magnetic properties of Ni-Cd nanoferrites

Here in we report the nanocrystalline Ni1-xCdxNdyFe2-yO4 (0 ≤ x ≤ 1.0 in steps of 0.2: y = 0.0; 0.1) ferrites were synthesized by novel solution combustion technique. The sintered powders have been characterized by X-ray diffraction (XRD), Fourier transmission infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), Energy dispersive analysis by x-rays (EDAX) methods. DC electrical conductivity carried out by two probe method. Magnetic parameters were measured using vibrating sample magnetometer with an applied magnetic field up to 15 kOe at 300K. The XRD results confirmed the formation of single phase cubic spinel structure formation. It was found that the lattice parameter increased with increase in Cd2+ ion. The crystallite sizes have been found in the range of 44.24 nm–15.467 nm. Moreover, the formation of two prominent absorption bands confirmed the spinel structure. The SEM micrographs evidenced almost spherical shaped, agglomerated and grainy structure of nanoferrites. Moreover, the Curie temperature (TC) was decreased with increasing temperature and exhibit the semiconducting behaviour. Further, saturation magnetization (MS), remanence magnetization (Mr); coercivity (HC) were decrease with increase in the magnetic field. The magnetic parameters; MS, Mr, nB increases attain maximum thereafter decreases with increase in Cd2+ ion and Nd3+ ion content.

Exploring electrochemical kinetic behaviors and interfacial charge transfer of pure and Ni-doped ZnFe2O4 nanoparticles-based sensing nanoplatform for ultra-sensitive detection of chloramphenicol

ZnFe2O4 (ZFO) nanomaterial was doped with a divalent transition metal cation of Ni2+ (NixZn1-xFe2O4, x=0, 0.2, 0.4, and 0.8) and characterized by various analytical techniques. Powder X-ray diffraction revealed the formation of a single-phase cubic spinel structure, while the stabilization of crystal structure for Ni2+-doped samples was observed. The average crystalline size, d-spacing, and lattice parameters increased with increasing in Ni2+ concentration within NixZn1-xFe2O4, due to differences in the ionic radius, the cation distribution at A-B sites, and the creation of surface oxygen vacancies within ZFO structure. From electrochemical measurements, NixZn1-xFe2O4-based electrodes showed excellent enhancements in charge transfer ability and conductivity with the highest rate constant (0.018 ms−1), the lowest peak-to-peak separation (206 mV), the lowest Rct (118 Ω), and the largest electrochemical active area (0.248 cm2), compared to that of bare SPE. Among them, Ni0.8Zn0.2Fe2O4/SPE provided outstanding electrochemical behaviors and achieved the best sensing performance with the widened concentration linear range from 0.25 to 50 μM and a rather low detection limit of 0.2 μM for chloramphenicol detection. The most important reason for this positive advance comes from the unique synergistic effects of Ni doping into the ZFO host structure. The excellent enhancements in adsorption capacity (Г) (1.4 times higher), number of oxygen vacancies, charge transfer rate constant (approximately 1.15 times higher), and catalytic rate constant (30 times greater) were recorded at Ni-doped ZFO-based electrodes, compared to pure ZFO-based electrode. Furthermore, the detailed hypotheses and possible mechanisms explaining these impressive enhancements were explored. Our work provides insight into the correlation between the Ni-doping and electrochemical characteristics, which has implications for tailoring the electrochemical performance of spinel ferrites across diverse applications and the design of novel spinel ferrite nanomaterials.

Influence of Ni substitution on Structural, Optical, magnetic and transport properties of Mn0.5-xNixZn0.4Cu0.1Fe1.95Al0.05O4

A series of spinel ferrites Mn0.5-xNixZn0.4Cu0.1Fe1.95Al0.05O4 have been prepared by auto-combustion technique. X-ray diffraction (XRD) and Field Emission Scanning Electron Microscopy (FESEM) have been used for structural and morphological investigations. The XRD patterns confirm the formation of cubic spinel structure of ferrites. The lattice constants decrease with the increase of Ni contents due to the smaller ionic radii of Ni2+ compared to Mn2+ as well as particle size decreases. Density is increased and porosity is decreased with the increase of Ni contents in the samples due to the higher atomic weight of Ni2+ compared to Mn2+. The FESEM analysis reveal that the average size of the irregularly shaped grains increased with Ni contents. The mixed spinel structure is further confirmed by the FTIR spectra, which show a doublet band at about 600 cm−1. The observed optical band gap and the particle size variations are comparable, and the quantum size effect supports this conclusion. The real part of initial permeability and relative quality factor increase with the increase of Ni contents due to increase of density and grain size as well as decrease of porosity. Also, it is found that magnetic loss decreased with the increase of Ni contents. All the samples exhibit ferrimagnetic behavior and the number of Bohr magneton has been calculated for all compositions. The dielectric constant shows large value in the lower frequencies and decreases with frequency shows dispersion due to Maxwell-Wagner space charge polarization. The investigation of electric modulus has demonstrated the existence of the hopping conduction mechanism. The AC conductivity is very low at lower frequency region and very large at higher frequency region which can be explain according to the polaron hopping model of Austin and Mott. The AC conductivity enhances nearly linearly with frequency, suggesting that the mechanism of conduction is due to small polaron hopping, which can be described according to Jonscher’s power law. Also, the effect of grain and grain boundary resistance on transport properties has been investigated using complex impedance analysis and it has been observed that both exhibit an increase trend as the Ni content increases.

Co-axially electrospun Li-rich layered Oxide@Spinel core-shell heterostructure nanofibers for enhanced stability and electrochemical performance

Lithium-rich layered oxides (LLO) possessing high specific capacity has the limitation of voltage fade, poor high C-rate performance and low conductivity. Spinel coating on LLO surface is known to mitigate the voltage fade, however, enabling high C-rate performance remains challenging. In this study, LLO nanofiber core with composition 0.6Li2MnO3·0.4LiMn0.25Ni0.38Co0.37O2 is prepared by electrospinning process and the same is coated with spinel LiMn1.5Ni0.5O4 shell to obtain LLO/spinel (LLO/S) core-shell heterostructure. The spinel shell coating is accomplished (i) by a novel co-axial (CA) electrospinning process and (ii) by wet chemical (WC) approach. The CA electrospinning process provides a uniform core-shell structure compared to the WC process. The electron microscopy studies reveal the fibrous microstructure in LLO/S heterostructures with energy dispersive spectroscopy compositional mapping showing the spinel composition on the surface. Higher concentration (>10 wt.%) of spinel coating are shown to break the fibers into particulates. X-ray diffraction and high-resolution transmission electron microscopy analysis confirm the spinel structure formation along with layered structure. While the capacity is slightly compromised compared to the pristine LLO nanofiber, the LLO/S heterostructure with 10 wt.% spinel coating exhibits a high reversible capacity of 268 mAhg-1 with minimal capacity loss during the 1st cycle (with coulombic efficiency 83.5%) and an excellent high C-rate capability (88 mAhg-1 at 10C-rate and 55 mAhg-1 at 20C-rate). The electrochemical studies also demonstrate the importance of optimal spinel content in the coating and the method of spinel coating on the layered material surface. The encapsulation of LLO with spinel layer which has 3D-diffusion pathways for Li-ion transport facilitates high ionic and electronic conductivity and hence leads to enhanced electrochemical performance of LLO/S heterostructured cathodes.

Evaluation of experimental and simulated gamma ray shielding ability of ZnCo2O4 and ZnCo2O4/graphene nanoparticles

Pristine zinc cobaltite (ZnCo2O4) and graphene zinc cobaltite nanoparticles (NPs) have been successfully synthesized by hydrothermal method. The physical properties of both structures were studied using field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). XRD results indicated a formation of spinel structure. The elemental composition of the samples has been determined through EDX analysis. From morphological investigation, the aggregation of grains and nano-sized quasi-spherical grains was observed. Nuclear radiation protection investigation for gamma-ray has been studied for both samples. The protection factors against gamma rays, including linear attenuation coefficients (LAC), mass attenuation coefficients (MAC), transmission Factor (TF), radiation protection efficiency (RPE) mean free path (MFP), half value layer (HVL) and tenth value layer (TVL) were calculated. In addition to the experimental examination, simulation with GEANT4 simulation code was also used for both samples to examine the shielding parameters. The most essential parameters of gamma shielding factors such as mass attenuation coefficients (MAC), mean free path (MFP), half value layer (HVL), tenth value layer (TVL) and linear attenuation coefficients (LAC) were evaluated both practically and by simulation. Practically, these values were: 0.75/0.78 cm2/g, 0.22/0.20 cm, 0.15/0.14 cm, 0.50/0.47 cm, and 4.55/4.86 cm−1, for ZnCo2O4 and ZnCo2O4/graphene samples, respectively. By simulation, these values were: 0.65/0.70 cm2/g, 0.25/0.22 cm, 0.17/0.16 cm, 0.59/0.52 cm, and 3.91/4.38 cm−1, for ZnCo2O4 and ZnCo2O4/graphene samples, respectively. The results show that the presence of graphene has affected all the protection parameters. Keywords: Zinc cobaltite, structural properties, gamma shielding, hydrothermal method.

Physical properties of La3+ ion doped Ni[sbnd]Zn based spinel ferrite nanomaterials for technological applications

Spinel ferrite nanoparticles are extensively utilized in various everyday applications due to their exceptional capabilities. They are highly effective and efficient for various applications such as energy storage devices, microwave, electrode design, fuel cells, and recording media. Based on these applications, five samples of lanthanum doped nickel‑zinc spinel ferrite Ni0.5Zn0.5LaxFe2-xO4 nanoparticles were synthesized using the sol-gel auto-combustion technique. The lanthanum concentrations varied as x = 0.00, 0.05, 0.10, 0.15 and 0.20. X-ray diffraction (XRD) analysis revealed the formation of single phase cubic spinel structure of the prepared samples. The crystallite size was determined using the Scherrer formula and the values lies in the range of 9.22 to 20.09 nm. The chemical composition of the prepared samples was confirmed using Fourier transform infrared spectroscopy (FTIR) analysis. Transmission electron microscopy (TEM) confirmed the agglomeration and spherical shape morphology of the nanoparticles with an average particle size of 40 nm. Magnetic properties along with La3+ ion concentrations were investigated using the vibrating sample magnetometer (VSM). The dielectric properties of the prepared samples were carried out using impedance analyzer with an applied frequency ranging from 1 MHz to 3 GHz. Furthermore, the polarization mechanism in the applied frequency range was discussed with relaxation behavior at high frequency. The impact of La3+ concentrations on different parameters such as dielectric constant, impedance, electric modulus, tangent loss, and Ac conductivity were also investigated. The investigation of dielectric parameters. The relaxation mechanism at high frequency provided a significant impact of such type of materials to store energy due lake of hopping between the tetra and octahedral sites by addition of La3+ doping. The prepared samples exhibit excellent magnetic as well dielectric properties which makes suitable for microwave devices and soft magnetic applications.

Spin dynamics investigation and structural analysis of ambient scalable Sr2+ doped zirconium ferrite nanoparticles synthesized by low temperature auto combustion route

Microwave spin resonance behaviour of Sr2+ doped Zirconium ferrite Zr1-xSrxFe2O4; (0 ≤ x ≥ 0.20) nanoparticles synthesized by auto combustion route has been investigated by electron paramagnetic resonance (EPR) which show a broad ferromagnetic resonance signal with a superimposed hump signal which is attributed to ferrite Fe3+ ions and oxygen vacancies which is in agreement with XRD and XPS. EPR shows low spin concentration and smaller relaxation time for Zr0.80Sr0.20Fe2O4 which can be used for hyperthermia and for use as a MRI contrast agent. EDS and XPS confirms the presence of Zr, Sr, Fe, O, and C and HRTEM images confirm growth along (220) and (311) with an interatomic distance of 0.3327 nm and 0.2622 nm respectively, thus, authenticating the formation of spinel structure in agreement with FTIR studies. The magnetic behaviour (M − H loop) shows high saturation magnetization and higher value of effective magnetocrystalline anisotropy (Keff) for Zr0.80Sr0.20Fe2O4.

Study on multifunctional magnesium copper zinc spinel ferrite nanoparticles prepared by hydrothermal route; Physical, electrical, and anti-microbial investigation

Polycrystalline spinel ferrite nanoparticles of Mg0.70-XCuXZn0.30Fe2O4(X=0.0,0.15,0.30,0.45,0.60) were prepared by hydrothermal approach. The structural modification by X-ray diffraction of Mg-Zn spinel ferrite with Cu2+ substitution was recorded through crystallite size (11–14 nm), Lattice dimension (8.34–8.38 A°), strain (7×10−3-9×10−3) and dislocation density (4×1015-7×1015) respectively. The formation of spinel structure (Fe-O) was identified by FTIR with a vibration band around 400–600 cm−1. Also, the Rietveld refined XRD pattern confirmed the presence of a cubical spinel structure. The electron microscopic (SEM) analysis revealed sphere-cubical agglomerates of the prepared material. TEM analysis revealed that the particles were inside the nanoscale range, with an average particle size of 15.97 nm determined using a lognormal histogram. The existence of the expected elements is confirmed by EDS spectra. From BET data, surface parameters including surface area (39.938–92.643 m2/gm), volume (2.355 × 10−1 to 2.52 × 10−1 gm/cm3), pore radius (5.0831–12.650 nm), and pore size distribution were determined. The magnetic parameters Ms (20–34 emu/g), Hc (30–39 Oe), and Mr (1.3–2.8 emu/g) obtained by VSM measurements indicate the single domain, pseudo single domain and multi-domain nature of as prepared nanoparticles and lower dielectric parameters at high frequency obtain from dielectric spectroscopy indicate the suitability of the material for switching devices, power application energy storage, and high-frequency applications. The antibacterial efficacy of the synthesized nanoparticles (NPs) was evaluated against different harmful bacteria and demonstrated the desired zone of inhibition (ZOI).

Controlling the physical properties of Ni1-xMnxFe2O4 multiferroic by the enhancement of ferroelectric phase through the increase of Mn content

The nanoparticles of the spinel ferrite system Ni1-xMnxFe2O4 with x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0 were prepared using the auto combustion flash method technique, by using the nitrates as cations source and urea as a fuel agent for combustion. The XRD pattern validates the formation of cubic spinel structure of Ni1-xMnxFe2O4 nanoparticles and traces of hematite phase. By increasing the annealing temperature, the lattice parameter and crystallite size were increased. At various frequencies, the dielectric properties and initial permeability were measured as a function of temperature. The DC resistivity was found to have a linear relationship with temperature, with two regions and one break point at Curie temperature (TC). SEM and TEM analyses are used to investigate the morphology of the samples, as well as the size and shape of the crystallites. The samples' morphology revealed the formation of a uniform and spherical structural distribution. The material transfer to multiferroic at high Mn content accordingly the ferroelectric and ferrimagnetic properties appear, which give the ability of the material to become magnetoelectric material.

Investigate structural, morphological, electrical, dielectric and magnetic properties of dysprosium doped Cobalt-Nickel ferrites and their response to gamma irradiation

Nanocrystalline Co1-xNixFe2-yDy0.5O4 ferrites were successfully prepared by the sol–gel auto-combustion method. The samples were gamma-irradiated using a cobalt-60 source. XRD analysis reveals the formation of cubic spinel structure. FTIR study is used to confirm the formation of the expected spinel ferrite structure. Two probe method was used to measure DC electrical resistivity and the Arrhenius relation was used to calculate activation energy for non-irradiated and irradiated ferrites. Frequency dependent dielectric properties of the non-irradiated and irradiated ferrites were studied at room temperature. The dielectric constant for most of the gamma-irradiated samples increases because defects are induced in the material which increases space charge polarization in the samples. Magnetic properties of non-irradiated and irradiated nano ferrites were studied using VSM. Coercivity decreases after irradiation because decrease in grain size which increases surface state pinning of the domains.

Effects of thermal, stress, and electric fields on microstructure and ion distribution of (Mg0.1Mn0.1Co0.1Ni0.2Ti0.1Cu0.1Zn0.2)Fe2.1O4 spinel ferrites

In this work, conventional sintering, hot-pressing sintering, and spark plasma sintering techniques were utilized to simulate the thermal field, thermal-stress field, and thermal-stress-electric field, respectively. The effects of these fields on the microstructure and cation distribution of the (Mg0.1Mn0.1Co0.1Ni0.2Ti0.1Cu0.1Zn0.2)Fe2.1O4 ferrite (HEF) material were comprehensively analyzed. The results indicate that in the temperature range of 1000–1100 °C, the thermal field provides the driving force for sintering, promotes grain growth (average particle size: 2→7 μm), and increases crystallinity degree. The stress field brings the particles into close contact with each other, facilitates diffusion, and delays grain growth (0.5→5 μm). The electric field reduces grain boundary energy, causes mass transfer, and makes the grains finer (0.5→0.7 μm) and more uniform. Mathematical model analysis reveals that the thermal field is beneficial to the random distribution of cations, which yields an inversion degree (γ) of about 2/3 and increases the configuration entropy of HEF. The stress field leads to lattice distortion, permits ions with larger radius to occupy tetrahedral positions, and changes the cell parameters and oxygen position parameter of HEF. Finally, the interaction between electric field and crystal charges increases the electrostatic field energy, which promotes the formation of positive spinel structure and maximizes the crystal field stability energy. X-ray photoelectron spectra, Raman spectra, and change in lattice constant confirm the rationality of the mathematical model, and can be used to establish the model of the crystal structure under field effects.

Effect of zinc doping on structural, bonding nature and magnetic properties of co-precipitated magnesium–nickel ferrites

Abstract This paper describes the electronic structure, bonding nature and magnetic properties of Mg0.5Ni0.5−x Zn x Fe2O4 (x = 0.1, 0.2, 0.3, 0.4) nano-spinel ferrite samples synthesized by the co-precipitation method. Spinel structure with Fd 3 ̄ $\bar{3}$ m space group is confirmed by XRD analysis with trace amounts of hematite. The results of XRD and FTIR confirm the formation of spinel structure. The estimated average crystallite size ranges from 35 to 59 nm by different methods. The FESEM analysis revealed that the samples have a generally porous aspect. Particle size analysis indicates that the average particle size is approximately 150 nm. Covalent bond exists between the tetrahedral A site – oxygen atom (A–O) and ionic nature exists between the octahedral B site – oxygen atom (B–O) in the two sub lattices of the ferrite unit cell, as determined by the maximum entropy method. Mg0.5Ni0.3Zn0.2Fe2O4 demonstrates high A–O covalency and B–O covalency/ionic boundary based on MEM electron density analysis.

Study of microstructure, magnetic and gas sensing properties of porous Ni0.4+xZn0.6-xCeyFe2-yO4 magnetic nanoparticles

The spinel ferrite systemsNi0.4+xZn0.6−xCeyFe2−yO4 (0≤x+y≤0.3) were synthesized by a modified glycol-thermal technique. X-ray diffractometer (XRD) confirmed formation of single phase cubic spinel structure with average crystallite sizes 8–21 nm. The crystallite sizes were found to be in agreement with the particle sizes obtained from the high resolution transmission electron microscopy (HRTEM) indicating formation of single domain nanoparticles. Scanning electron microscopy (SEM) showed a homogeneous spread of semi-spherical nanoparticles. Brunauer-Emmett-Teller (BET) revealed specific surface area ranging between 64 and 108 m2/g, while Barrett-Joyner-Halenda (BJH) showed the pore sizes varying between 48 and 126 nm. Cation distribution obtained from Rietveld refinement revealed all Ce3+ occupied B- sites whilst Ni2+, Zn2+, Fe3+ occupied both A and B sites. Magnetization measurements were performed using the vibration samples magnetometer (VSM). The saturation magnetization varied between 51 and 60 emu/g, while the coercivity dropped from 114 to 89Oe. The remnant magnetization varied between 3 and 12 emu/g. A correlation was observed between the saturation magnetization and the effective magnetic moments confirming cation distribution to be reliable. A strong correlation between initial susceptibility and unit cell volume was found. The crystallite sizes varied inversely with initial magnetic susceptibility. The magnetic characteristics of presented materials make them useful in high frequency device applications and has potential use as contrast agent in magnetic resonance imaging (MRI). 57Fe Mössbauer spectroscopy revealed the strengthening of ferromagnetic coupling. Gas sensing tests revealed a decrease in sensing response with the transition from paramagnetic state to ferromagnetic state. The Ni0.4Zn0.6Fe2O4 sample showed the best sensing response to SO2 at 100 °C compared to CO gas. However, at 150 °C the sample was more sensitive to CO gas than SO2 gas.

Effect of cation disorder on basic parameters of ZnFe2O4 nano-particles synthesized by honey mediated solution combustion technique

Nanotechnology contracts by the invention and practice of material using nanoscale dimension. Nanoscale measurement delivers nano-particles a bulky surface area (S) to volume ratio, hence very specific properties. Bulk zinc ferrite (ZnFe2O4) exhibits anti-ferromagnetism, with Néel temperature of 10K, is paramagnetic at room temperature. It displays normal spinel structure with Zn2+ has exclusive tetrahedral - A site preference, whereas Fe3+ ions occupy the octahedral - B site. Cationic disorder induced fractional overturn of the spinel structure, owing to partial immigration of Fe3+ ions from B to A site can prompt ferrimagnetism in nano zinc ferrite. Due to the large ratio of toxic chemicals and extreme environment employed in the chemical and physical production of these ferrites, green methods employing the use of bacteria, plants fungus have been adopted. Present work reports comprehensive study of the synthesis, structural and magnetic investigation of room temperature ferrimagnetism in ZnFe2O4 nanoparticles, prepared by sol gel auto-combustion mode and green synthesis method. Effect of conventional thermal annealing (ann. at 600oC for 3 hours) on magnetic properties is also reported. The structural and magnetic characteristics of as prepared and annealed ZnFe2O4 samples were determined by X-ray diffraction (XRD) and vibrating sample magnetometer (VSM). XRD confirms the formation of single-phase nano-crystalline cubic spinel structure of the samples.

Hydrothermal as a synthesis method for characterization of structural, morphological and magnetic properties of Co–Al ferrite nanoparticles

This work provides a set of structural, morphological, and magnetic results for the CoFe2-xAlxO4 (x = 0.00, 0.25, 0.50, 0.75, 1.00 at %) ferrite nanoparticles synthesized by the hydrothermal route. X-ray diffraction analysis (XRD), Field Emission Scanning Electron Microscopy (FESEM), Energy-Dispersive X-ray Spectroscopy (EDAX), High Resolution Transmission Electron Microscopy (HRTEM), Selected Area Electron Diffraction (SAED) microscopy and Fourier-Transform Infrared Microscopy (FTIR) were used to characterize the structural and morphological features of the prepared magnetic nanoparticles. Rietveld refinement carried out by the Material Analyses Using Diffraction (MAUD) software confirmed the formation of a single-phase spinel structure with no trace of impurity phase. FESEM micrographs showed the appearance of the ferrite nanoparticles with a size distribution in agreement with the data reported by XRD. HRTEM analysis showed the formation of cubic-shaped nanoparticles with dimensions near to the data extracted from XRD. The formation of spinel structure was approved by the FTIR spectra. The magnetic measurements through VSM analysis showed that the incorporation of Al3+ cations into the cobalt ferrite lattices decreases the values of saturation magnetization from about 69 emu/g to near 26 emu/g, which was attributed to the none-magnetic nature of Al3+ cations. The values of the coercive field, on the other hand, indicate a fluctuating trend as a function of Al3+ doping. The coercivity behavior was mainly affected by cation distribution, the variation of anisotropy constant, and the size of crystallites. All the obtained data showed that the magnetic ferrite nanoparticles could be synthesized successfully through the hydrothermal method as a technique that has not been used previously to prepare Co–Al ferrite nanoparticles.

Neem leaves mediated synthesis of CeO2 nanoparticles for X/gamma ray absorption applications.

Cerium oxide (CeO2) nanoparticles (NPs) exhibit a variety of properties, which have prompted researchers to explore CeO2 NPs in various applications such as biomedical, electrochemical, gas sensing and display applications. CeO2 NPs capabilities were impacted by the type of synthesis mechanism. CeO2 NPs were synthesized by solution combustion method using neem leaves extract as a reducing agent. The synthesized sample is characterized with different techniques. The Bragg reflections confirm the formation of cubic spinel structure. The surface morphology consists of agglomerated NPs. The direct energy band gap was found to be 2.9eV. X-ray radiation absorption properties were studied within 1keV-100GeV range. The results indicate that CeO2 NPs found to be potential in radiation applications.

Impact of the Sc3+/In3+ co-substitution on the structural, magnetic, and microwave characteristics of Co0.5Ni0.5Fe2O4 nanospinel ferrites

In this article, In3+ and Sc3+ ions dual-substituted NiCo nanospinel ferrites (ScIn→CoNiFe2O4 NSFs) have been synthesized through citrate-gel auto combustion method to investigate the effect of In3+ and Sc3+ ions on magnetic, and microwave characteristics. The following techniques TEM, SEM, EDX, and XRD were applied to characterize surface morphology, chemical composition, phase identification, and crystallinity of products, respectively. The XRD verified a phase formation of spinel structure with a minor amount of Sc2O3 was observed for products having x ≥ 0.04. The average crystal size (DXRD) of the products was estimated within the 33–68 nm range using the Scherrer equation. SEM and HR-TEM analyses exhibited accumulating sphere-shaped particles. By fitting the room-temperature spectra obtained from Mössbauer spectroscopy (Moss), Hyperfine interactions were determined. The cation distribution shows that there is a migration of In3+ ions in the lattice in an A→B direction with increasing concentrations while the B site is preferred by the larger Sc+3. M−H plots for 300 and 10 K illustrated all products carried out with a ferrimagnetic character. An enhancement in saturation magnetization (Ms) was remarked with Sc–In doping ratio up to 0.04 and thereafter a drop as the Sc–In concentration increased. The tendency in Ms values might be described by correlating it to the cation distribution amongst Oh and Td (octahedral and tetrahedral, respectively) sublattices. Temperature-dependent magnetization measurements were also investigated, which further confirmed the maintenance of the ferrimagnetic character throughout the temperature range 10–300 K. The peculiarities of the microwave properties have been analyzed by the measured S-parameters in the range of 6–18 GHz. It was assumed that the energy losses due to reflection are a combination of electrical and magnetic losses due to polarization processes and magnetization reversal processes in the region of inter-resonant processes. The average value of the reflection coefficient is −14.48 … −14.24 dB. A significant attenuation of the reflected wave energy opens up broad prospects for practical applications as coatings for providing electromagnetic compatibility.