O4 Nanoferrites Research Articles

Tunable annealing temperature for the structural, magnetic, optical, and dielectric characteristics of Mn0.5Zn0.5Ni0.5Fe1.5O4 nano-ferrite

The as-prepared Mn0.5Zn0.5Ni0.5Fe1.5O4 ferrite was prepared by the co-precipitation process and annealed at 300, 500, 900, and 1100 °C. The single-phase cubic spinel structure was confirmed by XRD patterns, Rietveld fitting, TEM imaging and several structural parameters, including crystalline size and lattice constant have been examined. The FTIR spectrum confirmed the main two absorption bands of tetrahedral and octahedral sites in ferrite, where the elastic parameters such as force constants and Debye temperature have been investigated. The saturation magnetization increases with the annealing temperature, while the energy band gap decreases with the annealing temperature, and also the ac conductivity decreases with annealing temperature.

Enhancing the magnetization, dielectric parameters and elastic parameters while simultaneously minimizing coercivity and dielectric loss in nickel-manganese-cobalt ferrite nanoparticles through Ce3+ doping assistance

This study focuses on examining how the rare-earth cerium incorporation affects the magnetic, dielectric, and mechanical characteristics of Ni0.5Mn0.25Co0.25CexFe2-xO4 spinel ferrite nanoparticles. (NMCCF). The nanoferrite Ni0.5Mn0.25Co0.25Ce0.04Fe1.96O4 acquires the lowest coercivity of 567 Oe and the highest saturation magnetization of 52.23 emu/g. All the NMCCFx nanoferrites exhibit a microwave frequency range of 9.47–11.55 GHz, suggesting potential applications in longitudinal recording media and microwave absorbance. Moreover, the nanoferrite Ni0.5Mn0.25Co0.25Ce0.1Fe1.9O4 demonstrates the highest dielectric value of 1871, with an enhancing ratio of 754 %, excellent conductivity at 3.12 μ(Ω.m)−1 along with a remarkably enhanced percentage of 369 %. Additionally, it shows a loss factor of 2.17, with a notable improvement percentage of 26 % compared to the pure NMCCF0 sample at 50 Hz and room temperature. The elastic moduli (longitudinal, shear, Young, and bulk) of the Ni0.5Mn0.25Co0.25Ce0.1Fe1.9O4 nanoferrite increased from 1.21 to 2.77 GPa, 0.25–0.76 GPa, 0.68–1.99 GPa, and 0.87–1.75 GPa, respectively. This study introduces a novel approach to Ni–Mn–Co–Ce spinel nanoferrites, highlighting their magnetic, electrical, and mechanical characteristics, which hold promise for electronic and high-frequency device applications.

Microwave-absorbing behavior of rare-earth-ion-doped copper manganese nanoferrites in X-band frequency

In this study, the technology important Cu0.5Mn0.5Fe2O4 and Cu0.5Mn0.5Fe1.80RE0.2O4 (RE = La, Gd, Nd, and Dy) nanoferrites were synthesized via sonochemical method and characterized to overcome the electromagnetic pollution problems. Crystalline, morphological, electrical, magnetic, and microwave-absorbing parameter were identified by doping of RE (La, Gd, Nd, and Dy) in Cu0.5Mn0.5Fe2O4 nanoferrites. The XRD analysis revealed a cubic spinel structure with a single-phase composition for Cu0.5Mn0.5Fe2O4 nanoferrites whereas Cu0.5Mn0.5Fe1.80RE0.2O4 (RE = La, Gd, Nd, and Dy) nanoferrites had a cubic structure with the presence of a secondary phase. SEM images confirmed the spherical shape of the particle and the grain size within the range of 19.25–28.19 nm, with elemental stoichiometry confirmed by EDS spectra. The dielectric constant and conductivity of Cu0.5Mn0.5Fe1.80RE0.2O4 nanoferrites were low at higher frequencies, which lead good candidates for microwave-absorbing technologies. The substitution of RE decreases saturation magnetization (43.38–23.96 emu/g) and squareness ratio values of prepared nanoferrites were less than 0.5. The SET values of the prepared nanoferrites were in the range of 32.31–41.81 dB. The minimal reflection loss (RL) values of Cu0.5Mn0.5Fe2O4 and Cu0.5Mn0.5Fe1.80RE0.2O4 nanoferrites were less than 10 dB and which indicated that the prepared nanoferrites possessed great potential for applications as microwave-absorbing materials.

Sm3+ doping-adjusted mechanical, dielectric, and radiation shielding properties of cobalt copper nanoferrites

The scarcity of research on the shielding properties of spinel ferrites underscores the necessity for more rigorous investigations. Consequently, this study introduces a facile synthesis method for Co, Cu, and Sm spinel nanoferrites (referred to as CCS nanoferrites) using the citrate combustion technique. The investigation focuses on their mechanical, dielectric, and gamma-ray shielding parameters. Gamma-ray shielding features are obtained theoretically via the Phy-X database. The particle size, nature, and distribution of the present CCS nanoferrites were analyzed using HR-TEM microscopy. HR-TEM results reveal both the spherical shapes and the aggregation of nanoparticles. These observations can be attributed to the interplay of high surface energy and magnetic interactions among the components of the CCS nanoferrites. The Co0.5Cu0.5Sm0.15Fe1.85O4 nanoferrite exhibits an optimal dielectric constant value of 4587, with an enhanced ratio of 1618% compared to the pristine CCS0 sample. Additionally, it demonstrates an optimal conductivity of 38.59 μ (Ω·m)−1, with an enhanced ratio of 1105%. Furthermore, the loss is reduced to 2.65, showing an improvement ratio of 54% compared to the pristine nanoferrite at room temperature and 50 Hz. Moreover, the longitudinal modulus, shear modulus, Young's modulus, and bulk modulus of the nanoferrite Co0.5Cu0.5Sm0.15Fe1.85O4 were increased from 1.79 to 4.96 GPa, 0.32–0.93 GPa, 0.88–2.56 GPa, and 1.37–3.73 GPa, respectively, when compared to the pristine sample. The comparative study of half-value layers at 0.662 MeV revealed that CCS nanoferrites exhibit smaller half-value layers than common radiation shielding materials. Additionally, the study highlighted the enhanced radiation shielding performance of the nanoferrites. Concerning the dielectric, mechanical, and ionizing radiation shielding properties of the CCS spinel nanoferrites, the CCS5 (with the highest Sm content) has the optimum ionizing radiation shielding ability with the highest dielectric and mechanical parameters compared to the other samples. The implications of these findings extend to potential applications in biomedicine, radiation protection, and the optimization of electronic devices operating in radiation fields.

Novel Mn0.5Zn0.5Al0.1MgxLixFe(1.9-x)O4 nanoferrites: synthesis, theoretical cation distribution, and improving their dielectric properties

The effect of Mg2+–Li1+ ions in modifying the structural, electrical, and magnetic characteristics of nanocrystalline Mn–Al–Zn ferrites was examined experimentally and theoretically in the current study. The chemical co-precipitation method was used to create the investigated ferrite samples, which have the chemical formula (Mn0.5Zn0.5 Al0.1Mgx Lix Fe(1.9-x)O4) and concentration range of the substituent (0 ≤ x ≤ 0.2). The cation distribution of the investigated system was assumed and confirmed. Furthermore, the activation energy, AC resistivity, dielectric loss tangent, and dielectric constant were investigated in terms of their compositional dependence. The final results showed that the increasing of Mg2+–Li1+ concentration enhanced the physical and dielectric properties of the prepared samples. The experimental findings show also that as temperature rises, ε′, tan δ, and σ all increase but they all decrease as Mg2+–Li1+ content increases. With increasing Mg2+–Li1+ concentration, the AC resistivity of the prepared samples also continuously increased, resulting in the sample with x = 0.2 having high resistivity, which can be used in specific technical applications such as transformer cores.

The impact of Bi3+ ions on magnetization, dielectric parameters, and conductivity of soft Mg-Cu ferrite nanoparticles

This paper investigates the bismuth ions leverage on magnetic and dielectric features of magnesium–copper nanoferrites Mg0.5Cu0.5BixFe2-xO4 (MCBF). The Mg0.5Cu0.5Bi0.1Fe1.9O4 nanoferrite exhibits superior magnetic properties compared to the pure Mg-Cu sample. These properties include a higher magnetization of 31.31 emu/g, with an enhancing ratio of 1.50 %. Additionally, it demonstrates a higher initial permeability of 17.84, with an enhancing ratio of 55.12 %. Furthermore, their coercivity is lower at 59.90 Oe, with an enhancing ratio of 50 %. All MCBF nanoferrites exhibit a high-frequency response between 6.106 and 6.926 GHz, making them suitable for microwave technology. The dielectric parameters dispersion shows normal behavior at different frequencies and temperatures. As for dielectric parameters dependence on Bi content, it exhibited a peculiar manner. At a temperature of 297 K and a frequency of 50 Hz, the nanoferrite Mg0.5Cu0.5Bi0.1Fe1.9O4 exhibits superior dielectric properties compared to the pure Mg-Cu sample. Specifically, it demonstrates the highest dielectric constant of 360.68, with an enhancing ratio of 125.97 %. Additionally, it displays the highest conductivity of 691.4 µ(Ω.m)-1, with an enhancing ratio of 1543.23 %. Furthermore, the nanoferrite exhibits a lower dielectric loss of 6.49, with an enhancing ratio of 80.22 % compared to the pure Mg-Cu sample. The conduction mechanism of the Mg0.5Cu0.5BixFe2-xO4 nanoferrites was determined by fitting the σac results via the Jonscher power law. This conduction mechanism is attributed to correlated barrier hopping (CBH) model up to 473 K, followed by small polaron tunneling (SPT), which reaches higher temperatures. Hence, the Mg0.5Cu0.5Bi0.1Fe1.9O4 nanoferrite has a remarkable magnetic and dielectric nature, which can be used as functional soft ferrite material in transformers and high-frequency electronic devices.

Mg-modified Zn-Co-Fe-La nano ferrites: A study of structural, morphological, vibrational, electro-optical, dielectric and magnetic evolution

The series of Zn0.4Co0.6−xMgxFe1.9La0.1O4 (x = 0.0, 0.15, 0.30, 0.45, 0.6) nanoferrites prepared via co-precipitation technique. Scherrer and Williamson-Hall (W-H) methods were used to find the crystallite size (29.6–39.2 nm and 31.6–36.3 nm, respectively) and lattice constant was calculated (8.406–8.395 Å). Moreover, Fourier transform infrared (FTIR) spectroscopy revealed the existence of absorption bands along with functional groups. The vibrations of O2- ions at the tetrahedral and octahedral sites were shown by the Raman five active modes. DC resistivity reduced in the range of 5.2961 × 108 Ω cm to 9.6453 × 107 Ω cm for x = 0.0 to x = 0.6, respectively. The maximum DC resistivity and activation energy (0.1035 eV) were obtained at the parent sample (Zn0.4Co0.6Fe1.9La0.1O4). The optical bandgaps reduced from 2.61 to 1.47 eV, as the Mg2+ contents increased. With increasing frequency the dielectric loss and the dielectric constant decrease. The magnetic parameters such as saturation magnetization (Ms= 60.82–25.94 emu/g), remnant magnetization (Mr = 47.82–18.64 emu/g), and coercivity (Hc = 1334–511 Oe) demonstrated reducing trends with the increase of Mg2+ doping. The best magnetic behavior of the as-prepared samples suitable in microwave devices was observed for Zn0.4Co0.6Fe1.9La0.1O4 sample.

Rare earth ions (La3+, Nd3+) substituted cobalt–strontium spinel ferrites for photocatalytic degradation of textile dyes

Abstract In the industrial sector, productive and effective treatment of toxic dye-based color pollutants is a key issue. Lanthanum and neodymium substituted cobalt–strontium (Co–Sr) spinel ferrite (Co0.5Sr0.5RExFe2-xO4, x = 0.00 and 0.06) catalysts were synthesized and used to degrade Congo red and rhodamine B dyes from an aqueous solution mixture in this study. For this specific purpose, RE3+ ions substituted Co–Sr spinel ferrite nanoparticles with photocatalytic degradation ability were prepared through sol–gel method. The degradation of CR and RhB in recently synthesized nanoferrites was also examined. SEM and XRD were used to characterize the prepared samples. The optical band gap values of synthesized spinel ferrites were examined with the help of Tauc plots by using UV-visible absorption. It was determined that the energy bandgap ranged from 2.91 to 2.52 eV. For Co0.5Sr0.5Fe2O4, Co0.5Sr0.5La0.06Fe1.94O4, and Co0.5Sr0.5Nd0.06Fe1.94O4 nanoferrites, the rates of CR and RhB dye degradation were 73–90% and 45–85%, respectively, at pH 5–7. The kinetics models successfully described the degradation reaction as pseudo-first-order kinetics. It was, therefore, concluded that the prepared samples can be used as effective photocatalysts in order to eliminate hazardous pollutants present in wastewater.

La3+ substituted Ni0.5 Co0.5 Fe2 O4 nanoferrites: Magnetically separable catalysts for sunlight-driven photo-oxidative degradation of Methylene Blue

LaxNi0.5Co0.5Fe2−xO4 nanoparticles (x = 0.0, 0.03, 0.06, 0.09, 0.12) were investigated in the current work as Methylene Blue degradation catalysts. Using the citrate-aided sol-gel auto-combustion approach, the nanoferrites with homogenous size distribution were produced. Powder X-ray diffraction was used to analyse the structure of the material. The optical characteristics of ferrite nanoparticles were investigated using diffused UV–visible reflectance spectroscopy. It was noted that when the concentration of La3+ increased, the band gap of produced ferrites shrank. Morphological and compositional studies were performed by FE-SEM and EDX spectra. Surface area was depicted using BET analysis. Raman Spectroscopy was used to estimate the parameters of vibration. Testing has been done on synthesized nanoferrites to see whether they can remove Methylene Blue's concentration in water. In addition, it was examined how La3+ incorporation in Ni0.5Co0.5Fe2O4 nanocomposites resulted in aspects of doping ratio, reaction time and amount of catalyst. The most effective material, La0.06Ni0.5Co0.5Fe1.94O4, achieved a 98.69 per cent efficiency in 140 min. Due to three positive characteristics, including high recycling (up to five cycles), stability, and simplicity of separation using an external magnet, toxic dyes in actual wastewaters can be photodegraded in sunlight using La3+ substituted Ni0.5Co0.5Fe2O4 nanoferrites as an efficient and competitive catalyst.

Sol-gel auto-combustion developed Nd and Dy co-doped Mg nanoferrites for photocatalytic water treatment, electrocatalytic water splitting and biological applications

Sol-gel auto-combustion synthesis was considered for development of MgNd0.5xDy0.5xFe2-xO4 (x = 0.00, 0.01, 0.02, 0.03) nanoferrites to analyze the structural, optical, morphological, photocatalytic, magnetic, electrocatalytic, and antibacterial traits of nanomaterials. X-ray diffraction (XRD) patterns illustrate the existence of spinel phase for synthesised nano ferrites with no impurity phases. With increased neodymium (Nd) and dysprosium (Dy) content, the energy band gap of produced nanoferrites was decreasing from 1.73 to 1.49 eV. The magnetic characteristics indicates that with Nd and Dy doping, excellent saturation magnetization (Ms) and coercivity (Hc) in the range of 27.47–32.30 emu/g and 51.79–80.28 Oe were observed for produced nanoferrites. Electrocatalytic traits of developed nanoferrites were investigated for HER and OER in 0.5 N H2SO4 and 0.1 N KOH electrolyte using a calomel electrode as a reference electrode, respectively. According to photodegradation investigation, doped samples performed better in terms of photocatalytic efficiency under the specific conditions (catalytic dose = 0.05 g, dye concentration = 10 mg/L− and pH = 7). The prepared MgNd0.015Dy0.015Fe1.97O4 (x = 0.03) nanoferrite sample shows higher photocatalytic activity due to increased active sites and smaller band gap. Furthermore, the catalyst efficiency did not decrease significantly after the five consecutive reuse cycles. The antibacterial effects of developed Mg spinel nanoferrites for gram-positive bacteria (Staphylococcus aureus) and gram-negative bacteria (Escherichia coli) are found to be effective. Therefore, with these superior electrocatalytic, photocatalytic, and antibacterial traits, the developed Mg nano ferrites are suitable for hydrogen evolution, wastewater treatment, and biological applications.

Investigations on the enhancement of thermomagnetic properties in Fe2.4Ga0.6O4

ABSTRACT The structural, magnetic and calorimetric properties of Fe2.4Ga0.6O4 nanoferrite have been investigated. X-ray and neutron diffraction coupled analyses using Rietveld refinements have shown that the samples under investigation, obtained by different bottom-up methods, crystalize with a cubic structure in the space group (N° 227). The Ga3+ ions preferentially occupying the tetrahedral sublattice of the inverse spinel partly screen the dipole–dipole interactions and lead to the reduction of the magnetic response of Fe3+ ones. Calorimetric measurements confirm that the nanosized Fe2.4Ga0.6O4 system weakly agglomerates and simultaneously collect and release optimal amount of heat under the influence of an alternating magnetic field with the 15.3 kA/m of maximum magnetic field strength and 532 kHz of frequency. The values of the specific absorption coefficients obtained for gallium ferrites, similar to those typical for cobalt ferrites used commercially in biomedicine, together with very low superparamagnetic blocking temperature validated by Mössbauer spectroscopy analysis, make the system an attractive therapeutic material.

Copper substitution effect on the structural, electrical, and magnetic properties of manganese and lanthanum (Mn1−xCuxLa0.1Fe1.9O4) nanoferrites

In this study, a sonochemical reactor was used to synthesize Mn1−xCuxLa0.1Fe1.9O4 nanoferrites with different compositions of x (0.09, 0.18, 0.27, and 0.36). Mn1−xCuxLa0.1Fe1.9O4 nanoferrites were subjected to X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), vibrating sample magnetometer, and electrochemical impedance spectroscopy to investigate their magnetic, electrical, and structural properties. Formation of a cubic crystalline structure was observed by the XRD patterns. The decreases in crystalline size could have been caused by an increase in Cu2+ ions in Mn1−xCuxLa0.1Fe1.9O4 nanoferrites. The impedance analysis revealed the presence of pseudocapacitance and resistive behavior in Mn1−xCuxLa0.1Fe1.9O4 nanoferrites. The hysteresis loops promoted the soft ferromagnetic behavior present in Mn1−xCuxLa0.1Fe1.9O4 nanoferrites. A decrease in saturation magnetization and an increase in coercivity were observed with an increase in the Cu2+ content of Mn1−xCuxLa0.1Fe1.9O4 nanoferrites.

Structure, Morphology and Electrical/Magnetic Properties of Ni-Mg Nano-Ferrites from a New Perspective.

Using the auto combustion flash method, (x = 0, 0.2, 0.6, 0.8 and 1) nano-ferrites were synthesized. All samples were thermally treated at 973 K for 3 h. The structural analysis for the synthesized samples was performed using XRD, high-resolution transmission electron microscopy (HRTEM), and FTIR. Scanning electron microscopy (SEM) was undertaken to explore the surface morphology of all the samples. The thermal stability of these samples was investigated using thermogravimetric analysis (TGA). XRD data show the presence of a single spinel phase for all the prepared samples. The intensity of the principal peak of the spinel phase decreases as Mg content increases, showing that Mg delays crystallinity. The Mg content raised the average grain size (D) from 0.084 μm to 0.1365 μm. TGA shows two stages of weight loss variation. The vibrating sample magnetometer (VSM) measurement shows that magnetic parameters, such as initial permeability (μi) and saturation magnetization (Ms), decay with rising Mg content. The permeability and magnetic anisotropy at different frequencies and temperatures were studied to show the samples’ magnetic behavior and determine the Curie temperature (TC), which depends on the internal structure. The electrical resistivity behavior shows the semi-conductivity trend of the samples. Finally, the dielectric constant increases sharply at high temperatures, explained by the increased mobility of charge carriers, and decreases with increasing frequency.

Photocatalytic degradation of environmental pollutant using nickel and cerium ions substituted Co0.6Zn0.4Fe2O4 nanoferrites

In the present investigation, toxic environmental pollutant, i.e., Congo red dye photocatalytic degradation was achieved using Co0.6Zn0.4−xNixCeyFe2−xO4 (x = 0.0, 0.1, 0.2, 0.3; y = 0.0, 0.05, 0.10, 0.15) ferrite-based nanomaterials. The nanoferrites were synthesized with the usage of sol–gel auto-combustion fabrication technique. Their microstructural, optical and magnetic, properties were analysed, using various characterization techniques. The observed XRD (X-ray diffraction) diffraction patterns indicate the existence of single-phase spinel cubic structure along with Fd3m space group symmetry and, the crystallite size calculated using Scherrer formula was found in the dimensions of 38–49 nm. The formation of agglomerated, dense, and spherical magnetic nanoparticles with an average grain size of 51 nm and 62 nm for the undoped specimen (x = 0.0, y = 0.0) and doped specimen (x = 0.2, y = 0.10) were observed from the FESEM (Field emitting scanning electron microscopy) micrographs analysis. From the M–H curves data, it was concluded that the maximum value of Ms (70.17 emu/g) and Hc (266.43 Oe) was attained by the Co0.6Zn0.1Ni0.3Ce0.15Fe1.85O4 nanoferrite. The present investigation concentrates on the photocatalytic degradation of Congo red dye under the natural solar irradiation in which we improved the photocatalytic efficiency upto 94.6% after 60 min of irradiation with the utilization of substituted Co0.6Zn0.1Ni0.3Ce0.15Fe1.85O4 nano photocatalyst. Thus, synthesized Co–Zn nanoferrites can be utilized for potential applications in wastewater treatment.

Structural, morphological, and magnetic study of low temperature synthesized Co0.75Ni0.25Fe1.95Dy0.05O4 nano ferrite

The nanoparticles of Co0.75Ni0.25Fe2−zDyzO4 (z = 0.0 and 0.05) were prepared by the sol-gel auto-combustion method. The cation distribution was calculated from the Rietveld refinement of the XRD pattern to confirm a mixed inverse spinel structure. The crystallite size was calculated by the Debye–Scherrer method, modified Scherrer method, Williamson Hall plot method, and size-strain plot method for prepared samples. The variation in crystallite size was observed due to the contribution of lattice strain on line peak broadening. From Fourier transform infrared (FT-IR) spectrum the absorption bands appeared at 574.79 cm−1 and 414.70 cm−1 reveals spinel ferrite structure for Co0.75Ni0.25Fe1.95Dy0.05O4. The particle size from a high-resolution scanning electron microscope (HR-SEM) the image was found to be 46.99 nm for Co0.75Ni0.25Fe1.95Dy0.05O4. Energy-dispersive X-ray spectrum (EDS) was confirmed the purity of the sample with good stoichiometry. The coercivity, retentivity, and saturation magnetization were estimated at 841.97 Oe, 30.95 emu g−1 and 61.80 emu g−1 respectively for Co0.75Ni0.25Fe1.95Dy0.05O4. The squareness ratio for Co0.75Ni0.25Fe1.95Dy0.05O4 nanoferrite was found to be 0.5 which is the ideal Stoner—Wohlfarth value. The experimental estimated net magnetic moment () per formula was less than the theoretical value calculated from Neel’s two sublattice model for prepared samples.

Insightful acetone gas sensing behaviour of Ce substituted MgFe2O4 spinel nano-ferrites

MgCexFe2-xO4 (0 ≤ x ≤ 0.2) nanoparticles have been produced by the glyco-thermal technique and characterized by X-ray diffraction, electron microscopy, X-ray photoelectron spectroscopy, Mössbauer spectroscopy and gas sensing analyses. The X-ray diffraction results indicated that a pure cubic spinel phase was formed for samples having a low concentration of Ce, but the high Ce doping (x = 0.2) of magnesium ferrite resulted in the formation of secondary phases. The crystallite size of the compounds ranged from 2.2 nm to 15.3 nm. The 57Fe Mössbauer spectra showed transformation from an ordered to a paramagnetic spin state with an increase in Ce concentration. Gas sensors fabricated from the spinel ferrites were tested towards various organic compound vapours (acetone, methanol, p-xylene, ethylbenzene, toluene, and benzene) at an operating temperature of 225 °C. The MgCe0.2Fe1.8O4 nanoferrite proved to possess quality sensor characteristics of high sensitivity and selectivity to acetone vapour, with a response of over 500@100 ppm concentration as well as reproducibility, reversibility, and stability of over 120 days. This sensor not only displayed high responses, but could also maintain them over 1, 3, 5, 10, 20, and 30 min of acetone exposure time. The sensor was resilient and sensitive to an oxygen reduced, inert ambient environment. Under relative humidity, the response was reduced, but stable, due to physisorbed water molecules.

Investigation of Structural, Optical, and Dielectric Properties of Co0.5Cd0.5-xCuxFe1.95Ce0.05O4 Nanoferrites

Co0.5Cd0.5-xCuxFe1.95Ce0.05O4 (0 ≤ x ≤ 0.5) nanoferrites were successfully synthesized via sol-gel-assisted autocombustion method. The effects of Cu substation in the spinel matrix on structural, optical, and dielectric properties have been studied. XRD data confirms the successful synthesis of single phase cubic spinel structure. FTIR spectroscopy and Raman spectroscopy further confirm the formation of single phase spinel structure. Ultraviolet-visible (UV-vis) spectroscopy is used to measure the energy bandgap of the prepared samples. The energy bandgap is found in the range 1.02 to 1.96 eV and decreases when Cu concentration increases. Dielectric parameters like dielectric constant, tangent loss, and ac impedance are determined as a function of frequency of applied field and are described with the help of Koop’s theory. It is observed that all these parameters decrease with increase in frequency and become independent of frequency above 1 MHz. The dielectric properties of Cu-substituted Co-Cd spinel ferrites make these ferrites potential candidate for applications in high frequency range.

Correlation between microstructure parameters and anti-cancer activity of the [Mn0.5Zn0.5](EuxNdxFe2-2x)O4 nanoferrites produced by modified sol-gel and ultrasonic methods

[Mn0.5Zn0.5](EuxNdxFe2-2x)O4 ferrite nanoparticles (FNP) were obtained by ultrasonic (USM) and sol-gel (SGM) methods. It was observed that SGM allows us to produce nanoparticles with the average crystal size of 10–40 nm and the specific surface area of 5–7.5 × 104 m2/g with a strong correlation between the chemical composition (x) and the crystal size distribution. At the same time using USM, we obtained nanoparticles with the average crystal size of 3–15 nm and the specific surface area of 1.5–1.7 × 105 m2/g without a strong correlation between Eu/Nd concentration and the crystal size distribution. The specific surface area and average crystal size are the main factors determining the antiproliferative activity of FNP. The anti-cancer activity of FNP was investigated both on cancerous cells, human adenocarcinoma cells and human colorectal carcinoma cells. It was established that samples obtained using USM were more effective in producing cytotoxic effects on cancer cells. Thus, we confirm a strong correlation between the main microstructure parameters for [Mn0.5Zn0.5](EuxNdxFe2-2x)O4 ferrite nanoparticles.

Relaxation time enhancement of cobalt zinc nanoferrites via Cr3+ doping

Cation distribution, structure analysis, elastic moduli, magnetic and dielectric features obtained by the citrate combustion technique of Co0.8Zn0.2CrxFe2-xO4 (x = 0, 0.02, 0.04, 0.06, 0.08 and 0.1) (CZC) nanoferrites were investigated. The most intense (311) peak is found to gradually shift towards higher diffraction angles, and so the lattice constant is found to decrease (from 8.3893 to 8.3698 Å, experimentally) and (from 8.3893 to 8.3853 Å, theoretically), as the Cr3+ content increase. The crystallite size of CZC nanoferrites initially increases from 38 to 42 nm for Cr3+content (x = 0.0 to x = 0.06), and then decrease from x = 0.08 onwards. Morphological contemplation (FE-SEM, HRTEM) manifests that the porosity diminishes significantly with increasing Cr3+ content meanwhile the particles have some agglomeration. The elastic moduli and Poisson's ratio of CZC ferrite samples were determined, theoretically and experimentally, and then corrected to zero porosity using Hosselman and Fulrath's model. An analogous behavior for experimental and theoretical magnetic moment is obtained, attached with an increment attitude of Yafet–Kittel angle on the B-sublattice, which increase (from 39° 42′ to 41° 51′) as the Cr3+ content increase. The value of impedance is increased (from 44 k Ω to 203 k Ω) with increasing Cr3+ content. Nyquist plot shows a single semicircle declaring that the predominant conduction is through the grain boundary volume. These results behold that substitution with Cr ions and porosity has prominent impacts on the various properties of Co-Zn nanoferrites, making it nominee for multilateral applications. The loss of Co0.8Zn0.2Cr0.1Fe1.9O4 nanoferrite (x = 0.1) is decreased ∼ 4 times with increasing relaxation time from 0.53 to 15.9 μs, which has good predictions for next generation cores of RF transformers.

Structural phase transition of spinel to hematite of as-prepared Fe2+-Cr nanoferrites by sintering temperature

This investigation presents effect of sintering temperature on the transition processes of as-synthesized cubic spinel Fe2+Cr0.4Fe1.6O4 nanoferrites by the co-precipitation method. In addition to parts of as-synthesized sample were sintered at the temperatures T = 300, 500, 700, 900 or 1100 °C in ambient air for 4 h, other parts were sintered at 250 °C for 1, 2 and 3 h. The structural phase of sample crystal was converted from cubic spinel–to- maghemite–to-hexagonal hematite with T. The effect of the sintering temperatures and transition process on the different properties of the samples was investigated. The threshold frequency and energy of transition electrons showed decrease against T. The specific surface area S revealed decrease against the crystallite size R, while the saturation magnetization MS was affected by R and porosity P. The density indicated effect on elastic wave velocities, VS and VL, while increase of strain ε enhanced the band gap energy Eg.