Nickel Cobalt Ferrite Research Articles

Evaluation of dissolution characteristics of magnetite in an inorganic acidic solution for the PHWR system decontamination

A protective oxide layer forms on the material surfaces of a Nuclear Power Plant during operation due to high temperature. These oxides can host radionuclides, the activated corrosion products of fission products, resulting in decommissioning workers' exposure. These deposited oxides are iron oxides such as Fe3O4, Fe2O3 and mixed ferrites such as nickel ferrites, chromium ferrites, and cobalt ferrites. Developing a new chemical decontamination technology for domestic CANDU-type reactors is challenging due to variations in oxide compositions from different structural materials in a Pressurized Water Reactor (PWR) system. The Korea Atomic Energy Research Institute (KAERI) has already developed a chemical decontamination process for PWRs called ‘HyBRID’ (Hydrazine-Based Reductive metal Ion Decontamination) that does not use organic acids or organic chelating agents at all. As the first step to developing a new chemical decontamination technology for the Pressurized Heavy Water Reactor (PHWR) system, we investigated magnetite dissolution behaviors in various HyBRID inorganic acidic solutions to assess their applicability to the PHWR reactor system, which forms a thicker oxide film.

Dielectrically modified Dy3+ substituted nickel-cobalt ferrites for high frequency devices

Keeping in view various applications of Ni–Co ferrites in high frequency devices, it is important to alter their properties. For this purpose, Dysprosium (Dy3+) substituted Ni–Co ferrites with chemical formula Ni0·3Co0.7DyxFe2-xO4 (0.00 ≤ x ≤ 0.20) were synthesized using sol-gel route. The structural analysis was executed using X-ray diffraction (XRD) and Fourier transform infra-red spectroscopy (FTIR). The crystalline size and lattice constant were calculated in the range 14–21 nm and 8.29–8.35 Å respectively. Two characteristic absorption bands were reported in FTIR spectra around 424 cm−1 and 550 cm−1. The dielectric parameters of these nano-ferrites exhibited decreasing tendency with applied frequency. At 1 GHz dielectric constant enhanced from 2.55 to 3.17 and at 0.5 GHz AC conductivity increased from 0.142 × 10−3-1.06 × 10−3 Ω−1-m−1 for x = 0.00–0.10. The Cole-Cole studies revealed formation of single semicircle. All these parameters suggest that these ferrites can be used in high frequency devices fabrication.

Co-Precipitation Synthesis of ZNCF Nanoparticle and their Structure, Morphological, and Magnetic Properties Characterization

The Zinc Nickel Cobalt Ferrite (ZNCF) Zn0.95−xNi0.05CoxFe2O4, for x= 0.01, 0.02, 0.03, 0.04, 0.05 and 0.06 were prepared by co-precipitation. XRD patterns show spinel ferrite with a cubic structure. The lattice parameter was found to increase linearly with cobalt concentration (x). FESEM gave the grain sizes in the range 1.61-1.38nm and particle size in the range 28-21 nm for x = 0.01 to 0.06. The porosity was in the range 92.6-92.9 %. The occupancy of metal ions in the two interstitial sites affects the exchange interaction. The higher grain size and lower porosity have a positive impact on magnetic saturation which makes them applicable in recording media.

Evaluation of Co0.7Ni0.3Fe2O4 nano-particle on structural, morphological, and magnetic properties as a heavy metal adsorbent in Cu, Cr

Progressively more complex technological advancements have been made, particularly with the invention of ferrite material manufacture. In this evaluation, the co-precipitation method was used to assess the structure, morphological, and magnetic characteristics of cobalt nickel ferrite for heavy metal adsorbent in Cu, and Cr material. Synthesized cobalt nickel ferrite of Co0.7Ni0.3Fe2O4 was analyzed structurally and morphologically using X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM), and its room temperature hysteresis loops were measured using a vibrating sample magnetometer (VSM). Atomic absorption spectroscopy was then used to determine the metal content (AAS). XRD study that the six peaks and well-defined reflection planes of (220), (311), (400), (422), (511), and (400) at the 2θ values of 30.12°, 35.57°, 43.29°, 53.71°, and 62.72° and there is no secondary phase in cobalt–nickel ferrite. FE-SEM results confirmed the spherical shape of the ferrite nanoparticle. The average particle size of Co0.7Ni0.3Fe2O4 is found with a range of 80 to 120 nm. The peaks of Fe, Ni, Co, and O elements as energy dispersive X-ray (EDX) spectra studied the ratio of the chemical composition of metal ions (Co: Ni) and iron to oxygen (Fe:O), The magnetic properties from VSM results evaluated that Ms of 34.46 emu/g, Mr of 14.91 emu/g, Hc of 671.58 Oe, independently. Correspondingly, AAS results from a removal efficiency of 99.86 % with capacity adsorption of 11.23 mg/L of Co0.7Ni0.3Fe2O4.

Palladium Decorated, Amine Functionalized Ni-, Cd- and Co-Ferrite Nanospheres as Novel and Effective Catalysts for 2,4-Dinitrotoluene Hydrogenation.

2,4-diaminotoluene (TDA) is one of the most important polyurethane precursors produced in large quantities by the hydrogenation of 2,4-dinitrotoluene using catalysts. Any improvement during the catalysis reaction is therefore of significant importance. Separation of the catalysts by filtration is cumbersome and causes catalyst loss. To solve this problem, we have developed magnetizable, amine functionalized ferrite supported palladium catalysts. Cobalt ferrite (CoFe2O4-NH2), nickel ferrite (NiFe2O4-NH2), and cadmium ferrite (CdFe2O4-NH2) magnetic catalyst supports were produced by a simple coprecipitation/sonochemical method. The nanospheres formed contain only magnetic (spinel) phases and show catalytic activity even without noble metals (palladium, platinum, rhodium, etc.) during the hydrogenation of 2,4-dinitrotoluene, 63% (n/n) conversion is also possible. By decorating the supports with palladium, almost 100% TDA selectivity and yield were ensured by using Pd/CoFe2O4-NH2 and Pd/NiFe2O4-NH2 catalysts. These catalysts possess highly favorable properties for industrial applications, such as easy separation from the reaction medium without loss by means of a magnetic field, enhanced reusability, and good dispersibility in aqueous medium. Contrary to non-functionalized supports, no significant leaching of precious metals could be detected even after four cycles.

Partial magnetic ion substitution of BiFeO3 Multiferroic photocatalyst for hydrogen evolution from water splitting

BiFeO 3 as a p-type photocatalyst in BiFeO 3 –CdWO 4 p-n heterojunction was modified by partial substitution of divalent Co 2+ and Ni 2+ at Fe-site to enhance the photocatalytic performance for H 2 evolution from pure water splitting. At high impurity concentrations, XRD and Raman spectroscopy revealed a phase transition from rhombohedral to orthorhombic/tetragonal with higher crystal symmetry due to larger ionic radii of Co 2+ and Ni 2+ relative to that of Fe 3+ . The excess amount of impurities also resulted in the formation of nickel ferrite (NiFe 2 O 4 ), cobalt ferrite (CoFe 2 O 4 ), sillenite (Bi 25 FeO 40 ) and mullite (Bi 2 Fe 4 O 9 ) as secondary phases. The high resolution XPS spectra of O 1s and Fe 2p indicted that the concentration of oxygen vacancy and Fe 2+ : Fe 3+ increased with doping BiFeO 3 , which is due to the structural distortion and defection. Moreover, magnetic property of BiFeO 3 was promoted by Co and Ni doping so that the residual magnetization increased from 0.009 emu/g up to 0.061 and 0.068 emu/g by 9 mol.% doping of Ni and Co, respectively. The enhanced magnetism can be attributed to the net magnetic moment caused by different magnetic moment of Fe 3+ , Co 2+ and Ni 2+ as well as the structural defection that may be a reason for spin spiral suppression. Doping with Co and Ni led to reducing band gap energy, suppression of charge recombination, and increment of charge density and mobility. The efficiency of photocatalytic H 2 evolution increased from 268.9 μmol/h gcat by pure BFO up to 449.6 and 494.7 μmol/h gcat by 9 mol.% Ni and Co doping, respectively. • BiFeO 3 was modified by substitution of Fe 3+ with larger divalent Co 2+ and Ni 2+ . • Crystal distortion and phase transition were revealed by XRD and Raman analyses. • Magnetic property was modified as a result of crystal distortion. • Charge recombination was efficiently suppressed by Co and Ni doping. • Photocatalytic H 2 evolution was boosted by 9 mol.% Co and Ni doping.

Purifications of Iraqi Petroleum Using Ceramic Ball Nano Cobalt Nickel Ferrite Filter

Iraqi petroleum, especially from the Al-Ahdab, has a big problem resulting from its high percentage of heavy metals. In this paper, heavy metals were reduced or removed from Iraqi petroleum using a Ceramic Ball Nano Cobalt Nickel Ferrite Filter (BCNF), synthesized by combining kaolin and palm frond in a 30% ratio with Co0.8Ni0.2Fe2O4 nanoparticles in a various ratios (5, 10, 15, and 20%). The sol-gel technique prepared Co0.8Ni0.2Fe2O4 nanoparticles. The structure and magnetic properties of the material are described using X-RD, FT-IR, and VSM techniques. In addition, the water ab-sorption ratio and apparent porosity were assessed. The results show that the ceramic ball Nano cobalt-nickel ferrite filter reduces V, Ni, and Fe in crude petroleum. As a result, heavy oil has been converted to the lightest petroleum obtainable. These filters will also become more popular because of their low preparation costs, ease of preparation, and ability to remove crude petroleum.

Mechanisms of the Oxygen Evolution Reaction on NiFe2O4 and CoFe2O4 Inverse-Spinel Oxides.

Spinel ferrites, especially Nickel ferrite, NiFe2O4, and Cobalt ferrite, CoFe2O4, are efficient and promising anode catalyst materials in the field of electrochemical water splitting. Using density functional theory, we extensively investigate and quantitatively model the mechanism and energetics of the oxygen evolution reaction (OER) on the (001) facets of their inverse-spinel structure, thought as the most abundant orientations under reaction conditions. We catalogue a wide set of intermediates and mechanistic pathways, including the lattice oxygen mechanism (LOM) and adsorbate evolution mechanism (AEM), along with critical (rate-determining) O–O bond formation barriers and transition-state structures. In the case of NiFe2O4, we predict a Fe-site-assisted LOM pathway as the preferred OER mechanism, with a barrier (ΔG⧧) of 0.84 eV at U = 1.63 V versus SHE and a turnover frequency (TOF) of 0.26 s–1 at 0.40 V overpotential. In the case of CoFe2O4, we find that a Fe-site-assisted LOM pathway (ΔG⧧ = 0.79 eV at U = 1.63 V vs SHE, TOF = 1.81 s–1 at 0.40 V overpotential) and a Co-site-assisted AEM pathway (ΔG⧧ = 0.79 eV at bias > U = 1.34 V vs SHE, TOF = 1.81 s–1 at bias >1.34 V) could both play a role, suggesting a coexistence of active sites, in keeping with experimental observations. The computationally predicted turnover frequencies exhibit a fair agreement with experimentally reported data and suggest CoFe2O4 as a more promising OER catalyst than NiFe2O4 in the pristine case, especially for the Co-site-assisted OER pathway, and may offer a basis for further progress and optimization.

A novel self-activation strategy for designing oxygen vacancies-rich nickel ferrite and cobalt ferrite microspheres with large specific surface area for overall water splitting

Nickel ferrite (NFO) and cobalt ferrite (CFO) have been explored as promising electrocatalysts for overall water splitting in virtue of unique characteristics. However, the poor intrinsic conductivity and the limited active sites of NFO and CFO give rise to sluggish charge transfer dynamics. It is the general approach that the target products implemented as shell are tightly wrapped on the sacrificial core of silicon dioxide (SiO2) to design the hollow/porous electrode materials, while employing SiO2 as sacrificial shell could be a novel method to improve the specific surface area (SSA) of NFO and CFO. Herein, the porous nickel ferrite (P–NFO (VO)) and cobalt ferrite (P-CFO (VO)) microspheres with rich oxygen vacancies and enhanced SSA are reported through the novel self-activation treatment along with reduction process. The simultaneous formation of rich pore channels and oxygen vacancies could expose numerous active sites, optimize electronic configuration, and boost charge transfer. As expected, the elaborately designed P–NFO (VO) and P-CFO (VO) microspheres achieve excellent achievement for HER with low overpotentials (102.9 and 100.7 mV) and relatively small Tafel slopes (45.2 and 60.1 mV/dec), respectively. Beyond that, P–NFO (VO) and P-CFO (VO) microspheres deliver favorable overpotentials of 336.3 and 384.2 mV at 10 mA/cm2 for OER, respectively, which is highly considerable to transition metal oxide-based electrocatalysts. Overall, the versatile strategy could be employed to construct other transition metal oxides with superior electrochemical properties.

A facile microwave-assisted combustion synthesis of NiCoFe2O4 anchored polymer nanocomposites as an efficient electrode material for asymmetric supercapacitor application

Renewable energy storage is very important and needs of the day for all handy electronic devices. Hybrid polymer nanocomposites (PNCs) have attracted great attention recently, for these applications. In the present work, nanostructure nickel-cobalt ferrite (NiCoFe2O4) dispersed Polyvinyl alcohol (PVA)/ Poly(vinyl) pyrrolidone (PVP) nanocomposites have been prepared by a simple solution casting method. Structural studies of prepared polymer nanocomposites have been established by X-ray diffraction analysis. The presence of functional and vibrational groups of polymer nanocomposites have been identified using FTIR spectroscopy. The surface characteristics of prepared PNCs have been obtained as a non-uniform rod-like structure with porous morphology in field emission scanning electron microscopy (FESEM). Temperature dependent dielectric and electronic spectral studies have been investigated. The electrochemical characteristics such as cyclic voltammetry (CV), Galvanostatic charge-discharge (GCD) and electrical impedance spectroscopy (EIS) have been analyzed. This study resulted in maximum specific capacitance as 13.49 F g−1 at a current density of 1 A g−1 for 1 wt.% of NiCoFe2O4 (NCF) nanoparticles in polymer blended electrode and 99.39% of columbic efficiency. The supercapacitor with NCF loaded PVA/PVP as electrode is introducing an excellent prospective for practical supercapacitors owing to high surface area, good energy density and power density.

Sintering of layered ferrite-BaTiO3 ceramics: Analysis of interfaces and effects of shrinkage mismatch

In the present work, densification and microstructure evolution of cobalt ferrite (FCO), nickel-cobalt ferrite (FNICO) and BaTiO3 (TB) ceramics under different sintering conditions were investigated. Subsequently, layered ferrite-BaTiO3 samples were formed by uniaxial pressing of the corresponding ceramic powders. These green samples were sintered with two different sintering schedules, aiming to study the ferrite-BaTiO3 interfaces after sintering. The analyses were made at the cross section of the interfaces and at the interface surfaces after separation of the layers. The sintered layered samples were utilized to analyze sintering mismatch, diffusion at the interfaces and identification of some newly formed phases. EDS analysis across the TB-FCO interface showed evidences of diffusion. It was observed that the FNICO layers were detached from TB during sintering, but the same was not observed in the TB-FCO samples, although shrinkage mismatch resulted in some defects. XRD analyses suggested the presence of Ti2O at the TB-FCO interface and BaTiNiFe10O19 at the TB-FNICO interface as products of the reactions between the ferrites and BaTiO3.

Evaluation of structural, dielectric and LPG gas sensing behavior of porous Ce3+- Sm3+ doped Cobalt nickel ferrite

The Co0.5Ni0.5CexSmyFe2-x-yO4 (CNCSF) XRD pattern revealed the purity of the samples without any secondary phase. The crystallite size CNCSF are in nano range. Further, the calculated lattice parameter of CNCSF are found to increasing with the RE content. From SEM micrographs surface morphology and the microstructure of the CNCSF was studied. The porous nature of the samples is revealed by SEM, which will aid in increasing their sensing response. Energy dispersive X-ray spectroscopy (EDS) patterns have confirmed the stoichiometric presence of Co2+ Ni2+, Ce3+, Sm3+ and Fe3+, those are used to prepare the CNCSF. The dielectric behaviour is similar to that of conventional spinel ferrite structures, in that the dielectric constant is highest at low frequencies and decreases at higher frequencies due to electron hopping, resulting in dielectric dispersion. Only one semicircle is seen in each Cole-Cole plot, which has uncovered that the contribution to conductivity is predominantly from the grain boundaries. At room temperature, the gas sensing responses of CNCSF thin films were investigated. For liquified petroleum gas (LPG), the gas sensing characteristics of the prepared thin films were investigated. At room temperature, the x = 0.03 thin films showed excellent sensitivity to liquified petroleum gas. The sensing response and recovery time of all of the thin films that had been prepared were reported. The sensing response of x = 0.03 thin films was highly stable over a period of 60 days on exposure to LPG (1000 PPMv), according to the stability analysis. The sample thin film with x = 0.03 can be utilized in gas sensor technology, particularly for the detection of LPG at room temperature, due to its increased sensitivity, quick response and recovery times, and stability.

Interconnected magnetic carbon@NixCo1-xFe2O4 nanospheres with core–shell structure: An efficient and thin electromagnetic wave absorber

The applications of cobalt ferrite and nickel ferrite composite materials on electromagnetic (EM) wave absorption are the research hotspot currently. However, the systematical comparison study between these two ferrites composites have rarely been carried out. Thus, the EM wave absorption performance of interconnected carbon@NixCo1-xFe2O4 composites with core–shell structures were investigated comprehensively in this work. A series of magnetic nanospheres including NiFe2O4, cobalt-doped nickel ferrite, nickel–cobalt ferrite, nickel-doped cobalt ferrite and CoFe2O4 were synthesized firstly, and then uniformly encapsulation by carbon rendered the corresponding C@NixCo1-xFe2O4 composites nanospheres. Synthesis reactions involved for C@NixCo1-xFe2O4 formation were investigated in detail, and afterwards their magnetic behavior, EM wave absorption performance and absorbing mechanism were thoroughly explored and analyzed. Results show that when nickel is dominant element and cobalt is doping element (Ni0.75Co0.25Fe2O4), the composite nanosphere exhibits optimum EM wave absorption performance. When the sample thickness is just 1.9 mm, its RLmin value can reach −51 dB, and the corresponding EAB width is 3.3 GHz. The synthesized C@Ni0.75Co0.25Fe2O4 can be qualified as an efficient and thin electromagnetic wave absorber, which is mainly attributed to its special structure, fair electromagnetic matching and impedance matching.

Structural Elucidation and Magnetic Behavior Evaluation of Nd-doped Nickel-Cobalt Spinel Ferrites

Nano ferrites crystals of Ni0.4Co0.6NdxFe2-xO4 for 0.00 ? x ? 0.08 with step size of 0.02 were synthesized by sol gel technique with annealing at 950 oC for 6 hours. Spinel phase along with a secondary phase for Nd concentration x ? 0.04 due to formation of NdFeO3 was observed in XRD patterns. Lattice constant and grain size were found in decreasing trend with increasing concentration of Nd as compared to that of undoped nickel cobalt ferrites. X-ray density and porosity both were increased with increasing concentration of neodymium. Two characteristics frequency bands were observed in the range of 400cm-1 to 550 cm-1 which showed successful formation of spinel structure. It is also the evidence of metal-oxygen bonding at octahedral and tetrahedral sites in spinel ferrites. Also, bands for carbon-hydrogen, carboxyl group, carbon-oxygen stretching and iron-cobalt alloys were observed in the FTIR spectra. By using these values of characteristics frequencies, octahedral and tetrahedral radii were calculated and found in decreasing trend with increasing concentration. Force constants are increasing with increase in neodymium concentration. Saturation magnetization, coercivity and remanence values were calculated from the M-H loops. Saturation magnetization showed the decreasing behavior with increase in neodymium concentration. Coercivity showed increasing values as compared to the base sample and also showing reciprocal relation with saturation magnetization. Magnetic moment is decreasing with increase in neodymium concentration.

The Effect of Viscous Dissipation and Thermal Radiation in Siskoferronanofluid Flow over a Porous Medium

This Paper contributes heat transfer phenomena in mixed convection flow of Siskoferronanofluidover a porous surface in the presence of a temperature gradient heat sink with prescribed heatflux. The effect of viscous dissipation and thermal radiation on the flow field is also taken in to consideration. The three types of ferromagnetic particles Nickel Zinc ferrite (Ni–ZnFe2O4), ManganeseZinc ferrite (Mn1/2Zn1/2Fe2O4) and Cobalt ferrite (CoFe2O4) are considered with water (H2O)and Ethylene Glycol (C2H6O2) as conventional base fluids. The RungeKuttaFehlberg method of numerical methodology is used to solve momentum and energy equations. With the help of graphs andtables, the effect of various associated physical parameters on the velocity, temperature, Skin frictioncoefficient and Nusselt number is studied. The present results indicate that the heat transfer rate ofEthylene Glycol based Siskoferronanofluid is higher than that of water based fluid and also waterbased Siskoferronanofluid reduces shear stress of the fluid flow rapidly than Ethylene glycol basedfluid. The accuracy of the results comparison table is validated with the current data.

The photocatalytic performance and structural characteristics of nickel cobalt ferrite nanocomposites after doping with bismuth

Here, a novel bismuth-doped nickel-cobalt ferrite (Ni0.5Co0.5Bi0.1Fe1.9O4) was synthesized using a sol-gel auto-combustion approach. The impact of bismuth substitution on the nickel-cobalt ferrite structural characteristics was investigated relative to the nickel-cobalt ferrite without bismuth substitution (Ni0.5Co0.5Fe2O4) based on diverse technical options (e.g., scanning electron microscopy-equipped with an energy dispersive X-ray spectrometer, X-ray diffraction, physisorption, and Fourier-transform infrared spectroscopy). Bismuth doping increased the surface area without affecting pore size. The X-ray diffraction pattern confirmed a nano-ferrite cubic spinel structure of the catalyst. Photodegradation of Congo red (CR) was tested using these nickel-cobalt ferrite catalysts under visible light across varying reaction parameters (e.g., pH, catalyst loading, dye concentration, and reaction time). The photo-degradation efficiency for CR in aqueous medium was the highest (98%) at pH 3 with 0.2 g catalyst loading in 100 mL under visible irradiation to reinforce the role of nanostructures as a potent photocatalyst (QY = 2.79 × 10−7 molecule photon−1). The kinetic reaction rate of Bi-doped spinel ferrite (3.5 µmol g−1 h−1) was1.25 times higher than those undoped materials. This study experimentally proved that the bismuth-doped nickel-cobalt ferrite photocatalyst is an effective option for removing industrial dyes.

Cobalt and nickel ferrites based capacitive deionization electrode materials for water desalination applications

Capacitive deionization (CDI) is an emerging technology for water desalination and is based on electrosorption of ions onto surfaces of electrically charged electrodes. The CDI electrode materials play a significant role in determining the process efficiency. In this study, pure and mixed nickel-cobalt ferrites CoxNi1-xFe2O4 (x = 0.0, 0.3, 0.5, 0.7 and 1.0) were synthesized using the sol-gel auto-combustion method and investigated as novel CDI electrode materials. The purity, structure, and morphology of the synthesized ferrite nanoparticles were analyzed by various techniques. The electrochemical performance of the synthesized materials was investigated, and the results showed that the mixed ferrite Co0.5Ni0.5Fe2O4 electrode possessed the highest specific capacitance of 255 F/g at a scan rate of 10 mV/s. The electrodes were used to treat 250 mg/L NaCl solution in a CDI cell at 1.2 V and a feed flow rate of 10 mL/min. Under optimized experimental conditions, the highest specific salt adsorption capacity was 21.84 mg/g, corresponding to 23.43% of NaCl removal efficiency. These electrodes were highly stable and easily regenerable with less than 5% loss in electrosorption capacity for six adsorption/desorption cycles. The recyclability, stability, and enhanced electrochemical performance of the fabricated electrodes establish cobalt-nickel ferrites as a promising material for use in CDI desalination application.

Sol–gel auto-ignition fabrication of Gd3+ incorporated Ni0.5Co0.5Fe2O4 multifunctional spinel ferrite nanocrystals and its impact on structural, optical and magnetic properties

Monophasic nanocrystals of rare earth gadolinium (Gd3+) ion doped nickel–cobalt ferrite, Ni0.5Co0.5GdyFe2−yO4 (y = 0.00, 0.025, 0.050, 0.075, 0.100 and 0.125) have been synthesized by l-ascorbic acid assisted sol–gel auto-ignition process. Thermogravimetric and differential scanning calorimetry, X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) with selected area electron diffraction (SAED) patterns, ultraviolet–visible spectrophotometry and vibrating sample magnetometer were employed to characterize the microstructure, optical and magnetic properties. Structural investigations verified the presence of cubic spinel phase short of any contamination peak. The average crystallite size was seen in nano-regime dimensions and well confirmed by TEM results. SAED patterns showed bright and intense ring of (311) plane revealed the establishment of spinel ferrite nanocrystals. Lattice constant (a) increases steadily with the rise in Gd3+ content following the Vegard’s law. FTIR spectra confirmed the creation of spinel ferrite structural geometry. Saturation magnetization (Ms) and a remanence magnetization (Mr) decreased from 29.77 to 20.78 emu/g and 21.62 to 15.79 emu/g, respectively, with increasing the Gd3+ content. However, coercivity (Hc) is significantly increased. The highest value of Hc = 1132 Oe was found for y = 0.075 sample. The reduction in Ms values can be justified owing to the replacement of Fe3+ existing at the octahedral [B]-sites by the Gd3+ ions which is paramagnetic at room temperature. The elucidation of magnetic parameters with Gd3+ doping was attributed to the discrepancy of anisotropy constant, the paramagnetic nature of Gd3+ and crystallite size effect.

Ceramic-Heterostructure-Based Magnetoelectric Voltage Transformer with an Adjustable Transformation Ratio.

A voltage transformer employing the magnetoelectric effect in a composite ceramic heterostructure with layers of a magnetostrictive nickel–cobalt ferrite and a piezoelectric lead zirconate–titanate is described. In contrast to electromagnetic and piezoelectric transformers, a unique feature of the presented transformer is the possibility of tuning the voltage transformation ratio K using a dc magnetic field. The dependences of the transformer characteristics on the frequency and the amplitude of the input voltage, the strength of the control magnetic field and the load resistance are investigated. The transformer operates in the voltage range between 0 and 112 V, and the voltage transformation ratio K is tuned between 0 and 14.1 when the control field H changes between 0 and 6.4 kA/m. The power at the transformer output reached 63 mW, and the power conversion efficiency was 34%. The methods for calculation of the frequency response, and the field and load characteristics of the transformer are proposed. The ways to improve performance characteristics of magnetoelectric transformers and their possible application areas are discussed.

Study the magnetic and dielectric properties of Sn substituted nickel–cobalt ferrite synthesized by auto combustion method

Nickel–cobalt ferrites with the stoichiometry of Ni0.4Co0.6–xSnxFe2O4 (where, x = 0, 0.02, 0.04, 0.06, 0.08, and 0.10) have been synthesized by the auto combustion method. The X-ray diffraction (XRD) pattern discloses a single-phase spinel structure, and the crystallite sizes of the nanoparticles are estimated at about 12–28 nm. The diffraction peak shifts towards the lesser angle and the lattice parameter slightly improves with the Sn substitution. The surface morphology and elemental composition are examined by the scanning electron microscope (SEM) and energy dispersive X-ray analysis (EDX), respectively. At room temperature, the bulk density, grain size, and coercivity are increased with the Sn substitution. The hysteresis loops of this sintered specimen display an improved magnetic behavior at ambient temperature. The saturation magnetization increases initially and reaches to the maximum at x = 0.02 (78.05 emu/g) then decreases with higher Sn substitution. All the sintered species retain in the multi magnetic domain. Prepared samples demonstrate a slight reduction both in dielectric constant (e׳) and loss tangent (tanδ) with an increment of the Sn substitution. The proposed work is expected to open the possible emersion of the ferrite in the high-frequency applications.