Electronic structure and magnetic properties of Ba1-xSrxCoFe11O19 hexaferrites

We have prepared Ba_1-xSr_xCoFe₁₁O₁₉ hexaferrite nanoparticles (NPs) by using a co-precipitation method. The crystal/electronic structures and magnetic properties were then studied. Results revealed that all Ba_1-xSr_xCoFe₁₁O₁₉ NPs with particle sizes of 100–300?nm crystallized in a hexagonal structure. Both the particle shape and the unit-cell parameters are changed when Sr content (x) increases. The analysis of the electronic structure based on the Fe and Co K-edge XAS spectra proved the oxidation states of Fe and Co to be 3?+?and 2?+?, respectively, which are stable versus an x change in Ba_1-xSr_xCoFe₁₁O₁₉. Local-structural studies also revealed the average bond length between Fe and O of 1.89–1.91?Å less changed by Sr doping. Though the electronic structures of Fe and Co were unchanged, the studies about the magnetic property demonstrated a strong dependence of M_s and H_c on Sr doping. While M_s decreases from 46.1?emu/g for x?=?0–34.2?emu/g for x?=?1, H_c tends to increase from 1630?Oe for x?=?0 to ~ 2200?Oe for x?=?0.5, but slightly decreases to 2040?Oe for x?=?1. We think that the addition of the exchange interaction between Fe³⁺ and Co²⁺ ions and the changes of local-geometric structures and microstructures influenced directly M_s and H_c of NPs.     

Rapid microwave-assisted synthesis and magnetic properties of high-entropy spinel (Cr0.2Mn0.2Fe0.2Co0.2-xNi0.2Znx)3O4 nanoparticles

High-entropy oxide (HEO) has recently become popular because of its unique multifunctional performance. In this study, we developed a novel microwave-assisted method for the production of HEO nanoparticles with the composition (Cr_0.2Fe_0.2Mn_0.2Co_0.2-xNi_0.2Zn_x)₃O₄ (x = 0, 0.05, 0.1, and 0.2). The results revealed that all metallic elements were uniformly distributed throughout the single-phase cubic spinel structure of the HEO nanoparticles. The particle size distributions of four fabricated samples ranged from 10 to 50 nm. Because of its numerous advantages such as the ultrafast and low-temperature fabrication of nanoscale and high-purity products at a relatively low cost, the suggested methodology is an excellent synthesis method. The original HEO spinel (x = 0) achieved saturated magnetization (M_s) and coercivity (H_c) values of 24.3 emu/g and 160 Oe, respectively, at room temperature. Zinc substitution in the HEO composition indicated that M_s and H_c decreased with increasing zinc concentration owing to its non-magnetic nature.     

Hierarchical spinel NixCo1-xFe2O4 microcubes derived from Fe-based MOF for high-sensitive acetone sensor

Hierarchically spinel Ni_xCo_1-xFe₂O₄ (0.0?≤?x?≤?0.5) microcubes were successfully prepared through a combined solvent evaporation strategy and morphology-inherited annealing treatment. By using the Fe-based metal-organic frameworks (MOFs), Fe₄(Fe(CN)₆)₃, and inorganic Ni²⁺and Co²⁺ acetate salts as co-templated precursors, hierarchical Ni-doped spinel CoFe₂O₄ architecture can be obtained, and the Ni/Co substitution ratios can be controlled systematically. The obtained cubic hierarchical Ni_xCo_1-xFe₂O₄, (0.0?≤?x?≤?0.5) composites presented highly acetone sensing properties, among which the Ni_0.1Co_0.9Fe₂O₄ composite showed the strongest response performance (with gas response (R_g/R_a) of 1.67 at 240?°C) and excellent reproducibility (for at least 14 cycles), and the proposed acetone sensing mechanism was also discussed. The presented solvent evaporation and co-templated strategy may allow precisely access to fabricating other heteroatom doped inorganic materials with intriguing morphologies, architectures, chemical compositions and tunable sensing properties.     

Synthesis and magnetic properties of monodisperse CoFe2O4 nanoparticles coated by SiO2

The monodisperse CoFe₂O₄ nanoparticles were synthesized by a modified chemical coprecipitation method. Coating SiO₂ on the surface of the CoFe₂O₄ nanoparticles was carried out to keep single domain particles non-interacting with cubic magnetocrystalline anisotropy. The Curie temperatures (T_c) of the monodisperse CoFe₂O₄ nanoparticles can be accurately measured because the SiO₂ shells prevented the aggregation and growth of nanoparticles at high temperature. The magnetic properties of the CoFe₂O₄@SiO₂ nanoparticles with core-shell structure in a wide temperature range (300～950?K) were investigated. It is remarkable that the coercive field (H_c) of CoFe₂O₄ nanoparticles increased from about 760?Oe to 1806?Oe after being coated with SiO₂, which increased by 137.6% compared to the uncoated samples at 300?K. The saturation magnetization (M_s) of the CoFe₂O₄@SiO₂ nanoparticles is 34.59?emu/g, which is about 52% of the naked CoFe₂O₄ nanoparticles value (66.51?emu/g) at 300?K. The hysteresis loops of the CoFe₂O₄@SiO₂ nanoparticles showed an orderly magnetic behavior at high temperature, such as the M_s, remanence magnetization (M_r) and H_c decreased as temperature increasing, being equal to zero near T_c. This is a good indication that the CoFe₂O₄@SiO₂ nanoparticles are suitable for a wide variety of technological applications at high temperature.     

Structural and thermoelectric properties of hydrothermal-processed Ag-doped Fe2O3

Fe_2-xAg_xO₃ (0?≤?x?≤?0.04) nanopowders with various Ag contents were synthesized at different hydrothermal reaction temperatures (150?°C and 180?°C). Their structural properties were fully investigated through an X-ray diffraction, a Fourier transform infrared spectroscopy, and an X-ray photoelectron spectroscopy. The hydrothermal reaction temperature, time, and Ag content remarkably affected the morphological characteristics and crystal structure of the synthesized powders. The Fe_2-xAg_xO₃ (0?≤?x?≤?0.04) powders synthesized at 150?°C for 6?h and the Fe_2-xAg_xO₃ (0.02?≤?x?≤?0.04) powders synthesized at 180?°C for 12?h formed the orthorhombic α-FeOOH phase with a rod-like morphology, whereas the Fe_2-xAg_xO₃ (0?≤?x?≤?0.01) powders synthesized at 180?°C for 12?h formed the rhombohedral α-Fe₂O₃ phase with a spherical-like morphology. The Fe_1.98Ag_0.02O₃ fabricated by utilizing Fe_1.98Ag_0.02O₃ powders synthesized at 180?°C showed the largest power factor (0.64?×10^?5 Wm^?1 K^?2) and dimensionless figure-of-merit (0.0036) at 800?°C.     

Effects of Y–Co co-substitution on the structural and magnetic properties of M-type strontium hexaferrites

Y³⁺- and Co²⁺-substituted Sr_1-xY_xFe_12-xCo_xO₁₉ (0 ≤ x ≤ 0.50) M-type hexaferrites were synthesized using a traditional oxide ceramic process to study their structural and static magnetic properties. The well-defined M-type phase structures of the pure and Y–Co co-substituted strontium ferrites were verified via XRD analysis. When the Y–Co substitution amount (x) exceeded 0.20, the Fe₂O₃, Y₃Fe₅O₁₂, SrFe₂O₄, and CoFe₂O₄ impurity phases coexisted in the M-type strontium hexaferrite structure. The lattice parameters a and c increased when x ≤ 0.20; however, a further increase in the Y–Co substitution caused them to decrease. The X-ray density d_x initially decreased when x ≤ 0.20, and subsequently increased with a further increase in Y–Co substitution. The density of the sintered samples d_s exhibited a decreasing trend with the increasing Y–Co substitution, inducing the porosity to increase. The saturation magnetization M_s monotonously decreased with the increasing Y–Co substitution amount. The in-plane and out-of-plane coercivities, H_c(ip) and H_c(op), initially increased as x increased from 0 to 0.20. When x > 0.20, however, H_c(ip) exhibited a decreasing trend; particularly, a linear decrease was observed as x increased from 0.30 to 0.50. The squareness ratio S reached its maximum (79.6%) at x = 0.20.     

Simultaneous improvement of coercivity and saturation magnetization of M-type strontium ferrite by Nd3+-Co2+ unequal co-substitution

We synthesized Sr_1-xNd_xFe_12-yCo_yO₁₉ (x = 0–0.25, y = 0–0.1) using a conventional ceramic route. The crystal structures were analyzed using X-ray diffraction. With increasing Nd³⁺ and Co²⁺ contents, lattice constant a increases, while lattice constant c decreases. In terms of magnetic properties, the saturation magnetization and coercivity are simultaneously increased when x = y = 0.1 (equal co-substitution). This is mainly because the bivalent Co²⁺ has a smaller magnetic moment and unquenched orbital moments. When substitution amount x is further increased (unequal co-substitution), the magnetic properties are further improved and reach the optimum values of M_s = 76.4 emu/g and H_c = 5115 Oe owing to the occupation of the 2a site by divalent Fe²⁺. The occupancies of Co²⁺ and Fe²⁺ are further verified using Raman spectroscopy.     

The role of Co ion substitution in SnFe2O4 spinel ferrite nanoparticles: Study of structural,vibrational, magnetic and optical properties

In order to accurately investigate the effect of cobalt substitutions in tin ferrite (SnFe₂O₄) properties, we prepared Co_xSn_1-xFe₂O₄ nanoparticles for different Co concentrations, x?=?0.0, 0.25, 0.50, 0.75, and 1.00 using a simple co-precipitation method. X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), vibrating sample magnetometer (VSM), field emission scanning electron microscopy (FESEM), Energy-dispersive X-ray spectroscopy (EDX) and diffuse reflectance spectra (DRS) are used to study of structural, magnetic, morphology, and optical properties. The XRD and FTIR results confirmed the formation of cubic spinel structure. The lattice parameter and unit cell volume of tin ferrite nanoparticles were found to increase by entering and increasing Co⁺² content in 0.25, and then significantly decrease for higher contents. In accordance with the XRD results, a slight shift in main band υ₁ (${\mathit{Fe}}_{\mathrm{tetra}}^{+3}?O)$ to lower wavenumber and then to higher wavenumber were observed in the IR spectra of Co content x?<?0.25 and x?>?0.25, respectively. In turn to, saturation magnetization, remanent magnetization and anisotropy constant of SnFe₂O₄ nanoparticles were gradually increased for x?=?0.50 and then decreased for x?>?0.50.     

Structure,morphology and magnetic properties of Au/Fe3O4 nanocomposites fabricated by a soft aqueous route

Magnetic Fe₃O₄ (magnetite) nanoparticles are synthesized via a chemical precipitation route in different alkaline environments (NH₃ or NaOH) and subsequently functionalized with a (propynylcarbamate)triethoxysilane moiety, with the aim of promoting the nucleation and subsequent stabilization of gold nanoparticles. The propynylcarbamate group is able to capture the gold precursor (HAuCl₄), spontaneously reduce it, and stabilize the resulting Au nanoaggregates. The obtained results show that though the dimensions of the starting magnetite substrate depend on the base used in the preparation, they remain unaltered upon the subsequent modification. Conversely, the average Au nanoparticle dimensions can be conveniently tailored as a function of the base used in Fe₃O₄ preparation and the presence/absence of the organic functionalization. The smallest dimensions (15?nm) are obtained for AuNP supported on propynylcarbamate-functionalized Fe₃O₄ prepared in the presence of ammonia. Magnetization measurements highlight that all the Au/Fe₃O₄ nanocomposites display a superparamagnetic behavior and those obtained using ammonia showed consistently smaller Hc and Mr values (av. values of 7.4?Oe and 0.8?emu/g) than those prepared with sodium hydroxide (av. values of 28?Oe and 2.8?emu/g).     

Redistribution of Cations Amongst Different Lattice Sites in Cu1−x Co x Fe2O4 Ferrospinels During Alkylation: Magnetic Study

A series of Cu_1?x Co _x Fe₂O₄ (x = 0, 0.25, 0.5, 0.75, 1.0) ferrospinels prepared by low temperature coprecipitation method and glycine nitrate combustion method has been studied in gas phase methylation of phenol. Phenol methylation gives mainly o-cresol and 2,6-xylenol as major products and among various compositions, x = 0.50 shows good catalytic performance irrespective of the preparation method. The difference in properties of the fresh and spent catalysts was thoroughly characterized by adopting various physico-chemical characterization techniques with special emphasize on magnetic measurements. Various conclusions derived from magnetic study are in good agreement with our previous study of XRD and Mossbauer on same catalyst system. Redistribution of cations occurred during the reaction is evidenced from the increase of saturation magnetization in the spent. Spent x = 0.0 shows high T _c close to the value of Fe₃O₄ indicating that the material has ended with a solid solution of Fe₃O₄ and CuFe₂O₄ along with other reduced phases.     

High-temperature thermoelectric properties of Sm3+-doped Ca3Co4O9+δ fabricated by spark plasma sintering

Ca_3-xSm_xCo₄O_9+δ (0 ≤ x ≤ 0.3) samples were fabricated by the sol-gel method followed by spark plasma sintering in vacuum. The high-temperature thermoelectric properties of the Ca_3-xSm_xCo₄O_9+δ were also studied, with an emphasis placed on the partial substitution of Sm³⁺ for Ca²⁺. The sintered Ca_3-xSm_xCo₄O_9+δ formed a monoclinic Ca₃Co₄O₉ phase and exhibited fine lamellar grains and dense morphology. With increased Sm³⁺ content, the electrical and thermal conductivities decreased, whereas the Seebeck coefficient significantly increased. Of the prepared samples, Ca_2.7Sm_0.3Co₄O_9+δ had the largest dimensionless figure-of-merit (0.175) at 800 °C. The results showed that the partial substitution of Sm³⁺ for Ca²⁺ in Ca₃Co₄O_9+δ is effective for enhancing its thermoelectric properties.     

Magnetic properties of randomly oriented BaM, SrM, Co2Y, Co2Z and Co2W hexagonal ferrite fibres

The microstructure and magnetic properties of randomly oriented BaFe₁₂O₁₉, SrFe₁₂O₁₉, Ba₂Co₂Fe₁₂O₂₂, Ba₃Co₂Fe₂₄O₄₁, Ba₃Ca_0.3Co₂Fe₂₄O₄₁ and BaCo₂Fe₁₆O₂₇ hexaferrite fibres were characterised. 2D and 3D AFM and MFM images were taken of a single BaM fibre. Magnetic properties of random ferrite fibres compared well to expected values for polycrystalline ceramics. The little-characterised Co₂W ferrite was found to have M_s and H_c similar to that of Co₂Z. Relatively small applied fields of <0.05 T were required to reverse the magnetisation of all the soft hexaplana ferrite fibres, and all had H_c < 40 kA/m, becoming demagnetised in fields <0.025 T. Random Co₂W fibres had a high M_r/M_s ratio of 0.56, (greater than M ferrites), despite being very magnetically soft (low coercivity), due to the unusual “lobed” shape of their hysteresis loop, which was attributed to their fibrous nature, and elongated growth of the grains along the fibre axis. Co₂Z had the lowest H_c of all the ferroxplana fibres.     

Resistive switching behavior and improved multiferroic properties of Bi0.9Er0.1Fe0.98Co0.02O3/Co1-xMnxFe2O4 bilayered thin films

Bilayered Bi_0.9Er_0.1Fe_0.98Co_0.02O₃/Co_1-xMn_xFe₂O₄ (BEFCO/CM_xFO) thin films were deposited by the sol-gel method. Structural variations between the triclinic-P1 and trigonal-R3c:H (two-phase coexistence) phases in the BEFCO layer were observed owing to the trigonal-R-3m:H phase existing in the CM_xFO layer. The oxygen vacancy concentrations of the BEFCO/CM_xFO bilayered films are reduced by Mn-doping in the bottom CFO layer. The BEFCO/CFO films showed high oxygen vacancy concentrations with a high leakage current. This induced changes of the significant potential barrier at the interface between the BEFCO and CM_xFO layers in the processes of electron capture and release. Thus, the BEFCO/CFO film exhibited obvious resistive switching (RS) effect. The high leakage current also caused a fake polarization phenomenon with a blow up of the P-E loop in the BEFCO/CFO films. However, the real and outstanding ferroelectric properties, which resulted from the fewer oxygen vacancies and the 38% triclinic-P1 structure, were obtained in the BEFCO/CM_0.3FO films (P_r~156.3?μC?cm^?2). In addition, the typical capacitance-voltage curve further confirmed its superior ferroelectric performance. The RS effect almost disappeared in the BEFCO/CM_0.3FO bilayered films. Moreover, the enhanced ferromagnetic properties (M_s~100.36?emu?cm^?3, M_r~55.38?emu?cm^?3) were obtained for the BEFCO/CM_0.1FO films, which was attributed to the magnetic properties of BEFCO (a more triclinic-P1 phase and numerous Fe²⁺ ions), in addition to the CM_xFO layer. The introduction of the doped magnetic layer into the bilayered films thus represented a highly effective method for enhancing the multiferroic properties of BFO.     

Low temperature sintering of magnetic Ni0.5Co0.5Fe2O4 ceramics prepared from mechanochemically synthesized nanopowders

The effect of mechanochemichally synthesized nanoceramics Ni_0.5Co_0.5Fe₂O₄ (NCF) on the sintering process was studied. After 60?h of mechanochemichal treatment, the amount of formed ferrite phase reaches to about 70?vol%. From 60–100?h 10% increase in volume fraction of synthesized magnetic phase can be observed. Further increment in process time had no remarkable effect on the NCF phase formation. After 60?h, ceramic nanoparticle formation is directly reflected by TEM image and specific surface area (28?m²/g equivalent to 40?nm in diameter). The coercivity (Hc) shows a drastic diminution from 1996 to about 159?Oe by 60?h process time. Further milling treatment has no observable effect on the values of Hc. Additionally, the magnetization saturation (Ms) increases up to ~13?emu/g by 60?h mechanical milling of powders mixture. Thereafter from 60?h to 100?h, the Ms rapidly increased from 13 to 32?Oe. Finally, with continuing mechanochemichal process up to 130?h the Ms slightly diminished (~29?emu/g). Additionally, compared to synthesized powders the higher values of M_S (65?emu/g) and lower values of H_C (140?Oe) for sintered ceramic were detected. The low sintering temperature (1300?°C) for magnetic NCF sample prepared from nanoparticles may be caused by the high activity of nanoceramics.     

Structural,magnetic, thermal and optical properties of Sn2+ cation doped magnetite nanoparticles

Tin doped nanomagnetites, Sn_xFe_3-xO₄, were synthesized with various concentrations of Sn²⁺ ion (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) by co-precipitation method. XRD, VSM, TG-DTA, SEM-EDX and UV–Vis were used to characterize and study the structural, magnetic, thermal, and optical properties of Sn_xFe_3-xO₄ nanoparticles. XRD confirmed the presence of cubic structure and spinel phase of tin doped magnetites. The d-spacing, lattice parameter, density, crystallite size and cation distribution were derived from the XRD analysis. The M − H curves exhibited changes in saturation magnetization (M_s), coercive field (H_c), remanent magnetization (M_r) and susceptibility (χ), with increasing concentration of non-magnetic Sn²⁺ ions. Differential thermal analysis was used to study the thermal stability of Sn_xFe_3-xO₄ nanoparticles. The SEM images revealed the surface morphology of the nanoparticles and the EDX spectra showed an increase in the Sn content and a corresponding decrease in the Fe content for the tin doped samples. The optical bandgap was found to be centered at 3.9 eV for the synthesized materials. This systematic study may be the first comprehensive report on synthesis and characterization of tin doped magnetites.     

Dielectric and magnetoelectric properties of BaTiO3–Co0.6Zn0.4Fe1.7Mn0.3O4 composite

In this paper we studied the structural, dielectric, magnetic and magnetoelectric properties of (x)BaTiO₃–(1 ? x)Co_0.6Zn_0.4Fe_1.7Mn_0.3O₄ particulate composite series where x = 0.50, 0.60 and 0.70. BaTiO₃–Co_0.6Zn_0.4Fe_1.7Mn_0.3O₄ composite has the advantage of being non-toxic and environmental friendly from the point of view of device fabrication. High ME voltage coefficients were obtained in the whole series with the highest value of α_E ～ 73 mV/cm Oe achieved in sample x = 0.50 containing equal mole fractions of both the component phases. This value of α_E is an order of magnitude higher than that of particulate sintered BaTiO₃–CoFe₂O₄ composites (～2–4 mV/cm Oe). Dielectric characteristics for these samples indicated two anomalies: (i) one at low temperature close to ferroelectric to paraelectric transition temperature of pure BaTiO₃ and (ii) another at higher temperature related to the magnetic transition in ferrite, a characteristic dielectric feature of composite sample.     

Oxidative Dehydrogenation of Ethylbenzene over Cu1-x Co x Fe2O4 Catalyst System: Influence of Acid–Base Property

A series of Cu–Co ferrites with the general formula Cu_1-x Co _x Fe₂O₄ (x = 0, 0.25, 0.50, 0.75 and 1.0) was prepared by a low-temperature hydroxide coprecipitation route. The catalyst systems were characterized by adopting various physicochemical techniques. The acid–base properties were studied in detail, and the catalytic activity as well as the selectivity for oxidative dehydrogenation of ethylbenzene was compared for various compositions. FTIR adsorption of pyridine is carried out to understand the relative acidity of various compositions of the systems. IR studies of spinel surface with adsorbed CO₂ and adsorption studies of electron acceptors such as 7,7,8,8-tetracyanoquinodimethane, 2,3,5,6-tetrachloro-1-4-benzoquinone and p-dinitrobenzene are carried out to evaluate the nature of basic sites and the strength and distribution of electron donor sites present on the spinel surface. It is found that acidity (basicity) of the Cu_1-x Co _x Fe₂O₄ spinel system increases (decreases) from x = 0 to 1. A good correlation was found between the activity for this reaction and the surface acid–base properties of the catalysts. Intermediate compositions show better catalytic performance, among which x = 0.50 is superior and demonstrates an intermediate acid–base character. It was observed that dehydrogenation of ethylbenzene to styrene proceeds mainly on an acid–base pair site.     

Co and Fe co-doping influence on functional properties of SrTiO3 for use as oxygen transport membranes

Perovskite-structured powders of SrTi_1-xCo_xO_3-δ (STC-x) with nominal stoichiometry of x?=?0–0.75 as well as SrTi_0.75Co_0.25-yFe_yO_3-δ (STCF-y) where y?=?0–0.25 were synthesized using the Pechini method. Thermal/chemical expansion behaviour, total electrical conductivities, and oxygen permeation rates were investigated. The substitution of Ti with Co leads to an increase in both electronic and ionic conductivities and, therefore, oxygen permeability. Thermal and chemical expansions also increase slightly. The optimum Co content was found to be 25–35% due to the trade-off between phase stability and permeability. The oxygen permeation rate of STC35 is comparable to that of state-of-the-art (La,Sr)(Co,Fe)O_3-δ, whereas the expansion coefficients are lower. Co-doping in STCF-y did not produce any significant differences in oxygen permeability at both high temperature and sample thickness (1.0?mm), i.e. in a solid-state diffusion-limited regime. At lower temperatures (<800?°C), STC25 exhibits higher permeability than STF25 due to the higher catalytic activity of Co compared to Fe.     

Effect of Nb substitution on magnetic,ferroelectric and photocatalytic properties of Bi0.95Sm0.05Fe1-xNbxO3 (0 ≤ x ≤ 0.1) nanoparticles

The single phase Bi_0.95Sm_0.05Fe_1-xNb_xO₃ (0 ≤ x ≤ 0.1) nanoparticles were synthesized by the sol-gel route, and the effect of Nb substitution on their magnetic, ferroelectric and photocatalytic properties were studied. X-ray diffractometry confirms a phase transformation from rhombohedral to orthorhombic with an increase in Nb substitution. The grain size decreases significantly, and the morphology of grains becomes homogeneous with the increase of Nb concentration. The maximum remnant magnetization (0.014 emu/g), coercivity (565 Oe) and polarization (0.592 μC/cm²) are observed in Bi_0.95Sm_0.05Fe_0.9Nb_0.1O₃. It has been observed that the energy band gap has been slightly reduced from 2.14 to 2.03 eV with Nb substitution, indicating an improvement of photocatalytic activity. The methylene blue degradation is used to represent the photocatalytic ability of Bi_0.95Sm_0.05Fe_1-xNb_xO₃ nanoparticles. The highest degradation efficiency (~74%) of methylene blue is obtained in Bi_0.95Sm_0.05Fe_0.93Nb_0.07O₃, which is much higher than that of Bi_0.95Sm_0.05FeO₃ (~51%) and can be attributed to the optimum particle size and the smallest energy band gap.     

Synthesis and analysis of structural,compositional, morphological,magnetic, electrical and surface charge properties of Zn-doped nickel ferrite nanoparticles

Zn-doped nickel ferrite nanoparticles (Zn_xNi_(1-x)Fe₂O₄) were synthesized using the co-precipitation technique. The structural and compositional studies of the Zn_xNi_(1-x)Fe₂O₄ nanoparticles revealed their face-centred cubic spinel structure and an appropriate amount of Zn doping in nickel ferrite nanoparticles, respectively. The morphological analysis had been carried out to obtain the particle size of the synthesized nanoparticles. The magnetic studies revealed the superparamagnetic nature of the Zn_xNi_(1-x)Fe₂O₄ nanoparticles, and the maximum magnetization of 30 emu/g for the Zn_0.2N_0.8Fe₂O₄ sample. The M ? H curves were fitted with the Langevin function to obtain the magnetic particle diameter of Zn_xNi_(1-x)Fe₂O₄ nanoparticles. The electrical conduction in Zn_xNi_(1-x)Fe₂O₄ nanoparticles was explained through the Verway hopping mechanism. The Zn_0.2N_0.8Fe₂O₄ nanoparticle exhibited a higher electrical conductivity of 42 μS/cm and surface charge of ?29/7 mV due to the enhanced hopping of Fe³⁺ ions in the octahedral sites. Owing to this nature, they were identified as the suitable candidates in the applications such as thermoelectrics, hyperthermia, magnetic coating and for the preparation of conducting ferrofluids.