Spinel Structure Research Articles

Novel Syntheses of Wide-Band Gap Semiconducting CdxZnx−1Co2O4 of Spinel Nanostructure: Characterization and Optical Properties

AbstractCadmium doped zinc cobaltite spinel structure in the form of CdxZnx-1Co2O4 (0 ≤ x ≤ 1) are synthesized by sol-gel method. The energy dispersive X-ray spectra confirm the synthesis of pure ZnCo2O4 and Cd doped samples nanoparticles. Scanning and transmission electron microscopes images of Cd ZnCo2O4 samples show the cubic crystal structure of the nanoparticles. A good crystallinity of the ZnCo2O4 and its dopants samples are indicated by the sharpness and strong peaks of X-ray diffraction patterns. The particle size is independent of the ratio of incorporated Cd into the ZnCo2O4 matrix. The FT-IR transmission spectrum of each Cdx Zn1-xCo2O4 complex shows two strong vibration peaks that are ascribed to the spinel structure’s octahedral and tetrahedral. The absorption spectra reveal three distinct absorption characteristics for Cdx Znx-1Co2O4 peaking at 268, 532 and 778 nm due to the photoexcitation of electrons from O 2p to Co 3d transitions and d-d transition of Co 3d. N2 adsorption–desorption isotherms for Cdx Znx-1Co2O4 indicate are carried out.

Morphology‐Dependent Catalytic Activity of ZnFe2O4 Spinel Toward Light Olefins from Fischer–Tropsch Synthesis

AbstractThe shape‐defined ZnFe2O4 spinel with cubic and octahedral morphology was hydrothermally synthesized, respectively, and used as catalyst precursor for Fischer–Tropsch synthesis (FTS). The structure of ZnFe2O4 spinel was changed to ZnO and Fe5C2 (Fe5C2/ZnO) after reduction and carbonization. Interestingly, ZnFe2O4 with cubic morphology exhibited much higher catalytic activity and selectivity toward low‐carbon olefins (C2–C4) than the octahedral one under identical conditions, and the latter tended to produce the saturated alkanes. The primary properties of ZnFe2O4 materials before and after reduction were systematically studied through a series of characteristic technologies to reveal the difference in catalytic performance between the two ZnFe2O4 spinels with different morphologies.

Research on Deoxygenation Pyrolysis of Larch Based on Microwave Heating

Aiming at problems such as low energy utilization efficiency and the high oxygen content of liquid products in the process of conventional biomass conversion to prepare liquid fuels, the deoxygenation pyrolysis technology route of larch based on microwave heating was proposed in this paper. Two kinds of calcium–iron composite oxygen carriers, including Ca2Fe2O5 with iron ore structure and CaFe2O4 with spinel structure, were successfully synthesized. The results showed that the selectivity of ideal products was improved under the action of single iron-based oxygen carriers; however, the deoxygenation effect was undesirable. Under the action of CaFe2O4, the selectivity of aromatics was increased to 27.17% and the selectivity of phenols was decreased to 36.46%, which mainly existed in the form of O1P with low oxygen content. The oxygen content of bio-oil was reduced to 27.70% and the calorific value was increased to 29.05 MJ/kg, thus leading to a great improvement in the quality of liquid products. After the pyrolysis reaction, the Fe2P3/2 XPS peak of CaFe2O4 shifted to a higher binding energy and was characterized as higher valence of iron oxide, which proved its “oxygen grabbing” capacity in microwave pyrolysis. The deoxygenation conversion of larch without an external hydrogen supply was achieved.

Optimization Strategies of Hybrid Lithium Titanate Oxide/Carbon Anodes for Lithium-Ion Batteries

Lithium-ion batteries, due to their high energy density, compact size, long lifetime, and low environmental impact, have achieved a dominant position in everyday life. These attributes have made them the preferred choice for powering portable devices such as laptops and smartphones, power tools, and electric vehicles. As technology advances rapidly, the demand for even more efficient energy storage devices continues to rise. In lithium-ion batteries, anodes play a crucial role, with lithium titanate oxide standing out as a highly promising material. This anode is favored for its exceptional cycle stability, safety features, and fast charging capabilities. The impressive cycle stability of lithium titanate oxide is largely due to its zero-strain nature, meaning it undergoes minimal volume changes during lithium-ion insertion and extraction. This stability enhances the anode’s durability, leading to longer battery life. In addition, the lithium titanate oxide anode operates at a voltage of approximately 1.55 V vs. Li+/Li, significantly reducing the risk of dendrite formation, a major safety concern that can cause short circuits and fires. The material’s spinel structure, with its large active surface area, further allows fast electron transfer and ion diffusion, facilitating fast charging. This review explores the characteristics of lithium titanate oxide, the various synthesis methods employed, and its integration with carbon materials to enhance cycle stability, coulombic efficiency, and safety. It also proposes strategies for optimizing lithium titanate oxide properties to create sustainable anodes with reduced environmental impact using eco-friendly routes.

Mechanical properties of (Ni, Fe)Cr2O4 polycrystal spinels studied by molecular dynamics simulations.

The elastic moduli and mechanical properties at the onset of crack in nanocrystalline and nanoporous (Ni, Fe)Cr2O4 compounds with a spinel structure are investigated by molecular dynamics simulations. The polycrystalline structures generated contain nanograins from 2.5 to 30nm in diameter. These structures are representative of the internal corrosion layer in nickel-based alloys. These simulations enabled us to establish the evolution of elastic moduli as a function of the composition, porosity, and grain size of the polycrystals. From this evolution, the initial database for the elastic properties of corrosion layers based on von Bertalanffy growth functions was determined. The onset of crack in polycrystals is also investigated via uniaxial tensile and shear deformation. Under shear deformation, flow stress as a function of grain size follows normal and inverse Hall-Petch regimes. The regime change occurs for grain sizes around 10nm. For grain sizes under this threshold, shear banding involving collective translation and rotation of nanograins dominates the plastic deformation. For grain sizes greater than 10nm, phase transition inside grains from a spinel to a post-spinel-like structure is observed as well. In that case, phase transition dominates the plastic deformation. Under uniaxial tensile deformation, intergranular decohesion occurs. The general law as a function of grain size for toughness, which is the material's capacity to absorb elastic and plastic energy prior to failure, is also established.

Construction of Ternary Zn0.5Cu0.5Co2O4 Spinel Structure on Nickel Foam: A Comprehensive Theoretical and Experimental Study from Single to Ternary Metal Oxides for High-Energy-Density Asymmetric Supercapacitor Application.

Developing nanostructured multi-transition metal-based spinel architectures represents a strategic approach for boosting the energy density of supercapacitors while preserving high power density. Here, the influence of incorporating Zn and Cu into Co3O4 spinel systems on supercapacitor performance is investigated by synthesizing single (ZnO, CuO, Co3O4), binary (ZnCo2O4, CuCo2O4), and ternary (Zn0.5Cu0.5Co2O4) oxides on nickel foam substrates. Theoretical and experimental analyses highlight that the flower-like structures of Zn0.5Cu0.5Co2O4, comprising nanowires and nanoribbons, effectively reduced transport barriers and enhanced ion adsorption, thereby improving electron/ion reaction kinetics. Oxygen vacancies induced defect states in Zn0.5Cu0.5Co2O4, shifting the d- and p-band center values closer to the Fermi level and enhancing electrochemical performance. The Zn0.5Cu0.5Co2O4 exhibits a specific capacity of 271 mA h g-1 (1776 F g-1) at 1 A g-1 with 97% capacity retention after 5000 charge/discharge cycles. In a Zn0.5Cu0.5Co2O4//activated carbon configuration, the device demonstrates superior energy and power densities of 122.2 Wh kg-1 and 800 W kg-1, respectively, maintaining 91% capacitance after 10000 cycles at 30 A g-1 with high coulombic efficiency. This study presents an effective strategy to enhance ion/charge transfer and adsorption in multi-transition metal spinel architectures, advancing the development of supercapacitor electrodes.

Longitudinal (α33) and transverse(α31) dynamic magnetoelectric hysteretic response for CoFe1.88Dy0.12O4–K0.5Na0.5NbO3 lead-free multiferroic laminates

The magnetoelectric (ME) laminate structures of CoFe1.88Dy0.12O4 (CFDO, Ferrite) and K0.50Na0.50NbO3 (KNN, ferroelectric/piezoelectric) phases were fabricated by silver epoxy bonding technique and tested the ME response in longitudinal and transverse mode. The CFDO reveals the cubic spinel structure while KNN reveals the perovskite orthorhombic crystal structures having dense microstructure. The CFDO confirms the phase segregation of the DyFeO3ortho-ferrite phase, while the KNN lead-free ceramic showed the Curie temperature of 416 °C, 13µC/cm2 maximum polarization, 25,296 × 10-15 m2/N figure of merit, piezoelectric charge coefficient d33 of 47 pC/N. The longitudinal (α33) and transverse (α31) dynamic magnetoelectric response is studied to figure out the effective magnetic field direction to get better values of magnetoelectric voltage sensitivity i.e. αME. Both modes revealed the hysteretic behavior i.e. lagging of ME voltage response to an applied magnetic field which evidences a true multiferroic character of CFDO/KNN laminates. Remarkably, the (CFDO /KNN/ CFDO) structure demonstrated a substantial magnetoelectric coefficient in LT (α31) mode of approximately 38.5 mV/cm·Oe at a magnetic field of 400 Oe and −37.55 mV/cm·Oe at a magnetic field of −400 Oe. Thus, here we present the magnetoelectric laminate structure of CFDO /KNN/ CFDO phases beneficial for magnetic field sensors.

Thermal decomposition behavior and kinetic mechanism of waste phosphors during sodium hydroxide roasting

Waste phosphors are critical rare earth secondary resources, and their recycling can help alleviate the depletion of rare earth mineral resources. However, stable Al–Mg spinel structures exist in waste phosphors. The direct acid leaching method remains difficult to use for leaching cerium and terbium. In this paper, the waste phosphors were first pretreated via alkali roasting. NaOH was used as an alkali roasting agent, thus achieving the decomposition of the Al–Mg spinel structure. On the basis of thermodynamic calculations, thermal decomposition experiments were performed. The results showed that when the temperature was greater than 500°C, the waste phosphors could be decomposed into MgO, Eu2O3, Y2O3, CeO2, Tb4O7, NaAlO2, and BaO. The Ce3+ and Tb3+ in the waste phosphors were partially oxidized to Ce4+ and Tb4+, respectively, during the roasting process. The BET surface area and the average pore diameter for the roasted products also increased. Under the conditions of roasting temperature at 900°C, NaOH/sample mass ratio of 2.5, and roasting time of 150min, the leaching efficiencies of Y, Eu, Ce, and Tb could reach 99.4%, 99.1%, 98.5%, and 98.8%. The decomposition process of waste phosphors conformed to the unreacted shrinking core model. In addition, the conversion processes of Ce and Tb depended on the chemical reaction. The results may provide a new direction of development for the resource utilization of waste phosphors.

Impact of Al3+ substitution on structural, Raman, transport electromagnetic properties of LiFe2O4 nanoparticles

Nanocrystalline Li0.5AlxFe2.5-xO4(x = 0.0 to 0.8 in steps, x = 0.2) compounds were prepared using the sol-gel auto-combustion technique. X-ray diffraction (XRD) analysis confirmed the single-phase cubic spinel structure, which showed that the lattice constant changed significantly, especially in the x = 0.6 sample, where it decreased clearly. The crystallite size decreased with increasing Aluminium content, reaching a small value of about 5 nm for the composition x = 0.8 sample. Raman peaks of pure LiFe2O4 were determined in both phases (alpha and beta), while smaller peaks at 198 and 236 cm−1 that related to the alpha phase were distinguished. All peaks diminished in intensity after Al3+ ions were doped to LiFe2O4 except for the peak at 700, where it became predominantly. The bandgap of the samples was deduced and analyzed from Tauc's plot according to UV–Vis spectra. The change in the electronic structure of the Li-Al ferrites, at which the size of the ferrite becomes close to the de Broglie wavelength, results in a band gap for the Al replaced by LiFe2O4 with different electronic configurations. The variation of the fundamental part of the dielectric constant (ε′), loss tangent (tan δ), and AC conductivity with frequency has been discussed with composition. The increase in Al3+ ion content affected the coercive force, as it decreased, while the saturation magnetism increased when adding Aluminium (x = 0.2) and then began to decline gradually.

Investigation and estimation of structural and dielectric properties of chromium-doped cobalt ferrites nano particles

Abstract Nano ferrite materials are of critical importance in meeting the global demand for microwave and electronic devices, as spinel ferrites possess remarkable morphological, structural, and dielectric characteristics. This study investigates chromium-doped ferrite nanoparticles with the chemical composition CoCrxFe2-xO4 (x = 0.00, 0.30, 0.60, and 0.90), synthesize using the sol–gel technique and subjected to annealing at 900 °C. Energy Dispersive x-ray Analysis EDAX patterns confirmed compositional stoichiometry. X- Ray Diffraction analysis reveals that all samples exhibit a cubic crystal structure. Replacing some of the ions with chromium (Cr3+) led to a decrease in the x-ray density form (5.329–5.324). The average crystallite size in the fabricated samples ranged from 46.07 to 31.84 nm, and the lattice parameters decrease from 8.382 to 8.364 Å as the chromium content increase. Infrared spectra show that lower frequency band (ν2) at around 479.69-392 .60 cm–1 and a higher frequency band (ν1) within a range from 611.05–57661 cm–1 a clear indication of spinel structure characteristics. The examination using FE-SEM indicates that the produced materials exhibit porosity and amorphous characteristics. The significant tangent loss observe at lower frequencies suggests that these materials may have potential applications in medium-frequency devices. Consequently, spinel nanoferrites can offer advantages for advanced electronic and microwave technologies.

Effect of Cr substitution in ZnFe2O4 nanoparticles on the electron transfer at electrochemical interfaces

In this study, we explored the effect of Cr³⁺ substitution by partially and fully replacing Fe³⁺ in the normal spinel ZnFe₂O₄ crystal structure at electrochemical interfaces. The resulting ZnCrₓFe₂₋ₓO₄ nanomaterials exhibited an average particle size between 20 and 50 nm with a spherical morphology. The materials also demonstrated energy band gaps ranging from 2.1 to 3.1 eV. X-ray diffraction (XRD) analysis confirmed that all the synthesized materials maintained a normal spinel structure, attributed to the octahedral site preference energy (OSPE) of Zn²⁺, Fe³⁺, and Cr³⁺ ions. Electrochemical performance assessments revealed that the ZnFe₂O₄-based sensor achieved a sensitivity of (37.8 ± 0.2) μA/mM with a kinetic rate constant of (13.1 ± 2.8) ms⁻¹, while the ZnCr₂O₄-based sensor exhibited a sensitivity of (32.4 ± 0.5) μA/mM and a kinetic rate constant of (3.73 ± 0.55) ms⁻¹ in the detection of paracetamol, whereas ZnCrFeO4 sensor has produced the second-best sensitivity (35.7 ± 0.1 μA/mM) and the rate constant (4.53 ± 0.54 ms⁻¹) with the lowest limit of detection (1.94 ± 0.01 μM). These differences in electrochemical performance were correlated with the variations in the energy band gaps caused by the restructuring of the normal spinel structure. Our findings indicate that the ZnFe₂O₄ sensor has a higher potential for direct electron transfer, whereas the other sensors are more likely to facilitate surface-mediated electron transfer.

Principles of ensuring thermal stability in innovative technology of periclase-spinel refractories

This article presents the results of research on the structural-phase regularities and behavior of periclase-spinel refractories under high-gradient thermal loads. The findings from the analysis of structural-phase variability in the refractory samples are used to achieve the desired thermal resistance. Based on the investigation of the subsolidus structure of the MgO–FeO–Al2O3–TiO2 system, predictions were made regarding the characteristics of solid-phase exchange reactions, considering the existence of solid solutions with various types of crystal structures in specific areas of the system. This enabled the application of new principles for ensuring thermal stability in the developed periclase-spinel refractories, specifically through organizing a fragmented, micro-cracked structure by combining solid-phase exchange reactions with the establishment of mobile equilibrium upon reaching stationary-state temperatures. An additional feature is the possibility of phase invertibility of solid spinel solutions, including changes in the type of spinel structure, in particular quandilite. Physicochemical research methods confirmed the enhanced ability of the material to flexibly adapt its phase composition and microstructure to thermal loads. The feasibility of these principles for achieving the structural-phase adaptability of the material to thermal shocks was validated by electron microscopy analysis.

Enhancing Corrosion Resistance of Mild Steel with a Hybrid Surface Coating: Film-Forming Zinc Titanate/Oleic Acid Composites

Coatings made from ceramic materials have shown remarkable effectiveness in preventing surface corrosion on mild steel surfaces. The coating's stability was enhanced by incorporating various elements into the matrix. This study incorporated an organic fatty acid, specifically oleic acid, into the zinc titanate. It forms a ZT/OA hybrid film-like coating on the MS surface. The synthesized ZT/OA nanomaterials were thoroughly characterized using PXRD, FT-IR, and SEM. The cubic spinel structure of ZnTiO3 and its spherical morphology were revealed from these techniques. The ZT/OA composites were applied to the surface of mild steel, and a film was formed under ambient conditions at a temperature of 150°C. An investigation was conducted on the electrochemical corrosion behaviors of ZT/OA composites in three electrode systems using both saline and acidic mediums. This study involved measuring the impedance and Tafel polarization corrosion data. The results indicate that the ZT40 (60 wt% oleic acid-doped) sample Showed a significantly higher resistance of 37638 Ω cm2, coupled with an impressive inhibition efficiency of 99.3% under saline conditions. Furthermore, under acidic conditions, the ZT40 sample exhibited excellent performance, as evidenced by the results of 691 Ω cm2 and 97% inhibition efficiency.

Nanostructured spinel ferrites: A comprehensive study on the synthesis, characterization, and magnetic properties of Zn and Mn substituted magnetite nanoparticles produced through the co-precipitation method

Seven cubic spinel ferrite nanoparticles were successfully synthesized through the co-precipitation method. These nanoparticles include Fe3O4, Zn0.4Fe0.62+Fe23+O4, Mn0.4Fe0.62+Fe23+O4, Zn0.6Mn0.4Fe0.42+Fe1.63+O4, Zn0.4Mn0.6Fe0.42+Fe1.63+O4, Zn0.4Mn0.4Fe0.22+Fe23+O4, and Zn0.4Mn0.4Fe0.42+Fe1.83+O4. The Rietveld method was used to analyze X-ray diffraction data, confirming that all samples have a single-phase cubic spinel structure. The presence of zinc and manganese ions in magnetite lattice leads to changes in lattice parameters and crystallite size, resulting in a range of 7–12 nm crystallite sizes. Fourier transform infrared spectroscopy (FT-IR) analysis of nanoparticles reveals two significant adsorption peaks at 560-576 cm−1 and 437-449 cm−1, corresponding to metal ion stretching vibrations at tetrahedral and octahedral sites. The X-ray photoelectron spectroscopy (XPS) analysis revealed the presence of iron, zinc, and manganese in various oxidation states. Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) images showed spherical, agglomerated nanoparticles. The study confirmed the elemental composition and mapping images of prepared samples using energy-dispersive X-ray spectroscopy (EDS). The magnetic properties of the synthesized nanoparticles were meticulously examined utilizing a vibrating sample magnetometer (VSM) at room temperature. A direct correlation is established between the structural alterations induced by Zn2+/Mn2+ and their subsequent effects on magnetic characteristics, specifically through the reallocation of cations and the mechanisms of electron hopping occurring at the B-sites. The structural modifications result in enhanced superparamagnetic behavior, exhibiting saturation magnetization values between 46.01 and 69.38 emu/g. The sustainable characteristics of these materials render them highly viable options for applications in environmental remediation and green technology.

Solar Selectivity of Silver Nanoparticles Modified Copper Oxide Nanocomposite Thin Films Prepared by Facile Chemical Oxidation Method

AbstractSilver nanoparticles modified copper oxide nanocomposite thin films (Ag‐CuO NC TFs) and pristine CuO TF were successfully synthesized on copper substrates using a chemical oxidation route. X‐ray diffractometry (XRD) characterization of Ag‐CuO NC TFs revealed the formation of monoclinic crystal structured CuO. Scanning electron microscopy (SEM) images showed a star‐like grain morphology of the Ag‐CuO NC TFs. Energy dispersive X‐ray spectroscopy (EDX) analysis ascertained the presence of anticipated elements without impurities. Fourier transform infrared spectroscopy (FTIR) investigation confirmed the presence of Ag NPs on CuO in the Ag‐CuO NC TFs. Raman spectroscopy examination indicated the presence of a spinel structure with vibrational and tetrahedral sites. UV‐Vis‐NIR reflectance analysis demonstrated that Ag‐CuO NC TFs with 2.0 wt.% Ag NPs exhibited solar absorptance of 72.39 %, thermal emittance of 4.3 %, and a highest solar selectivity of 16.83 among the prepared thin films. These results suggest that the Ag‐CuO NC TFs could be promising candidates for use as solar selective absorbers in solar thermal energy conversion devices.

AFe2O4 (A=Cu, Ni, Co, Mg, Ce, Mn) Catalysts for Hydrogen‐Rich Syngas Production from Corn Straw Pyrolysis‐Catalytic Steam Reforming

CuFe2O4, an iron‐based spinel catalyst, along with NiFe2O4, CoFe2O4, MgFe2O4, CeFe2O4, and MnFe2O4 are prepared using the sol–gel method. Different modified transition metals have been investigated to determine the influence on hydrogen production in a fixed‐bed reactor. The results indicated that all the prepared catalysts exhibit a spinel structure. At a reaction temperature of 700 °C, with a water–carbon molar ratio of S/C = 1.5 and a biomass‐to‐catalyst mass ratio of 1:1, the performance ranking of the AFe2O4 spinel catalysts is as follows: CeFe2O4 > CuFe2O4 > MnFe2O4 > NiFe2O4 > CoFe2O4 > MgFe2O4 > no catalyst. CeFe2O4 and CuFe2O4 catalysts demonstrate superior performance, with hydrogen volume fractions of 42.26% and 41.63% respectively. The AFe2O4 catalyst exhibits effective catalytic activity in the production of hydrogen from corn straw using water vapor, with the synergistic effect of A metal and Fe enhancing the catalytic activity of AFe2O4.

Exploring the Crystal Structure and Electronic Properties of γ-Al2O3: Machine Learning Drives Future Material Innovations.

For decades, researchers have struggled to determine the precise crystal structure of γ-Al2O3 due to its atomic-level disorder and the challenges associated with obtaining high-purity, high-crystallinity γ-Al2O3 in laboratory settings. This study investigates the crystal structure and electronic properties of γ-Al2O3 coatings under the influence of an external electric field, integrating machine learning with density functional theory (DFT). A potential 160-atom supercell structure was identified from over 600,000 γ-Al2O3 configurations and confirmed through high-resolution transmission electron microscopy and selected area electron diffraction. The findings indicate that γ-Al2O3 deviates from the conventional spinel structure, suggesting that octahedral vacancies can reduce the system's energy. Under an external electric field, the material's band structure and density of states (DOS) undergo significant changes: the bandgap narrows from 3.996 to 0 eV, resulting in metallic behavior, while the projected density of states (PDOS) exhibits peak broadening and splitting of oxygen atom PDOS below the Fermi level. These alterations elucidate the variations in the electrical conductivity of alumina coatings under an electric field. These findings clarify the mechanisms of γ-Al2O3's electronic property modulation and offer insights into its covalent and ionic mixed bonding as a wide-bandgap semiconductor. This discovery is essential for understanding dielectric breakdown in insulating materials.

Synthesis, magnetic and structural properties of (1-x)LiFe5O8–(x)LiZn2.5Ti2.5O8 spinel solid solutions

Compounds with the spinel structure present a technologically important class of materials. Spinels show a great variety of magnetic and magnetoelectric phenomena owing to the facile entrance of transition metals in the cationic sublattices. One of such examples is lithium ferrite LiFe5O8 with high ferrimagnetic phase transition temperature and cationic order-disorder transformations. The latter are important as they influence the crystal symmetry, which is crucial for physical properties. In this work we synthesize a series of (1-x)LiFe5O8–(x)LiZn2.5Ti2.5O8 (0≤x≤1) solid solutions and characterize them with various experimental and theoretical methods. The solid solutions experience a series of concentrational phase transformations between atomically ordered (P43(1)32) and disordered (Fd3¯m) phases. The variation with concetration x of Fe3+ occupancies in cationic sublattices is studied using Mössbauer spectroscopy. The Mössbauer and magnetic measurements reveal sharp suppression of magnetic properties at x≥0.5 when the number of Fe3+ ions in the A-sublattice vanishes. The magnetic behaviour in the studied series of solid solutions is confirmed by Monte Carlo calculations with magnetic exchange interactions determined using the density functional theory.

“Investigating impact of Ni-Cd substitution on structural magnetic and optical properties of nanosize Al ferrites”

Ferrites are among the most extensively studied materials, specifically due to their amazing and diverse characteristics. Therefore, we synthesized NixCd1-xAlyFe2-yO4 (NCAF) ferrites using a microwave auto-combustion process, with x varying from 0.0 to 1.0 and y set at 0.1. We conducted a meticulous characterization of their structural, surface morphological, magnetic, molecular vibrational and optical properties. X-ray diffraction confirms the lattice parameter and a single-phase spinel structure. Rietveld refined XRD patterns identified the Fd-3m space group cubic spinel phase. HR-TEM examination shows pseudo-spherical particles with an average size of 40–45 nm. Surface topography exhibits tiny, spherical microstructures. The lognormal histogram showed an average particle size of 56.6 nm–124.8 nm, decreasing with nickel concentration. At a nickel concentration (x) of 0.6, saturation magnetization (Ms) increases and then decreases at 1.0. FTIR confirms no organic phase and spinel development. Absorption measurements determined the band gap energy, which Tauc plot revealed to be 2.5870–2.1657 eV. We used the Kubelka-Munk function to find the band gap energy in the UV–Vis diffuse reflectance spectra (DRS), which was between 2.0027 and 1.6817 eV.

Single-Nanometer Spinel with Precise Cation Distribution for Enhanced Oxygen Reduction.

Designing spinel nanocrystals (NCs) with tailored structural composition and cation distribution is crucial for superior catalytic performance but remarkably challenging due to their intricate nature. Here, an aggregation growth restricted hot-injection method is presented by meticulously investigating the fundamental nucleation and aggregation-driven growth kinetics governing spinel NC formation to address this challenge. Through controlled collision probability of nuclei during growth, this approach enables the synthesis of spinel NCs with unprecedented, single nanometer (1.2nm). Single-nanometer CoMn2O4 spinel via this method exhibits a highly tailored structure with a maximized population of highly active octahedral Mn atoms, thereby optimizing oxygen intermediate adsorption during oxygen reduction reaction (ORR). Consequently, it exhibits a remarkable half-wave potential of 0.88V in ORR and leads to a superior power density (170.9mW cm-2) in zinc-air battery, outperforming commercial Pt/C and most reported spinel oxides, revealing a clear structure-property relationship. This structure design strategy is readily adaptable for the precise synthesis and engineering of various spinel structures, opening new avenues for developing advanced electrocatalysts and energy storage materials.