Sol Gel Auto-combustion Method Research Articles

The potential of Gd doping as a promising approach for enhancing the adsorption properties of nickel-cobalt ferrites.

The study shows that the addition of gadolinium ions has a significant impact on the structure, morphology, and adsorption properties of Ni-Co spinel ferrite that was synthesized by the sol-gel auto-combustion method. The research also indicates that the higher the Gd content, the greater the increase in the lattice parameter, which suggests that Gd3+ ions uniformly replaced the octahedral Fe3+ ions. The morphology and chemical composition of Gd-doped Ni-Co ferrites have been studied using SEM and EDS. Gd adding to the NiCoFe matrix increases the BET surface area by 50% (from 48 to 72 m2/g) and promotes the formation of mesopores with an average radius from 3.9 to 4.9nm. The pHPZC values of Gd-doped ferrites are in the range of 7.22-7.39, which means that the ferrite surface will acquire a positive charge at natural pH, so this will promote the adsorption of Congo red anionic dye through electrostatic interaction forces. Langmuir, Freundlich, and Dubinin-Radushkevich models were used to explain the mechanism of CR adsorption on the Ni0.5Co0.5GdxFe2-xO4 adsorbent surface. The ionic-covalent parameter has been estimated to describe the surface acid-base properties. Overall, this study highlights the potential of Gd3+ doping as a promising approach for enhancing the adsorption properties of nickel-cobalt ferrites.

Structural and Electrical Studies of Polycrystalline Pr𝑥Y1−𝑥FeO3 Materials Prepared Through Sol-Gel Route

Objectives: Investigations on structural, morphological and electrical studies of Pr substituted YFeO3 samples synthesized through sol-gel route are presented in this paper. Methods: PrxY1-xFeO3 (x=0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) samples are synthesized by sol-gel auto combustion method. Structural characterization of the samples is done by using X-ray diffraction (XRD), Field emission scanning electron microscope (FESEM) and Energy dispersive X-ray (EDX) techniques. Electrical properties are studied by J-E and Ln J-Ln E measurements. Findings: Rietveld refined XRD structural analysis shows sharp intense peaks indicating the crystalline nature of the samples and all the samples possess distorted orthorhombic structure with space group Pbnm. FESEM analysis shows non-uniform nature of grain size with increasing porosity. EDX data confirms elemental composition, weight and atomic percentage of the prepared samples which further confirms their purity. The leakage current density increases with increase in Pr doping. The slopes of Ln J-Ln E graphs of all the samples are in the range of 1.11 to 1.51 confirming that Ohmic conduction is predominant conduction mechanism. Novelty: Investigations on the effect of Pr substitution on electrical properties of single phase YFeO3­ samples reveal that the substitution of Pr in YFeO3 decreases the ferroelectric nature of the samples. Keywords: Sol-gel method, XRD, FESEM, EDX, Electrical Properties

Enhanced photocatalytic and antimicrobial properties of nickel-doped barium M-type hexaferrites synthesized via citrate sol-gel method

Industrial activities release waste into aquatic sources, which is hazardous because of the pathogenic and cytotoxic behaviour of the contaminants present in the effluent. To address this issue, the citrate sol-gel auto-combustion method synthesized nickel-substituted barium M-type hexaferrites BaNixFe12−xO19 (x = 0.0, 0.1, 0.2) nanoparticles. The nanoparticles show the single-phase hexaferrite structure having a crystallite size of 52.47 to 49.30 nm with the space group P63/mmc. Magnetic study of nanoparticles indicates that increased nickel ions give rise to saturation magnetization, whereas coercivity decreases. The band gap values of the pure and Ni-doped barium hexaferrites determined by Tauc plots have been noticed to range from 1.42 eV to 1.26 eV. The photocatalytic activity of nanoparticles for methyl orange (MO) dye has been investigated. The nanoparticles have shown a dye degradation efficiency of 84.5 % within 100 min. The antimicrobial properties of the synthesized nanoparticles have also been studied. The effectiveness of synthesized nanoparticles against two types of bacteria, gram-positive Staphylococcus aureus and gram-negative Escherichia coli, as well as against two pathogenic fungi, Candida albicans and Aspergillus niger, has been investigated. The antibacterial effect has been demonstrated by all samples at all concentrations, with MIC values ranging from 1 to 4 mg/ml. Therefore, this study investigates the potential applications of nickel-doped barium M-type hexaferrites nanoparticles in real-world biological settings, suggesting their promising role in fighting against bacterial and fungal infections.

LaxNiy Mn2-(x+y)O3/g-C3N4 composite: A multifunctional material for photocatalytic and adsorptive removal of pollutants with statistical evaluation

The disposal of tons of organic chemicals annually in water resources is an alarming threat to the environment. Among the various remediation techniques, the combination of adsorption and degradation is a highly effective and economical strategy for eliminating these contaminants. In this study, a novel LaxNiyMn2-(x+y)O3/g-C3N4 composite [x,y = (0.00,0.00), (0.03,0.06), (0.06,0.03), (0.045,0.045)] is synthesized by a low-temperature and cost-efficient sol-gel auto-combustion method to address this issue. Field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) were used to characterize the morphology and crystal structure of the composite, respectively. The optical properties of the composite were investigated by a UV–visible spectrophotometer. The photocatalytic performance of the prepared samples was evaluated against crystal violet and 4-nitrophenol under solar irradiation. The doped composite La0.06Ni0.03Mn1.91O3/g-C3N4 exhibited superior degradation efficiency of 87.54 % for crystal violet in 60 min, compared to 56.2 % for the undoped composite. The same composite also achieved 78 % reduction of 4-nitrophenol without any external reducing agent. Furthermore, adsorption isotherms models and statistical analysis were applied to the composite to elucidate the adsorption mechanism and the optimal conditions. The results demonstrated that the composite is an excellent candidate for environmental remediation due to its remarkable degradation and adsorption capabilities against organic pollutants.

Rietveld analysis and cation distribution of Co substituted Ni–Zn ferrite nanoparticles

This study investigates the cation distribution in Co-substituted Ni–Zn ferrite nanoparticles synthesized via the sol-gel auto-combustion method. The research aims to understand the modifications in cationic distributions at the nanoscale compared to bulk counterparts and their impact on electromagnetic properties. Rietveld structural analysis, lattice constant determination, and magnetic moment measurements were employed to analyze the nanoparticles. The results reveal a single-phase spinel structure with cubic symmetry, crystallite sizes between 26.2 and 36.4 nm, and saturation magnetizations ranging from 50 to 68 emu/g. Results and calculated cation distributions of these ferrite nanoparticles were evaluated in terms of compositional modifications, particle sizes, and related inversion degree parameters. The study confirms the cation distributions based on X-ray and magnetic data, highlighting the importance of cationic inversions in designing nanoscale ferrites with improved electromagnetic characteristics for electronic applications.

Influence of synthesis methods on the structural, dielectric and magnetic properties of cobalt ferrites

A systematic study comprising structural, magnetic and dielectric properties of the cobalt ferrite (CoFe2O4) powders at first is carried out by way of synthesizing the materials using different preparatory methods, such as conventional solid-state method, wet chemical sol-gel autocombustion method using citric acid as well as glycine, separately as fuels. X-ray diffraction (XRD) studies reveal the formation of spinel phase with clear variations of peak intensities in all the samples. Morphology studies using scanning electron microscopy (SEM) reveal well grown grains in solid state synthesized sample compared to sol-gel autocombustion samples. The variations observed in the grain growth as well as densities (porosity) were attributed to typical temperature treatment conducted on the samples. Dielectric tests provide the evidence of space charge polarization in all the samples. Magnetic studies using vibrating sample magnetometry (VSM) provide the values of saturation magnetization and coercivity of the samples explored. The sol-gel autocombustion sample using glycine matrix (Cogly) shows higher saturation magnetization (Ms = 59.2 emu/gm) comparing to other samples whereas, sample with citric acid matrix results with lower Ms value as 36.5 emu/gm. The typical reasons for the observed variations in structural, microstructural, magnetic, dielectric and impedance properties of these materials were well addressed in terms of theoretical aspects and presented in this paper.

Tailoring Structural and Magnetic Properties: Cd²⁺ and Cu²⁺ Co-Doped Ni-Zn Ferrite Nanoparticles via Sol-Gel Auto-Combustion

In this research work, we have incorporated paramagnetic Cu2+ and diamagnetic Cd2+ cations in spinel ferrites. By adjusting the concentrations of Cu and Cd, it is possible to achieve a balance between enhanced electrical conductivity, desired magnetic properties, and suitable structural characteristics for applications in high-frequency devices, magnetic sensors, and electromagnetic interference (EMI) suppression through a synergistic effect. The sol-gel auto-combustion method was employed to synthesize Cd²⁺ and Cu²⁺ co-doped Ni₀.₅Zn₀.₅₋ₓ₋ᵧCuₓCdᵧFe₂O₄ (x = y = 0.0, 0.05, 0.1, 0.15, 0.2) ferrite nanoparticles. Structural, morphological-compositional, functional, and magnetic properties of the nanoparticles were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy with energy dispersive spectroscopy (FESEM-EDS), Fourier-transform infrared spectroscopy (FT-IR), and vibrating sample magnetometry (VSM). The XRD results confirmed the single-phase spinel structures with lattice constants increasing with higher dopant concentrations. The average crystallite sizes were found in the range of 38.14 - 42.68 nm and lattice constants in the range of 8.389 - 8.423 Å. Morphological analysis revealed agglomeration, consistent with the stoichiometric proportions during synthesis. There is a decreasing trend in nanograin sizes in the range of 40 to 73 nm with the concentration. FT-IR spectra verified the spinel structures through characteristic absorption bands around 600 cm⁻¹ and 400 cm⁻¹. Magnetic measurements indicated a decrease in saturation magnetization with increasing dopant levels indicating their potential use in electromagnetic wave absorption and magnetic memory devices.

Influence of CoFe2O4 content on the multifunctional properties of BiFeO3–CoFe2O4 core-shell nanocomposites

The utilization of magnetoelectric composites, particularly core-shell configurations, enhances their versatile applications in various sectors such as medicine and data storage. Among these composites, the perovskite-spinel combination is distinguished by its significant potential. A series of (1-x) BiFeO3-(x) CoFe2O4 (where x = 0.0, 0.2, 0.5, and 1.0) nano core-shell structures were synthesized using a sol-gel auto-combustion method to explore their multifunctional capabilities. Structural analyses identified peaks corresponding to both perovskite and spinel phases. Field Emission Scanning Electron Microscopy revealed a reduction in average particle size with an increase in CoFe2O4 content.The particle size in the BFO80-CFO20 sample has been reduced from 243 nm to 34 nm. Additionally, Transmission Electron Microscopy images of the BFO80-CFO20 sample highlighted the evolution of core-shell structures. Our findings indicate that higher CFO concentrations significantly affect the dielectric, ferroelectric, and optical properties. The bandgaps of the nanocomposites BFO80-CFO20 and BFO50-CFO50 were estimated to be 1.43 eV and 1.39 eV, respectively. Magnetic analysis showed increases in both saturation magnetization and remanent magnetization with increased CFO content, while the coercive field followed a different trend. The saturation magnetization values for the samples BFO, BFO80-CFO20, BFO50-CFO50, and CFO were calculated as 0.205, 14.612, 28.374, and 74.105 (emugr), respectively. The measured values for the same samples were 0.08, 5.07, 11.34, and 34.01 (emugr), respectively. Further, the electrochemical properties were thoroughly investigated using cyclic voltammetry, linear sweep voltammetry, and electrochemical impedance spectroscopy.

Synthesis and characterization of CuFe2O4 spinel ferrite for supercapacitor application

The present work describes the synthesis of spinel ferrites which is potentially active material for electrodes of supercapacitors with high theoretical capacitance. Using nitrate salts of respective metal ions with citric acid as a chelating agent CuFe2O4 spinel ferrite was prepared by using the sol-gel auto-combustion method. The formation of single-phase nano particles of CuFe2O4 spinel ferrite is confirmed form the X-ray diffraction pattern. The spherical morphology of copper ferrite nano particles is displayed by Field-emission Scanning Electron Microscopy. The electrochemical properties of CuFe2O4 spinel ferrite has been investigated by Cyclic Voltammetry (CV) and Galvanostatic Charge-Discharge (GCD) tests. The specific capacitance of the prepared CuFe2O4 spinel ferrite is 238 F/g at the current density of 0.5 A/g. The corresponding power density is 118.29 W/kg and the energy density is 62.5 Wh/kg. The resultant CuFe2O4 spinel ferrite nanoparticles exhibit excellent electrochemical performance and can be a promising candidate for supercapacitor application.

Magnetic resonance behavior modulation of Ba3Co1.6−xZnxCu0.4Fe24O41 hexaferrites for microwave absorption and surface wave suppression

The intrinsic high magnetocrystalline anisotropy equivalent field can help the hexaferrites break through Snoek's limit and increase the resonance frequency. This is advantageous for microwave absorption applications in the mid to low-frequency range of gigahertz. In this study, we prepared Z-type Ba3Co1.6−xZnxCu0.4Fe24O41 hexaferrites using the sol-gel auto-combustion method. By changing the ratio of Co and Zn ions, the magnetocrystalline anisotropy of ferrite is further manipulated, resulting in significant changes in their magnetic resonance frequency and intensity. Ba3Zn1.6Cu0.4Fe24O41 with high-frequency resonance achieved the lowest reflectivity of −72.18 dB at 15.56 GHz, while Ba3Co1.5Zn0.1Cu0.4Fe24O41 with stronger loss obtained the widest bandwidth of 4.93 GHz (6.14–11.07). Additionally, we investigated surface wave suppression properties previously overlooked. Ba3Co1.5Zn0.1Cu0.4Fe24O41 can achieve a larger attenuation at low frequency under low thickness, which has an excellent effect on reducing backscattering. This work provides a useful reference for the preparation and application of high-performance magnetic-loss materials.

Green Synthesis of ZnO Nanoparticles and Ag-Doped ZnO Nanocomposite Utilizing Sansevieria trifasciata for High-Performance Asymmetric Supercapacitors.

This study provides a comprehensive analysis of a biofabricated nanomaterial derived from Sansevieria trifasciata root extract, evaluating its structural, morphological, and optical properties for use in asymmetric supercapacitors. The nanomaterial comprises pristine ZnO nanoparticles (ZnO NPs) and a 1% Ag-doped ZnO nanocomposite (Ag@ZnO NC), synthesized through a green-assisted sol-gel autocombustion method. Employing techniques such as X-ray diffraction, ultraviolet-visible near-infrared, scanning electron microscopy-energy-dispersive X-rayspectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, and transmission electron microscopy, the study confirms a hexagonal wurtzite structure and nanocrystallites with spherical and hexagonal shapes (30 nm). Optical analysis reveals a red shift in the band gap with Ag doping, indicating improved conductivity. The material shows potential applications in solar cells, optoelectronics, spintronics, wastewater treatment, and high-performance asymmetric supercapacitors. Raman spectra validate the wurtzite phase and identify intrinsic defects. Electrochemical tests demonstrate remarkable supercapacitive behavior with a 94% capacitance retention after 10,000 cycles, highlighting its promise as advanced asymmetric supercapacitors.

Impact of Gd-substitution on structural, dielectric, spectroscopic, Raman, and photo luminance properties of Ba0.4Sr0.6Co2Fe16O27 ceramics

This paper represents a detailed study of Gd3+ substitutions on Structural, Dielectric, Spectroscopic, Raman, and Photo luminance Properties of Ba0.4Sr0.6Co2Fe16O27 magnetic oxides were prepared using the sol-gel auto combustion method. All of these specimens were sintered at 1100 °C for 5 h. X-ray diffraction analysis (XRD) confirmed the single-phase detection and structural analysis. The lattice parameters a and c show the insignificant behavior 5.893–5.933 Å, and 32.049–32.476 Å with the concentration of gadolinium ions. The crystallite size ranged from 25 to 30 nm, demonstrating a growing tendency as Gd-substitution was enhanced. The discrepancy in the ionic radii of iron (Fe3+) and substituent elements (Gd3+) is the cause of the variation in cell volume and lattice constants. FTIR spectroscopy confirmed the presence of absorption bands (590 and 3000 cm−1) for prepared BaSr-based W-type hexa-ferrites. The vibrational bands of metal oxide ions are responsible for the 590 and 685 cm−1 peaks. The Raman spectrum showed six discrete, brittle peaks: 320, 440, 620, 690, 1300, and 1600 of synthesized nanomaterials—the dielectric constant and dielectric loss increase by substituting the Gd3+ ion. The dielectric parameters and dielectric loss at higher frequencies suggest that the prepared material may be excellent for switching, sensing, and high-frequency applications.

Magnetic and magnetostrictive properties of Cu-doped cobalt ferrite

The Cu-doped cobalt ferrites CuxCo1-xFe2O4 (CCFO) were synthesized by a glycine-nitrate sol-gel auto-combustion method and investigated for structural, magnetic and magnetostrictive properties. X-ray diffraction and scanning electron microscopy analysis revealed the formation of single cubic-spinel phase for all the as-prepared powders, followed by the sintered samples with grain sizes around 2.5 µm. The variation in stoichiometric composition can be used to tailor magnetic and magnetostrictive properties. Saturation magnetization MS decreases from 84.8 to 60.4 emu/g with increasing Cu content from x = 0.0 to x = 0.50, accompanied with a reduction in coercivity HC from 1.21 to 0.41 kOe. The introduction Cu into CFO is conductive to the decline in magnetocrystalline anisotropy, giving rise to an improvement in magnetostriction at low applied fields. An optimized composition in the CuxCo1-xFe2O4 ferrites is found to be around x = 0.30, achieving good magnetoelastic properties, i.e., a large saturation magnetostriction (–λS ∼ 240 ppm), a high strain sensitivity (–dλ/dH ∼ 1.44 nm/A), as well as a low magnetocrystalline anisotropy coefficient (K1 ∼ 3.7 × 106 erg/cm3). The excellent magnetoelastic properties and the combination in a facile synthesis process for sintered polycrystalline ferrites, suggest promising prospects in magnetostriction applications.

Structural, Morphological and Ferroelectric Properties of Sr-Cd Co-Doped Nickel Ferrite for Energy Storage Devices

Ferroelectric materials, renowned for their capacity to demonstrate spontaneous electric polarization reversible through an external electric field, are essential in numerous technological applications owing to their distinctive characteristics. For this, a series of spinel Sr-Cd co-doped nickel ferrite nanomaterials Cd0.5−xSrxNi0.5Fe2O4 (x = 0.0, 0.1, 0.2 and 0.3) were prepared through the standard sol-gel auto combustion method The XRD patterns showed that the prepared samples have a cubic spinel structure. The crystallite sizes of the samples vary from 29 to 40 nm. The morphology of prepared samples showed uniformly distributed spheres. Magnetic properties showed the soft magnetic nature of the prepared ferrites. The ferroelectric study revealed that Sr-Cd substituted ferrites exhibited the elliptical nature of ferroelectric loops at normal room temperature. The maximum polarization has been achieved at x = 0.3. The understanding of current and voltage (I–V) showed a slowly decreasing tendency of leakage current on both sides symmetrically against the increasing Sr content. The conductivity of the prepared spinel increases as a function of higher Sr doping. The real part of dielectric constant increases with increasing frequency. The materials show large elliptical loops indicating high asymmetric ferroelectric energy storage capability.

A Study on Fine-Tuning the Optical Energy Band Gap and Various Optical Parameters with the Impact of Gadolinium Composition in NGFO Ferrite Nanoparticles

In the present work, gadolinium-doped nickel ferrite nanoparticles with the chemical composition NiFe2−xGdxO4 (X = 0.00, 0.05, 0.10, 0.15, 0.20, and 0.25) have been prepared by the sol-gel auto-combustion method and calcinated at 700 ∘C. The spinel ferrite phase formation was confirmed with the XRD graphs. In all the samples, the typical absorbance peak was observed in between 250–300 nm. Tauc plots were used to calculate the optical energy band gap, found in the range of 4.033–4.144 eV, and it was also calculated using x-ray density to be in the range of 3.690–4.300 eV. Both of them were observed in good agreement with each other, and we conclude that the Gd composition could finely tune the optical energy band gap. The impact of Gd composition was clearly observed on optical parameters. The refractive index, reflectivity, absorption coefficient, optical dielectric constant, and dielectric susceptibility have shown the increasing tendency from 2.1140 to 2.2325, 12.80 to 14.53%, 5.4380 to 6.3032 cm−1, 3.4690 to 3.9840 and 0.2760 to 0.3170, respectively, whereas the transmission coefficient decreased from 0.7730 to 0.7461.

Supercapacitor properties of Ni2+ incrementally substituted with Co2+ in cubic spinel NixCo1-xFe2O4 nanoparticles by sol-gel auto combustion method

The nanoparticle powder of Ni1-xCoxFe2O4 (x = 0.00, 0.25, 0.50, 0.75, 1.00) spinel ferrite was successfully prepared by the sol-gel auto-combustion method. The synthesized nanomaterials were used to prepare spinel ferrite supercapacitor electrode material. The structured phase of prepared nanoparticle powders was studied using XRD which shows the prepared sample consists of nanocrystalline single phase, with cubic spinel ferrite. Furthermore, using FESEM surface morphology of prepared samples was investigated. Ni1-xCoxFe2O4 nanoparticles spinel ferrite structure was verified by FT-IR, which detected distinctive vibrational bands at octahedral and tetrahedral locations.The spinel ferrite type materials are good active electrode materials. In this study, the prepared Ni1-xCoxFe2O4 electrode material is used as cathode material for supercapacitor. The electrochemical behavior of prepared samples was studied and compared by using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) in 1 M KOH electrolyte. An electrochemical measurement study of prepared samples shows excellent performance and desirable cycling stability for supercapacitors. The prepared Ni0.5Co0.5Fe2O4 spinel ferrite gives the highest specific capacitance of 1282 F/g at a current density of 5 mA/cm2 with corresponding energy density of 30 Wh/kg and power density of 301 W/kg. Also, they exhibited outstanding cycling stability for 5000 cycles with 91.24 % capacity retention.

Improved magnetic, electrical, and dielectric characteristics of graphene nano-platelets (GNPs)-Integrated Ni0·4Cd0·6Fe1.97Sm0.03O4 ferrite composites synthesized via sol-gel auto-combustion method

This research work analyzes the impact of graphene nanoplatelets (GNPs) on the structural, electrical, dielectric, optical, and magnetic properties of the Ni0·4Cd0·6Fe1.97Sm0.03O4/x-GNPs (SNCF/GNPs) composites (x = 0 %, 2.5 %, and 5 %) prepared via the sol-gel auto-combustion route. The results revealed that SNCF particles were distributed on GNPs which improved the multifaceted properties of SNCF spinel ferrites. XRD analysis confirmed the FCC spinel structure with a minimum crystallite size (D) of 18.99 nm for sample with 5 wt %GNPs. The DC electrical resistivity decreased from 9.06 × 1011 Ω-cm at 313K to 1.41 × 108 Ω-cm at 673K, revealing the semi-conducting nature of composites. The improved electroconductivity and reduced bandgap energy are observed for samples with minimum resistivity 1.02 × 105 Ω-cm at 673K and 1.70 eV energy, respectively, containing 5 wt %GNPs. Samples show higher permittivity values at low frequency and decreased at high frequency. The maximum ac conductivity is observed for composite with 5 wt %GNPs which is attributed to the hopping mechanism. Finally, the magnetization (Ms) increased from 52.24 to 79.71 emu/g with increasing GNPs contents. Hence, the synthesized composites with 5 wt %GNPs are more favorable than the pure sample for application in waste-water treatment, high-frequency devices, and energy storage devices.

Influence of Zr4+-Co2+ substitution on structure, morphology and dielectric properties of BaZn2U-type hexaferrites

A series of Zr4+-Co2+ substituted U-type hexaferrites (Ba4Zn2Fe36-2xZrxCoxO60 (0.0 ≤ x ≤ 1.0, having Δx = 0.25)) were synthesized via sol-gel auto-combustion method. The samples were sintered at 1200 ° C for 6 h. The impact of Zr–Co substitution on phase, structure, morphology, and dielectric behavior were investigated through XRD, FTIR, SEM, XPS and VNA. XRD studies shows that the U-type hexaferrite phase has been developed and the increase in lattice constants (a & c), cell volume, c/a ratio, and percentage porosity was observed. Sample with x = 0.25 exhibited the smallest crystallite size (34.5 nm). The existence of signature metal-oxygen vibrational bands for hexaferrites was observed by FTIR spectra. SEM analysis reflects that the substitution produces a significant effect on morphology and grain size of the samples. X-ray photoelectron spectra (XPS) of sample x = 1.0 confirmed the chemical and elemental composition. The dielectric constant, dielectric loss, and ac conductivity increases with increasing frequency and decreases with Zr–Co substitution. The lowest reflection loss of RL = −64.5 dB (with MW absorption >99.9 %) was observed for the composition x = 0.5 with pellet thickness of 1.73 mm at 1.05 GHz frequency. Due to the improved bandwidth and better absorption, these hexaferrites can be used in microwave and high frequency applications.

Sr-doped CuFe2O4 nanoparticles: Exploring structural, magnetic, and blood compatibility characteristics

The aim of this study is to investigate the structural, magnetic, and blood compatibility properties of Sr2+ substituted for Cu2+ in Cu1−xSrxFe2O4 (x = 0.0 to 1 with a 0.25 increment) nanoparticles synthesized via the sol-gel auto-combustion technique. Regardless of the substitution rate, the sol-gel auto-combustion method consistently yields powders with sizes ranging from 20 to 40 nm. The specific surface area of the produced powders is determined as 12 m2/g. X-ray diffraction analysis reveals that CuFe2O4 exhibits a singular phase; however, as the Sr2+ ion substitution increases, the emergence of various secondary phases becomes apparent, with their proportions increasing with the substitution rate. The magnetic characteristics of the synthesized powders exhibit variations in magnetization, correlating with the distribution of cations in the sublattice points. Coercivities are influenced by both anisotropy and secondary phases. Saturation magnetization decreases from 31.3 (CuFe2O4) to 7.6 (SrFe2O4) emu/g with Sr replacement. The lowest observed coercivity is 429.5 Oe in powders prepared with CuFe2O4 composition, while the highest is measured at 583.8 Oe in nanopowders prepared with Cu0.5Sr0.5Fe2O4 composition. Moreover, blood compatibility experiments indicate significantly low hemolysis ratios for Cu1−xSrxFe2O4 nanoparticles. Additionally, all examined samples exhibit an increase in Soret band intensity compared to the negative control test, suggesting potential biocompatibility.

High Entropy Spinel Oxide (AlCrCoNiFe2)O as Highly Active Oxygen Evolution Reaction Catalysts.

The advancement of water electrolyzer technologies and the production of sustainable hydrogen fuel heavily rely on the development of efficient and cost-effective electrocatalysts for the oxygen evolution reaction (OER). High entropy ceramics, characterized by their unique properties, such as lattice distortion and high configurational entropy, hold significant promise for catalytic applications. In this study, we utilized the sol-gel autocombustion method to synthesize high entropy ceramics containing a combination of 3d transition metals and aluminum ((AlCrCoNiFe2)O). We then compared their electrocatalytic performance with other series of synthesized multimetal and monometallic oxides for the OER under alkaline conditions. Our electrochemical analysis revealed that the high entropy ceramics exhibited excellent performance and the lowest charge transfer resistance, Tafel slope (29 mV·dec-1), and overpotential (η10 = 230 mV). These remarkable results can be primarily attributed to the high entropy effect induced by the addition of Al, Cr, Co, Ni, and Fe, which introduces increased disorder and complexity into the material's structure. This, in turn, facilitates more efficient OER catalysis by providing diverse active sites and promoting optimal electronic configurations for the reaction. Furthermore, the strong electronic interactions among the constituent elements in the metallic spinels further enhance their catalytic activity in the initiation of the OER process. Combined with the reduced charge transfer resistance, these factors collectively play pivotal roles in enhancing the OER performance of the electrocatalysts. Overall, our study provides valuable insights into the design and development of high-performance electrocatalysts for sustainable energy applications. By harnessing the high entropy effect and leveraging strong electronic interactions, electrocatalytic materials can be tailored to improve efficiency and stability, thus advancing the progress of clean energy technologies.