Search Results (183)

This study reports the synthesis and characterization of Co_xNi_1−xFe₂O₄ (x = 0, 0.2, 0.4, 0.6, 0.8, 1) nanoparticles using a co-precipitation method. In this approach, metal ions are precipitated in the presence of a stabilizing agent, which is a common and effective method for nanoparticle preparation. The microstructure and magnetic properties were studied after calcination at 600 °C and heat treatment at 1000 °C. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy confirmed the formation of a single-phase spinel structure. The average crystallite size, calculated using the (311) diffraction peak and the Scherrer equation, ranged from 13 to 19 nm. Scanning electron microscopy (SEM) showed that the nanoparticles had a spherical morphology. Thermogravimetric and differential thermal analysis (TG-DTA) revealed a three-step weight loss process. Magnetic measurements, including remanent magnetization, saturation magnetization, and coercivity, were performed using a vibrating sample magnetometer (VSM) at room temperature. The replacement of Ni²⁺ with Co²⁺ enhanced the magnetic properties, resulting in increased magnetic moment and anisotropy. These effects are attributed to changes in cation distribution, exchange interactions, surface effects, and magnetocrystalline anisotropy. Overall, Co²⁺ doping improved the magnetic behavior of nickel ferrite, indicating its potential for application in memory devices and magnetic recording media. Full article

This report is on Co and Ti substituted M-type barium and strontium hexagonal ferrites that are reported to be single phase multiferroics due to a transition from Neel type ferrimagnetic order to a spiral spin structure that is accompanied by a ferroelectric polarization in an applied magnetic field. The focus here is the nature of magnetoelectric (ME) interactions in the bilayers of ferroelectric PZT and Co and Ti substituted BaM and SrM. The ME coupling in the ferrite-PZT bilayers arise due to the transfer of magnetostriction-induced mechanical deformation in a magnetic field in the ferrite resulting in an induced electric field in PZT. Polycrystalline Co and Ti doped ferrites, Ba (CoTi)_x Fe_12−2xO_19, (BCTx), and Sr (CoTi)_x Fe_12−2xO₁₉ (SCTx) (x = 0–4) were found to be free of impurity phases for all x-values except for SCTx, which had a small amount of α-Fe₂O₃ in the X-ray diffraction patterns for x ≤ 2.0. The magnetostriction for the ferrites increased with applied filed H to a maximum value of around 2 to 6 ppm for H~5 kOe. BCTx/SCTx samples showed ferromagnetic resonance (FMR) for x = 1.5–2.0, and the estimated anisotropy field was on the order of 5 kOe. The magnetization increased with the amount of Co and Ti doping, and it decreased rapidly with x for x > 1.0. Measurements of ME coupling strengths were conducted on the bilayers of BCTx/SCTx platelets bonded to PZT. The bilayer was subjected to an AC and DC magnetic field H, and the magnetoelectric voltage coefficient (MEVC) was measured as a function of H and frequency of the AC field. For BCTx-PZT, the maximum value of MEVC at low frequency was ~5 mV/cm Oe, and a 40-fold increase at electromechanical resonance (EMR). SCTx–PZT composites also showed a similar behavior with the highest MEVC value of ~14 mV/cm Oe at low frequencies and ~200 mV/cm Oe at EMR. All the bilayers showed ME coupling for zero magnetic bias due to the magnetocrystalline anisotropy field in the ferrite that provided a built-in bias field. Full article

The effect of strontium substitution on the crystal tructure, as well as the magnetic, and electrical properties of lanthanum ferrite (LaFeO₃) synthesized by high-energy ball milling, is studied, with an emphasis on magnetodielectric coupling. X-ray diffraction (XRD) confirmed the successful synthesis of orthorhombic La_1−xSr_xFeO₃ for doping levels up to 0.2 mol. At 0.3 mol Sr²⁺, two phases appear: La_0.6Sr_0.4FeO_2.976 and La_0.8Sr_1.2FeO_3.714, the latter being metastable. This phase vanishes at 0.5 mol. The Fourier Transform Infrared Spectroscopy (FT-IR) and Scanning Electron Microscopy coupled with Energy Dispersive X-ray Spectroscopy (SEM-EDS) analysis confirmed these results using a vibrating sample magnetometer (VSM), whose measurements show ferromagnetism at 0.1 and 0.3 mol Sr²⁺, attributed to crystal distortion, magnetic spin rearrangement, and as consequence, modifications in the double-exchange interactions. Dielectric tests reveal that higher Sr²⁺ concentrations lead to increased relative permittivity, dielectric losses, and conductivity, linked to oxygen vacancy formation. This study demonstrates a room-temperature magnetodielectric coupling of 32% in Sr-doped lanthanum ferrite, highlighting its potential for technological applications. Full article

This study focuses on the structural and electrochemical behavior of the compound ZnLaFeO₄ as a negative electrode material for nickel–metal hydride (Ni-MH) batteries. The material was synthesized by a sol–gel hydrothermal method to assess the influence of lanthanum doping on the ZnFe₂O₄ spinel structure. X-ray diffraction revealed the formation of a dominant LaFeO₃ perovskite phase, with ZnFe₂O₄ and La₂O₃ as secondary phases. SEM analysis showed agglomerated grains with an irregular morphology. Electrochemical characterization at room temperature and a discharge rate of C/10 (full charge in 10 h) revealed a maximum discharge capacity of 106 mAhg⁻¹. Although La³⁺ doping modified the microstructure and slowed the activation process, the electrode exhibited stable cycling with moderate polarization behavior. The decrease in capacity during cycling is due mainly to higher internal resistance. These results highlight the potential and limitations of La-doped spinel ferrites as alternative negative electrodes for Ni-MH systems. Full article

Bismuth ferrite (BiFeO₃, BFO) is a promising multiferroic material, but its optoelectronic potential is limited by a wide bandgap and charge recombination. Here, we report the sol–gel synthesis of Co-doped BiFeO₃/Bi₂₅FeO₄₀ heterostructured nanopowders (x = 0.07, 0.15) alongside pristine BFO to explore Co doping and phase engineering as strategies to enhance their functional properties. Using X-ray diffraction (XRD) with Rietveld refinement, Fourier-transform infrared spectroscopy (FTIR), field-emission scanning electron microscopy (FE-SEM), UV-Vis spectroscopy, and dielectric analysis, we reveal a biphasic structure (rhombohedral R3c and cubic I23 phases) with tuned phase ratios (~73:27 for x = 0.07; ~76:24 for x = 0.15). Co doping induces lattice strain and oxygen vacancies, reducing the bandgap from 1.78 eV in BFO to 1.31 eV in BFO_0.15 and boosting visible light absorption. Dielectric measurements show reduced permittivity and altered conduction, driven by [Co²⁺-V₀^••] defect dipoles. These synergistic modifications, including phase segregation, defect chemistry, and nanoscale morphology, significantly enhance optoelectronic performance, making these heterostructures compelling for photocatalytic and photovoltaic applications. Full article

In this study, praseodymium-doped cobalt ferrite nanoparticles (CoFe_2−yPr_yO₄, y = 0–0.2) were synthesized via sol-gel auto-combustion and systematically characterized to assess their structural, morphological, magnetic, and biological properties. X-ray diffraction (XRD) confirmed single-phase cubic cobalt ferrite formation for samples with y ≤ 0.05 and the emergence of a secondary orthorhombic PrFeO₃ phase at higher dopant concentrations. FTIR spectroscopy identified characteristic metal–oxygen vibrations and revealed a progressive shift of absorption bands with increasing praseodymium (Pr) content. Vibrating sample magnetometry (VSM) demonstrated a gradual decline in saturation (Ms) and remanent (Mr) magnetization with Pr doping, an effect further intensified by cyclodextrin surface coating. TEM analyses revealed a particle size increase correlated with dopant level, while SEM images displayed a porous morphology typical of combustion-synthesized ferrites. In vitro cell viability assays showed minimal toxicity in normal human keratinocytes (HaCaT), while significant antiproliferative activity was observed against human cancer cell lines A375 (melanoma), MCF-7 (breast adenocarcinoma), and HT-29 (colorectal adenocarcinoma), particularly in Pr 6-CD and Pr 7-CD samples. These findings suggest that Pr substitution and cyclodextrin coating can effectively modulate the physicochemical and anticancer properties of cobalt ferrite nanoparticles, making them promising candidates for future biomedical applications. Full article

Various types of strain, as well as chemical pressure induced by dopants, can effectively tailor the performance of perovskite thin films, including their optical, electrical or photoelectrochemical properties. The control of these functional properties through such engineering techniques is key to fulfilling the application-specific requirements of ferroelectric devices in various fields. Numerous models and experimental data have been published on this subject, especially on ferrite-based ferroelectric materials. Within this paper, the mechanisms of tuning ferroelectric intrinsic properties, such as polarization and ferroelectric domain configurations, through epitaxial strain and doping, as well as the role of these techniques in influencing functional properties such as dielectric and photoelectrochemical ones, are presented. This review examines the significant improvements in dielectric properties and photoelectrochemical efficiency achieved by the strategical control of key functionalities including dielectric losses, domain structures, charge separation and surface reactions in strained/doped ferroelectric thin films, highlighting the advancements and research progress made in this field in recent years. Full article

Polycrystalline nickel–zinc (NiZn) ferrites are widely used in high-frequency applications due to their excellent magnetic properties such as low power losses, high magnetic permeability, and adequate saturation induction. However, data on their power loss behavior at 10 MHz, particularly at elevated temperatures, remain limited in the literature. This study investigates the magnetic performance of Co-doped NiZn ferrites at 10 MHz, under varying induction fields (3–10 mT) and temperatures (20–120 °C), with a focus on reducing high-temperature losses. Ferrite samples were synthesized using the conventional mixed oxide method and systematically varied in composition (Fe, Co content and Ni/Zn molar ratio). Key findings reveal that the incorporation of cobalt significantly enhances high-temperature performance by shifting resonance frequencies, attributed to increased domain wall pinning. Samples with optimized compositions and processing demonstrated power losses at 10 MHz, 10 mT and 25 °C, 100 °C and 120 °C as low as 310 mW cm⁻³, 1233 mW cm⁻³ and 1400 mW cm⁻³, respectively, with relative initial permeabilities exceeding 80 at these temperatures. These results provide insights into the design of high-frequency magnetic components and highlight strategies to minimize high-temperature losses. Full article

In order to meet the demand for high-frequency current sensors in 5G communication and new energy fields, there is an urgent need to develop high-performance nickel-zinc ferrite-based co-fired ceramic magnetic cores. In this study, a nickel-zinc ferrite core based on low temperature co-fired ceramic (LTCC) technology was developed. The regulation mechanism of BaCo_0.06Bi_0.94O₃ doping on the low-temperature sintering characteristics of NiZn ferrites was systematically investigated. The results show that the introduction of BaCo_0.06Bi_0.94O₃ reduces the sintering temperature to 900 °C and significantly improves the density and grain uniformity of ceramics. When the doping amount is 0.75 wt%, the sample exhibits the lowest coercivity of 35.61 Oe and the following optimal soft magnetic properties: initial permeability of 73.74 (at a frequency of 1 MHz) and quality factor of 19.64 (at a frequency of 1 MHz). The highest saturation magnetization reaches 66.07 emu/g at 1 wt% doping. The results show that BaCo_0.06Bi_0.94O₃ doping can regulate the grain boundary liquid phase distribution and modulate the magnetocrystalline anisotropy, which provides an experimental basis and optimization strategy for the application of LTCC technology in high-frequency current sensors. Full article

The continuous discovery of novel effective antibacterial agents using nano-based materials is of high significance. In this study, we utilized Polymerylated divalent-metal-doped ferrite nanoparticles (PMFe₂O₄ NPs) and studied their antibacterial inhibition effects. Different panels of PVP- and PEG-coated metal-doped MFe₂O₄ (M ≅ Co, Ni, and Zn) were prepared via the Ko-precipitation Hydrolytic Basic (KHB) methodology and thoroughly analyzed using TEM, XRD, FTIR, and VSM. The as-synthesized doped ferrites displayed stable quasi-spherical particles (7–15 nm in size), well-ordered crystalline cubic spinel phases, and high-saturation magnetizations reaching up to 68 emu/g. The antibacterial efficacy of the doped ferrites was then assessed against a Gram-negative E. coli bacterial strain. The results demonstrated that both metal doping and polymer functionalization influence the antimicrobial efficacies and performance of the ferrite NPs. The presence of the PVP polymer along with the divalent metal ions, particularly Co and Ni, resulted in the highest antibacterial inhibition and effective inactivation of the bacterial cells. The antibacterial performance was as follows: PVP-CoFe₂O₄ > PVP-NiFe₂O₄ > PVP-ZnFe₂O₄. Lastly, cell viability assays conducted on human breast fibroblast (HBF) cells confirmed the good safety profiles of the doped ferrites. These interesting results demonstrate the distinctive inhibitory features of the biocompatible metal-doped ferrites in enhancing bacterial killing and highlights their promising potential as effective antimicrobial agents, with possible applications in areas such as water disinfection, biomedical devices, and antimicrobial coatings. Full article

Nickel-doped iron oxide/graphene oxide powders were synthesized by the co-precipitation method varying the Ni/Fe ratio, and the activity of the materials towards the oxygen reduction reaction in a microbial fuel cell (MFC) was studied. The samples presented X-ray diffraction peaks associated with magnetite, maghemite and Ni ferrite, as well as evidence of hematite. Raman spectra confirmed the presence of maghemite (γ-Fe₂O₃) and NiFe₂O₄. Scanning electron micrographs showed exfoliated sheets decorated with nanoparticles, and transmission electron micrographs showed spherical nanoparticles about 10 nm in diameter well distributed on the individual graphene sheet. The electrocatalytic activity for the oxygen reduction reaction (ORR) was studied by cyclic voltammetry in an air-saturated electrolyte, finding that the best catalyst was the sample with a 1:2 Ni/Fe ratio, using a catalyst concentration of 15 mg·cm⁻² on graphite felt. The 1:2 Ni/Fe catalyst provided an oxygen reduction potential of 397 mV and a maximum oxygen reduction current of −0.13 mA; for comparison, an electrode prepared with GO/γ-Fe₂O₃ showed a maximum ORR of 369 mV and a maximum current of −0.03 mA. Microbial fuel cells with a vertical proton membrane were prepared with Ni-doped Fe₃O₄ and Fe₃O₄/graphene oxide and tested for 24 h; they reached a stable OCV of +400 mV and +300 mV OCV, and an efficiency of 508 mW·m⁻² and 139 mW·m⁻², respectively. The better performance of Ni-doped material was attributed to the combined presence of catalytic activity between γ-Fe₂O₃ and NiFe₂O₄, coupled with lower wettability, which led to better dispersion onto the electrode. Full article

The effects of CoFe₂O₄ nanoparticles on the properties of an electro-optical liquid crystal cell based on the nematic composition of 4-Cyano-4′-pentylbiphenyl (5CB) under the influence of different forms of bias voltage were studied. Detailed results were established for the application of sinusoidal voltages with various frequencies and amplitudes. At the input signal, with a frequency of 500 kHz, a resonant current increase was obtained in the electrical circuit, followed by a decrease in the current with an increase in the frequency. This indicates the formation of a consistent oscillatory circuit. The quality factor of the nanoparticle system does not depend on the amplitude of the controlled voltage. Liquid crystal cells with constant quality can be used in a number of devices and technologies, including extended sensing devices, where stable electrical properties are required. Full article

Here, we report the hydrothermal synthesis of BFO (bismuth ferrite) and Bi_1−xAg_xFeO₃ (x = 0.01, 0.02) ultrafine nanopowders. The diffraction patterns show that all obtained particles belong to the R3c space group. On top of that, crystal structure prediction has been accomplished using bond valence calculations (BVCs). Several promising perovskite structures have been proposed together with experimentally observed modifications of BFO as a function of silver doping. Magnetization measurements were performed on BFO, both pure and substituted with 1% and 2% of Ag. The addition of Ag in BFO did not affect the Neel temperature, T_N = 630 K for all samples; instead, the influence of Ag was observed in the increase in the value and irreversibility of magnetization, which are usual characteristics of weak ferromagnetism. Our calculations based on density functional theory (DFT) are in agreement with the experimental finding of enhanced magnetization upon Ag doping of antiferromagnetic BFO, which is assigned to the perturbation of magnetic-type interactions between Fe atoms by Ag substitutional doping. Additionally, electronic and magnetic properties were studied for all phases predicted by the BVCs study. DFT predicted half-metallicity in the γ phase of BFO, which may be of great interest for further study and potential applications. Full article

This study investigates the application of double metal oxide zinc ferrite (ZnFe₂O₃) doped within zeolitic imidazolate framework-8 (ZIF-8) composites for structural, electrochemical, and supercapacitor characterization. The structural characterization has been carried out using XRD, FTIR, DTA, UV-VIS, and HRTEM. By incorporating ZnFe₂O₃, significant enhancements in the structural integrity and morphology of the ZIF-8 matrices have been achieved, with a decrease in the average crystallite size by about 23%. At 500 °C, the DTA analysis indicated that the weight loss associated with ZnFe₂O₃ decreased by approximately 5%. The estimated E_g values are 3.08 eV and 3.28 eV for ZIF-8 and ZIF-8@ZnFe₂O₃, respectively. Regarding the electrochemical performance of the ZIF-8@ZnFe₂O₃, the anodic peak current density is approximately 0.0025 A (at around 0.5 V), at a scan rate of 10 mV/s. The peak current values increase more rapidly, by about 41%, with increasing scan rate when ZnFe₂O₃ is present, indicating a synergistic effect between the ZIF-8 and ZnFe₂O₃ components. The high observed current density peak at 0.03 V can be attributed to the Fe²⁺/Fe³⁺ redox couple, facilitated by the ZnFe₂O₃ component. The ZnFe₂O₃ addition enhances the electrochemical activity of ZIF-8, leading to increased peak current values at various scan rates. This suggests that the ZnFe₂O₃ may facilitate charge transfer or improve the conductivity of the material. Full article

Various metal-based nanomaterials have been the focus of research regarding their use in controlling pests and diseases and in improving crop yield and quality. In this study, we synthesized via a solvothermal procedure pegylated zinc-doped ferrite (ZnFer) NPs and characterized their physicochemical properties by X-ray diffraction (XRD), vibrating sample magnetometry (VSM), thermogravimetric analysis (TGA), FT-IR and UV–Vis spectroscopies, as well as transmission electron microscopy (TEM). Subsequently, their impact on tomato photosynthetic efficiency was evaluated by using chlorophyll a fluorescence imaging analysis to estimate the light energy use efficiency of photosystem II (PSII), 30, 60, and 180 min after foliar spray of tomato plants with distilled water (control plants) or 15 mg L⁻¹ and 30 mg L⁻¹ ZnFer NPs. The PSII responses of tomato leaves to foliar spray with ZnFer NPs showed time- and dose-dependent biphasic hormetic responses, characterized by a short-time inhibitory effect by the low dose and stimulatory effect by the high dose, while at a longer exposure period, the reverse phenomenon was recorded by the low and high doses. An inhibitory effect on PSII function was observed after more than ~120 min exposure to both ZnFer NPs concentrations, implying a negative effect on PSII photochemistry. We may conclude that the synthesized ZnFer NPs, despite their ability to induce hormesis of PSII photochemistry, have a negative impact on photosynthetic function. Full article