Space Group Fd3m Research Articles

Synthesis, characterization, and optical properties of NiCr2O4 and CoCr2O4 spinel nanostructures for photocatalytic applications

This study focuses on the synthesis and characterization of two cubic spinel oxides, NiCr2O4 and CoCr2O4, utilizing X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, and UV-Visible (UV-Vis) spectroscopy. The investigation aimed to explore their structural and optical properties for potential applications in advanced technologies such as catalysis, sensors, and optoelectronics. XRD analysis confirmed that both NiCr2O4 and CoCr2O4 crystallize in the cubic spinel structure with the space group Fd-3m. The lattice parameters, 8.307 Å for NiCr2O4 and 8.285 Å for CoCr2O4, reveal slight variations attributed to the differing ionic radii of Ni2+ and Co2+, with both compounds exhibiting high crystallinity. FT-IR spectroscopy confirmed the presence of metal-oxygen bonding characteristic of spinel structures. In NiCr2O4, the Ni-O and Cr-O stretching vibrations were identified at 681 cm−1 and 485 cm−1, respectively, while CoCr2O4 exhibited similar vibrations at 570 cm−1 and 485 cm−1. UV-Vis spectroscopy demonstrated significant optical absorption in the UV and visible regions. NiCr2O4 displayed absorption peaks at 237 nm, 295 nm, 406 nm, and 580 nm, whereas CoCr2O4 exhibited peaks at 247 nm, 295 nm, 411 nm, and 574 nm. Analysis using Tauc plots determined optical band gaps of 2.969 eV for NiCr2O4 and 2.015 eV for CoCr2O4, confirming their semiconducting nature and suitability for visible-light-driven applications.

Application of nanocrystalline spinel MFe2O4, (M = Co and Cu) in waste water treatment

Abstract Transition metal spinel ferrites MFe2O4 (M = Cu and Co) were successfully synthesized following the co-precipitation method and their structural, optical, photocatalytic, antimicrobial and toxicity properties have been studied. The characterization of the title compound has been carried out using XRD, SEM, EDS, FT-IR and UV spectroscopy. The XRD studies confirmed a cubic spinel structure with the Fd-3m space group and CuFe2O4 and CoFe2O4 exist in the nanocrystalline size of 43 nm and 17 nm, respectively. The SEM images revealed the agglomerated nature of the ferrite nanoparticles, and the EDAX spectrum confirmed the elemental compositions of the samples and their purity. The FT-IR spectra indicated the presence of metal–oxygen stretching bands. The ferrite samples demonstrated photocatalytic activity in the visible region, as assessed by the degradation of methylene blue (MB), in an aqueous solution under visible irradiation. After 105 minutes, CuFe2O4 and CoFe2O4 catalysts exhibited degradation of 72% and 56% for the MB solution. Through broth dilution, MFe2O4 (M=Cu and Co) nanoparticles were evaluated for their antimicrobial activity using S. aureus and E. coli, as well as gram-positive and gram-negative bacteria. Studies indicated that CoFe2O4 nanoparticles exhibit better antibacterial activity when compared to CuFe2O4. However, the antifungal activity study indicated that CuFe2O4 nanoparticles exhibit better antifungal activity when compared to CoFe2O4 nanoparticles. The toxicity of the nanomaterials was tested by mixing MFe2O4 (M = Cu and Co) with food and administering it orally to Drosophila melanogaster. The results indicated that the functionalized CuFe2O4 nanoparticles are non-toxic for the living organisms. Hence, optimized NCs have the potential for degrading dyes from polluted water as well as acting as antimicrobial agents by rupturing the cells of pathogens. They have potential applications in both environmental safety and biomedicine.

Unveiling the role of sintering temperatures in the physical properties of Cu-Mg ferrite nanoparticles for photocatalytic application

This research presents an explicit analysis of the effects of sintering temperature (Ts) on the structural, morphological, magnetic, and optical properties of Cu0.5Mg0.5Fe2O4 nanoferrites synthesized via the sol-gel method. To accomplish it, Cu-Mg ferrite NPs were sintered at temperatures ranging from 300 to 800 °C in increments of 100 with a constant holding duration of 5 h. Thermogravimetric analysis was used to observe the degradation of organic components and the thermally stable zone of the material. XRD analysis and SAED patterns revealed the formation of a single face-centred cubic (fcc) spinel structure with an Fd–3m space group. The particle's crystallite sizes have grown from 4.54 to 102.54 nm as Ts have increased, consistent with TEM results. Further evidence for the creation of spinel structure was provided by two prominent absorption bands in FTIR spectroscopy below 1000 cm−1. The particles were found to have a densely packed, nearly spherical morphology, as confirmed by TEM images. The EDS was utilized to identify the chemical species that were present in the sample. A significant correlation was observed between particle size and magnetic properties. The field-dependent magnetization investigations revealed that particles with crystallite sizes of 4.54 and 5.10 nm were superparamagnetic, while those measuring 11.68, 23.81, 42.95, and 102.54 nm exhibited ferrimagnetic characteristics. Furthermore, it was revealed that an increase in sintering temperature results in a concurrent amplification of crystallites, which subsequently heightens the saturation magnetization of the prepared NPs from 9.49 to 33.04 emu/g. The coercivity value clarifies the sintering effect of transforming the particle from a single-domain to a multi-domain magnetic state. The finite-size scaling formula precisely characterizes the changes in Curie temperature. In addition, the semiconducting characteristics of Cu-Mg ferrite NPs were confirmed through DRS, which unfolded an optical band gap within the range of 1.84–2.26 eV. The Mulliken electronegativity approach unveiled the prospective efficacy of these NPs in photocatalytically generating O2 from water. Cu-Mg nanoferrites exhibit a favourable bandgap and potential as a photocatalyst, rendering them a potentially fruitful addition to the family of ferrite materials utilized in photocatalytic and associated solar energy applications.

Anticancer, Anti-inflammatory, Anti-oxidant, Structural, Magnetic, and Photoluminescence studies of Eu2 + substituted in CuZnFe2O4 for nano-ferrites for biological applications

In the present study, the synthesis of copper -zinc doped europium nano in the stoichiometric ratios (Cu0.75Zn0.25EuxFe2-xO4, where x = 0, 0.05, 0.10, 0.15, 0.20, and 0.25) ferrite is synthesized through the sol-gel method, and characterized through several characterizations like XRD, FTIR, SEM, TEM, VSM, UV-Visible, Anti-cancer studies of triple-negative breast cancer MDAMB-231, Anti-inflammatory, Anti-oxidant. XRD confirms that the samples have cubic spinel structures with an Fd-3m space group. And the crystallite size is confirmed where it lies between 13-28 nm. According to XRD measurements, the samples are single-phase, with crystallite diameters ranging from 13 nm to 28 nm. The Rietveld refinement was performed using FullProf software to determine the structural parameters of the cubic spinel system Cu0.75Zn0.25EuxFe2-xO4 doped with Eu3+ at varying concentrations, where (x = 0, 0.05, 0.1, 0.15, 0.20, 0.25). These single-phase nanostructured ferrites show extended lattice characteristics, depending on the doping concentration of Eu²⁺. The SEM analyses determined the average particle size of the synthesized materials, and this value agrees with the PXRD and TEM results. The impact of dopants on vibrational modes and chemical bonding was investigated using FTIR spectroscopy. The UV-visible investigation found the direct energy band gap, ranging from 2.25 to 1.17 eV. The synthesized chemical has ferromagnetic characteristics, according to the VSM study. Higher concentrations of Eu dopant cause an intensification in photoluminescence (PL), which is indicative of changes to the electronic structure of the material that Favor's luminescence. Because of their special magnetic and optical characteristics, copper-zinc-europium-doped ferrites have become attractive candidates for anti-inflammatory, anti-cancer, and antioxidant medications.

Structural, Dielectric, and Impedance Spectroscopic studies of (Zn0.4Mn0.4Ni0.2Ce0.2Fe1.8O4)1-x/(MWCNTs)x Nanocomposites for Future Energy Storage Applications

The novel Zn0.4Mn0.4Ni0.2Ce0.2Fe1.8O4 (ZMNCF) nanoparticles were first produced using the sol-gel auto-combustion method and then dispersed onto the surface of multi-walled carbon nanotubes (MWCNTs) with the aid of ultra-sonication and a series of different concentration of (ZMNCF)1-x/(MWCNTs)x; x = 0 – 20 wt. % nanocomposites were created. X-ray diffraction (XRD) analysis confirmed the Fd-3m space group and spinel structure of synthesized nanoparticles and revealed that the increasing concentration of MWCNTs has a great influence on the structural properties of the spinel ferrites. Transmission electron microscopy (TEM) was used to study the distribution, size and symmetry of nanoparticles and the accumulation of ZMNCF nanoparticles on the outer surfaces of MWCNTs. The estimation of different vibrational bands was examined using Fourier transform infrared (FTIR) spectroscopy. The dielectric and impedance measurements were studied in the frequency spectrum of 25 Hz to 2 MHz at room temperature. A detailed study of polarization mechanisms, Maxwell-Wagner model, and Koop’s theory and the effect of increasing concentration of MWCNTs on grain and grain boundaries have been discussed. The AC conductivity measurements conducted on the synthesized nanoparticles demonstrated an enhancement in conductivity upon the addition of MWCNTs. The percolation threshold for the nanocomposite was found to be between 10 and 15 wt. %, corresponding to a significant increase in conductivity due to the formation of a continuous conductive network. The valuable responses in dielectric properties showed that the synthesized nanocomposites could be used in future energy storage devices.

Annealing-induced changes in Sol-Gel synthesized nano-CoFe2O4: A study of structure, morphology and magnetism

Magnetic nano-sized CoFe₂O₄ spinel ferrites were synthesized using the sol-gel auto-combustion technique, and the impact of annealing temperature on their structural and magnetic properties was systematically studied. Samples were annealed at 500 °C, 700 °C, and 900 °C for 5 hours. XRD analysis confirmed crystallization in the Fd3m space group, with average crystallite sizes ranging from 30 to 34 nm. Structural parameters such as ionic radii, bond lengths, and cation distribution were also calculated, revealing partial inversion with an inversion factor of 0.68. FE-SEM analysis showed uniform morphology and increasing grain size with higher annealing temperatures. EDS confirmed stoichiometric Co and Fe ion content, while FTIR indicated strong metal-oxide bonds characteristic of CoFe₂O₄. Magnetic measurements demonstrated that higher annealing temperatures enhanced saturation magnetization and magnetocrystalline anisotropy while reducing coercivity, highlighting the significant influence of annealing temperature on CoFe₂O₄ nanoparticles' performance.

Synthesis, Cathode Properties and Crystal and Electronic Structure Changes in Charge/Discharge Process of Spinel Type Cathode-Materials 0.3MgCo2-XMnxO4-0.7Mg(Mg0.33V1.67-yNiy)O4 for Magnesium Secondary Batteries

In recent years, attention has focused on the development of next-generation rechargeable batteries using multivalent cations with even higher capacities and longer lifetimes. Among these, magnesium secondary batteries have attracted attention due to their high volumetric energy density, safety aspects, and low cost. In spinel-type Mg1+yCo2-x-yMnxO4, charge and discharge capacities were reported to increase by substituting Mn1). The authors synthesized Mg1.33V1.57Ni0.1O4, and reported that the discharge capacity after 14 cycles was 160 mAh g-1 and the capacity retention rate was high2). Mg1.33V1.57Mn0.1O4 showed the largest discharge capacity of 256 mAh g-1 at 13th cycles while the initial capacity was only 73 mAh g-1 at 90°C3). Furthermore, the authors investigated the spinel solid solution αMgCo1.5Mn0.5O4-(1-α)Mg(Mg0.33V1.57Ni0.1)O4 as a new cathode material and evaluated its battery properties, and as a result found that the initial discharge capacity at α = 0.3 was 180 mAh g-1 with the discharge capacity maintained after 60 cycles4 ).In this study, with the aim of increasing the discharge capacity of these cathode materials, new spinel type cathode material with increased Mn and Ni substitution amount, the solid solution 0.3MgCo2-xMnxO4-0.7Mg(Mg0.33V1.67-yNiy)O4 (x= 0.6, y=0.1, 0.15, 0.2) were synthesized and their battery properties were evaluated. The well-characterized sample (x= 0.6, y=0.15) was also evaluated for battery properties as a function of operating temperature. In addition, the average, local and electronic structure analyses of the pristine samples and the electrodes after charge/discharge process were carried out to elucidate the relationship between the battery properties.0.3MgCo2-xMnxO4-0.7Mg(Mg0.33V1.67-yNiy)O4 (x=0.6, y=0.1 0.15 0.2) was synthesized by the reverse co-precipitation method. The obtained samples were analyzed to identify the phase by powder X-ray diffraction, to determine the metal composition by ICP-AES. The charge-discharge tests were carried out at 90 °C and 40 °C in a 3-type cell. Synchrotron XRD (BL19B2, SPring-8) was performed on the pristine samples and some of the post-charge/discharge electrodes, and Rietveld analysis (RIETAN-FP) revealed the average structure; XAFS (BL14B2, SPring-8) investigated the valence of transition metal elements in the pristine and after charge-discharge electrodes.The products were assigned to the spinel structure with space group Fd-3m by X-ray powder diffraction. The Mg and Co and Mn and Ni contents were higher and the V content was lower than the nominal composition by ICP-AES. The charge/discharge cycling tests showed that the sample (x=0.6, y=0.15) exhibited the highest battery characteristics, with an initial discharge capacity of ca. 280 mAh g-1 and a discharge capacity of ca. 220 mAh g-1 after 19 cycles at 90°C with a cut-off voltage from 1.500 to -0.900 V vs. Ag/Ag+ (4.000 V ~ 1.445 V vs. Mg/Mg2+) (Fig.1). The sample (x=0.6, y=0.15) also showed good battery properties with a maximum discharge capacity of ca. 128 mAh g-1 at 40°C.Based on Rietveld analysis results, the pristine samples showed good fitting. The cation mixing decreased with increasing Mn and Ni substitution content. The electronic structure was analyzed by maximum entropy method (MEM) based on Rietveld analysis results, which showed that Mg insertion was easier than in αMgCo1.5Mn0.5O4-(1-α)Mg(Mg0.33V1.57Ni0.1)O4 (α=0.3)1).Rietveld analysis of the electrode (90°C) after the charge-discharge test of the sample with the best properties (x=0.6, y=0.15) showed that the ratio of spinel phase to rock salt phase was almost the same after the first discharge and after the 5th discharge. This suggests that a reversible phase transition occurs with the charge/discharge process.From the XANES spectra, the valence of all the transition metals shift to the lower valence side after discharge, with Mn in particular showing a significant shift. The EXAFS analysis revealed a relaxation of the distortion between Ni and the other metals, which may be one of the reasons for the improved battery performance due to the increased Ni substitution. Acknowledgements This research was financially supported by JST ALCA-SPRING project (JPMJAL1301) and GteX Program Japan Grant Number JPMJGX23S1. We are deeply grateful for the cooperation of Dr. T. Honma and Dr. H. Ofuchi of JASRI for the XAFS analyses (SPring-8, BL14B2), Dr. K. Osaka of JASRI for the measurement of the synchrotron X-ray diffraction (SPring-8, BL19B2). References 1) Y. Idemoto, et al., J. Power Sources, 482, 228920 (2021).2) Y. Idemoto, et al., J. Power Sources, 455, 227962 (2020).3) Y. Idemoto, et al, J. Electroanal. Chem., 928, 1107064 (2023).4) Y. Idemoto, et al, Electrochemistry, 90(2), 027002(2022). Figure 1

La3+ doped ZnFe2O4 synthesized via green chemistry approach using Uncaria gambir Roxb: A study on structural, optical, magnetic, and photocatalytic properties

Lanthanum-doped zinc ferrite (ZFLa) nanoparticles were synthesized via a hydrothermal method, utilizing Uncaria gambir Roxb leaf extract as a capping and stabilizing agent. X-ray diffraction (XRD) and Le Bail refinement confirmed a cubic spinel structure formation with an Fd-3m space group. Fourier-transform infrared spectroscopy (FTIR) analysis indicated a shift of the vibration mode of the tetrahedral site to a higher frequency with increasing lanthanum concentration. Raman spectroscopy revealed an additional peak in the A1g mode at 605 cm−1 for ZnFe1.9La0.1O4 (ZFLa10), suggesting the formation of an inverse spinel structure due to a complex cation distribution at the tetrahedral sites. Scanning electron microscopy (SEM) showed that all samples exhibited spherical grains at the nanoscale, with particle size decreasing as lanthanum concentration increased. UV–Vis diffuse reflectance spectroscopy (DRS) indicated band gap energies within the visible light range (1.84 to 1.86 eV). Brunauer-Emmett-Teller (BET) analysis confirms the increased surface area and pore diameter due to the introduction of La3+ ions, the specific surface area and pore diameter were 96.76 m2/g and 8.78 nm for ZFLa0, and 106.21 m2/g and 10.49 nm for ZFLa10, respectively. The adsorption percentage increased from 17.59 % for ZFLa0 to 55.56 % for ZFLa10. Photocatalytic investigations demonstrated that all catalysts exhibited good activity in degrading Direct Red 81 dye, with ZFLa10 showing the highest photocatalytic activity under direct sunlight, achieving up to 99.68 % degradation of the dye. Stability tests demonstrated remarkable durability, with ZFLa10 maintaining 90.20 % degradation efficiency after five cycles, establishing it as an excellent photocatalyst candidate.

Improved structural and dielectric traits of Cd-Zn spinel ferrites by co-substitution of La3+ and Er3+ cations

In the present work, the effect of co-doping of rare earth (Re3+), La and Er cations on the physical and dielectric performance of Cd-Zn spinel ferrites fabricated by sol-gel auto combustion method is reported. The prepared ferrites were doubly calcinated at 550 ℃ and 750 ℃ for 2 hours and 8 hours, respectively. The obtained samples were investigated using XRD, FTIR and dielectric measurements. XRD powder patterns verified the single-phase growth of spinel structure of all the as-synthesized ferrites with Fd-3m space group. The obtained results revealed that the Lattice constant reduces with increasing Er3+ concentrations, while crystallite size showed increasing behavior with increasing Er3+ concentration. FTIR results revealed the existence of two major absorptionbands i.e. low frequency bands in range 405-428 cm-1 and high frequency bands in range 523- 550 cm-1 which are evidence of spinel structure formation. LCR measurements are used to investigate the impact of co-doping of La3+ and Er3+ on the various dielectric parameters of prepared samples in response to frequency. Dielectric constant and loss decreased with the incorporation of Er3+, while an increase in ac conductivity was observed. The observed properties reveal that the prepared materials are suitable candidates for application in the high-speed microwave and radio frequency devices.

Synthesis and dielectric evaluations of Er doped Mg-Mn-Cr ferrites

In this study solgel auto-combustion technique was successfully implanted to synthesized Er-doped soft ferrites with the chemical formula Mg₀.₂Mn₀.₈Cr0.03Fe1.97-xErₓO₄ (MMCE ferrites). The required stoichiometric amounts of the chemicals, along with citric acid as a polymerization mediator, were calculated and used. The electrical and structural properties of Er-substituted Mg-Mn-Cr ferrite were characterized using various techniques. X-ray diffraction analysis confirmed that all samples exhibited a single-phase spinel structure with an Fd-3m space group, with X-ray density, lattice constant, and crystallite size varying based on Er concentration. Fourier Transform Infrared (FTIR) spectroscopy revealed stretching and cation vibrations of other groups in the wave number range of 250 cm⁻¹ to 1500 cm⁻¹. Scanning electron microscope (SEM) images showed that the particles were agglomerated, forming larger, closely packed clusters. DC resistivity measurements indicated that the resistivity of the samples increased significantly, reaching 10¹⁰ Ω·m at the highest La concentration. Currently, rare-earth-substituted ferrite nanoparticles are widely used in high-frequency microwave devices due to their exceptional electrical properties, making ferrites highly valuable.

Comprehensive analysis of the synthesized Zinc-doped yttrium titanate pyrochlore solid solution: Structural, vibrational, and electrochemical insights

A novel Zinc-doped Yttrium Titanate (YTZ) solid solution with a pyrochlore structure, synthesized via a solid-state route, was investigated for its potential in hydrogen storage applications. Comprehensive characterization using various techniques confirmed the formation of a cubic crystal structure with the Fd-3m space group for compositions within the ZnO content range from x = 0 to 0.30. A subtle increase in the lattice parameter (a) was observed with increasing substitution levels (x). This increase is attributed to the substitution of Zn2+ on Ti4+ sites and the concomitant creation of vacancies in both the anionic and cationic sublattices, as revealed by quantitative Rietveld analysis. The YTZ solid solution exhibits semiconducting behavior with a band gap ranging from 3.10 to 3.25 eV that may contribute to its hydrogen storage properties. Notably, the YTZ0.25 composition displayed a remarkable hydrogen storage capacity of 1200 mAh/g. This can be attributed to the presence of active redox species, favorable morphology, and the structural vacancies introduced by Zn2+ substitution, which facilitate hydrogen interaction. These findings position YTZ solid solution as a promising candidate for clean energy technologies, particularly in the realm of hydrogen storage.

Non-cytotoxic, biocompatible pyrochlore Cerium Zirconium Oxide nanoparticles for asymmetric supercapacitor applications

A novel biocompatible and non-cytotoxic Ce2Zr2O7 (CZO) nano-sized particles were developed by a straightforward hydrothermal method. Cubic structure with Fd-3m space group (227) of prepared nanoparticles has been confirmed from X-ray diffraction (XRD) patterns. Nano-sphere like particle morphology was conspicuously noticed from the FE-SEM and TEM investigations thoroughly. Particle size, inter-planar distance, SAED pattern and elemental presence were affirmatively evaluated. The elemental presence in the sample and their ionic states were systematically investigated through X-ray photoelectron spectroscopy analysis. We have investigated the cytotoxicity of the Ce2Zr2O7 nanoparticles on C2C12 (mouse myoblast cell line) cells and observed to be non-cytotoxicity on C2C12 cells which supports the eco-friendly and biocompatible nanoparticles. We have investigated the electrochemical performance of Ce2Zr2O7 nanoparticles using various electrolytes such as Na2SO4, Li2SO4 and KOH. We have obtained the predominant electrochemical performance of 250 F g−1 at 0.05 A g−1 along with appreciable cycling durability from KOH electrolyte interestingly. In addition, we fabricated asymmetric supercapacitor device and evaluated its energy and power densities systematically. We have evaluated maximum energy and power densities are in the order of 13 Wh kg−1 and 3692 W kg−1, respectively. Therefore, eco-friendly and biocompatible Ce2Zr2O7 nanoparticles could be suggested as a contender for the electrode substance for supercapacitor applications. This investigation has also been an usher hope of further technological advancement in the field of nano-biomedical along with energy storage research fields.

“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.

Investigation of Structural, Elastic and Magnetic Properties of CoCr2-xZrxO4 Nanoparticles.

This study investigates the impact of zirconium substitution on the structural, elastic and magnetic properties of CoCr2O4 nanoparticles. A series of CoCr2-xZrxO4 nanoparticles, x = 0.00, 0.05, 0.10, 0.15 and 0.20, are synthesized via the co-precipitation method. X-ray diffraction (XRD) patterns affirm the formation of single-phase cubic structure with the space group Fd3m. Special attention is given to accurately calculating the average crystallite size (D) and lattice parameter (a) using Williamson-Hall (W-H) analysis and the Nelson-Riley (N-R) extrapolation function, respectively. The increase in Zr4+ content leads to a reduction in crystallite size and an increase in the lattice parameter. Elastic properties are estimated from force constants and the lattice constant, determined from FTIR and XRD, respectively. The observed changes in the elastic constants are attributed to the strength of interatomic bonding. The stiffness constants decrease, while Poisson's ratio increases with increasing Zr4+ content, reflecting the increase in the ductility of the prepared samples. As the Zr4+ content increases, the stiffness constants decrease, and Poisson's ratio increases, reflecting enhanced ductility of the samples. Furthermore, as Zr4+ content rises, Young's modulus, the rigidity modulus and Debye temperature decrease. The magnetic hysteresis loop measurements are carried out at room temperature using a vibrating sample magnetometer (VSM) over a field range of 25 kg. Unsubstituted CoCr2O4 exhibits ferrimagnetic behavior. As Zr4+ content increases, saturation magnetization (Ms) and magnetic moment decrease, while remanent magnetization (Mr) and coercivity (Hc) initially decrease up to x = 0.10, then increase with further increases in x. The novel key of this study is how Zr4+ substitution in CoCr2O4 nanoparticles can effectively modify their elastic moduli and magnetic properties, making them suitable for various applications such as flexible electronics, protective coatings, energy storage components and biomedical implants.

Comprehensive Characterization of Bi1.34Fe0.66Nb1.34O6.35 Ceramics: Structural, Morphological, Electrical, and Magnetic Properties

Recent research in solid-state physics and materials engineering focuses on the development of new dielectric materials, with bismuth-based pyrochlores being already extensively applied in communications technology for their excellent dielectric properties and relatively low sintering temperatures. Herein, the structural, morphological, electrical, and magnetic properties of Bi1.34Fe0.66Nb1.34O6.35 ceramic, prepared by the sol–gel method and sintered at 500 °C, are investigated. The Rietveld refinement of the XRD pattern showed a cubic phase belonging to the space group Fd-3m and a crystallite size of 42 nm. Transmission electron microscopy further confirmed the crystallite size and the homogeneous distribution of Bi, Fe, Nb, and O elements, as evidenced by high-angle annular dark field imaging and STEM-EDX mapping. The morphology of the sample, assessed by scanning electron microscopy, is characterized by submicron-sized spherical particles. Dielectric spectroscopic studies revealed that the dielectric properties, strongly influenced by frequency and temperature, indicate the material’s potential for energy storage due to lower dielectric loss compared to the dielectric constant. The observed relaxation phenomena, confirmed through variations in dielectric loss and loss tangent, highlight the influence of grain boundaries and temperature on electron hopping and charge carrier dynamics. Using SQUID magnetometry, we identified two distinct magnetic phases. The primary phase, corresponding to the Bi1.34Fe0.66Nb1.34O6.35 ceramic, exhibits an antiferromagnetic behavior below its Néel temperature at around 8.8 K. A secondary high-Curie temperature ferrimagnetic phase, likely vestigial maghemite and/or magnetite, was also detected, indicating an estimated fraction below 0.02 wt.%.

Enhanced photodegradation of organic dyes using copper and zinc aluminate nanophotocatalysts

This study aims to enhance the photocatalytic efficiency of CuxZn1-xAl2O4 (x = 0.0, 0.2, 0.4, 0.6, and 0.8) nanophotocatalysts synthesized via a sol-gel self-combustion method. Rietveld analysis confirmed the formation of single-phase spinels with a face-centered cubic structure and Fd-3m space group symmetry, while electron density distribution analysis supported the ionic character of bonding within the material. Subsequent UV–visible spectroscopy revealed that the addition of Cu(II) reduced the band gap from 4.66 eV to 2.54 eV, facilitating enhanced light absorption. Consequently, the catalyst with x = 0.8 deteriorated 95 % of methyl orange (MO) and 93 % of rhodamine-B (RhB) in 120 min of visible light irradiation, following a pseudo-first-order kinetic model. The Cu0.8Zn0.2Al2O4 sample demonstrated significant reusability and stability, with degradation rates of 93–79 % for RhB and 95–81 % for MO after four cycles. Scavenging studies indicated that photoexcited holes (h), hydroxyl radicals (OH•), and superoxide radicals (O₂•⁻) were key factors in the degradation process. This study presents an improved approach for enhancing the photodegradation performance of the Cu0.8Zn0.2Al2O4 catalyst for pharmaceutical and wastewater treatment applications.

Crystallite Size Effects on Electrical Properties of Nickel Chromite (NiCr2O4) Spinel Ceramics: A Study of Structural, Magnetic, and Dielectric Transitions

The effect of sintering temperature on the structural, magnetic, and dielectric properties of NiCr2O4 ceramics was investigated. A powder X-ray analysis indicates that the prepared nanocrystallites effectively inhibit the cooperative Jahn–Teller distortion, thereby stabilizing the high-temperature cubic phase structure with space group Fd-3m. Multiple transitions are confirmed by temperature-dependent magnetization M(T) data. Moreover, the magnetization value decreases and the Curie temperature increases with a decrease in the crystallite size. The low-temperature-dependent real permittivity (ε′-T) for a NiCr2O4 crystallite size of 78 nm exhibits a broad maximum at 40 K that is independent of frequency. This establishes a correlation between electric ordering and the underlying magnetic structure. The temperature dependency of the dielectric constant at fixed frequencies for both NiCr2O4 crystallite sizes rises with temperature for a certain range of frequencies. A significant improvement is evident: the dielectric constant (ε’) at room temperature reaches approximately 5738 for the sample with 28 nm crystallites, while the 78 nm crystallite sample shows a noticeable drop to ε’~174. The frequency-dependent conductivity curves for both types of NiCr2O4 nanocrystallites have different conductivity values. The lower-crystallite-size sample demonstrates higher conductivity values than the 78 nm crystallite size one. This observation is attributed to the decrease in crystallite size, which increases the number of grain boundaries and, consequently, scatters a higher number of charge carriers.

Tunable annealing effect to enhance structural and magnetic properties of spinel cobalt magnesium ferrite nanoparticles

Cobalt magnesium ferrite nanoparticles, with the chemical formula Co0.5Mg0.5Fe2O4 (CMFO), were synthesized via co-precipitation and subjected to annealing at 200–800 °C with a step size of 200. Thermal analysis for the as-dried sample was investigated through thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The presence of a plateau region in the DTA curve above 366 °C, combined with the slight weight loss noted in the TGA curve, indicates that the ferrite sample, specifically CMFO, has successfully transitioned into its final phase. X-ray diffraction and Fourier transform infrared spectroscopy (FTIR) analysis unveiled the formation of spinel CMFO NPs belonging to the Fd-3m space group. The Williamson–Hall method showed particle size increasing from 8.20 to 52.15 nm and tensile microstrain decreasing from 6.90 to 1.84 × 10−3 with higher annealing temperatures, noted by the shift of the (311) plane. TEM images confirmed the formation of smaller nanoparticles with minimal agglomeration. Particles of nearly uniform size are achieved at the optimum annealing temperature of 600 °C, owing to its narrow distribution profile. The experimental magnetization data were analyzed using the Langevin function and the law of approach to saturation to determine the saturation magnetization, spanning from 15.46 to 43.90 emu/g. The magnetic characteristics of the annealed samples exhibited a rise in coercive force, reaching up to 349.74 Oe with the elevation of the annealing temperature. The range of attributes exhibited by CMFO makes it highly advantageous for various applications, including sensor technology, high-frequency devices, and energy storage devices.

Sol–gel derived Bi2NiNb2O9 pyrochlore: Synthesis, characterization and dielectric properties

The Pechini method was used for the first time to synthesize the phase-pure nickel-containing cubic pyrochlore Bi2NiNb2O9 (space group Fd-3m, a = 10.5371(5) Å), while the solid-phase reaction method provided no possibility to obtain impurities-free pyrochlore. At a synthesis temperature of 950°С, low-porosity ceramics with indistinct grain boundaries were formed. The results of elemental mapping indicated a uniform distribution of metal atoms on the surface of the sample. The X-ray energy dispersive analysis showed that the chemical composition of the synthesized sample corresponded to the predetermined theoretical composition. The calcination of the sample synthesized by the Pechini method was studied by the thermal analysis up to 1100°С. The functional composition of intermediate synthesis products was analyzed by vibrational spectroscopy (FTIR). In the FTIR spectrum of pyrochlore (4000–400 cm−1), absorption bands were identified at 829, 540, 654, and 490 cm−1. The dielectric properties of the pyrochlore were studied using an impedance spectroscopy. Pyrochlore Bi2NiNb2O9 has the high relative dielectric permittivity of 145 and low dielectric losses of 0.001 (at 24°С, 1 MHz), which make it a promising for dielectric in multilayer ceramic capacitors.

Photocatalytic degradation of methylene blue in aqueous media using magnesium-substituted copper ferrite as a magnetic catalyst

In this study, copper nanosized ferrites substituted with magnesium ions were synthesized using the sol-gel self-combustion method, with polyethylene glycol (MW 2000) serving as both fuel and chelating agent. Structural properties were investigated using X-ray diffraction. It was confirmed that all samples crystallized as cubic spinels with space group Fd3m. Optical studies showed band gaps increasing from 1.51 eV for CuFe2O4 to 1.62 eV for MgFe2O4, suggesting modifications in electronic structure due to magnesium substitution. Photocatalytic studies revealed that CuFe2O4 exhibited the most efficient degradation of Methylene Blue dye, with near-complete degradation at 160 minutes. Magnesium-substituted samples (x = 0.4 and x = 0.6) also showed significant degradation, though at a slower rate compared to pure CuFe2O4. Photocatalytic performance, particularly in degrading Methylene Blue, was evaluated using various kinetic models such as First- and Second-Order Kinetics, the Langmuir-Hinshelwood model, and the two-parameter Weibull distribution.