Sol-gel Auto-combustion Route Research Articles

Impact of chromium substitution on structural, spectroscopic, and dielectric properties of Ba4Ni2Fe36O60 ceramics

Cr-substituted Ni2U hexaferrite series (Ba4Ni2Fe36-xCrxO60for x = 0.0 to x = 2.0 with a step size of 0.5) was prepared via sol-gel auto-combustion route and annealed at 1200 °C for 6 h. The samples were investigated using XRD, FTIR, SEM, XPS, and high frequency (1 MHz–6 GHz) dielectric and microwave absorption measurements (VNA). XRD studies revealed that Cr3+ ions successfully substituted in BaNi2U-type hexaferrite and have a single-phase structure. The average crystallite size decreased while the percentage of porosity increased with the substitution. FTIR spectra confirmed the formation of the hexaferrite phase in all compositions. SEM micrographs revealed that the prepared samples are hexagonal. XPS spectra show the presence of all constituent elements in the samples. The dielectric constant, dielectric loss, and A.C. conductivity of samples was analyzed. Cole-Cole plots with single semicircles of different radii show the grain and grain boundaries affecting the conduction process. Moreover, Cr-substitution enhanced the microwave absorption capability. The hexaferrite sample Ba4Ni2Fe35 Cr1.0O60, with a pellet thickness of 1.81 mm, showed the highest M.W. absorption at 1.09 GHz frequency with a reflection loss (R.L.) value of −55 dB. The hexagonal-shaped morphology, high porosity, and enhanced reflection loss value suggest their use in high-frequency microwave applications.

Microwave absorption properties of ytterbium substituted X-type ferrite in P-, L-, S-, and C-band

Ba1.5Sr0.5Zn2Fe28-xYbxO46 (x = 0.00, 0.07, 0.14, 0.21, and 0.28) hexaferrite were synthesized via sol-gel auto-combustion route to investigate the microwave absorption performance in different frequency bands. The structure has a single phase, and the variation in lattice parameter was observed due to Yb-content as host iron Fe3+ and substituted Yb3+ having different ionic radii. Microwave absorbing materials (MAMs) need to be lightweight, and the maximum crystallite size of prepared material is 41 nm. The physical properties vary with substitution, and the X-ray density value is higher than the bulk density, and the porosity of the prepared sample increases when the bulk density decreases. Micro-strain values are inverse to the crystallite size because Yb3+ has larger ionic radii than Fe3+. Rietveld refinement of the XRD patterns was conducted with a lower significance value. FTIR bands observed between 414 and 500 cm−1 are present due to iron-oxygen bond stretching and bending vibrations at octahedral and tetrahedral lattice sites. The cation distribution is highly responsible for the peak position of octahedral and tetrahedral sites—the dielectric constant increases with frequency because of dipole, interfacial, and electronic/atomic polarization. AC conductivity is very low, reflecting that the material can be used as a dielectric medium in the microwave frequency range's L, S, and C bands. The best MAM among all prepared materials is Ba1.5Sr0.5Zn2Fe27.72Yb0.28O46 which can be used for global positioning systems, weather radar, and satellite feeds as it has an excellent dielectric loss, remarkable tangential loss, and the reflection loss in P-, L-, S-, and C-bands. Other real-life application of all prepared materials are multi-layer chip inductor and longitudinal media recording.

Effect of Ba substitution on dielectric and magnetic properties in La2MnNiO6 double perovskite

This paper reports the synthesis of single-phase La2-xBaxMnNiO6 (x = 0.0 and 0.5) double-perovskite using sol-gel auto-combustion route. ADXRD studies confirm the pure phase formation of the compound with the space group R3‾c and that no other structural transformation was observed even after Ba substitution. FESEM analysis show the formation of uniformly distributed ball-shaped nanoparticles and EDX spectra endorses the stoichiometric composition of the as prepared samples. The existence of mixed oxidation states of Ni and Mn ions is validated by XPS. The dielectric properties studied in the temperature range 100 K–320 K show the enhancement in the dielectric constant and the relaxor nature of the compound upon Ba substitution. The fitting of power law and Arrott's plot validates the presence of short-range ordering i.e. Griffith-like phase. The dielectric and magnetic properties are strongly linked and correlated based on enhanced antisite disorder (∼10 %). The ESR spectroscopy was used to calculate spin relaxation time and verify the existence of double exchange interaction in the compound.

Tuning the structural and optical parameters of Li1.2Ni0.4Fe2O4 for efficient degradation of dye and pharmaceutical compounds

Sol-gel auto-combustion route was used for the fabrication of lithium and dysprosium co-doped nickel ferrite (LNDFO). The composite of LNDFO with gCN (LNDFO@gCN) was prepared via ultra-sonication method. The synthesized samples were tested by photodegrading organic pollutants. Different characterization techniques were employed to examine the structure, morphology, elemental composition, and bandgap of prepared photocatalysts. The optical bandgap energy of LNFO, LNDFO, and LNDFO@gCN was 2.92 eV, 2.73 eV, and 2.64 eV, respectively. LNDFO@gCN had the lowest recombination rate of charged species and greater surface area, which makes it an efficient photocatalyst. The degradation shown by LNDFO@gCN for panadol, MB, and phenol was 90.04 %, 93 %, and 89.5 % respectively. EIS and Mott-Schottky analysis revealed that the charge transfer resistance of fabricated composite was less than bare and doped samples, and they were n-type semiconductor materials. As compared to all fabricated photocatalysts, LNDFO@gCN was most efficient photocatalyst due to its high degradation ability, easy formation, and higher charge separation rate.

Influence of Ni-doping on CuCo2O4 electrode for enhanced supercapacitor performance and sustainable energy storage

This work provides a revolutionary strategy for creating high-performance supercapacitors by designing and fabricating a unique nanostructured bimetallic oxide electrode. The proposed electrode leveraged the synergistic effects of metal oxides to enhance both energy density and charge-discharge kinetics. Ni-doped CuCo2O4 nanostructures (Cu1-xNixCo2O4) were synthesized in incremental order (x = 0.0, 0.05, 0.10, and 0.15) by facile sol-gel auto-combustion route. The nanostructures analyzed through x-ray diffraction, FTIR spectroscopy, Micro-Raman spectroscopy, x-ray photoelectron spectroscopy (XPS) and Scanning electron microscopy revealed the single phase and polycrystalline nature of CuCo2O4, with some impurity phases of CuO. The surface morphology studies showed numerous pores among the grains of Cu1-xNixCo2O4. Cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy (EIS) were used to investigate the electrochemical performance of synthesized Cu1-xNixCo2O4 samples. In a 3 M KOH electrolyte solution, the Cu1-xNixCo2O4 electrodes with x = 0.05 exhibited 2340 Fg−1 specific capacitance at 5 mVs−1, demonstrating superior electrochemical performance with excellent rate capability. Furthermore, it exhibited 35.88 Whkg−1 energy density, an exceptional 2484.74 Wkg−1 power density, and retained 99.9 % capacitance after 5000 cycles, demonstrating good stability. The results suggest that porous bimetallic oxide nanostructures can be promising candidates for the development of high-performance, environmentally friendly supercapacitors.

Modulated magnetostriction and multiferroic properties in the PVDF-based cobalt ferrite particulate composites

Multiferroic materials (MFM) have drawn substantial attention for developing smart magnetodielectric devices. Herein, cobalt ferrite CoFe2O4 (CFO) was synthesized by a glycine–nitrate sol-gel auto-combustion route and, PVDF-based particulate composite films embedded with CFO have been developed. A comprehensive investigation evaluated the effects of magnetostriction, initiated from the embedded CFO phase, on magnetodielectric characteristics of composite films. The structural, electrical, magnetostrictive and magnetodielectric properties were investigated. The embedded CFO particulate endows PVDF matrix at a higher β–phase forming ability, which enhances the ferroelectricity with a polarisation (Pmax∼1.09 μC/cm2@ 850 kV/cm), a higher dielectric constant (εr∼12.33) and lower dielectric loss. The typical magnetic hysteresis loop was obtained with saturation magnetization (MS∼4.96 emu/g) and coercivity (HC∼1.49 kOe), revealing the ferromagnetic ordering in composite films. The response of the magnetodielectric (MD) is observed at room temperature, that is, a large negative MD coefficient ∼2.1 % @ Hcr∼5.0 kOe is achieved for Co0.9Fe2.1O4/PVDF composite films, while MD∼0.65 %@ Hcr∼1.0 kOe is obtained for Co1.1Fe1.9O4/PVDF films, accompanied by a maximum MD∼4.35 % at resonance frequency. The variation in the MD performance reveals a close correlation to the modulated magnetostriction, such as the magnetocrystalline anisotropy, field-induced coefficient and magnetostrictive susceptibility, indicating the strain-mediated coupling MD effect. The multiferroic properties in CoxFe3–xO4/PVDF composites have potential for magneto-dielectric sensing applications. Furthermore, this work would be exploited to understand MD coupling mechanism and develop MFM for multifunctional devices.

Magnetic response of Ho3+ doped Ni0.4Cu0.6HoyFe2-yO4 spinel ferrites and their correlation with crystallite size

This study investigates the magnetic response of Ho3+ doped Ni0.4Cu0.6HoyFe2-yO4 (y = 0.0, 0.02, 0.04, 0.06, and 0.08) spinel ferrites (SFs) and their correlation with crystallite size. The synthesis was achieved using a sol-gel auto-combustion (SGAC) route and performed different characterizations, including X-ray diffraction (XRD), Scanning electron microscope (SEM), Energy dispersive x-ray (EDX), Inductively coupled plasma atomic emission spectroscopy (ICP-AES), and vibrating sample magnetometer (VSM) analysis. The cubic spinel phase was verified via XRD in pure NCF and Ho3+ doped NCF samples. The lattice constant (a) was improved from 8.344 Å to 8.378 Å. The substitution of Ho3+ ions led to a decrease in porosity from 42.22 % to 39.54 %. The introduction of Ho3+ ions also reduced the crystallite size (D) from 37.05 nm to 27.72 nm. The specific surface area (S) was increased from 27.44 g/cm2 to 36.14 g/cm2 with the doping of Ho3+. The average particle size (DS) was decreased from 54 nm to 35 nm. The EDX and ICP-AES analyses confirmed the good agreement with the theoretical composition. The VSM measurements provided insights into their magnetic properties. Furthermore, the doping of Ho3+ ions enhanced coercivity (HC), while reducing saturation magnetization (MS) from 64.35 emu/g to 16.22 emu/g. The decrease in crystalline anisotropy (K) observed at higher concentrations of Ho3+ may result from the increase in coercivity, potentially attributable to the smaller crystallite size of the single-domain SFs particles. The single-phase matrix and their magnetic behaviour showed that the Ho3+ doped Ni–Cu SFs samples are suitable for high-frequency applications.

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.

Optimization of dielectric response in BiFeO3–CoFe2O4 nanocomposites for high frequency energy storage devices

The rapid development of smart and sophisticated miniaturized electronic devices put a high demand for high permittivity material. In the current report, we analyze structural, morphological, and dielectric response of spinel-perovskite composites consisting of CoFe2O4 (CFO) as the spinel phase and BiFeO3 (BFO) as the perovskites phase. Here pristine BFO and CFO are fabricated using Sol—Gel auto-combustion route and their composites with a recipe (1-x) BiFeO3 - (x) CoFe2O4 (x = 0.0, 0.1, 0.2 and 0.3) using solid-state reaction technique. Structural investigation identifies presence of rhombohedral perovskite phase of BFO and cubic spinel phase of CFO and thus guarantees the formation of the composite. The crystallite size increases from 16 to 36 nm for BFO and 39.5–54 nm for CFO. The distribution of well-shaped particles with a reduction in grain size in range of 50–400 nm is witnessed in morphological analysis with the increment of CFO contents in composites. Elemental purity and the presence of various elements according to their stoichiometric ratio are witnessed during elemental investigation. A detailed analysis of the dielectric permittivity, electric modulus, and impedance of these compositions is carried out to investigate their suitability for electronic and energy storage devices. The nanocomposites under study exhibit a dielectric constant of 1126 at 100 Hz for x = 0.3, which decreases to 102 at 1 MHz. Concurrently, the tangent loss for x = 0.3 is observed to be 3.37 at 100 Hz, decreasing to 0.31 at 1 MHz. However, a decrease in dielectric loss and increase in impedance is noticed when the concentration of CFO in BFO nano-composite is increased which reflects the reduction in power losses and better control in electronic conductivity and thus highlights the role of these compositions for advanced energy storage electronic devices.

Influence of bismuth and cobalt doping on structural, dielectric, and magnetic properties of M-type calcium hexagonal ferrites

M-type hexagonal ferrites have been getting considerable attention owing to their promising application in electronic fields. Though, the growth of nanosized M-type hexagonal ferrites is still a big challenge. Herein the fabrication of M-type hexaferrite with nominal composition Ca1-xBixFe12-xCoxO19 (x=0.00, 0.05, 0.10, 0.15, 0.20) with high quality is reported by the sol-gel auto combustion route. The objective of the study is to improve the structural, spectral, dielectric, and magnetic characteristics of M-type hexagonal ferrite which was achieved through the variation of concentration of Cobalt and Bismuth. X-ray diffraction (XRD) patterns confirmed the single-phase M-type hexagonal structure. The crystallite size of all samples was found to be in the range of 42–49 nm. Other parameters such as lattice parameters a & c, unit cell volume, crystallite size, X-ray density, Bulk density, and porosity were also calculated. The doping contents were found to decrease the bulk and X-ray densities while increasing the porosity. Fourier-transform infrared (FTIR) spectra showed the formation of metal-oxygen stretching vibrations that confirmed the formation of hexagonal ferrites. The scanning electron microscopy (SEM) images revealed a regular platelet hexagonal structure and homogeneously distributed grains were examined. The dielectric constant was high at low frequency and then decreased with increasing frequency, while the dielectric loss was decreased appreciably with doping. The saturation magnetization ranged from 15.51 to 38.27 emu/g, coercivity increased from 207.93 to 1359.69 Oe, and the squareness ratio was found to be in the range of 0.19–0.78. The dielectric and magnetic properties of Ca1-xBixFe12-xCoxO19 (x=0.00, 0.05, 0.10, 0.15, 0.20) with the variation of Co and Bi revealed that these materials are good candidates for modern devices.

Advancements in multiferroic, dielectric, and impedance properties of copper–yttrium co-doped cobalt ferrite for hydroelectric cell applications

This paper explores yttrium and copper co-doped cobalt ferrite [Co1−x Cu x Fe1.85Y0.15O4] synthesized via the sol–gel auto-combustion route (0.0 ⩽ x ⩽ 0.08). Investigating the impact of co-dopants on CoFe2O4, the study reveals altered cation distribution affecting the structure, multiferroic, and electrical properties. X-ray diffraction studies show nanocrystalline co-doped cobalt ferrites with lattice expansion and smaller grains due to Cu–Y co-doping. Fourier transform infrared spectroscopy confirms inverse spinel family classification with tetrahedral lattice shrinkage. Field emission scanning electron microscopy indicates a grain size of approximately 0.12 μm. Ferroelectric analysis reveals a peak saturation polarization of 23.42 μC cm−2 for 8% copper doping, attributed to increased Fe3+ ions at tetrahedral sites. Saturation magnetization peaks at 54.4706 emu g−1 for 2% Cu2+ ion substitution [Co0.98Cu0.02Fe1.85Y0.15O4] and decreases to 37.09 emu g−1 for 4% Cu substitution due to irregular iron atom distribution at tetrahedral sites. Dielectric studies uncover Maxwell–Wagner polarization and high resistance in grain and grain boundaries using impedance spectroscopy. Fabricated hydroelectric cells exhibit improved ionic diffusion, suggesting their use in potential hydroelectric cell applications.

Influence of Ni2+ ions on structural, spectral and dielectric properties of Sr–Co spinel ferrites synthesized by sol-gel auto-combustion route

Nickel substituted Sr–Co nano spinel ferrites with composition Sr0.5-xNixCo0.5Fe2O4 (0.0, 0.1, 0.2, and 0.3) were prepared with the help of a sol-gel auto combustion route. The prepared materials were sintered at 800 for four and a half hours. Analysis of XRD confirmed that the material is composed of a cubic spinel structure with a single phase, and its space group is Fd-3m. Rietveld refinement of X-ray diffraction data was done for all prepared compositions using FULLPROF software. As the composition under study contains more nickel than lattice constant, crystalline size, X-ray density, and bulk density decrease. The dielectric properties were observed about frequency. The dielectric properties revealed that dielectric loss, dielectric constant, and ac conductivity decrease with increasing the Ni2+ content. The activation energy (ΔE) was calculated from the slope of Arrhenius plots. The ΔE found in the range of 0.580–0.096 eV. The analysis of XPS was carried out to examine the elemental state of annealed samples. The prepared material is suitable for employment in applications involving high frequencies because the Ni-doped Sr–Co ferrites with the greatest Ni2+ concentration have the lowest dielectric loss, dielectric constant, and tangent loss value.

Microstructural, morphological and magnetic behaviour of Al3+ replaced BaFe11.5Co0.5O19 hexaferrites synthesized via sol-gel auto combustion route

In this work, polycrystalline BaFe11.5-xAlxCo0.5O19 (0≤x≤2) hexaferrite samples were synthesised by means of the sol–gel technique. Thereafter, the magnetic and structural properties are thoroughly examined. Cell refinement and XRD examination verified a magnetoplumbite hexaferrite arrangement with a space group of P63/mmc for each sample. The parameters ‘a’ and ‘c’ in the lattice fall in value from 5.885 Å to 5.875 Å and from 23.117 Å to 23.049 Å, respectively. Both the average crystallite size and the unit cell volume exhibit a declining trend as the doping level increases. For M-type hexaferrites, the optimal range of c/a values is determined to be 3.923–3.928. X-ray density (dx) and bulk density (db) decline with rising doping contents until x=1.5 doping content, at which point they exhibit an increasing trend. The results showed that as the doping amount increased, the saturation and remanence magnetizations decreased. Coercivity and magnetocrystalline anisotropy are rising together. Both the anisotropy field (Ha) and the anisotropy parameter (B) exhibit a rising trend with doping content. Coercivity of 5.896 kOe, anisotropic applied field of 1.84 kOe, saturation magnetization of 42.68 emu g−1, remanence magnetization of 24.414 (emu/g), and magnetic moment per formula unit-(mB) of 11.19 μ B are the best magnetic properties obtained for the BaFe10Al1.5Co0.5O19 sample.

Synthesis, characterization, DFT calculations, and anticancer properties of VI-period and f-block elements-substituted zinc oxide nanopowders

Nanotechnology provides promising ways in which a wide range of new materials can be manufactured which appear to have enormous potential in the field of biomedicine and life sciences. ZnO can be applied in many physical and optical processes and used as a good anti-cancer agent. ZnO NPs are recognized as SAFE or GRAS, non-toxic and biocompatible particles. In this study, wurtzite ZnO samples co-doped by rare earth elements (Tb, Er) were prepared via sol-gel auto-combustion route and their crystallographic structure as well as their morphologies were examined using XRD and TEM techniques. The analysis disclosed that all synthesized products crystallized in a hexagonal structure and the crystallites/particles size diminished with the increase of co-doping content. The electronic structure and optical properties of the different products were assessed using DFT calculations. Doping Tb and Er rare earth elements into ZnO has a significant effect on its optoelectronic properties. The computational study showed that the co-doping of Tb and Er on pure ZnO decreased the band gap and increased the refractive index. The extinction spectrum of pristine ZnO showed a peak in the ultraviolet region at 5 eV, while those of the co-doped ZnO samples displayed stronger peaks in the infrared region (near 0.4 eV). The anticancer properties of Tb/Er co-doped ZnO nanoparticles were examined on cervical cancer (HeLa cells) and colon cancer (HCT-116) by using an in vitro MTT assay. The cell viability assay findings indicated a reduction in HeLa and HCT-116 cells after 48 h of treatment of the synthesized samples. The treatment with co-doped ZnO nanoparticles produced chromatin condensation and formation of apoptotic bodies in HCT-166 cells, which indicates that the prepared co-doped ZnO nanoparticles induced programmed cell death in HCT-116 cells. According to these results, it can be concluded that the prepared Tb/Er co-doped ZnO nanoparticles have promising applications in developing new optoelectronic devices and also in treating cervical and colon cancers.

Structural, physicochemical and electrical properties of Co2Y-type barium hexaferrites

Y-type hexaferrite ceramic materials of nominal composition Ba2Co2CrxYxFe12-2xO22 (x = 0.00, 0.03, 0.06, 0.09, and 0.12) were synthesized by sol-gel auto combustion route. Y-type hexaferrites are technologically important ceramic materials for fabricating modern electronic devices and microwave absorbers due to their unique electrical and dielectric properties and reflection loss behavior. XRD classifies the single-phase formations with space group R 3‾ m. The crystallite size of the synthesized samples was calculated in (34–41) nm range. The specific absorption band in FTIR spectra approves the (Fe–O) stretching vibrations at wavenumbers 446 and 478 cm−1. The substitution of iron by Cr3+ and Y3+ increases DC resistivity from 1.03 × 1011 to 1.17 × 1012 Ω cm by limiting the electrons jumping between ferrous and ferric ions. The activation energy and drift mobility were also calculated among the substituting content of Cr3+-Y3+. The dielectric response in 1 MHz–6 GHz frequency was determined and the effect of substitution has been observed. The Maxwell-Wagner (MW) bilayer model is used to study dispersion in dielectric parameters with reference to applied frequency. The maximum values of dielectric losses were obtained at 6 GHz in the range of 0.37–0.60. The coercivity values confirms the soft magnetic nature of synthesized samples. The microwave absorption (MW) properties of synthesized materials were improved upon Cr3+-Y3+ substitution. Minimum reflection loss RLmin = −66 dB (99.99% absorption of MW) at 1.46 GHz frequency and 1.96 mm thickness was obtained for x = 0.09 composition. All investigated samples are efficient materials for stealth technology, radar cross-reduction, EM interference shielding, and high-frequency applications.

Comparative Study of Rare Earth Nd and Sm Doping on the Structural, Morphological, Optical, Magnetic, and Electromagnetic Traits of Mg-Zn-Cu Spinel Nanoferrites

In the current study, the magnetic nanoparticles of neodymium and samarium substituted Mg-Zn-Cu, with a chemical composition of Mg0.5Zn0.5Cu0.05RxFe1.95-xO4 (x = 0.05; R = Nd, Sm) were produced via the sol-gel auto-combustion route. XRD indicates the evolution of a cubic symmetry having Fd3m space group and no impurities at the room temperature. The FESEM images show the irregularly shaped and agglomerated grains in all samples. FTIR examination reveals the stretching vibrations among the metal cations and anions at interstitial vacancies. The M-H graphs demonstrates that the prepared nanoferrites have low rentivity (0.18–0.84 emu g−1) and coercivity (11.25–34.03 Oe) indicating the formation of superparamagnetic nature. From the electromagnetic traits, the observed sample’s real magnetic permeability (μ″) and permittivity (ε′) along with dielectric loss and magnetic loss reduced with increasing applied field frequency, indicating the typical behaviour of spinel nanoferrites. This may be explained by Maxwell-Wagner interfacial polarisation and the electron hopping among the ferrous and ferric ions. The variations in coercivity, anisotropy constant, and electromagnetic traits provide strong evidence that all of the samples are thermally stable and have the potential to be used in solenoids and transformers, and also, in the more resistive devices that operate at the high frequency.

GO optimization strategies for improved capacity retention in transition metal oxides based ternary nanocomposites for high-performance supercapacitors

This work presents the optimization of GO in transition metal oxide based ternary nanocomposites (NiO/ZnO@(GO)x)for electrode materials in supercapacitor applications. The nanocomposites were synthesized using a straightforward sol-gel auto combustion route followed by sonication. It was observed from XRD analysis that crystallite sizes of NiO/ZnO@(GO)x nanocomposites vary between 49 and 24 nm. According to morphological study, the TEM images depict a hybrid nanoarchitecture with NiO/ZnO nanoparticles dispersed on graphene sheets. The maximum specific capacitance of 1833.9Fg−1 was obtained for NZG3 (NiO/ZnO with 6% GO).Furthermore, largest capacity retention of 98.7% was achieved for NZG3 after 6000 continuous cycles. NZ demonstrated 96% capacitance retention, for NZG1 it was 97.2% and capacity retention for NZG3, it was 98.7%. Therefore,optimized concentration of GO in NiO/ZnOnancomposite to achieve maximum specific capacitance and cyclic stability was found to be forNZG3 nanocomposite. The Rs values attained were found to be 6.7 Ω, 5.8 Ω, 5.4 Ω, 4.4 Ω and 4.9 Ω for NZ, NZG1, NZG2, NZG3 and NZG4 respectively whereas Rctvalues for NZ and NZG electrodes i.e. NZG1, NZG2, NZG3 and NZG4 10.0 Ω, 9.4 Ω,8.5 Ω,7.8 Ω and 8.1 Ω respectively, demonstrating that GO plays an important role in enhancing conductivity.

Dielectric and magnetic response of Cu-Co-Sm ferrite impregnated with graphene nanoplatelets for high-frequency device applications

This work studied a composite of graphene nanoplatelets (GNPs) impregnated copper-cobalt-samarium ferrites Cu0.5Co0.5Fe1.97Sm0.03O4/GNPs synthesized via sol-gel auto-combustion route. The structural, electrical, dielectric, and optical properties of the as-prepared composites were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), EDX, I-V characteristics, impedance measurement, raman spectroscopy, scanning electron microscopy (SEM), vibrating sample magnetometry (VSM) analysis, and UV–visible spectroscopy. XRD confirmed that the spinel ferrites had a crystalline single-phase FCC structure with the lattice constant of around 8.33 Å, and the crystallite size range from 54.10 nm to 51.85 nm. SEM analysis confirmed the homogenous dispersion of spinel ferrites in graphene sheets, and EDX confirmed the presence of all elements in ferrite composites with GNPs. Furthermore, the spinel matrix was confirmed by the Raman and UV-visible analysis. A minimum particle size of 21.73 nm was determined using TEM, and the minimum value of activation energy (0.01 eV) was obtained from IV characteristics for ferrite composite with 2.5% GNPs. Further, our ferrite composites with GNPs demonstrated improved electroconductive properties, with conductivity ranging from 5.88×10−8S/cm to 1.04×10−6S/cm at 673 K. The real & imaginary part of permittivity, dielectric constant (ε’), and impedance (Z) were also improved with the addition of GNPs. At low frequencies, a permeability loss value of 0.81 was obtained for the ferrite composite with 5% GNPs. VSM analysis confirmed that the saturation magnetization decreased in ferrite composites with graphene nanoplatelets. The minimum value of skin depth of 1.03 mm was observed at 1.25 % GNPs. Our ferrite composites with GNPs exhibited minimal eddy current at high frequencies, making them promising candidates for high-frequency device applications.

Structural, morphological, dielectric, and spectral properties of Sr-Mg-Ho X-type magnetic nano materials suitable for microwave absorption application

Holmium (Ho3+) substituted Sr2Mg2Fe28O46 X-type hexa-ferrites were synthesized using the sol-gel auto-combustion route. The single phase of Sr2Mg2Fe28-xHoxO46 where 0.00 ≤ x ≤ 0.20, Δx = 0.05, X-type hexa-ferrites was confirmed using XRD peaks. The crystalline size was studied from XRD data and found to be in the 11 nm–24 nm range. The micro strain increased with the substitution of Ho3+. FTIR exposed the specific stretching vibration and absorption peaks in the 400 cm−1 - 600 cm−1 range. The force constant (ko) decreased from 1.74 N/cm to 1.65 N/cm with the increasing concentration of Ho3+. The grain size range is 371–493 nm, measured by SEM analysis, and plate-like structure plays a crucial role in enhancing the permeability of magnetic material. Transmission electron microscopy (TEM) analysis showed the hexagonal structure of X-type ferrites (x = 0.20). The results of the X-ray photoelectron spectroscopy (XPS) experiment confirmed the presence of all metal ions in the given composition with their required valences. The dielectric constant, dielectric loss, and tangent loss are found to increase with the substitution of the Ho3+ ion. In addition, the higher values of dielectric parameters and dielectric loss suggest that the material may suitable for high-frequency applications and best for microwave absorbers. Our aim is to discuss the characteristics and applications of microwave absorption materials, understand their behavior, and contribute to the development of upcoming novel devices. The resonance peak's appearance shows that these materials are best for multilayer chip inductors and EMI attenuation.

Impact of samarium on structural and dielectric properties of U-type hexaferrites synthesized by a sol-gel auto combustion route: Analysis of XPS, Raman and FTIR spectra

In this work, the impact of rare earth element samarium "Sm" substitution on Ba4Co2SmxFe36-xO60 U-type hexaferrites was studied in detail. Five compositions with step size x = 0.00, 0.025, 0.050, 0.075 and 0.1 were synthesized. These five series were prepared using the sol-gel auto-combustion method and the samples were sintered for 6 h at 1250 °C. The synthesized samples were characterized by XRD, FTIR, Raman Spectroscopy, X-ray photoelectron Spectroscopy and vector network analyzer (VNA). The structure crystallography of Ba4Co2SmxFe36-xO60 was examined via XRD. The impact of Sm3+ substitution was assessed across all lattice parameters. Lattice constants 'a' and 'c' were found between 5.886 and 5.881 Å and 113.179 to 113.037 Å, respectively. FTIR was used to learn more about the crystal structure and atomic vibrations between 400 and 1000 cm−1 wave number, where higher frequency bands appear at 570 cm−1 (tetrahedral site) and the lower frequency band occurred at 424 cm−1 due to the metal-oxygen stretching vibration (Fe-O) bond at the octahedral site. Each spectrum supported a U-type hexagonal structure i.e. an investigation of the chemical and intermolecular bonds via Raman spectra. XPS confirms the presence of elements in materials. Different dielectric parameters were observed in the 1 MHz to 6 GHz range of all prepared samples. Cole-Cole graphs of prepared materials highlighted the influence of grain boundaries. A solitary semicircle in the impedance of a specific section of grain boundaries was evidenced through Cole-Cole plots. Dielectric properties strongly depend on electron hopping between Fe2+ and Fe3+ ions. The optimized parameters suggest the utility of these materials in microwave devices, multilayer chip inductors and high-frequency electrical circuit applications to reduce skin effects.