Citrate Sol Gel Route Research Articles

Structural, optical, magnetic, and photocatalytic analysis of exclusive metal aluminates against Congo Red dye under UV light

The exclusive ZnAl2O4 (ZAO), CaAl2O4 (CAO), and MgAl2O4 (MAO) nanocrystallites were prepared by the citrate sol–gel route and further annealed at 600 °C for 2 h. XRD and Rietveld refinement were conducted to explore the crystal structure and to optimize the profile parameters. FTIR confirmed the vibrational peaks of relevant functional groups. The additional stretching and bending IR modes in MAO sample emphasized structural disorders like antisites/native defects. The UV-DRS spectra of these samples analyzed the direct bandgap in 2.76–4.29 eV range. HR-TEM micrographs characterize the well-developed nanosized grains. From VSM data, several magnetic parameters were collected for prepared aluminates and found MAO as best ferromagnetic material with the highest coercive field value (1235 Oe). PL spectra of metal aluminates suggest that the broad peak in violet-blue is attributed to the band edge emission, and finite peaks in higher wavelength regions have appeared due to the large density of surface traps and oxygen vacancies. The photocatalytic mechanism of ZAO, MAO & CAO nanopowder was elucidated on the Congo Red dye (10–70 ppm) solution after exposure to UV light. The highest value of rate constant (k = 0.0118 min−1) suggests that the MAO (0.3 g l−1) sample would be an efficient photocatalyst (98%) under UV light owing to its large surface area (125 m2 g−1) and suitable bandgap. The overall results advocate the practical applicability of aluminate photocatalysts in water treatment, spintronics, and photonics.

Composites of Zn-Co spinel ferrites and PANI: Structural, magnetic, microwave absorption characterization in 18–40 GHz

The present research work deals with the fabrication of composites containing spinel ferrites and polyaniline as high-performance microwave absorbers. The composites were prepared by the inter-mixing of Zn-Co spinel ferrites and PANI polymer in a 4:1 M ratio using the mechanical blending technique. The sol–gel citrate route was employed to synthesize Zn-Co spinel ferrites, while the oxidative polymerization method was used to synthesize PANI. The structural, morphological, magnetic, and microwave absorption properties of the composite samples were characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), vibrating sample magnetometer (VSM), and vector network analyzer (VNA), respectively. The X-ray diffraction patterns indicated the crystalline nature of spinel ferrites and the amorphous nature of PANI. The magnetic properties revealed that saturation magnetization (Ms) increased significantly with the addition of spinel ferrites into PANI owing to its magnetic nature. The microwave absorption results showed that the minimum reflection loss (RL) reached up to −26.63 dB at 20.72 GHz with the effective bandwidth of 5.95 GHz in the K-band and −39.16 dB at 35.68 GHz with the effective bandwidth of 8.1 GHz in the Ka-band for composition NZP. This study indicated that the prepared SF/PANI composites can be proposed as a promising absorbent in the K-band and Ka-band.

Cu-Doped SrTiO3 Nanostructured Catalysts for CO2 Conversion into Solar Fuels Using Localised Surface Plasmon Resonance

Carbon dioxide valorisation is one of the most discussed topics amongst researchers; indeed, finding a way to significantly reduce CO2 concentration in the atmosphere is crucial in order to mitigate climate change effects in the next decades. In this study, SrTiO3-supported Cu nanoparticles are exploited as Localised Surface Plasmon Resonance (LSPR)-mediated catalysts for CO2 reduction. The materials were prepared via sol–gel citrate route methodology, inserting Cu as a dopant in the perovskite structure; reducing treatments at different temperatures were performed to promote copper atom exsolution, thus forming nanostructures upon the surface. The perovskitic structure was confirmed via ex situ and operando XRD analysis, while compositional analysis was carried out through XPS and EDS; SEM and TEM images revealed morphological changes with different reducing treatments, and bulk reducibility was analysed with H2-TPR, revealing different Cu species in the material. Band gap analysis via DRS showed the successful incorporation of copper in the perovskite, affecting the light absorption properties. Finally, catalytic tests showed that copper nanoparticles play a role in CO2 activation with sunlight, proving that LSPR could be exploited for catalytic means.

Characterization of sol-gel synthesized Zn0.25Co0.75(NiZr)xFe2-2xO4 (0.05 ≤ x ≤ 0.25) spinel ferrites based microwave absorbers in Ka frequency band

A series of nickel and zirconium co-substituted zinc-cobalt spinel ferrites with the chemical formula Zn0.25Co0.75(NiZr)xFe2-2xO4 (0.05 ≤ x ≤ 0.25, Δx = 0.05) was successfully synthesized using the sol-gel citrate route to curb the rapidly growing electromagnetic pollution caused due to 5G technologies. A comprehensive study of the structural, morphological, magnetic, optical, electromagnetic, and microwave absorption characteristics was carried out to analyze the effect of Ni2+ and Zr4+ ionic substitution. X-ray diffraction confirmed the formation of nanoparticles having a cubic spinel structure with an Fd-3m space group. Magnetic parameters like saturation magnetization and remanent magnetization were found to decrease with increasing the level of substitution. The permittivity, permeability, and absorption properties were investigated in the Ka-band (26.5–40 GHz). Composition x = 0.10 yielded an optimum value of reflection loss up to −50.34 dB at a matching frequency of 29.20 GHz and a matching thickness of 1.3 mm. The results obtained suggest that the synthesized materials prove to be good microwave absorbers for next-generation devices and applications.

Study of magnetic, elastic and Ka-band absorption properties of Zn1−xCoxFe2O4 (0.00 ≤ x ≤ 1.00) spinel ferrites

Magnetic, elastic, electromagnetic, and microwave absorption properties of cobalt-substituted zinc spinel ferrites Zn1-xCoxFe2O4 (0.00 ≤ x ≤ 1.00, Δx = 0.25) fabricated via the sol–gel citrate route are analyzed. The hysteresis loops of constituent ferrites revealed the rapid rise in saturation magnetization and coercivity with the doping of cobalt ions. The FT-IR spectra exhibit two vibrational bands in the scope of 521–560 cm−1 and 397–404 cm−1. Complex permittivity (ɛr) and complex permeability (µr) are analyzed using a vector network analyzer in Ka-band. The absorption is maximized by tuning the thickness of the sample from 0.8 mm to 3.5 mm using the quarter wavelength model. Maximum absorption of 99.14 % at a matching frequency of 34.60 GHz and a matching thickness of 1 mm is obtained by the composition with × = 0.75. The prepared ferrite composition proves to be an efficient microwave-absorbing material at high frequencies ranging from 26.5 to 40 GHz.

Influence of Sr and Ce Codoping on Structural, Electrical and Thermoelectric Properties of CaMnO3

Polycrystalline samples of CaMnO3 and Ca1-x-ySrxCeyMnO3 with Ce/Sr double substitution (x = 0.02, 0.04, 0.06; y = 0.02) were prepared by citrate sol-gel route. The samples’ phase was confirmed using the X-ray diffraction (XRD) technique, revealing that they only contain a single phase with an orthorhombic perovskite structure and no impurity phases. Also, the increase in lattice parameters with Sr2+ doping was observed. Rietveld refinement was done on the X-ray pattern using Fullprof software to find parameters. Using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), analyses of morphology and elemental compositions were performed. On sintered samples, electrical resistivity measurements were made using DC four-probe techniques. And conduction mechanism was explained based on a small polaron hopping mechanism. Between 308 K and 673 K, thermoelectric characteristics were studied. Ca0.94Sr0.04Ce0.02MnO3 has the highest power factor of all the prepared co-doped Ce/Sr samples.

Fabrication of Zn0.25Co0.75(MnZr)xFe2–2xO4 spinel ferrites as broadband microwave absorbers in 26.5–40 GHz frequency range

With the advent of 5 G technologies, developing microwave-absorbing materials is an urgent need to address the issues caused by harmful electromagnetic pollution. For this purpose, a novel ferrite series with composition Zn0.25Co0.75(MnZr)xFe2–2xO4 (0.05 ≤ x ≤ 0.25, ∆x = 0.05) was successfully synthesized using the sol-gel citrate route. Also, the effects of the co-substitution of Mn and Zr on the structural, morphological, magnetic, electromagnetic, and microwave absorption characteristics of zinc-cobalt spinel ferrites were studied. The X-ray diffraction patterns indicated the formation of nanoparticles having a cubic spinel lattice structure. Coercivity was found to decrease whereas saturation magnetization increased with the increasing level of substitution from MZ 0.05 to MZ 0.25. In Ka-band, the experimental results showed that MZ 0.15 outperformed all the prepared compositions by exhibiting a minimum reflection loss of −27.99 dB and an efficient absorption bandwidth of 6.5 GHz at a narrow sample thickness of 2.2 mm. The simulation performed by varying the sample thickness revealed that the high values of gross loss tangent and excellent impedance matching lead the composition MZ 0.20 to achieve the optimum value of reflection loss of − 42.71 dB at a matching frequency of 29.20 GHz and a matching thickness of 1.1 mm. These findings suggested that the fabricated materials prove to be efficient absorbers in the 26.5–40 GHz frequency range.

Structural, Electrical, and Thermoelectric Properties of La and Sr Co-Doped CaMnO3 Compounds

Polycrystalline samples of CaMnO3 and Ca0.98-xSrxLa0.02MnO3(x = 0.00, 0.02, 0.04, 0.06) were prepared by citrate sol-gel route. X-ray diffraction technique was used to confirm the single phase of the samples. Morphology, Elemental compositions were carried out using scanning electron microscopy & energy dispersive spectroscopy respectively. Raman spectroscopy measurements reveal that the structural distortion is mainly due to the rotation of MnO6 octahedral than Jahn Teller. Electrical resistivity measurements were carried out on sintered samples using the DC four-probe method and they disclose that La and Sr Co-doping can lower the resistivity. Thermoelectric properties were evaluated in the range of 303 K and 673 K, indicating that the majority of charge carriers are electrons. Among all the prepared co-doped La/Sr samples, Ca0.94Sr0.04La0.02MnO3 possess a higher power factor.

Microwave absorption characteristics of cobalt doped zinc spinel ferrites in Ku-band (12.4–18 GHz)

This research study targets to fabricate microwave absorbers with narrow sample thickness, strong absorption power and broad bandwidth simultaneously. The zinc-cobalt spinel ferrites with compositional formula Zn1-xCoxFe2O4 (x = 0.00, 0.25, 0.50, 0.75 and 1.00) are successfully synthesized via sol–gel citrate route by sintering at 1000 °C. Vector network analyzer is employed to determine dielectric permittivity εr=ε′-jε" and magnetic permeability μr=μ′-jμ" in Ku-band. Enhancement in dielectric losses from 0.3051 to 0.4066 and magnetic losses from 0.0087 to 0.5911 with increasing cobalt concentration from x = 0.00 to x = 1.00 at 12.4 GHz frequency helps in achieving good absorption. Normalized wave impedance and quarter wavelength model are used to maximize absorption or minimize reflection. Significant absorption is achieved by tuning thickness of the sample from 1.8 mm to 3 mm. The composition x = 0.75 exhibits superior absorbing properties by showing reflection loss as low as −31.45 dB along with −10 dB bandwidth of 5.6 GHz at a matching thickness of 2.2 mm. The fabricated ferrite samples are proved to be promising applicants for absorption of electromagnetic interference (EMI) in radar and stealth technology.

Chitosan-based Dy2O3/CuFe3O4 bio-nanocomposite development, characterization, and drug release kinetics

Chitosan (CS)/metal oxide (MO) nano-carriers have recently attracted attention due to their great integration into several biomedical applications. Herein, CS and dysprosium oxide based bio-nanocomposites (Dy2O3/CuFe3O4/CS) were prepared using a citrate sol-gel route for biomedical settings at large and drug delivery, in particular. The chemical structure, average crystallite size, and surface morphology of Dy2O3/CuFe3O4/CS bio-nanocomposites were characterized using spectroscopic techniques, including FT-IR, PXRD, and SEM. The prepared nano composite's drug loading or release kinetics were investigated by FT-IR, zeta potential (ZP), and ultraviolet-visible spectroscopy (UV–Vis). In the FT-IR spectrum, the peaks in the range of 800–400 cm−1 confirmed the formation of meta-oxides, while amide bands at 1661 and 1638 cm−1 revealed the existence of CS in the bio-nanocomposite. The peaks at 2θ = 35.46 and 28.5, 39.4 indicated the presence and chemical interaction of Dy2O3 and CuFe3O4, respectively. The crystallite size was <20 nm. The model drug used in the loading and in vitro release assays was ciprofloxacin hydrochloride. Ciprofloxacin's CF stretch caused a modest peak to be seen at 1082 cm−1 and changed in zeta potential value from 7.90 mV to 8.88 mV endorsing that the drug had been loaded onto the nanomaterial. The loading efficiency (%) of CIP onto the composite was from 25 to 30 %, calculated from optical density measurements. Different kinetic models, such as zero-order, first-order, Higuchi, Hixon-Crowell, and Korsmeyer-Peppas, were determined to confirm the drug release mechanism. The percent (%) of drug release from the surface of Dy2O3/CuFe3O4/CS in PBS (pH 7.4), acidic (pH 2.2) and basic (pH 9.4) dissolution media were found to be 70, 28 and 20 %, respectively. Drug kinetics showed that mainly the release is fickian type followed “Fick's law of diffusion”, slightly deviated from fickian release (dissolution-dependent system). Korsmeyer-Peppas (R2 0.9773, n < 0.4) and Higuchi's (R2 0.9846) models were the best for fitting controlled drug release data. The results revealed that the Dy2O3/CuFe3O4/CS bio-nanocomposite has good potential for a controlled drug delivery system.

Colossal permittivity, resistive and magnetic properties of zinc substituted manganese ferrites

Zinc substituted manganese ferrites, i.e., Mn1−xZnxFe2O4 (0.0 ≤ x ≤ 1.0) were synthesized by the citrate sol-gel route. Rietveld refinement of the X-ray diffraction patterns revealed the development of a single-phase cubic spinel structure with space group Fd3̅m. The stoichiometry of the prepared samples was confirmed by energy dispersive X-ray spectroscopy. The 57Fe Mössbauer study suggested the presence of Fe3+ and Fe2.5+ (mixed Fe3+ and Fe2+) ions at the tetrahedral and octahedral sites of the mixed spinel structure, respectively. However, the fraction of Fe2+/Fe3+ ions present at the octahedral site strongly depends on the site preference of Mn2+ and Zn2+ ions for both sites. Thus, the cation distribution among the tetrahedral and octahedral sites altered with increasing Zn2+ substitution (x). Impedance spectroscopy analysis displayed an enhancement in the resistive properties of MnFe2O4 with Zn2+ substitution, while the dielectric permittivity of the prepared samples exhibited a colossal value of the order of 104–107 at room temperature. This enhancement in the resistive and dielectric properties can be understood in terms of particle size, cation distributions, and conductivity inhomogeneity at the grain boundaries. The temperature-dependent ac conductivity analysis proposed that the short-range hopping of oxygen vacancies is responsible for the conduction process in the prepared samples. Here, our findings of high resistance (107), colossal permittivity (106), diminished tangent loss (0.018), and high magnetization (48 emu/g) for the Mn0.4Zn0.6Fe2O4 make this composition promising for radar absorbing applications.

Uncovering the consequences of Ag1+ on nano-structural, magneto-optical, antibacterial, and antifungal response of nickel oxide particles

Metal oxide nanoparticles existing in transition metal series have intensely earned high research interest among material scientists by virtue of their dispersive magnetic nature desirable for antimicrobial action. Herein, we report the unsubstituted and silver (Ag) doped nickel oxide nanoparticles with varying dopant concentrations AgxNi1−xO (x = 0.00, 0.05, 0.10, and 0.15 M) prepared via flexible sol–gel citrate route at optimum temperature. The well-resolved prominent peaks from X-ray Diffraction (XRD) pattern confirmed the micro-structural attributes of NiO particles and the corresponding crystallite size decreases from 25.67 to 10.93 nm (nm) upon doping. The bandgap energy evaluated from the Tauc plot traced an increasing trend from 2.48 to 3.09 eV affirming the blue shift reasoned with the Burstein Moss phenomenon. Scanning Electron Microscopy (SEM) analysis portrayed the formation of spherical nanoparticles and the particle size was calculated. The phase purity and the chemical composition of nanoparticles were elucidated from Energy Dispersive X-ray (EDX) spectra which endorse only the presence of Ni, Ag, and O metals. Fourier Transform Infra-Red (FTIR) spectroscopy analysis operated in an IR vibrational spectral span confirms the functional group matrix. Dielectric constant and loss of doped nanoparticles were discussed where the loss decreases with increasing dopant concentration. Saturation magnetization (Ms) and coercivity (Hc) were calculated from Vibrating Sample Magnetometer (VSM) studies where Ms perform a declining tendency from 39.96 to 2.86 emu/g which is favorable in the construction of antennas and memory storage equipment. In addition, the nanoparticles were tested against different bacterial and fungal organisms to examine their antimicrobial activity wherein the high concentration (Ag0.15Ni0.85O) doped nanoparticles exhibited a higher antimicrobial response.

НОВІ ЗМІШАНІ МАНГАНІТИ-ХРОМІТИ RMn1–xCrxO3 ТА МАНГАНІТИ-ГАЛАТИ RMn1–xGaxO3

Nanocrystalline powders of new mixed manganites-chromites RMn0.5Cr0.5O3 (R = Pr, Sm, Er) and manganites-gallates RMn1-xGaxO3 (R = Pr, Sm, Eu; x = 0.25, 0.5) with orthorhombic perovskite structure were obtained by sol-gel citrate route. Crytal structure parameters and microstructural parameters of the materials were established depending on the synthesis conditions. Based on the resuts obtained formation of conntinuos solid solutions RMn1-xCrxO3 in the RMnO3-RCrO3 systems and limited solid solitions in the RMnO3-RGaO3 systems were predicted.

Size reduction-induced properties modifications of antiferromagnetic dielectric nanocrystalline Ba2NiMO6 (M = W, Te) double perovskites

Abstract The main objective of this work was to synthesize phase pure double perovskites Ba2NiTeO6 (BNTO) and Ba2NiWO6 (BNWO) in nanocrystalline form and to reveal the impact of nanocrystallinity on their magnetic and dielectric properties. The studied double perovskites were synthesized in nanocrystalline form by employing a citrate sol-gel route. A detailed investigation of their structure and properties using X-ray powder diffraction, scanning electron microscopy, Raman spectroscopy technique, energy-dispersive X-ray spectroscopy, SQUID magnetometry and electrical measurements is carefully described. Rietveld refinement of X-ray powder diffraction patterns revealed phase purity of both compounds: BNTO is trigonal (R-3m) while BNWO is cubic (Fm-3m). Raman spectroscopy studies reveal optical phonons that correspond to vibrations of Te6+/W6+O6 octahedra, while scanning electron microscopy images show irregular plate-like nanocrystals. Magnetic property measurements speak in favor of antiferromagnetic order but, in both compounds, size reduction affected their properties. BNTO has Néel temperature (TN) of 10.3 K which is higher than previously reported for its bulk form. Magnetic ground state of BNWO can be explained as canted antiferromagnetism with TN = 48.2 K. Room temperature measurements of dielectric constants at various frequencies suggest that these materials are high-κ dielectrics with low dielectric loss. The Nyquist plot reveals depressed a semicircle arc typical for non-Debye type of relaxation phenomena for BNWO ceramic, whereas for BNTO ceramic an almost straight line of Zʹʹ versus Z' has been observed, indicating its high insulating behavior. To conclude, size-dependent properties of studied double perovskites are discussed, introducing a possibility for implementation in electronic devices.

Nanocrystalline Antiferromagnetic High-κ Dielectric Sr2NiMO6 (M = Te, W) with Double Perovskite Structure Type.

Double perovskites have been extensively studied in materials chemistry due to their excellent properties and novel features attributed to the coexistence of ferro/ferri/antiferro-magnetic ground state and semiconductor band gap within the same material. Double perovskites with Sr2NiMO6 (M = Te, W) structure type have been synthesized using simple, non-toxic and costless aqueous citrate sol-gel route. The reaction yielded phase-pure nanocrystalline powders of two compounds: Sr2NiWO6 (SNWO) and Sr2NiTeO6 (SNTO). According to the Rietveld refinement of powder X-ray diffraction data at room temperature, Sr2NiWO6 is tetragonal (I4/m) and Sr2NiTeO6 is monoclinic (C12/m1), with average crystallite sizes of 49 and 77 nm, respectively. Structural studies have been additionally performed by Raman spectroscopy revealing optical phonons typical for vibrations of Te6+/W6+O6 octahedra. Both SNTO and SNWO possess high values of dielectric constants (341 and 308, respectively) with low dielectric loss (0.06 for SNWO) at a frequency of 1 kHz. These values decrease exponentially with the increase of frequency to 1000 kHz, with the dielectric constant being around 260 for both compounds and dielectric loss being 0.01 for SNWO and 0.04 for SNTO. The Nyquist plot for both samples confirms the non-Debye type of relaxation behavior and the dominance of shorter-range movement of charge carriers. Magnetic studies of both compounds revealed antiferromagnetic behavior, with Néel temperature (TN) being 57 K for SNWO and 35 K for SNTO.

Copper-Containing Films Obtained by the Simple Citrate Sol–Gel Route for NO2 Detection: Adsorption and Kinetic Study

The citrate sol–gel method was utilized for the fabrication of copper-containing films sensitive to NO2 gas. Effect of annealing temperature on the film phase composition, morphology, and sensor response was studied. X-ray diffraction reveals the formation of Cu2Cl(OH)3 phase at 250 °C and the CuO phase at 350 and 500 °C. It was found out that the films annealed at 250 °C and 350 °C showed the best sensor characteristics. The influence of thermal degradation on the probability of percolation effect in films and its connection to a decrease of gas sensitivity was studied. The kinetics of the NO2 gas adsorption on the film’s surface was described following the Elovich model. Activation energy estimated from the ln(S) vs. 1/T plots was 252 and 30 kJ/mol for the films annealed at 250 and 350 °C, respectively.

Structural modifications in Co–Zn nanoferrites by Gd substitution triggering to dielectric and gas sensing applications

The structural modifications in Co–Zn ferrites due to the substitution of Gd3+ ions and their credible use as low loss dielectrics and H2S gas sensors are reported in the present study. The structural modifications lead to the enhancement in physical properties of the ferrites making it suitable for the applications. The nanocrystals of Co0·7Zn0·3Fe2-xGdxO4 (0 ≤ x ≤ 0.1, Δx = 0.025) were obtained using self-ignited citrate sol-gel route of synthesis. The X-ray diffractograms of the ferrites were refined by Rietveld method using the full-proof pdf software. The refinement asserts the creation of mono phase spinel ferrite crystals. The morphology of ferrite crystals analyzed from scanning electron microscopy (SEM) profiles depict that the ferrites exhibit the porous nature. The transmission electron microscopy (TEM) images confirms the nanocrystalline nature of the ferrites with an average dimension of 25 nm and high resolution TEM (HRTEM) confirms the spinel phase created within the ferrites. The frequency variation of dielectric parameters was analyzed to study the relaxation phenomenon in ferrites. The values of dielectric constant, dielectric loss and loss tangent were reported to decline with frequency and the Gd3+composition (x). The a.c. electrical conductivity increases with frequency and decreases with composition ‘x’. The room temperature gas sensing response of the ferrite for the hazardous H2S gas was much higher than that for LPG, SO2, NO2 and H2 gases. The ferrite sample with x = 0.025 exhibits a better sensor performance for H2S gas with small recovery and response time. The nanocrystalline nature, porosity and morphology of the ferrites bear control over response and other parameters.

PrCo1−xFexO3 perovskite powders for possible photocatalytic applications

Mixed perovskites PrCo1−xFexO3 have been synthesized by the solgel citrate route with the following calcinations in air at 600–800 °C. The prepared samples have been studied using DTA–TG, XRD, FTIR and UV–Vis spectroscopy, and nitrogen low-temperature adsorption–desorption. Electronic structure and magnetic properties of the mixed praseodymium cobaltites–ferrites were calculated within the projector augmented wave method, implemented in the ABINIT software package. The prepared perovskites have been tested as photocatalysts of dyes degradation under visible illumination. It has been established that only the crystalline perovskite phase is photocatalytically active. The prepared materials are semiconductors with band gap within 1.7–2.6 eV and intense absorption of visible light. This fact as well as sufficiently high specific surface area and developed meso–macroporous structure ensures their increased photocatalytic activity. The most active in the PrCo1−xFexO3 series is the sample with Co/Fe = 1:9 due to the highest specific surface area, low value of the band gap, and higher deformation of orthorhombic perovskite structure.

Structural, magnetic, and microwave absorption properties of SrCexFe12-xO19/PVP composites

Ce-substituted strontium hexagonal M-type SrCexFe12-xO19 ferrites (x = 0.0, 0.03, 0.05, 0.07, and 0.1) and various concentrations of poly(N-vinilpyrrolidone) (PVP) polymer were prepared by citrate sol-gel auto-combustion route, and their structural and magnetic properties were studied. The Fourier transform infrared spectroscopy (FT-IR) revealed bands at 437, 549, and 598 cm−1, related to the stretching vibrating bonds of Fe-O. The X-ray diffraction analysis (XRD) showed that in all samples, the SrFe12O9 phase is completely formed, and the peaks are taken with the standard card (JCPDS 01-084-1531) correspond to the type of strontium hexaferrite with the P63/mmc space group. Field emission scanning electron microscopy (FESEM) analysis revealed the hexagonal like the shape of all samples. Vibrating sample magnetometer (VSM) results showed ferromagnetic nature for all the specimens. By increasing the dopants content, coercivity (Hc) and saturation magnetization (Ms) erratically changed but Hc decreased with increasing PVP amount. The complex permittivity, complex permeability and microwave absorption properties of the resulting powder were measured in the range of 8–13 GHz.

X-Band Microwave Analysis and Characterization of Zinc Substituted Nickel Ferrites Prepared by Sol–Gel Citrate Route

Structural, dielectric and electromagnetic properties of spinel ferrites Ni1 − xZnxFe2O4 have been reported in this study. Zinc substituted nickel ferrites Ni1 − xZnxFe2O4 (x = 0 to 1, Δx = 0.2) have been prepared with the sol gel citrate route with final sintering temperature of 1000°C for 8 h. The structural parameters of these ferrites are measured with the help of x-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy and Raman spectroscopy. The dielectric properties of the prepared ferrites have been measured with the help of an impedance analyzer and analyzed as a function of frequency in the MHz frequency range. The electromagnetic properties of these Ni-Zn ferrites in the X-band frequencies (8.2–12.4 GHz) have been obtained from the vector network analyzer (VNA) data. A study of reflection loss (RL) revealed that a minimum RL of − 17.54 dB is achieved at 9.62 GHz with matching thickness of 3.5 mm and absorption bandwidth of 3.108 GHz.