Sol-gel Auto-combustion Technique Research Articles

Synthesis and Application of Strontium-Doped Zinc Ferrite Nanomaterial in Humidity Sensing

Humidity sensors, being an important component of the Internet of Things (IoT) and artificial intelligence (AI), are currently used in noncontact sensing, electronic skin, respiratory analysis, etc. In this study, the sol-gel auto-combustion technique was used to prepare strontium-doped zinc ferrite (ZnFe2O4) nanomaterials. The synthesized materials have been characterized using Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction (PXRD), energy dispersive X-ray (EDX), and field emission scanning electron microscopy (FESEM) techniques. The doping of strontium increases the lattice parameter and reduces the crystallite size. The synthesized nanoparticles were used to design a humidity sensor for the first time, and several humidity sensing properties were investigated. The designed humidity sensor has a response and recovery times of 19 s and 81 s, respectively. It has low humidity hysteresis, excellent repeatability, and a minute ageing effect.A comparison of the present study with previous reports suggests that the developed humidity sensor is promising in terms of recovery, response times, and material.

Designing Tb-doped Mn-Ni-Cu ferrite meta-absorbers for a broad frequency range: Magnetodielectric, physical, reflection loss, and absorptivity characteristics

Developing meta-absorbers with exceptional EM wave absorption, shielding capacity, and superior dissipation performance remains worthwhile in the gigahertz (GHz) range. Electromagnetic pollution has a detrimental impact on the health of living organisms due to the emergence of high-frequency waves from communication devices. The challenges were addressed by preparing, designing, and simulating ferrite-based meta-absorbers. The nanoferrites of Tb-doped Mn-Ni-Cu (Mn0.2Ni0.3Cu0.5TbxFe2-xO4) with different levels of Tb (x = 0.00, 0.025, 0.05, 0.075) were prepared utilizing the sol-gel auto combustion technique. The phase, structural, elastic, and magnetic features of the Tb-doped Mn-Ni-Cu ferrites were examined using XRD, FESEM, FTIR, and VSM techniques, respectively. The MAUD software was utilized to obtain refinement and precise structural characteristics. The force constant, phase, and elastic properties were also assessed. The magnetization and coercivity exhibited a reduction. An assessment was conducted on the performance of field switching and high-frequency response. At high frequencies, the dielectric characteristics, such as complex permeability and permittivity, exhibit greater values, while losses diminish. At a frequency of 4.6 GHz, a reflection loss (RL) of −54.21 dB was measured for x = 0.05, whereas a reflection loss of −54.03 dB was measured for x = 0.075. The meta-absorbers of Tb-doped Mn-Ni-Cu ferrites were designed and simulated. The absorptivity of the Tb-doped Mn-Ni-Cu ferrite substrate material is illustrated. The meta-absorber exhibited three distinct absorption peaks at frequencies of 1.5, 2.5, and 4.5–6 GHz, respectively. The absorptivity of the material likewise rises with an increase in the incidence angle; the material's absorptivity also increases. The TM mode exhibited the highest values at an angle of 60 degrees, while the TE mode displayed the highest values at an angle of 0 degrees. Tb-doped Mn-Ni-Cu ferrites are effective for electromagnetic interference (EMI), multilayer ceramic integrated circuits (MLCIs), shielding, and absorbing high-frequency signals in 5 G applications.

Tailoring the Surface of Sintered Magnesia–Chromia Catalyst with a Sol–Gel Auto-Combustion Technique

Tailoring the Surface of Sintered Magnesia–Chromia Catalyst with a Sol–Gel Auto-Combustion Technique

Tweaking the structural, micro–structural, optical and dielectric properties of anatase titanium dioxide via doping of nitrogen ions

The pure nanostructured anatase titanium dioxide (TiO2) and subsequent nitrogen–doped derivatives (TiO2–xNx; where, x = 0.005, 0.01, 0.05) were synthesized by sol–gel auto–combustion technique. XRD analysis confirms the formation of pure anatase phase of TiO2 up to doping of 1 mol% (x = 0.01) of nitrogen having tetragonal structure with space group of I41/amd whereas an additional monoclinic phase of TiO2–B was observed at 5 mol% of nitrogen doping in TiO2. This sample has smallest crystallite size of ∼4.7 ± 0.2 nm corresponding to TiO2–B phase and ∼12.0 ± 0.1 nm corresponding to anatase phase. XRD also reveals that the crystallite size of all other samples having pure anatase phase ranges between ∼8.7 ± 0.1 nm & 13.9 ± 0.1 nm. The crystalline phase revealed from XRD of all samples was further supported by the Raman analysis. The direct optical band gap of pure TiO2 (∼3.4 eV) was reduced non–monotonically after nitrogen doping in the ranges from ∼2.8 eV (TiO1.95N0.05) to ∼2.0 eV (TiO1.99N0.01). FTIR spectra confirm the metal oxide bond formation, surface adsorption of water molecules and presence of residual hydroxyl group in all crystalline samples. HRTEM analysis validates the coexistence of secondary phase of TiO2–B along with anatase phase of TiO2 in studied highest doped sample (TiO1.95N0.05) including its broader particle size distribution as compared to pure TiO2. The electrical studies reveal that the highest values of dielectric constant and ac conductivity can be realized for pure TiO2 and at 1 mol% (x = 0.01) of nitrogen doping, among all the studied nitrogen doped samples.

Exploring the structural, optical, dielectric and magnetic properties of rare earth samarium doped Ca-Mg based Ca0.5Mg0.5Fe12−xSmxO19 ferrite nanoparticles

The emergence of M-type hexaferrite presents an encouraging alternative to rare earth magnets, due to its economic feasibility and outstanding magnetic properties. This makes it a viable option for applications in the electric automotive and magnetic industry applications. In this study, we utilized a sol–gel auto-combustion technique to synthesize a series of samarium (Sm) doped calcium-magnesium (Ca-Mg) hexaferrite samples having chemical formula Ca0.5Mg0.5Fe12−xSmxO19 (x = 0.00, 0.05, 0.10, 0.15, and 0.20). The XRD analysis confirmed the crystal structure of the synthesized materials, revealing a consistent magneto-plumbite phase across all samples. Scanning electron microscopy (SEM) investigations further confirmed the homogeneous distribution and agglomeration of nanostructures. FTIR analysis identified the presence of two primary absorption bands in Ca-Mg hexaferrites with both bands exhibiting a shift towards lower frequency ranges with increasing doping levels. The dielectric loss (ε″) and dielectric constant (ε′) were higher at lower frequencies but decreased as the frequency increased. Additionally, higher concentrations of samarium resulted in further reductions in both dielectric loss (ε″) and dielectric constant (ε′). Notably, saturation magnetization (Ms) and remanence (Mr) values demonstrated an increasing trend with higher degrees of Sm+3 substitution, while coercivity (Hc) values exhibited relative stability. Our findings indicate that these materials possess promising magnetic parameters falling within the ranges of 31.52–37.77 emu·g−1 for Ms, 18.16–21.53 emu·g−1 for Mr, and 2.088–2.243 kOe for Hc, suggesting their potential utility across diverse applications including permanent magnets used in electric vehicle motors, storage devices, microwave components, and electromagnetic radiation absorbers.

Investigation of structural, optical, and magnetic properties of NiFe2O4 for efficient photocatalytic degradation of organic pollutants through photo fenton reactions

Nowadays, water pollution generated from textile effluents is one of the major problems for the human race and ecology. Hence, development of sustainable strategies to lower the water pollution level has become a burning need. In this regard, the present study focuses on the preparation of nano catalyst NiFe2O4 to catalyze the chemical reactions on industrial organic dyes for their fast cleansing from water. By sol-gel auto-combustion technique, NiFe2O4 nanoparticles were synthesized and exposed to thermal process at temperatures of 400, 600, and 800 °C. Highly crystalline phase with spinel cubic structured NiFe2O4 was formed with a crystal size of 18.71 nm, which was confirmed by XRD analysis. The FTIR spectra showed two fundamental absorption bands in the range 597.80–412.59 cm−1, which are the characteristics of tetrahedral M − O and octahedral M − O bond in NiFe2O4. The surface morphology of calcined NiFe2O4 was investigated by scanning electron microscope (SEM). The nanoparticle size analyzer exhibited that the synthesized NiFe2O4 nanoparticles had an average particle size of ∼ 291.3 nm. Three stage decomposition patterns were observed for NiFe2O4, which was analyzed by a temperature programmed STA. Zeta potential analyzer showed that the synthesized sample S1 and S2 were stable in the dispersion medium. Also, NiFe2O4 exhibited optical band gap energies for direct band transitions within the visible spectrum measured to be 1.43–1.45 eV, rendering them effective as photocatalysts under sunlight. The samples showed magnetic measurements by VSM with saturation magnetization, coercivity, remnant magnetization value of 66.81 emu/g, 4.13 Oe and 12.94 emu/g, respectively. The synthesized photocatalyst, NiFe2O4, at 400 °C, significantly degraded three toxic organic pollutants—Methylene blue, Rhodamine B, and Congo Red—under visible light through ‘Photo-Fenton’ reaction mechanisms. Among the three dyes, Methylene Blue exhibited the highest degradation percentage with a rate constant of 0.0149 min−1 and followed pseudo-first-order kinetic model.

Cr-doped Li-based [formula omitted]-(Beta) type hexaferrites: XRD, FTIR, XPS and dielectric evaluations for high-frequency applications

The rapid growth of electronic technology and communications have led to increase demand for high performance microwave absorbing materials. Ferrites are frequently used to absorb microwaves and protect against electromagnetic contamination. In the present study, β-type hexaferrite samples with different chemical compositions of LiFe11-xCrxO17 (x = 0.0, 0.1, 0.3, and 0.5) have been manufactured through the sol-gel auto-combustion technique. The effect of substituting Cr3+ on its structural, electrical and dielectric characteristics was examined. The XRD evaluation helped to develop a single-phase structure for all samples. The substitution of Cr3+ has changed the structural characteristics. FTIR analysis was used to investigate the vibrational properties of Cr-doped β-type hexaferrite. Two absorption bands in the infrared spectroscopy were used to indicate the tetrahedral and octahedral sites. XPS results revealed the incorporation of every metal ion related to their particular electronic states. The dielectric studies were determined in terms of frequency (1–6 GHz) and every sample behavior was described using the Maxwel-Wagner and Koop theories. Impedance analysis was utilized to study the effects of relaxation time and grain boundaries on the electrical features of the produced nanomaterials. Impedance Cole-Cole plots prove that all samples exhibit non-Debye-type multiple relaxation processes. It was observed that among all the synthesized samples, LiFe10.9Cr0.1O17 has a minimum reflection loss of −37.80 dB at 1.22 GHz. Cr-doped β-type hexaferrite results suggested using and designing hexaferrite-based nanocomposite for high-frequency absorbers in the microwave range.

Structural, dielectric and Magnetic properties of Samarium doped (Ni–Zn) based Spinel Ferrite (Ni0.5Zn0.5SmxFe2-xO4) nanomaterials

Samarium doped Ni-Zn ferrites (Ni0.5Zn0.5SmxFe2-xO4) were synthesized using sol-gel auto-combustion technique with Sm3+ doping concentrations varying as x = 0.00, 0.05, 0.10, 0.15, and 0.20. The prepared nanomaterials were examined using X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), complex impedance spectroscopy (CIS) and vibrating sample magnetometer (VSM). The XRD examination verified the pure FCC spinel phase of all samples with no impurity peak. The FTIR analysis for spinel molecules formation identified two frequency bands at the octa and tetrahedral sites. The TEM analysis confirmed the shape, size and distribution of prepared nanoparticles. The different dielectric properties were analyzed with a frequency range of 1 MHz–3 GHz and the impact of doping was also studied simultaneously. Magnetic nature of prepared materials was investigated at room using the VSM. It is found that the prepared nanomaterials are suitable for high energy storage as well as magnetic applications.

Physical properties of La3+ ion doped Ni[sbnd]Zn based spinel ferrite nanomaterials for technological applications

Spinel ferrite nanoparticles are extensively utilized in various everyday applications due to their exceptional capabilities. They are highly effective and efficient for various applications such as energy storage devices, microwave, electrode design, fuel cells, and recording media. Based on these applications, five samples of lanthanum doped nickel‑zinc spinel ferrite Ni0.5Zn0.5LaxFe2-xO4 nanoparticles were synthesized using the sol-gel auto-combustion technique. The lanthanum concentrations varied as x = 0.00, 0.05, 0.10, 0.15 and 0.20. X-ray diffraction (XRD) analysis revealed the formation of single phase cubic spinel structure of the prepared samples. The crystallite size was determined using the Scherrer formula and the values lies in the range of 9.22 to 20.09 nm. The chemical composition of the prepared samples was confirmed using Fourier transform infrared spectroscopy (FTIR) analysis. Transmission electron microscopy (TEM) confirmed the agglomeration and spherical shape morphology of the nanoparticles with an average particle size of 40 nm. Magnetic properties along with La3+ ion concentrations were investigated using the vibrating sample magnetometer (VSM). The dielectric properties of the prepared samples were carried out using impedance analyzer with an applied frequency ranging from 1 MHz to 3 GHz. Furthermore, the polarization mechanism in the applied frequency range was discussed with relaxation behavior at high frequency. The impact of La3+ concentrations on different parameters such as dielectric constant, impedance, electric modulus, tangent loss, and Ac conductivity were also investigated. The investigation of dielectric parameters. The relaxation mechanism at high frequency provided a significant impact of such type of materials to store energy due lake of hopping between the tetra and octahedral sites by addition of La3+ doping. The prepared samples exhibit excellent magnetic as well dielectric properties which makes suitable for microwave devices and soft magnetic applications.

Synthesis and characterization of cerium doped NiZn nano ferrites as substrate material for multi band MIMO antenna.

In addressing issues related to electromagnetic interference, the demand for ferrite materials with exceptional magnetic and dielectric properties has escalated recently. In this research, sol-gel auto combustion technique prepared Nickel zinc ferrites substituted with cerium, denoted as Ni0.5Zn0.5Ce0.02Fe1.98O4.X-ray diffraction (XRD), Vibrating Sample Magnetometer (VSM), and Field Emissions Scanning Electron Microscope (FESEM) were used to investigate the structure, magnetic properties, and morphology of Cerium doped NiZn Nano ferrites, respectively. The magnetic and dielectric properties of the sample was examined within a frequency range of 2.5-5.5 GHz. Sample exhibits low permittivity (2.2), high permeability (1.4), low dielectric (0.35) and magnetic loss tangent (-0.5) and highest saturation magnetization measuring 30.28 emu/g. A Novel Double-band, 4x4 MIMO window grill-modeled antennas operating on 3.5 GHz and 4.8 GHz frequency bands for 5G smartphones is designed using the CST microwave studio suite. The performance of window grilled 4x4 MIMO antenna model with Cerium doped NiZn nano ferrites as substrate, is investigated and found the return loss of -35 and -32 dB, with the bandwidth of 200MHz, gain (1.89 & 4.38dBi), envelope correlation coefficient (0.00185), channel capacity loss (0.2bps/Hz), and interterminal isolation of (22& 19dB).The results show that the antenna size is reduced with improved bandwidth, higher isolation and better diversity gain performance using Cerium doped NiZn nano ferrite substrate compared to conventional dielectric substrates.

Enhanced room temperature ferromagnetism and versatile optical properties in MgFe2O4 spinel ferrite prepared under different calcination temperatures

This study employs the sol-gel auto combustion technique fueled by diethanolamine (DEA) to synthesize nanocrystalline magnesium ferrite (MgFe2O4) powders. During the study, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–visible diffuse reflectance spectroscopy (UV-DRS), photoluminescence spectroscopy (PL), and vibrating sample magnetometry (VSM) were then used in order to determine how differing calcination temperatures influence the structure, chemical bonding, surface texture, morphology, optical, fluorescence, and magnetic properties of the resulting MgFe2O4 powders. The findings from the XRD and FT-IR analysis indicate that a single-phase spinel structure is formed in each of the MgFe2O4 samples. According to UV-DRS analysis, optimal calcination improved sample reflection levels in comparison to the visible and infrared spectral findings for the as-synthesized sample. The calcined samples exhibited bandgap energy (Eg) ranging from 2.11 eV to 2.14 eV, which was greater than the 2.02 eV of the as-synthesized sample. Examination of the PL spectra in the range of 380–700 nm revealed various light emission bands for the samples, which increased significantly in intensity at higher calcination temperatures. Furthermore, higher calcination temperatures also increased the magnetization of the MgFe2O4 spinel powders, while coercivity dropped significantly.

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

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

Envisioning the structural and room temperature impedance spectroscopy study of praseodymium modified lanthanum ferrites

Praseodymium-modified lanthanum ferrites with general formula La1-xPrxFeO3 [x = 0.0, 0.1, 0.3, 0.5] were prepared using the sol-gel auto combustion technique. The X-ray diffraction patterns of all samples supported the orthorhombic crystal structure with the Pbnm space group. With increasing Pr concentration, it was discovered that the average crystallite size dropped from 44.29 to 29.83 nm. An LCR metre was used to evaluate the frequency-dependent dielectric characteristics between 100 Hz and 1 MHz at room temperature. A single semicircle on the Nyquist plots highlights the impact of grain resistance on electrical behaviour. The depressed semicircles at intermediate frequencies might be created by the grain boundary effect, while semicircles depressed at high frequencies imply grain conduction. The dielectric behaviour of lanthanum ferrites is explained based on Koop’s theory. The loss factor resulting from domain wall resonance displayed the same dielectric constant dispersion behaviour. At high frequencies, orthoferrites were shown to have lower dielectric losses. This is due to the constrained motion of the domain wall, which suggests that magnetically tunable filters and oscillators are possible practical uses.

Structural, optical, and electrical characteristics of anatase titanium dioxide tailored by doping of nitrogen and copper ions

Pure anatase TiO2 nanoparticles and its mono–doped and co–doped derivatives [i.e. (TiN0.007O1.993); (Ti0.998Cu0.002O2); (Ti0.998Cu0.002N0.007O1.993)] were prepared by sol–gel auto–combustion technique. Further, the effects of copper (Cu) and nitrogen (N) dopants have been investigated on structural, optical and dielectric properties of nanostructured TiO2 using X–ray diffraction (XRD), Raman spectroscopy, ultraviolet–visible (UV–Vis) spectroscopy and dielectric spectroscopy measurement respectively. The Rietveld refinement analysis of XRD data and Raman spectra revealed that all the synthesized samples have pure anatase phase having tetragonal structure with space group of I41/amd. The pure anatase phase of doped samples illustrate the substitution of Cu ions at Ti4+ sites and N ions at O2− sites in the TiO2 host lattice. The crystallite size of TiO2 and its derivatives has been observed in the range of 11–14 nm. The band gap of TiO2 reduced from 3.2 to 1.9 eV with mono–doping and co–doping of the N and Cu in TiO2 lattice as confirmed by UV–Vis spectroscopy. This red–shift might be occur due to the possible formation of N–2p and Cu–3d localized levels (mono–doping case), and the creation of isolated intermediate states (co–doping case). The dielectric spectroscopy was carried out to investigate the electrical properties in details and explained in terms of structural and intrinsic ionic behaviour of different dopants. The detected band gap energies in N/Cu mono–doped and co–doped anatase TiO2 fall within the visible spectrum, rendering them suitable for harnessing solar energy in photocatalysis and photovoltaic applications.

Effect of rare earth doping on the electromagnetic response of hard ferrites SrFe12O19 for potential application in high-frequency devices

This work explores the synthesis, characterization, and potential application of rare earth doping on hard ferrites, focusing on their unique electromagnetic properties for potential applications in radio frequency (RF) devices. This study investigates the influence of rare earth (Sm+3) doping on structural and dielectric properties of strontium ferrite. Samarium doped strontium ferrite with composition Sr1-xSmxFe12O19(x = 0.0,0.1,0.2,0.3) is prepared using the sol-gel auto combustion technique. The prepared samples' crystal structural and morphological properties were studied using an X-ray diffractometer (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and RAMAN spectroscopy. XRD patterns of rare earth substituted strontium ferrite confirmed the formation of a hexagonal phase together with an impurity phase of Fe2O3 for x = 0.3. FTIR analysis establishes metal and Oxygen (M-O) stretching vibrations in Sr1-xSmxFe12O19 due to various interstitial sites in its structure. The Raman result shows the presence of four Raman active modes in prepared powders. Meanwhile, the broadening of Raman peaks with Sm2+ doping is also observed. Electromagnetic properties were obtained in the frequency region 2–18 GHz. An increasing tendency is observed in the real part of permittivity and permeability of all doped samples in the frequency region 2–18 GHz. The reflection loss was observed for sample x = 0.2 with the maximum value of > -40 dB at 18 GHz, and the adequate absorption bandwidth is 10 GHz from 8 GHz to above 18 GHz. On the basis of these results, among all prepared samples, Sr0.8Sm0.2 Fe12O19 is found to be the most suitable candidate for microwave absorbers.

Aluminium and praseodymium doped M-type hexaferrites for electric vehicle applications

The booming demand for electric vehicles, driven by the pursuit of enhanced efficiency, faces significant hurdles attributed to the costly integration of rare earth magnets like NdFeB. M-type strontium ferrite emerges as a promising alternative owing to its economic viability and exceptional magnetic characteristics, rendering it suitable for electric vehicle motor applications. This research focuses on the synthesis and characterization of SrFe12O19 and Sr1-xPrxFe10Al2O19 (where x = 0.00 to 0.20) hexaferrites, with praseodymium (Pr) substitution. Magnetic particles were synthesized utilizing the sol-gel auto-combustion technique, employing a calcination temperature of 1100 °C for a duration of 4 h. Structural and magnetic studies of aluminium-praseodymium (Al–Pr) doped samples are performed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and vibrating-sample magnetometry (VSM). The structural analysis reveals a decrease in both particle size from 42 nm to 31.76 nm and lattice parameter with increasing doping concentration. Magnetic analysis yields crucial insights: Al3+ doping induces a substantial rise in coercivity from 5500 Oe to 10,500 Oe which is quite comparable to NdFeB, while Pr doping shows a subtle impact, enhancing remanence from 17 emu/g to 23.05 emu/g. These findings underscore the potential for optimizing magnetic properties through meticulous control of dopant concentrations in M-type hexaferrites, thereby positioning them as promising substitutes for rare earth magnets.

Structural and magnetic properties of GdFeO3 nanomaterial prepared through one-step sol-gel auto combustion technique

Structural and magnetic properties of GdFeO3 nanomaterial prepared through one-step sol-gel auto combustion technique

Synthesis and characterization of zinc doped nickel nanoferrites via sol-gel auto-combustion technique

Over the last few decades, numerous researchers have made significant contributions to the development of spinel ferrite owing to its unique and versatile structural, spectroscopic, and magnetic characteristics. These ferrites are extensively used in various applications such as microwaves, drug delivery, gas sensors, and electronic devices. Their technological applications require low porosity, high density, and specified microstructure. In this work, we prepared Zinc-doped Nickel nanoferrites Ni1-xZnxFe2O4 (x= 0, 0.1, 0.2, 0.3) using the sol-gel auto-combustion technique. Structural analysis of prepared samples was done using X-ray diffraction and Scanning Electron Microscopy, the elemental composition was examined using EDAX and optical studies using UV-visible spectroscopy. The average crystallite size was found in the 40.6 to 64.92 nm range. EDAX analysis confirmed the presence of expected elements in the samples. From UV-visible spectroscopy characterization studies it was observed that as particle size increases, there will be an increase in the band gap energy of ferrite nanoparticles. The Nickel-Zinc nanoferrite absorbs energy in the range of 233nm to 237nm.

Effect of coercive aluminium on the structural and magnetic characteristics of calcium and magnesium based hexaferrites

Aluminum substituted Calcium-Magnesium (Ca-Mg) hexaferrites having general formula Ca0.5Mg0.5Fe12-xAlxO19 (where x is increased with increment of 0.5 from 0.0 to 2.0) are prepared by sol–gel auto combustion technique. X-ray diffraction patterns confirm the hexagonal structure with no evidence of secondary phases. The reduction in lattice parameters is observed as the Al+3 doping level increases. This can be attributed to the short ionic radii of Al+3 ions (0.535 Å) compared to Fe+3 ions (0.645 Å). The obtained c/a ratio falls within the acceptable range of 3.98. Consequently, the formation of magnetoplumbite structure is also confirmed. The SEM image reveals the uniform distribution of particles. The exchange of Fe+3 ions with coercive Al+3 ions led to a decline in saturation magnetization Ms and a significant increase in the coercivity Hc. The magnetic moment mB and Mr of hexaferrites exhibit a decline when Al ions are introduced. This reduction can be ascribed to several factors: the substitution of non-magnetic Al3+ ions in place of Fe3+ ions, the spin-canted ordering of Fe3+ ions, and the valency of Fe ions from 3+ to 2+.

Optimization of switching charge and recoverable energy density mediated by structural transformation in Sr-substituted BaNiO3 perovskites.

Because of their distinctive characteristics, ferroelectric perovskites are considered among the most potent and auspicious candidates for energy storage and pulsed power devices. But their energy storage properties and switching capabilities need to be further enhanced which can be done by substitutions of appropriate cations. Hence, a series of lead-free Ba1-xSrxNiO3 (x = 0.00, 0.33, 0.67, and 1.00) ceramics was fabricated using a sol-gel auto combustion technique. Rietveld's refinement of X-ray diffraction plots verified the complete development of the required hexagonal perovskite structure. Scanning electron microscopy images revealed a gradual increase in average grain sizes and agglomeration with the increase in Sr-content. Moreover, the existence of all the constituent elements exactly in proportion to their stoichiometric ratios was verified by energy dispersive X-ray spectroscopy. The characteristic parameters of ferroelectric materials such as ferroelectric response, electrical conductivity, and switching charge density were also determined. The P-E loops indicated that with the increase in Sr-content, the coercive field, remanent polarization, and maximum polarization all decreased gradually, but the recoverable energy density (Wrec) increased as the loops became slimmer. The maximum value of Wrec was found in the Ba0.33Sr0.67NiO3 sample. Moreover, SrNiO3 exhibited minimum energy loss with the highest efficiency of ∼47.21%. The existence of a current barrier in all the samples was proved from the low leakage current values (∼10-7 A). In addition, the pure SrNiO3 showed a low electrical conductivity and minimum value of switching charge density. All these findings make SrNiO3 a promising candidate for fast switching and energy storage applications.