Sol Gel Auto-combustion Method Research Articles

BOOSTING THE MICROWAVE ABSORPTION PROPERTIES USING GRAPHENE FUNCTIONALIZED WITH MG-MN-ZN-BI FERRITES

Graphene (Gr) composites with Mg0.5Mn0.375Zn0.125Bi0.05Fe1.95O4 (MMZB nano ferrites), (Gr= 0%, 1%, 2%, 3%, 4%) were synthesized by using the sol gel auto combustion method. XRD, FTIR and Uv-Vis confirmed the significant improvement in structural, vibrational and optical properties of MMZB ferrites\Gr composites with fusion of Gr. The lattice parameter ‘a’ varies with increasing Gr concertation. From the FT-IR spectra the absorption bands observed in the range of 541-563 cm-1 and 421-461 cm-1 are attributed to the fusion of Gr in MMZB Ferrite/Gr Composites. The d.c resistivity of ferrite samples increased as the temperature increased in ferromagnetic region up to curie temperature, after that its decreased. However, increase in resistivity was observed with increasing Gr concentration except at Gr = 3%. The values of optical band gap were found to decreased from 4.45 to 3.50 eV with increasing Gr content. It has been observed that both the dielectric constant and loss factor decreased with the increase of frequency. The minimum dielectric loss was observed for Gr =4 %. The values of saturation magnetization and microwave frequency decreases with fusion of Gr. A remarkable change in microstructures, electrical and magnetic properties was observed with fusion of Gr. Due to these promising properties these materials may be used for microwave frequency devices.

Structural, Dielectric and Impedance Phenomena in Copper Ferrite Nano Powders for Hydroelectric Cell Application

Multiferroic materials have become the new era of research because it exhibits the presence of more than two ferroic orderings in its same phase. The pure copper ferrite nano powders have been prepared using sol-gel auto combustion method. The particle size is found to be near about 30-40 nm. Pure copper ferrite nanoparticles have been chosen to prepare because of its improved dielectric and structural properties. The sharpened peaks obtained from the XRD diffraction pattern confirms the crystalline nature of the sample. The structural and impedance studies of pure copper ferrites has also been reported. The SEM analysis confirms the formation of nanoparticles by revealing the value of grain size in nanometer range. The dielectric studies exhibit the Maxwell Wagner polarization and impedance spectroscopy confirms the contribution in conductivity from both grains and grain boundaries at room temperature. The fabrication of hydroelectric cell having area=0.75 cm2 has been done using pure copper ferrite nanoparticles which have shown improved value of current in wet state as compared to other ferrites like cobalt ferrites and bismuth ferrites. These all properties are responsible for improving the structural stability and thus this material can be suggested for fabricating the hydroelectric cells.

Evaluating of novel Mn–Mg–Co ferrite nanoparticles for biomedical applications: From synthesis to biological activities

We have investigated, for the first time, the hyperthermia properties, antibacterial, anticancer and antioxidant activities, as well as their toxicity, of Mn0.25Mg0.25Co0.5Fe2O4 nanoparticles synthesized by the sol-gel auto-combustion method. X-ray diffraction results revealed a pure phase and good crystallinity of the synthesized. In addition, the Fourier transform infrared (FTIR) spectrum confirmed the formation of the crystallographic sites of the synthesized structure. In terms of morphology, scanning electron microscopy (SEM) showed that the nanoparticles were agglomerated. In addition, transmission electron microscopy (TEM) revealed that the nanoparticles had a cubic shape and a nanometric size of around 32 nm. Energy-dispersive X-ray spectroscopy (EDS) confirmed the chemical composition of the nanoparticles. With regard to magnetic properties, magnetic measurements showed almost ferrimagnetic behavior, with a saturation magnetization of 38.90 emu/g at room temperature. Hyperthermia measurements revealed relatively good heating efficiencies, with SAR value of 33W/g, good temperature rise and short time to reach magnetic hyperthermia temperature 42 °C (8 min). For biological activities the nanoparticles showed an excellent capacity to neutralize free radicals, eliminating 97% of DPPH and 95% of hydrogen peroxide. The dose of 40 mg/kg of the nanoparticles caused significant alterations in hematological and biochemical profiles. The material showed a significant effect on various bacterial strains, including Staphylococcus aureus and Bacillus subtilis. The synthesized nanoparticles also showed significant activity against various cell lines, including MCF-7 and HeLa. These results strongly suggest the promising utilization of Mn0.25Mg0.25Co0.5Fe2O4, in many applications as a potential candidate for magnetic-mediated hyperthermia.

Characterization of Nano-Structured Magnesium-Aluminum Ferrites Synthesized by Citrate-Gel Auto Combustion Method

An effort is made to find the solution to the new challenges of modification advancements in ferrite technologies. The hypothetical variation in the structural, magnetic, and electrical properties of cubic spinel magnesium aluminum ferrites introduced by the substitution of doping elements has been rationalized and proven. The outcome of aluminum substitution on the magnesium ferrites has been examined and investigated. Spinel ferrites having compositions of MgAlxFe2-xO4 (x = 0.1, 0.2, 0.3, 0.4) were prepared by the sol-gel auto-combustion method. The prepared sample’s characterization, such as scanning electron microscopy (SEM), DC electrical resistivity, AC electrical resistivity, and dielectric properties measurements, were tested using the respective instruments. The grain size and crystal size of all samples were measured from the micrographs of SEM and XRD Data. It is found that the average grain size is within the range of 300 nm - 550 nm for all different series that are formed, keeping the samples at 1100 °C sintering temperatures. A two-probe method experiment with a temperature range of 30 °C to 500 °C gives data on DC electrical resistivity. The Curie temperature depends on the sintering temperature, and it increases with increasing doping concentration. Also, doping influences grain size, which decreases with increasing concentration. Analyzing the SEM micrographs, it is found that the average grain size must decrease in tendency with increasing Al content. DC electrical resistivity exhibits excellent semiconducting behavior. Frequency dependence, dielectric constant, and dielectric loss factors were measured, keeping the frequency range of 75 Hz to 130 MHz at room temperature. The result shows that the dielectric constant (e) and dielectric loss tangent (tan™) decrease with the increase in frequency, while the AC resistivity and Q-factor increase. Comparing the electrical properties of four compositions, it can be suggested that the mixed ferrite, sample-4 (x = 0.3), shows the highest Q-factor of all at 1100 °C.

Intercorrelations of structural-magnetic properties of La0.7A0.3MnO3 (A=Ba, Sr, Pb) manganites and the energy harvesting applications of their flexible nanocomposite films

Ferromagnetic La0.7Ba0.3MnO3 (LBMO), La0.7Sr0.3MnO3 (LSMO) and La0.7Pb0.3MnO3 (LPMO) nanoparticles (NPs) were prepared by sol-gel auto-combustion method. Microstructural analysis of these NPs was done using electron microscopy. The variation of crystallite size and the corresponding lattice strain of the prepared NPs were analyzed with Williamson-Hall plot. Elemental composition and oxidation states of the prepared NPs were analyzed with x-ray photoelectron spectroscopy. Comparative studies on the variation of ∠Mn-O-Mn bond angle and the Mn-O bond length with the increase of mean radius of A-site ion are reported which in turn alter the structural and magnetic properties of LBMO, LSMO and LPMO NPs. Further, 0.5 vol% (0–3) LBMO/P(VDF-TrFE), LSMO/P(VDF-TrFE) and LPMO/P(VDF-TrFE) flexible nanocomposite films were prepared by solution casting method and these were used to show direct magnetoelectric effect-based energy harvesting from magnetic noise generated from cooling/exhaust fan and electric cable wire carrying current at 50 Hz.

Structural, optical, electrical and magnetic properties of lithium zinc ferrite – Silica nanocomposites

Lithium zinc ferrite - silica nanocomposites; with a formula [Li0.5−x/2ZnxFe2.5−x/2O4]30%[SiO2]70%, have been synthesized using ultrasonic assisted sol-gel auto combustion method. Thrust of the study is to investigate effect of zinc substitution in lithium ferrite (dispersed in silica matrix) on structural, optical, electrical and magnetic properties. X-ray diffraction (XRD), UV Visible (UV-Vis), Transmission Electron Microscopy (TEM), Complex Impedance Spectroscopy (CIS) and Vibrating Sample Magnetometry (VSM) have been employed to investigate the samples. XRD patterns confirm the phase purity and revealed that incorporation of Zn2+ at Li+ sites expand the unit cell dimensions from 8.3281 Å to 8.4398 Å, strain and crystallite size escalates from 0.29 to 1.42 and 18.28–27.50 nm respectively. Results from TEM and XRD match well indicating least agglomeration. Optical bandgap and refractive index show a significant effect on increasing zinc content. The impedance (Z) is found to reduce with increase in Zn2+ and may be attributed to enhancement in crystal boundaries. Dielectric properties were explored using cole-cole theoretical fitting of permittivity (ε), universal dielectric response (UDR) model, Koop’s theory and Maxwell–Wagner (M-W) mechanism. Complex electrical modulus (M*) formulation has been employed to explore the transport mechanism. Cole-cole plots in M* reveal that all the samples, except x = 0.50, show relaxation originating from grain boundaries whereas x = 0.50 sample shows contributions from both, grain and grain boundaries. Equivalent circuits have been derived using M* spectrum and are presented with circuit parameters. Frequency dependent AC conductivity (σac) curves have been fitted successfully using Jonscher’s power law; σac for a typical sample x = 0.50 was fitted using double power law. All samples have η ≤ 1, confirming correlated barrier hopping (CBH) mechanism of conductivity. Present system exhibits lower dc conductivity due to highly resistive silica in the samples. Magnetic properties have been studied using Vibrating Sample Magnetometry (VSM). Zn2+ substitution has a significant impact on magnetization due to migration of cations.

Fabrication and Characterization of Dielectric ZnCr2O4 Nanopowders and Thin Films for Parallel-Plate Capacitor Applications.

We report here the successful shape-controlled synthesis of dielectric spinel-type ZnCr2O4 nanoparticles by using a simple sol-gel auto-combustion method followed by successive heat treatment steps of the resulting powders at temperatures from 500 to 900 °C and from 5 to 11 h, in air. A systematic study of the dependence of the morphology of the nanoparticles on the annealing time and temperature was performed by using field effect scanning electron microscopy (FE-SEM), powder X-ray diffraction (PXRD) and structure refinement by the Rietveld method, dynamic lattice analysis and broadband dielectric spectrometry, respectively. It was observed for the first time that when the aerobic post-synthesis heat treatment temperature increases progressively from 500 to 900 °C, the ZnCr2O4 nanoparticles: (i) increase in size from 10 to 350 nm and (ii) develop well-defined facets, changing their shape from shapeless to truncated octahedrons and eventually pseudo-octahedra. The samples were found to exhibit high dielectric constant values and low dielectric losses with the best dielectric performance characteristics displayed by the 350 nm pseudo-octahedral nanoparticles whose permittivity reaches a value of ε = 1500 and a dielectric loss tan δ = 5 × 10-4 at a frequency of 1 Hz. Nanoparticulate ZnCr2O4-based thin films with a thickness varying from 0.5 to 2 μm were fabricated by the drop-casting method and subsequently incorporated into planar capacitors whose dielectric performance was characterized. This study undoubtedly shows that the dielectric properties of nanostructured zinc chromite powders can be engineered by the rational control of their morphology upon the variation of the post-synthesis heat treatment process.

Exploring the structural and magnetic characteristics of ferrous ferric oxide nanoparticles doped with Ca2+ ions for nanoscale devices

In this study, we investigate the effect of Ca2+ substitution on the structural and magnetic characteristics of ferrous ferric oxide CaxFe3-xO4 (x = 0.2 and 0.4) nanoparticles produced by the sol–gel auto combustion method with citric acid as a fuel agent. X-Ray Diffraction (XRD) results show that the average crystallite size is in the range of 20–22 nm and lattice parameter decreases with increasing calcium concentration. Field Emission Scanning Electron Microscope (FESEM) image shows the crystalline nature of calcium-substituted ferrous ferric oxide nanoparticles. Electron Diffraction Spectra (EDS) confirms the presence of Fe, Ca, and O atoms in prepared sample. Vibrating Sample Magnetometer (VSM) measures the magnetic field at room temperature which confirm the existence of a superparamagnetic behavior of Ca2+ substituted ferrous ferric oxide nanoparticles which plays an essential role in nanoscale devices such as MRI, MRAM, spin valve, MTJ, and bio-sensing devices applications.

Structural, magnetic, and dielectric studies of bismuth-doped nickel nanoferrites synthesized via sol–gel autocombustion method

Structural, magnetic, and dielectric studies of bismuth-doped nickel nanoferrites synthesized via sol–gel autocombustion method

Surface modified ZnO nano structures: Electrochemical studies for energy applications and removal of emerging organic pollutant dye by photo induced hetero-catalysis

Surface modified Cu-ZnO nanostructures with different ratios of Cu (0.0 %, 2.5 %, 5.0 %, 7.5 % and 10.0 %) have been fabricated using a simplified sol gel auto combustion method (SGAC). The utilization of aqueous methanolic solution (50:50 ratio) as the reaction medium, with zinc chloride, ZnCl2, serving as a precursor to modified Cu-ZnO nanostructures and ZnO nanostructures (NSs) in particular, was a novel aspect of this study. XRD, FTIR, SEM, EDX, and UV–Visible spectrum analyses were carried out for the analysis of products. The prepared materials were used to study the electrochemical and photocatalytic properties. By introducing Cu metal on the surface of ZnO, the electrical conductivity was increased, and this attribute was investigated using energy band gap calculations and CV analysis. The energy band gap of fabricated nanostructures found to be decreased from 3.36 to 3.20 eV. The Cu modified ZnO based electrode showed the enhanced relative electron transport and increased peak current which made it to be more efficient in electrochemical applications. Degradation study of Tartrazine azo dye (organic) was carried out to examine the photo-induced catalytic activities of prepared materials under solar radiations, UV-light and darkness. The photocatalytic activity was revealed to be optimum up to 86.12 % when exposed to solar radiations and also with increasing Cu concentration up to 10.0 % on the ZnO surface. When compared to pure ZnO, all synthesized Cu modified ZnO NSs exhibited increased peak current, enhanced relative electron transport and optimized photo-induced catalytic degradation of organic pollutant dye. It was revealed that products manufactured using the SGAC technique had higher quality and produced better results for the intended applications than those previously reported.

Sol-gel auto-combustion synthesis and characterization of Nd3+ doped Cu0.5Co0.5Fe2-xNdxO4 (x = 0.0, 0.1, 0.2, 0.3, 0.4, & 0.5) spinel ferrites

Rare earth metal Neodymium (Nd3+) doped nano-crystalline Copper-Cobalt (Cu-Co) spinel ferrites which are represented as Cu0.5Co0.5NdxFe2-xO4 (x = 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5) chemically were prepared through “sol-gel auto-combustion method”. The structural/mechanical, morphological and infrared characteristics were studied in comprehension in the light of Nd3+ doping, using industrial standard techniques. For all of the prepared samples, an X-ray investigation confirms the production of cubic spinel structures in a single phase without the presence of any secondary or impurity phases. Crystallite size and the lattice parameter of Cu0.5Co0.5Nd0Fe2-0O4 found 40 nm and 8.361 Å respectively. The findings demonstrate a clear correlation between increasing Nd3+ content and a decrease in both the crystallite size and lattice parameter. Surface texture and morphology was examined through Scanning Electron Microscopy. According to the results of SEM investigation, the grain size ranged from 13 nm to 0.2 μm. The stretching modes of vibrations at 466 cm−1, 660 cm−1, and 274 cm−1, which are typical modes of spinel ferrites, were discovered via micro-Raman spectroscopy. Optical behaviour of ferrite material observed by UV–Visible spectroscopy. For undoped samples, UV–vis indicated a maximum wavelength of 249 nm, but for doped samples, which are varied through 0.1, 0.2, 0.3, 0.4, and 0.5, the wavelength ranges from 230 to 237 nm. The saturation magnetization was observed to increase with a further increase in Nd3+ concentration (x = 0.5), which may be helpful in storage devices.

Enhanced saturation magnetization in La3+ doped NiCo ferrites prepared by sol–gel auto-combustion method

Lanthanum doped nickel–cobalt nano ferrites with chemical formula Ni0.5Co0.5LaxFe2–xO4 (x = 0.05, 0.10, 0.15 and 0.20) were prepared using a simple sol–gel auto combustion method. The basic structural properties were determined by X-ray diffraction method and the formation of single phased spinel ferrite was confirmed. The crystalline size decreased from 25 to 11 nm and lattice parameter a increases with increase of La doping. The surface morphology of these ferrites was observed by field-emission scanning electron microscopy (FESEM) and agglomerated irregular grains are observed with increase of the rare earth element La doping. Energy-dispersive X-ray spectroscopy (EDX) result confirms the presence of the required elements. The Fourier transform infrared spectroscopy (FTIR) spectrum indicates the formation of the spinel ferrite structure with M−O bonds. Optical direct band measurements from ultraviolet–visible spectroscopy (UV-Vis) spectroscopy indicate that the direct band gap decreases from 1.39 to 1.19 eV for x = 0.05 to x = 0.15, then increases to 1.28 eV for x = 0.20. The room temperature magnetic properties of these ferrites were studied by a vibrating sample magnetometer (VSM). The enhanced saturation magnetization of 49.73 emu/g is observed for x = 0.10 and then saturation magnetizations are gradually decreased for x = 0.15 and x = 0.20. Interestingly the remanent magnetization and coercivity also follow the same trend.

Enhanced photodegradation of Congo red dye under sunlight irradiation by p-n NiFe2O4/TiO2 heterostructure

This work is dedicated to the investigation of NiFe2O4, prepared by sol gel auto-combustion method using glycine as fuel, to degrade a hazardous dye (Congo red) under sunlight irradiation. TiO2-NiFe2O4 Z‐scheme has constructed via solid dispersion technique to improve the photoactivity by decreasing the recombination of electron/hole (e-/h+) pairs. The photocatalysts are characterized by X-ray diffraction, Fourier Transform infrared spectroscopy and Scanning electronic microscopy with integrated EDX. The optical characterization indicates a direct transition of NiFe2O4 with the band gap (Eg) of 1.64 eV, and an indirect transition for TiO2 (Eg= 3.21 eV). Electrochemical characterization is used to determine the flat band potential (Efb) using the Mott-Schottky plot of the interfacial capacitance, which confirmed the p and n type behavior of NiFe2O4 (Efb=+ 0.05 VSCE) and TiO2 (Efb=+ 0.31 VSCE), respectively. Electrochemical impedance spectroscopy (EIS) shows that NiFe2O4 has a low charge transfer resistance (950 Ω cm2) smaller than that of TiO2. The kinetics of Congo red adsorption is well fitted by a pseudo-second order model. The photodegradation tests confirm that p-NiFe2O4/n-TiO2 hetero-structure facilitates the charge separation of photogenerated electrons and holes by reducing the recombination of (e-/h+) pairs. This increases the overall efficiency of the photocatalytic process, which reaches 97 % of Congo red oxidation after 180 min for the composition (p-NiFe2O4/n-TiO2 (0.75/0.25)).

Effect of Ce3+ on structural, morphological, dc electrical resistivity and magnetic studies of Co nano ferrites

The sol-gel auto-combustion method produced rare earth Ce3+ substituted Cobalt ferrite nanomaterials, CoFe2-xCexO4 (x = 0.0, 0.04, 0.08, and 0.12). An X-ray diffractometer, a Field effect scanning electron microscope, a Fourier transform infrared spectrometer, a DC electrical resistivity, and a vibrating sample magnetometer were used to investigate them. The structural, dc resistivity and magnetic properties were examined using standard techniques. XRD analysis revealed a cubic spinel structure in a single phase without any impurity phase for all the prepared samples. With increasing Ce3+ content, a decrease in crystallite size was observed according to Scherrer's formula. Grain size and surface morphology determined from FESEM analysis were 20 to 30 nm. The samples' cubic spinel ferrite properties may be seen in the FTIR data, which show two distinct absorption bands related to the octahedral site at 400 cm-1 and the tetrahedral site at 600 cm-1. FTIR also confirms the presence of Ce3+ in the crystal structure. As the Ce3+ content increases, the DC resistivity decreases, confirming the material's semiconducting nature and temperature increase in all the synthesized samples. The magnetic behaviour strongly influences the substitution of Ce3+ ions. The samples' paramagnetic properties are enhanced by saturation magnetization. The size of the particles affects their coercivity. For the use of nano cobalt ferrite particles in high-density recording media, the MS and HC can be modified.

Bioinspired ferromagnetic CoFe2O4 nanoparticles: Potential pharmaceutical and medical applications

Abstract The primary goal of this work was to develop a cost-effective, non-toxic, eco-friendly, and simple approach for the green synthesis of CoFe2O4 nanoparticles (NPs) using Aloe vera leaf extract by the sol–gel auto-combustion method. In order to figure out their structural, morphological, and magnetic properties, the synthesized NPs were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR), scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscope (TEM), dynamic light scattering (DLS), zeta potential, and vibrating-sample magnetometer (VSM). XRD analysis showed that particles had a single-phase spinel crystalline structure with an average crystalline size of 33.5 nm. Under VSM studies, the produced NPs exhibit a soft ferromagnetic property. SEM revealed that the as-prepared NPs were agglomerated due to their magnetic behavior. To the best of our knowledge, the anticandidal, antibiofilm, antibacterial, and anticancer activities of CoFe2O4 NPs toward drug-resistant gram-positive and gram-negative bacteria, as well as fungal strains, have been comprehensively investigated for the first time. The synthesized NPs had a minimal inhibitory concentration of 0.25–0.75 mg/ml against the tested pathogens. CoFe2O4 NPs inhibited the biofilm formation by 37.3–61.8% in selected strains at concentrations of 0.125–0.5 mg/ml. It was observed that the NPs not only suppress biofilm formation but also eradicate established mature biofilms by 50.9–64.49% that was further supported by SEM. SEM analysis shows that NPs significantly inhibit the colonization and aggregation of tested biofilm strains. Light microscopic analysis revealed that NPs completely inhibit the development of hyphae and filaments in Candida albicans, which significantly attenuates their pathogenicity. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays and 4′,6-diamidino-2-phenylindole (DAPI) staining demonstrate that NPs significantly inhibit the proliferation of HCT-116 and HeLa cells. Furthermore, the SEM images of treated cells showed wrinkled and damaged cell walls, indicating the disruption and disorganization of the membrane. This study showed that the synthesized NPs were effective in inhibiting the growth of drug-resistant bacteria, candida, and their preformed biofilms as well. Thus, these NPs with broad-spectrum applications could be exploited in medical settings to diminish biofilm-based infections caused by these pathogenic strains.

The Synthesis of (1-x-y)BiFeO<sub>3</sub>-xBaTiO<sub>3</sub>-yKVO<sub>3</sub> (x=0.33, 0.38, y=0.01) Composition and its Effect on the Electrical Properties

(1-x)BiFeO3-xBaTiO3-0.01KVO3 with (x = 0.33 and 0.38) (abbreviated FTV33 and FTV38) was successfully prepared using three precursors that had been synthesized before the calcination process. BaTiO3 was synthesized using the coprecipitation method, BiFeO3 was synthesized using the sol-gel auto-combustion method, and KVO3 was synthesized using the conventional solid-state method. Thermal analysis was carried out to determine the calcination temperature from 600 0C for 2h to 600 0C for 4h. X-ray diffraction (XRD) has been carried out to identify the phase after calcination at temperatures, respectively. The phase identification of the XRD pattern has been carried out by Match software shows that the powder and FTV33 and FTV38 have a pseudo-cubic structure with a P4mm space group and rhombohedral with an R3c space group. The XRD pattern is refined by the Rietveld method by Rietica software and the crystalline size is determined by MAUD software. The doping effect of KVO3 on its electrical properties was systematically investigated and show that FTV33 is more conductive and has larger capacitance grains. Based on the previous XRD analysis, Ba2+ and K+ ions replaced Bi3+ at site A. On the other hand, Ti4+ and V5+ substituted Fe3+ at site B which was different from the host's oxidation state.

Room-Temperature Ferromagnetism in Mn-Doped ZnO Nanoparticles Synthesized by the Sol-Gel Method.

In the current work, pure ZnO and Mn-doped ZnO nanoparticles were synthesized by the sol-gel autocombustion method. Structural analysis and phase determination were done by X-ray diffraction, and a hexagonal wurtzite structure was exhibited with disparate microstructures for all samples. Mn2+ ions were well composed, as evidenced by the fluctuation of lattice parameters, dislocation density, and lattice strain. Crystallite size decreases from 38.42 to 27.54 nm by increasing the doping concentration. Field emission scanning electron microscopy results shows the combination of evenly distributed spherical-like and hexagon-like structures. Fourier transform infrared spectra revealed that when Mn content increased, the absorption bands red-shifted. The drop in the energy band gap from 3.25 eV for ZnO to 2.99 eV for Zn0.96Mn0.04O was predicted by ultraviolet-visible absorption spectra. This red shift in the energy band gap can be explained by the sp-d exchange interaction between the band electrons of ZnO and localized d electrons of Mn. A study of magnetic properties revealed the change of the diamagnetic attribute for pure ZnO to the room-temperature ferromagnetic attribute of doped samples. In the current study, room-temperature ferromagnetism was achieved for Mn-doped ZnO nanoparticles, which can serve as a desirable option for practical applications in the future.

Synthesis, characterizations and magnetic properties of nanoscale CoVxFe2-xO4 (0.0 ≤ x ≤ 0.9) materials synthesized via sol-gel autocombustion route

Nanostructured materials of CoVxFe2-xO4 (0.0 ≤ x ≤ 0.9) have been synthesized by sol-gel autocombustion method. Phase purity and nanocrystalline nature of the materials were examined by powder XRD measurements. Morphology and microstructure of the materials were ascertained by FESEM technique. The estimated crystallite sizes (d) decrease from 30 nm to 8 nm, as a result of progressive increase in V content, x, in CoVxFe2-xO4 materials. The values of the observed lattice parameters (a) decrease continuously as a function of increasing V content, x, i.e. from 8.349(5) Å to 8.284(5) Å for the values of x = 0.0 and x = 0.9, respectively. Alterations of M − O bond lengths in CoVxFe2-xO4 materials in FTIR studies indicate the incorporation of vanadium in cobalt ferrite. The values of the saturation magnetizations (Ms) and coercivities (Hc) of CoVxFe2-xO4 materials are found to be in the range of 77.58 emu/g – 37.76 emu/g and 1264 Oe – 991 Oe for various values of x from x = 0.0 to x = 0.9, respectively. The observed trends in magnetic parameters of CoVxFe2-xO4 materials have been interpreted on basis of increasing vanadium content in the materials, cation distributions, size and surface effects.

Dielectrically modified Nd3+ doped (Ni–Mn) based spinel ferrite Ni0.5Mn0.5NdxFe2-xO4 nanoparticles for energy storage applications

The neodymium doped Ni–Mn based spinel ferrites nanomaterials Ni0.5Mn0.5NdxFe2-xO4 with doping concentration of 0.00–0.20 were synthesized by sol gel auto-combustion method. All the samples in fine powder were annealed at 600 °C in a muffle furnace for 4 h to remove the impurities and absorbed gases. In XRD patterns, the obtained high intense diffraction peak at (311) is good evidence that the prepared materials are spinel ferrites. With the help of Scherer method, the crystallite size was calculated in nanometer ranging from 13 to 19 nm. Further, the calculated crystallite size was correlated with Williams's Hall, modified Scherrer and size strain plot (SSP) method. The study of surface morphology by scanning electron microscopy (SEM) revealed that some grains are non-uniform at different concentration of neodymium. Fourier transform infrared-spectroscopy (FTIR) analysis was used to study the relationship between transmittance and wavenumber. The pattern obtained from tetrahedral and octahedral site represents two frequency band v1 and v2. The electrical properties like dielectric constant, tangent loss, electric modulus and ac conductivity were studied by impedance analyzer in applied frequency range 1 MHz–3 GHz and result was explained by using Maxwell Wigner method. It was found that there are some relaxation peaks were observed at high frequency due to hopping of electrons. By using Vibrating sample magnetometer (VSM), the magnetic properties were studied in the applied magnetic field ranging from -3kOe to 3 kOe. The hysteresis loop shows the decreasing in retentivity (Mr), magnetization (Ms) and coercive field (Hc). In conclusion, these prepared materials are very useful for energy storage device applications.

Magnetic anisotropy and (BH)max studies in microwave sintered Al- substituted strontium hexaferrite

Al-substituted strontium hexaferrite (SrFe12-xAlxO19) has been synthesized by the sol-gel auto-combustion method, followed by microwave sintering at 1100 °C. The Rietveld refinement of XRD patterns reveals the hexagonal crystal symmetry with P63/mmc space group. Lattice contraction has been observed with the increasing Al3+ concentration in SrFe12-xAlxO19. The anisotropy field is found to be ∼25 kOe for SrFe11·5Al0·5O19. The (BH)max (maximum energy product) of 1.20 MGOe is obtained for x = 0.0 whereas there is a 63.66% enhancement of coercivity for SrFe11·5Al0·5O19 at 300 K. However, the highest (BH)max of 1.84 MGOe has been achieved at 60 K for SrFe11·5Al0·5O19. The criterion for a permanent magnet is satisfied by analyzing the hardness parameter. All the samples are found to be magnetically hard with (BH)max in the range (1.00–1.20) MGOe at 300 K.