Study of the Structural and Magnetic Properties of Co-Substituted Ba2Mg2Fe12O22 Hexaferrites Synthesized by Sonochemical Co-Precipitation

Ba2Mg0.4Co1.6Fe12O22 was prepared in powder form by sonochemical co-precipitation and examined by X-ray diffraction, Mössbauer spectroscopy and magnetization measurements. Careful XRD data analyses revealed the Y-type hexaferrite structure as an almost pure phase with a very small amount of CoFe2O4 as an impurity phase (about 1.4%). No substantial changes were observed in the unit cell parameters of Ba2Mg0.4Co1.6Fe12O22 in comparison with the unsubstituted compound. The Mössbauer parameters for Ba2Mg0.4Co1.6Fe12O22 were close to those previously found (within the limits of uncertainty) for undoped Ba2Mg2Fe12O22. Isomer shifts (0.27–0.38 mm/s) typical for high-spin Fe3+ in various environments were evaluated and no ferrous Fe2+ form was observed. However, despite the indicated lack of changes in the iron oxidation state, the cationic substitution resulted in a significant increase in the magnetization and in a modification of the thermomagnetic curves. The magnetization values at 50 kOe were 34.5 emu/g at 4.2 K and 30.5 emu/g at 300 K. The zero-field-cooled (ZFC) and field-cooled (FC) magnetization curves were measured in magnetic fields of 50 Oe, 100 Oe, 500 Oe and 1000 Oe, and revealed the presence of two magnetic phase transitions. Both transitions are shifted to higher temperatures compared to the undoped compound, while the ferrimagnetic arrangement at room temperature is transformed to a helical spin order at about 195 K, which is considered to be a prerequisite for the material to exhibit multiferroic properties

Optical and structural properties of sol - Gel derived ZnO:F thin films

In the present work, we report the influence of the fluorine doping (two different concentrations) in ZnO films and the annealing temperatures on the film structural, vibrational and optical properties. ZnO:F films are successfully deposited by a facile sol-gel approach. X-Ray diffraction (XRD) analysis shows that F doping induces an improved film crystalinity. The ZnO:F films are polycrystalline with wurtzite structure. Fourier Transform Infrared (FTIR) study reveals that fluorine affects the shapes and positions of the absorption bands. The optical transparency of ZnO:F films is higher than that of undoped ZnO.The optical band gap has been determined from spectrophotometric data. The optical band gap values become narrower with increasing the annealing temperatures, due to the bigger crystallite sizes. © 2019 Author(s)

Preparation and Investigation of Sol–Gel TiO₂-NiO Films: Structural, Optical and Electrochromic Properties

TiO2 and TiO2-NiO films were successfully derived by a sol–gel dip coating technology. The impact of the thermal treatments (300–600 °C) on the structural, optical and electrochromic properties was investigated. X-ray diffraction (XRD) analysis showed that TiO2 films were polycrystalline and evolved in the anatase phase. The composite TiO2-NiO films, treated at annealing temperatures below 500 °C, contained anatase titania, a small inclusion of cubic NiO and an amorphous fraction. The formation of NiTiO3 was exposed after the highest annealing at 600 °C. The presence of Ti-O-Ni bonds was determined in the composite films by Fourier-transform infrared (FTIR) spectroscopy. The optical properties and the optical band gap of TiO2-NiO films were investigated and discussed. The transparency of the electrochromic TiO2-NiO films was 76.8 and 78.3% in the 380–700 nm spectral range after film thermal treatments at 300 and 500 °C. NiO incorporation led to the narrowing of the optical band gap. The electrochromic (EC) properties of the composite films were improved compared to TiO2 films. They had higher diffusion coefficients. Their color efficiencies are 37.6 (550 nm) and 52.2 cm2/C (600 nm)

Deposition of Sol–Gel ZnO:Mg Films and Investigation of Their Structural and Optical Properties

This work presents a facile sol–gel method for the deposition of ZnO and ZnO:Mg films. The films are spin coated on silicon and quartz substrates. The impact of magnesium concentrations (0, 0.5, 1, 2 and 3 wt%) and post-annealing treatments (300–600 °C) on the film’s structural, vibrational and optical properties is investigated. Undoped ZnO films crystallize in the wurtzite phase, with crystallite sizes ranging from 9.1 nm (300 °C) to 29.7 nm (600 °C). Mg doping deteriorates the film crystallization and shifting of 002 peak towards higher diffraction angles is observed, indicating the successful incorporation of Mg into the ZnO matrix. ZnO:Mg films (2 wt%) possess the smallest crystallite size, ranging from 6.2 nm (300 °C) to 25.2 nm (600 °C). The highest Mg concentration (3 wt%) results into a segregation of the MgO phase. Lattice constants, texture coefficients and Zn–O bond lengths are discussed. The diminution of the c lattice parameter is related to the replacement of Zn2+ by Mg2+ in the ZnO host lattice. The vibrational properties are studied by Fourier transform infrared (FTIR) spectroscopy. IR lines related to Mg–O bonds are found for ZnO:Mg films with dopant concentrations of 2 and 3 wt%. The optical characterization showed that the transmittance of ZnO:Mg thin films increased from 74.5% (undoped ZnO) to about 89.1% and the optical band gap energy from 3.24 to 3.56 eV. Mg doping leads to a higher refractive index compared to undoped ZnO films. The FESEM (field emission scanning electron microscopy) technique is used for observation of the surface morphology modification of ZnO:Mg films. The doped ZnO films possess a smoother grained surface structure, opposite to the wrinkle-type morphology of undoped sol–gel ZnO films. The smoother surface leads to improved transparency of ZnO:Mg films

Influence of Fluorine and Nitrogen Co-Doping on the Structural and Morphological Properties of Sol-Gel ZnO Films

peer reviewedThe structural, vibrational, optical and morphological properties of ZnO:N:F films, obtained by the sol-gel method, were investigated. The effect of single (fluorine, nitrogen) and F, N co-doping and thermal treatments (300–600 °C) on the properties of ZnO films was analyzed. X-ray Diffraction (XRD) revealed that ZnO:N:F films crystallized in a polycrystalline wurtzite structure. F and N incorporation changed lattice parameters, crystallite sizes, texture coefficients (TC) and residual stress. TC (002) of ZnO:N:F films increased with annealing, reaching 1.94 at 600 °C lower than the TC (002) of ZnO and ZnO:N films. The shifting of the characteristic absorption bands and/or the appearance of new IR lines were detected for ZnO:N:F samples. The highest transmittance (90.98%) in the visible spectral region was found for ZnO:F films. ZnO:N:F films possessed optical transparency up to 88.18% and their transmittance decreased at the higher annealings. The optical band gap (Eg) values of ZnO:N:F films were changed with fluorine and nitrogen concentrations. The formation of the wrinkle-like structures on the surface of ZnO and ZnO:N films was depicted in Field Emission Scanning Electron Microscopy (FESEM) images. The F, N dual doping modified ZnO morphology and suppressed wrinkle formation

Influence of Fluorine and Nitrogen Co-Doping on the Structural and Morphological Properties of Sol-Gel ZnO Films

The structural, vibrational, optical and morphological properties of ZnO:N:F films, obtained by the sol-gel method, were investigated. The effect of single (fluorine, nitrogen) and F, N co-doping and thermal treatments (300–600 °C) on the properties of ZnO films was analyzed. X-ray Diffraction (XRD) revealed that ZnO:N:F films crystallized in a polycrystalline wurtzite structure. F and N incorporation changed lattice parameters, crystallite sizes, texture coefficients (TC) and residual stress. TC (002) of ZnO:N:F films increased with annealing, reaching 1.94 at 600 °C lower than the TC (002) of ZnO and ZnO:N films. The shifting of the characteristic absorption bands and/or the appearance of new IR lines were detected for ZnO:N:F samples. The highest transmittance (90.98%) in the visible spectral region was found for ZnO:F films. ZnO:N:F films possessed optical transparency up to 88.18% and their transmittance decreased at the higher annealings. The optical band gap (Eg) values of ZnO:N:F films were changed with fluorine and nitrogen concentrations. The formation of the wrinkle-like structures on the surface of ZnO and ZnO:N films was depicted in Field Emission Scanning Electron Microscopy (FESEM) images. The F, N dual doping modified ZnO morphology and suppressed wrinkle formation

Synthesis and investigation of the properties of hexaferrites obtained by microemulsion techniques

peer reviewedThe hexaferrites have been intensively investigated as materials for permanent magnets, high-density recording media, microwave devices, bio-medical applications and, recently, as multiferroic materials. It is well known that the electrical, optical and magnetic properties of materials vary widely with the particle size and shape and with the degree of crystallinity. In general, the technologies for preparation of hexaferrites require high-temperature annealing, which impedes the fabrication of nanosized hexaferrites characterized by a narrow particle-size distribution. The microemulsion method has been proposed precisely in order to overcome the difficulties related to controlling the size distribution of the particles of oxide materials and, especially, hexaferrites, since one of the advantages of this technique is the preparation of very uniform particles. The high homogeneity of the nanosized precipitate particles produced is due to the fact that each of the aqueous drops acts as a nanosized reactor for nanoparticles formation. The M-type hexaferrite is the most commonly studied member of the hexaferrite family. This review chapter will be focused on the synthesis and properties of hexaferrites (particularly nanosized hexaferrites) obtained by microemulsion. The different microemulsion systems will be presented and their influence on the structure and magnetic properties of the M-type hexaferrite will be discussed. A special emphasis will be placed on the preparation of hexaferrite powders with nanometer particle sizes via two approaches of the microemulsion technique, namely, single microemulsion and double microemulsion; original results will be presented

Synthesis, structural characterization and antibacterial activity of cotton fabric modified with a hydrogel containing barium hexaferrite nanoparticles

Barium hexaferrite nanoparticles were synthesized by co-precipitation of Ba2+ and Fe3+ cations with NaOH under of high-power ultrasound. The nanoparticles were dispersed in an aqueous solution of the hydrogel precursors. This solution was used to impregnate the cotton fabric dyed with a photoinitiator. The composite material BaFe12O19 nanoparticles-hydrogel-cotton fabric was prepared by surface initiated photopolymerization under visible light. The modification of the cotton fabric and uniform distribution of the nanoparticles in the structure of the hydrogel were analyzed by scanning electron microscopy (SEM), IR spectroscopy, X-ray diffraction analysis (XRD), fluorescence and colourimetric analyses. The antibacterial efficacy of the material was evaluated against Gram-negative Escherichia coli and Pseudomonas aeruginosa. © 2016 Elsevier B.V. All rights reserved

Structural and magnetic properties of nanosized barium hexaferrite powders obtained by microemulsion technique

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