With a view to the proven multiferroic properties of the title representatives of the Y-type hexaferrites as single crystals we present here a comparative study of their microstructure and magnetic ...properties for powders. The polycrystalline materials of Ba
0.5
Sr
1.5
Zn
2
Fe
12
O
22
(S1) and its doped with aluminium derivative Ba
0.5
Sr
1.5
Zn
2
Al
0.08
Fe
11.92
O
22
(S2) were synthesized by two different techniques: citric-acid sol-gel auto-combustion and sonochemical co-precipitation. Their atomic-level structure determination was checked by X-ray and neutron diffraction, electron diffraction and imaging methods, and their physical characterization was carried out by magnetometry. SEM images show that the microstructure strongly depends on the method of synthesis: non-uniform hexagonal grans are formed in case of auto-combustion whereas particles of nearly perfect hexagonal shape are observed in case of sonochemical co-precipitation. With lowering the temperature to 5 K several magnetic phase transitions were observed, more clearly pronounced in S2 powders. Neutron diffraction data in vicinity and above room temperature help in revealing the effect of magnetic dilution on the observed magnetic properties.
We report results on the structural and microwave properties and magnetic phase transitions in polycrystalline Sr
Co
Fe
O
hexaferrite synthesized by sol-gel auto-combustion and acting as a filler in ...a composite microwave absorbing material. The zero-field-cooled (ZFC) and field-cooled (FC) magnetization curves revealed a change in the magnetization behavior at 293 K. The reflection losses in the 1-20 GHz range of the Sr
Co
Fe
O
powder dispersed homogeneously in a polymer matrix of silicon rubber were investigated in both the absence and presence of a magnetic field. In the latter case, a dramatic rise in the attenuation was observed. The microwave reflection losses reached the maximum value of 32.63 dB at 17.29 GHz in the Ku-band. The sensitivity of the microwave properties of the composite material to the external magnetic field was manifested by the appearance of new reflection losses maxima. At a fixed thickness
of the composite, the attenuation peak frequency can be adjusted to a certain value either by changing the filling density or by applying an external magnetic field.
With a view to the proven multiferroic properties of the title representatives of the Y-type hexaferrites as single crystals we present here a comparative study of their microstructure and magnetic ...properties for powders. The polycrystalline materials of Ba0.5Sr1.5Zn2Fe12O22 (S1) and its doped with aluminium derivative Ba0.5Sr1.5Zn2Al0.08Fe11.92O22 (S2) were synthesized by two different techniques: citric-acid sol-gel auto-combustion and sonochemical co-precipitation. Their atomic-level structure determination was checked by X-ray and neutron diffraction, electron diffraction and imaging methods, and their physical characterization was carried out by magnetometry. SEM images show that the microstructure strongly depends on the method of synthesis: non-uniform hexagonal grans are formed in case of auto-combustion whereas particles of nearly perfect hexagonal shape are observed in case of sonochemical co-precipitation. With lowering the temperature to 5 K several magnetic phase transitions were observed, more clearly pronounced in S2 powders. Neutron diffraction data in vicinity and above room temperature help in revealing the effect of magnetic dilution on the observed magnetic properties.
Nitrogen and gallium co-doped ZnO films have been successfully obtained by a sol-gel technology using spin coating. ZnO:N, ZnO:Ga and co-doped (N, Ga) ZnO films are deposited on silicon and quartz ...substrates. The structural, morphological and optical properties of ZnO:N:Ga thin films are studied depending on the thermal treatments (300–600 °C) and the two dopants: N and Ga. The investigations of the doped ZnO films have been performed by using X-ray Diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), Field Emission Scanning Electron microscope (FESEM) and UV–VIS–NIR spectrophotometry. It has been found that the co-doped (N, Ga) ZnO films are crystallized in the wurtzite structure with no impurity phases. The optical transparency of ZnO:Ga and ZnO:N:Ga films is above 80% in the spectral range of 400–800 nm, revealing a significant improvement compared to undoped ZnO films. Gallium and nitrogen co-doping in ZnO results in the modification of the surface morphologies changing from wrinkle-like (undoped ZnO) to closed packed grained microstructure (ZnO:N:Ga films).
Display omitted
•Successfull sol-gel deposition of co-doped ZnO:N:Ga thin films.•Crystallite sizes, texture coefficients and lattice parameters for ZnO, ZnO:N, ZnO:Ga and ZnO:N:Ga films are studied.•Improved transmittance and enlarged optical band gap of ZnO:Ga and ZnO:N:Ga films.•N and Ga co-doping modifies film morphology from wrinkle network (ZnO) to grained structure of ZnO:N:Ga films.
We report a complete procedure to achieve multilayer YBa sub(2)Cu sub(3)O sub(7- delta ) (YBCO) thick films by electrophoretic deposition on silver tubes using a suspension of YBCO powder in butanol. ...With the aim to optimize the magnetic shielding performances of the coatings, we have carried out an extensive investigation of the influence of the deposition parameters, the multilayer deposition sequence and the intermediate/final heat treatments on the coating microstructure. Using the optimized conditions, a 24-layer YBCO coating has been successfully prepared on an 80 mm long Ag tube: the melt growth processed multilayered YBCO thick film thus obtained can shield an applied magnetic field of 1.9 mT at 77 K, the highest value per thickness unit reported so far in the literature for these materials.
Abstract
We report on the stereolithography printing of a hydroxyapatite powder dispersed in an acrylate-based resin with a focus on the influence of the laser power, the scanning speed and the layer ...thickness on the dimensional accuracy of the green, debinded and sintered parts and on the microstructural and mechanical properties of the sintered parts.
In this study, electrophoretic deposition (EPD) of hydroxyapatite (HA) powder on titanium plate was performed using butanol as solvent under direct current (DC) and alternating current (AC) fields. ...The zeta potential of the suspensions was measured to define their stability and the charge on the particles. Coating thickness was varied by adjusting the voltage and time of deposition. Surface morphology and cross section thickness were studied using scanning electron microscopy and image analysis software. Surface crack density was calculated from the micrographs. The results showed that the samples of similar thickness have higher grain density when coated using AC as compared to DC EPD. This facile but novel test proves the capability of AC-EPD to attain denser and uniform HA coatings from non-aqueous medium.
Structural study of thick hexaferrite films Koutzarova, T; Georgieva, B; Kolev, S ...
Journal of physics. Conference series,
04/2020, Letnik:
1492, Številka:
1
Journal Article, Web Resource
Recenzirano
Odprti dostop
We present details of the microstructural properties of Y- (Ba2Mg2Fe12O22, Ba0.5Sr1.5Zn2Fe12O22, Ba0.5Sr1.5Zn2Al0.08Fe11.92O22) and Z-type (Sr3Co2Fe24O41) hexaferrite thick films deposited by screen ...printing and drop casting on unpolished polycrystalline Al2O3 substrates. The hexaferrites thick films obtained by drop casting exhibited considerable roughness and porousness compared with those obtained by screen printing. We found that the powders' morphology significantly affects the microstructure of the thick films formed by screen printing. The microstructural analysis of the thick films shows that their microstructure differs from that of the powders. Further, during the annealing process the grains in the thick films grow and form hexagonal particles, the latter having the largest size, best shape and being best observed in the case of the Ba2Mg2Fe12O22 film.
We report studies of the structural and microstructural properties of Sr3Co2Fe24O41 in bulk form and as thick films. The precursor powders for the bulk form were prepared following the sol-gel ...auto-combustion method. The prepared pellets were synthesized at 1200 °C to produce Sr3Co2Fe24O41. The XRD spectra of the bulks showed the characteristic peaks corresponding to the Z-type hexaferrite structure as a main phase and second phases of CoFe2O4 and Sr3Fe2O7-x. The microstructure analysis of the cross-section of the bulk pellets revealed a hexagonal sheet structure. Large areas were observed of packages of hexagonal sheets where the separate hexagonal particles were ordered along the c axis. Sr3Co2Fe24O41 thick films were deposited from a suspension containing the Sr3Co2Fe24O41 powder. The microstructural analysis of the thick films showed that the particles had the perfect hexagonal shape typical for hexaferrites.
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