scholarly journals Effect of Samarium Substitution on the Structural and Magnetic Properties of Nanocrystalline Cobalt Ferrite

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Sheena Xavier ◽  
Smitha Thankachan ◽  
Binu P. Jacob ◽  
E. M. Mohammed
Keyword(s):  
Crystallite Size ◽  
Single Phase ◽  
Sol Gel ◽  
Average Crystallite Size ◽  
Lattice Parameter ◽  
Magnetic Characteristics ◽  
Typical Sample ◽  
Cobalt Ferrites ◽  
Phase Spinel ◽  
Structural Characterizations

A series of samarium-substituted cobalt ferrites (CoFe2−xSmxO4 with x=0.00, 0.05, 0.10, 0.15, 0.20, 0.25) was synthesized by the sol-gel method. The structural characterizations of all the prepared samples were done using XRD and FTIR. These studies confirmed the formation of single-phase spinel structure in all the compositions. The increase in the value of lattice parameter with increase in samarium concentration suggests the expansion of unit cell. The Hall-Williamson analysis is used for estimating the average crystallite size and lattice strain induced due to the substitution of samarium in the prepared samples. Crystallinity and the crystallite size are observed to increase with the concentration of samarium. The surface morphology and particle size of a typical sample were determined using SEM and TEM respectively. The substitution of samarium strongly influences the magnetic characteristics, and this is confirmed from the magnetization measurements at room temperature.

AN INVESTIGATION INTO MECHANOCHEMICAL SYNTHESIS OF NANOCRYSTALLINE HEXAFERRITE POWDER

2011 ◽  
Vol 25 (07) ◽  
pp. 987-993
Author(s):  
S. SADEGHI-NIARAKI ◽  
S. A. SEYYED EBRAHIMI ◽  
SH. RAYGAN
Keyword(s):  
Crystallite Size ◽  
Single Phase ◽  
Sol Gel ◽  
Milled Powder ◽  
Particle Morphology ◽  
Average Crystallite Size ◽  
Phase Evolution ◽  
High Energy ◽  
Strontium Hexaferrite ◽  
Electron Microscopes

Nanocrystalline strontium hexaferrite powder has been prepared by a new mechanochemical method in which the single phase hexaferrite was obtained via a sol–gel autocombustion process followed by an intermediate high energy milling step and subsequent annealing. The effects of the intermediate milling on the phase evolution, crystallite size and annealing behavior of the final products were investigated using the X-ray diffraction (XRD) technique. The single phase strontium hexaferrite was obtained at an annealing temperature of 800°C, while this temperature was 1,000°C for the powder synthesized without milling. It could be seen that an intermediate milling accelerates the formation of strontium hexaferrite during the calcination process. The results showed that in the milled powder, the average crystallite size of the ferrite was about 40 nm and much smaller than that of the nonmilled powder. Magnetic properties were also measured by a vibrating sample magnetometer (VSM). The particle morphology was then studied by scanning and transmission electron microscopes (SEM and TEM).

scholarly journals The Structural and Magnetic Properties of Gadolinium Doped CoFe2O4Nanoferrites

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Qing Lin ◽  
Jinpei Lin ◽  
Yun He ◽  
Ruijun Wang ◽  
Jianghui Dong
Keyword(s):  
Magnetic Properties ◽  
Saturation Magnetization ◽  
Crystallite Size ◽  
Room Temperature ◽  
Cobalt Ferrite ◽  
Sol Gel ◽  
Average Crystallite Size ◽  
Lattice Parameter ◽  
Cubic Phase ◽  
Structural And Magnetic Properties

Gadolinium substituted cobalt ferrite CoGdxFe2−xO4(x= 0, 0.04, 0.08) powders have been prepared by a sol-gel autocombustion method. XRD results indicate the production of a single cubic phase of ferrites. The lattice parameter increases and the average crystallite size decreases with the substitution of Gd3+ions. SEM shows that the ferrite powers are nanoparticles. Room temperature Mössbauer spectra of CoGdxFe22−xO4are two normal Zeeman-split sextets, which display ferrimagnetic behavior. The saturation magnetization decreases and the coercivity increases by the Gd3+ions.

Effect of hydrolysis catalyst on the Ti deficiency and crystallite size of sol-gel-TiO2 crystalline phases

1995 ◽  
Vol 10 (11) ◽  
pp. 2788-2796 ◽  
Author(s):  
Bokhimi A. Morales ◽  
O. Novaro ◽  
T. López ◽  
E. Sánchez ◽  
R. Gómez
Keyword(s):  
Thin Films ◽  
Crystallite Size ◽  
Single Phase ◽  
Sol Gel ◽  
Average Crystallite Size ◽  
Structure Parameters ◽  
Growing Up ◽  
Hydrogen Atoms ◽  
Crystalline Phases ◽  
X Ray

We prepared sol-gel titania by using different hydrolysis catalysts, and characterized it by x-ray powder diffraction. The structure of the crystalline phases—brookite, anatase, and rutile—in the samples annealed between 70 and 900 °C was refined by using the Rietveld technique. From the refinement we obtained the structure parameters, the concentration of each phase, and their average crystallite size. These quantities and their evolution with temperature depended on the hydrolysis catalyst. Anatase and rutile were deficient in Ti, suggesting that their crystalline structure contained hydrogen atoms, forming OH− ions inside. In anatase this deficiency depended on its crystallite size, but it was constant in rutile. When anatase was annealed, it dehydroxylized, producing either crystallitc growing up or its conversion into rutile. From the analysis we also found the conditions for obtaining single-phase samples that could be used as precursors for making up titania single-phase thin films.

scholarly journals Characterization of Mechanically Alloyed Nanocrystalline Fe(Al): Crystallite Size and Dislocation Density

2010 ◽  
Vol 2010 ◽  
pp. 1-8 ◽  
Author(s):  
M. Mhadhbi ◽  
M. Khitouni ◽  
L. Escoda ◽  
J. J. Suñol ◽  
M. Dammak
Keyword(s):  
Solid Solution ◽  
Dislocation Density ◽  
Crystallite Size ◽  
Average Crystallite Size ◽  
High Energy ◽  
Lattice Parameter ◽  
X Ray Diffraction ◽  
Mechanically Alloyed ◽  
Scanning Calorimetry ◽  
High Energy Ball Mill

A nanostructured disordered Fe(Al) solid solution was obtained from elemental powders of Fe and Al using a high-energy ball mill. The transformations occurring in the material during milling were studied with the use of X-ray diffraction. In addition lattice microstrain, average crystallite size, dislocation density, and the lattice parameter were determined. Scanning electron microscopy (SEM) was employed to examine the morphology of the samples as a function of milling times. Thermal behaviour of the milled powders was examined by differential scanning calorimetry (DSC). The results, as well as dissimilarity between calorimetric curves of the powders after 2 and 20 h of milling, indicated the formation of a nanostructured Fe(Al) solid solution.

scholarly journals Ga-Substituted Cobalt-Chromium Spinels as Ceramic Pigments Produced by Sol–Gel Synthesis

Crystals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1078
Author(s):  
Egle Grazenaite ◽  
Edita Garskaite ◽  
Zivile Stankeviciute ◽  
Eva Raudonyte-Svirbutaviciene ◽  
Aleksej Zarkov ◽  
...  
Keyword(s):  
Phase Composition ◽  
Crystallite Size ◽  
Single Phase ◽  
Sol Gel ◽  
Ceramic Pigments ◽  
Blue Color ◽  
Cobalt Chromium ◽  
Light Blue ◽  
Sol Gel Synthesis ◽  
First Time

For the first time to the best of our knowledge, cobalt-chromium spinels CoCr2−xGaxO4 with different amounts of gallium (x = 0–2 with a step of 0.5) were synthesized via the aqueous sol–gel route as ceramic pigments. The phase composition, crystallite size, morphological features, and color parameters of new compositions and their corresponding ceramic glazes were investigated using XRD, CIELab, SEM, and optical microscopy. It was demonstrated that the formation of single-phase CoCr2−xGaxO4 samples was problematic. Full substitution of Cr3+ by Ga3+ ion in the spinel resulted in the formation of light blue powders, which yielded violetish blue color for the corresponding ceramic glaze.

Structural, magnetic and high frequency (1–6 GHz) parameters of Sr-substituted BaFe2O4 monoferrites synthesized by sol–gel method

2019 ◽  
Vol 33 (19) ◽  
pp. 1950219 ◽  
Author(s):  
Mukhtar Ahmad ◽  
Jawaria Shaheen ◽  
Waseem Abbas Hashmi ◽  
Majid Niaz Akhtar ◽  
Muhammad Asif
Keyword(s):  
Single Phase ◽  
Sol Gel ◽  
Combustion Method ◽  
Xrd Analysis ◽  
Anisotropy Constant ◽  
Dielectric Parameters ◽  
Single Phase Sample ◽  
Heat Treated Sample ◽  
Auto Combustion ◽  
Phase Spinel

In this work, Sr-substituted samples of single-phase spinel monoferrites with chemical formula [Formula: see text] (x = 0.00, 0.33, 0.67, 1.00) were synthesized using sol–gel auto-combustion method. In order to confirm the single-phase formation of these samples, a sample (x = 0.00) was chosen for heat treatment at different temperatures (100, 300, 400, 600 and [Formula: see text]) for 4 h. The heat treated sample was then investigated by X-ray diffraction (XRD) analysis and results showed that a single-phase sample can be successfully synthesized at a temperature of [Formula: see text], which is much lower than that reported in earlier literature for synthesis of same structured samples. All the synthesized samples were then sintered at [Formula: see text] for 4 h to achieve better crystallinity. From XRD patterns, lattice parameters, cell volume and XRD density as a function of Sr-substitution were calculated. Scanning electron microscopy (SEM) results showed that the grain size increased as the temperature was increased. Fourier transform infrared spectroscopy (FTIR) results confirmed the single-phase spinel monoferrites at [Formula: see text]. From M–H loops (x = 0.0, 0.33, 0.67 and 1.00), different magnetic parameters such as saturation magnetization [Formula: see text], remanance [Formula: see text], coercivity [Formula: see text] and magnetic moment [Formula: see text] were calculated. Magnetocrystalline anisotropy constant and Y–K angles of Sr-doped Ba monoferrites were also calculated. In addition, the variation of different dielectric parameters (real permittivity, imaginary permittivity, real permeability, imaginary permeability, ac conductivity and loss tangent) as a function of frequency (1–6 GHz) has been discussed in this work. The results suggest that the synthesized materials have many advantages over previously reported single-phase spinel monoferrites.

Magnetic Properties of the La0.50Ba0.50MnO3 Nanomanganites

2009 ◽  
Vol 152-153 ◽  
pp. 135-138 ◽  
Author(s):  
S.V. Trukhanov ◽  
A.V. Trukhanov ◽  
Christian E. Botez ◽  
H. Szymczak
Keyword(s):  
Magnetic Properties ◽  
Crystallite Size ◽  
Sol Gel ◽  
Exchange Interactions ◽  
Average Crystallite Size ◽  
Anomalous Behavior ◽  
Air Atmosphere ◽  
Crystallite Surface ◽  
Step Heat Treatment ◽  
Lattice Compression

Nanocrystalline La0.50Ba0.50MnO3 manganite was synthesized by an optimized sol-gel method. The initial sample was subjected to step-by-step heat treatment under air atmosphere. The ion stoichiometry, the morphology of crystallites of ceramics, and the magnetic properties were studied. It is established that the average crystallite size increases with increasing annealing temperature. All of the samples studied are characterized by a perovskite-like cubic structure, with the unit cell parameter a increasing continuously with the average crystallite size. The most significant lattice compression occurs in the sample with an average crystallite size of ~ 30 nm. The increase in the average crystallite size causes a nonmonotonic increase in the Curie temperature and in the spontaneous magnetic moment. The anomalous behavior of the magnetic properties of the La0.50Ba0.50MnO3 manganites obtained is explained by the competition between two size effects, namely, the frustration of the indirect exchange interactions Mn3+ – O – Mn4+ on the nanocrystallite surface and the crystal lattice compression due to the crystallite surface tension.

The Structure and Ferromagnetic Properties of the Single Phase Bi0.95Eu0.05Fe0.95Co0.05O3 Nanoparticles Prepared by Sol-Gel

2012 ◽  
Vol 512-515 ◽  
pp. 1434-1437
Author(s):  
Xing Ao Li ◽  
Peng Li ◽  
Yong Tao Li ◽  
Jian Ping Yang ◽  
Qiu Fei Bai ◽  
...  
Keyword(s):  
Single Phase ◽  
Sol Gel ◽  
Mixed Valence ◽  
Magnetic Characteristics ◽  
X Ray Diffraction ◽  
X Ray ◽  
Valence States ◽  
Sol Gel Process ◽  
X Ray Absorption ◽  
Fe Ions

Bi0.95Eu0.05Fe0.95Co0.05O3 Nanoparticles sample was prepared by sol-gel process. The microstructure of samples was analysised by X-ray diffraction(XRD), the result indicated that it was the single phase rhombohedral perovskite structure. The morphology of samples was measured by scanning electron microsopy(SEM), the SEM photograph of samples indicated that the nanoparticles of Bi0.95Eu0.05Fe0.95Co0.05O3 sample were small than that of BiFeO3. The valence states of Fe ions in the samples was analysised by the X-ray absorption spectroscopy（XAS）. The XAS of Fe2p showed that it was the mixed valence states (Fe2+ and Fe3+) of Fe ions in samples, and the binding energy of Bi0.95Eu0.05Fe0.95Co0.05O3 was bigger than that of BiFeO3.The magnetic characteristics of the samples were measured by vibrating sample magnetometer (VSM)，the results showed that the weak metamagnetism were obtained from clear hysteresis loop and the magnetic saturation reached 0.408emu/g，compared with BiFeO3 sample, the magnetic properties were significantly enhanced.

Electric Field Enhanced Synthesis of Nanostructured Tantalum Carbide

2002 ◽  
Vol 17 (3) ◽  
pp. 609-613 ◽  
Author(s):  
Olivia A. Graeve ◽  
Zuhair A. Munir
Keyword(s):  
Melting Point ◽  
Crystallite Size ◽  
Applied Field ◽  
Average Crystallite Size ◽  
Combustion Method ◽  
Lattice Parameter ◽  
Tantalum Carbide ◽  
Low Field ◽  
Combustion Wave Velocity ◽  
High Fields

Nanocrystalline TaC was synthesized by the field-activated combustion method. The crystallite size ranged from about 30 to 55 nm, depending on the applied field. At low fields (8.54 ≤ E < 16.39 V cm−1) the average crystallite size was relatively unaffected by the field, but it showed a significant increase at fields higher than 16.39 V cm−1. From temperature measurements, this field was found to coincide with the melting of Ta. The combustion wave velocity likewise showed a significant increase when the temperature was at the melting point. The composition of the product showed a dependence on the magnitude of the applied field. At low field values (above a threshold) the product contained Ta2C. When synthesized at high fields, the product showed the presence of TaC phase only. The lattice parameter and the C/Ta ratio showed a slight dependence on the field, both increasing with an increase in the magnitude of the field.

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