scholarly journals CoFe2O4-SiO2 Composites: Preparation and Magnetodielectric Properties

2016 ◽  
Vol 2016 ◽  
pp. 1-7 ◽  
Author(s):  
T. Ramesh ◽  
S. Bharadwaj ◽  
S. R. Murthy
Keyword(s):  
Cobalt Ferrite ◽  
Microwave Sintering ◽  
Magnetic Hysteresis ◽  
Hysteresis Loops ◽  
Complex Permeability ◽  
X Ray Diffraction ◽  
Microwave Hydrothermal ◽  
Morphological Studies ◽  
Metal Nitrates ◽  
Sintering Method

Cobalt ferrite (CoFe2O4) and silica (SiO2) nanopowders have been prepared by the microwave hydrothermal (M-H) method using metal nitrates as precursors of CoFe2O4 and tetraethyl orthosilicate as a precursor of SiO2. The synthesized powders were characterized by XRD and FESEM. The (100-x) (CoFe2O4) + xSiO2 (where x = 0%, 10%, 20%, and 30%) composites with different weight percentages have been prepared using ball mill method. The composite samples were sintered at 800°C/60 min using the microwave sintering method and then their structural and morphological studies were investigated using X-ray diffraction (XRD), Fourier transformation infrared (FTIR) spectra, and scanning electron microscopy (SEM), respectively. The effect of SiO2 content on the magnetic and electrical properties of CoFe2O4/SiO2 nanocomposites has been studied via the magnetic hysteresis loops, complex permeability, permittivity spectra, and DC resistivity measurements. The synthesized nanocomposites with adjustable grain sizes and controllable magnetic properties make the applicability of cobalt ferrite even more versatile.

SYNTHESIS OF NANOCRYSTALLINE YIG USING MICROWAVE-HYDROTHERMAL METHOD

2009 ◽  
Vol 23 (17) ◽  
pp. 3637-3642 ◽  
Author(s):  
K. SADHANA ◽  
R. S. SHINDE ◽  
S. R. MURTHY
Keyword(s):  
Sintering Temperature ◽  
Microwave Sintering ◽  
Complex Permeability ◽  
X Ray Diffraction ◽  
X Ray ◽  
Microwave Hydrothermal ◽  
Transmission Electron ◽  
Dielectric Constant And Loss ◽  
Iron Garnet ◽  
Sintering Method

The aim of present research is to study the influence of sintering temperature on the preparation of nanocrystalline Yttrium Iron garnet (YIG) with improved magnetic properties. The nanocrystalline YIG powders were synthesized using Microwave-Hydrothermal (M-H) method. The synthesized powders were characterized using X-ray diffraction (XRD) and Transmission Electron Microscope (TEM). The powders were sintered at various temperatures using microwave sintering method. The sintered samples were characterized using XRD. The complex permeability, dielectric constant and loss tangent of sintered YIG ceramic were also measured and discussed in this paper

Permittivity Relaxation Variation for Additive Doping in Cobalt Ferrite at High Frequencies

2019 ◽  
Vol 201 (1) ◽  
pp. 155-162
Author(s):  
S. Bharadwaj ◽  
Suman Kumar Burnwal ◽  
Subimal Deb ◽  
S. Ragini ◽  
S. R. Murthy
Keyword(s):  
Dielectric Relaxation ◽  
Cobalt Ferrite ◽  
Microwave Sintering ◽  
Least Square ◽  
High Frequencies ◽  
Microwave Hydrothermal ◽  
Least Square Fit ◽  
C 30 ◽  
Linear Least Square ◽  
Sintering Method

We present a comparative study of the variation in dielectric relaxation for the additives SiO2, TiO2 and ZrO2 in cobalt ferrite. CoFe2O4 was prepared using microwave hydrothermal system and sintered at 900 °C/30 min using microwave sintering method. Real and imaginary parts of permittivity were measured in the frequency range of 1 MHz to 1.8 GHz for these samples. A shift in the dielectric relaxation towards higher frequencies for doped samples is observed as expected in percolating systems. A non-linear least square fit of the electron oscillator model is used to parameterize absorption in the samples.

Formation of Tricalcium Silicate Prepared by Electric and Microwave Sintering

2010 ◽  
Vol 148-149 ◽  
pp. 1119-1123
Author(s):  
Kai Ke ◽  
Bao Guo Ma ◽  
Xiao Liang Wang ◽  
Xiang Guo Li
Keyword(s):  
Heating Temperature ◽  
Microwave Sintering ◽  
Electric Heating ◽  
Tricalcium Silicate ◽  
Experimental Results ◽  
X Ray Diffraction ◽  
X Ray ◽  
Conventional Sintering ◽  
Sintering Method

A microwave sintering method was used to prepare C3S from Ca(OH)2, SiO2 and MexOy. f-CaO assay, X-ray diffraction and SEM were used to characterize the sintered samples.The results indicated that ion oxides played a very important role in C3S formation in conventional sintering, the use of MexOy as an additive was so effective in promoting C3S formation. The experimental results showed that samples were heated at an electric heating temperature(1500°C) and then further sintered with microwave for 30~60 min, tricalcium silicate could be formed with kilogram step. The new burning technique can greatly increase the forming speed of tricalcium silicate, MnO2, CuO and Ni2O3 could enhance the microwave sintering.

scholarly journals Iron-Doped Lithium Tantalate Thin Films Deposited by Magnetron Sputtering: A Study of the Iron Role in the Structure and the Derived Magnetic Properties

Crystals ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 50 ◽  
Author(s):  
Sergio David Villalobos Mendoza ◽  
José Trinidad Holguín Momaca ◽  
José Trinidad Elizalde Galindo ◽  
Diana María Carrillo Flores ◽  
Sion Federico Olive Méndez ◽  
...  
Keyword(s):  
Thin Films ◽  
Magnetron Sputtering ◽  
Magnetic Hysteresis ◽  
Hysteresis Loops ◽  
Blocking Temperature ◽  
Ferromagnetic Behavior ◽  
Zero Field ◽  
Cooling Curves ◽  
X Ray Diffraction ◽  
Field Cooling

Fe-doped LiTaO3 thin films with a low and high Fe concentration (labeled as LTO:Fe-LC and LTO:Fe-HC, respectively) were deposited by magnetron sputtering from two home-made targets. The dopant directly influenced the crystalline structure of the LiTaO3 thin films, causing the contraction of the unit cell, which was related to the incorporation of Fe3+ ions into the LiTaO3 structure, which occupied Li positions. This substitution was corroborated by Raman spectroscopy, where the bands associated with Li-O bonds broadened in the spectra of the samples. Magnetic hysteresis loops, zero-field cooling curves, and field cooling curves were obtained in a vibrating sample magnetometer. The LTO:Fe-HC sample demonstrates superparamagnetic behavior with a blocking temperature of 100 K, mainly associated with the appearance of Fe clusters in the thin film. On the other hand, a room temperature ferromagnetic behavior was found in the LTO:Fe-LC layer where saturation magnetization (3.80 kAm−1) and magnetic coercivities were not temperature-dependent. Moreover, the crystallinity and morphology of the samples were evaluated by X-ray diffraction and scanning electron microscopy, respectively.

Influence of the Process for Obtaining Massive Amorphous Materials on the Defects of the Structure in the Alloy Fe61+xCo10-xY8W1B20 , where x = 0 or 1

2018 ◽  
Vol 69 (9) ◽  
pp. 2546-255 ◽  
Author(s):  
Marcin Nabialek ◽  
Bartlomiej Jez ◽  
Kinga Jez
Keyword(s):  
Amorphous Materials ◽  
Magnetic Hysteresis ◽  
Hysteresis Loops ◽  
Amorphous Structure ◽  
Stiffness Parameter ◽  
Copper Mold ◽  
X Ray Diffraction ◽  
X Ray ◽  
Magnetic Hysteresis Loops ◽  
Vibration Magnetometer

As part of the work, a rapid cooled alloy was produced with the chemical composition Fe61+xCo10-xY8W1B20, where: x = 0 or 1 using two methods, suction in and injecting the molten alloy into the copper mold. The material was obtained in the form of 10 mm x 5 mm x 0.5 mm plates. Studies on the structure of the obtained alloys were carried out using X-ray diffraction. Obtained X-ray diffraction images are typical for amorphous materials. Using the vibration magnetometer, static magnetic hysteresis loops and primary magnetization curves were measured. The produced samples are characterized by a saturation value above 1T and a coercive field value below 200 A/m. Based on the theory of H. Kronm�ller, numerical analysis of the curves of the original magnetization was carried out. It has been found that the process of magnetizing the produced materials has defects of the amorphous structure in the form of pseudo-location dipoles and free volumes. In addition, the spin wave stiffness parameter was determined.

Energy-Storage Study in Lead-Free Anti-Ferroelectric Bi0.5Na0.5TiO3-BaTiO3-K0.5Na0.5NbO3 Ceramics

2013 ◽  
Vol 745-746 ◽  
pp. 679-684 ◽  
Author(s):  
Feng Gao ◽  
Xian Lin Dong ◽  
Chao Liang Mao ◽  
Fei Cao ◽  
Gen Shui Wang
Keyword(s):  
Energy Storage ◽  
Hysteresis Loops ◽  
Dielectric Constants ◽  
Lead Free ◽  
X Ray Diffraction ◽  
Phase Measurements ◽  
Storage Study ◽  
Saturated Polarization ◽  
Diffraction Patterns ◽  
Sintering Method

Lead-free (1-x-y)Bi0.5Na0.5TiO3-xBaTiO3-yK0.5Na0.5NbO3 (BNT-BT-KNN) ceramics were fabricated by traditional sintering method. The X-ray diffraction patterns showed that the ceramics are all crystallized into a perovskite structure phase. Measurements of temperature-dependent dielectric constants showed the two typical shoulders observed in the BNT-BT binary system, indicating that the ceramics are also of relaxor anti-ferroelectric nature. Moreover, it was observed that the dielectric constants decreased sharply with the increase of KNN addition, while maintained the same level when the BNT/BT ratio changed. The P-E hysteresis loops showed that the saturated polarization and the remnant polarization both decreased with the increasing addition of KNN, while the reduction of the BNT/BT ratio enhancesd the saturated polarization. The energy-storage density calculated from the P-E loops also increased with the decrease of KNN addition and BNT/BT ratio, which further demonstrated that the key for improving the energy density of BNT-BT-KNN ceramics is relatively low addition of KNN and low BNT/BT ratio.

Structural and Magnetic Properties of CoFe2O4 / Si (001) Thin Films via Sol-Gel Method

2013 ◽  
Vol 744 ◽  
pp. 315-318
Author(s):  
Wei Rao ◽  
Ding Guo Li ◽  
Hong Chun Yan
Keyword(s):  
Thin Films ◽  
Magnetic Properties ◽  
Exchange Coupling ◽  
Cobalt Ferrite ◽  
Sol Gel ◽  
Magnetic Hysteresis ◽  
Vibrating Sample Magnetometer ◽  
X Ray Diffraction ◽  
X Ray ◽  
Calcined Temperature

Cobalt ferrite (CoFe2O4) thin films have been prepared on Si (001) substrates, with different calcined temperatures (Tcal=400°C~800°C). The films structure was studied by X-ray diffraction (XRD) and their surface was examined by scanning electron microscopy (SEM). The magnetic properties were measured with a vibrating sample magnetometer (VSM). For low calcined temperatures, the films presented a mixture of a CoFe2O4phase, with the cubic spinel structure, and cobalt and iron antiferromagnet oxides with CoO and FeO stoichiometries. As the calcined temperature increased, the CoO and FeO relative content strongly decreased, so that for Tcal=800°Cthe films were composed mainly by polycrystalline CoFe2O4. The magnetic hysteresis cycles measured in the films were horizontally shifted due to an exchange coupling field originated by the presence of the antiferromagnetic phases.

MgB2 Thick Film Grown on Silicon Carbide Substrate by Hybrid Physical-Chemical Vapor Deposition

2007 ◽  
Vol 546-549 ◽  
pp. 2067-2070
Author(s):  
Fen Li ◽  
Tao Guo ◽  
Kai Cheng Zhang ◽  
Li Ping Chen ◽  
Chin Ping Chen ◽  
...  
Keyword(s):  
Magnetic Hysteresis ◽  
Chemical Deposition ◽  
Hysteresis Loops ◽  
Chemical Vapor ◽  
X Ray Diffraction ◽  
X Ray ◽  
Bean Model ◽  
Physical Chemical ◽  
Silicon Carbide Substrate ◽  
Magnetic Hysteresis Loops

We have successfully synthesized MgB2 thick films on 4H-SiC substrate by hybrid physical-chemical deposition (HPCVD). They have TC above 40 K, X-ray diffraction (XRD) shows the polycrystal bulk like structure. And JC estimated using magnetic hysteresis loops (MHLs) and Bean model is 7.4 MA/cm2 in self field, at 5 K.

Structure and Magnetic Properties of Ga Substituted Ni-Ferrites

2013 ◽  
Vol 446-447 ◽  
pp. 68-72
Author(s):  
Ahmad Amirabadizadeh ◽  
Zobedeh Momeni Larimi ◽  
Saeideh Eghbali
Keyword(s):  
Magnetic Properties ◽  
Single Phase ◽  
Sol Gel ◽  
Magnetic Hysteresis ◽  
Hysteresis Loops ◽  
X Ray Diffraction ◽  
Auto Ignition ◽  
Transmission Electron ◽  
Magnetic Hysteresis Loops ◽  
Ga Content

Nanocrystalline Ga doped nickel ferrite [(NiFe2-xGaxO4 (x=0.0, 0.1, 0.3, 0.5 and 0.7)] powders have been synthesized by sol-gel auto-ignition method and the effect of non-magnetic gadillum content on the nanosize particles and magnetic properties has been studied. The X-ray diffraction (XRD) revealed that the powders obtained are single phase with spinel structure. The calculated grain size from XRD data have been verified using transmission electron microscopy (TEM). TEM photograph shows that the powders consist of nanometer sized grain. The size of nanoparticles decreases as the non magnetic Ga content increases. Magnetic hysteresis loops were measured at room temperature with maximum applied magnetic field of 20 KOe. As Ga content increases, the measured magnetic hysteresis curves became border and saturation magnetization (MS) increased up to x= 0.3 and further increase of x leads the magnetization to decrease. The results are explained according to the assumed cation distribution.

scholarly journals Morin-type transition in 5C pyrrhotite

2020 ◽  
Vol 105 (9) ◽  
pp. 1404-1411
Author(s):  
Charles R.S. Haines ◽  
Giulio I. Lampronti ◽  
Wim T. Klooster ◽  
Simon J. Coles ◽  
Sian E. Dutton ◽  
...  
Keyword(s):  
Heat Capacity ◽  
Magnetic Hysteresis ◽  
Hysteresis Loops ◽  
Theoretical Treatment ◽  
X Ray Diffraction ◽  
Resonant Ultrasound Spectroscopy ◽  
Magnetic Structures ◽  
Vacancy Ordering ◽  
First Order Transition ◽  
Resonant Ultrasound

Abstract We report the discovery of a low-temperature spin-flop transition in 5C pyrrhotite at ~155 K that is similar to those seen in hematite at 260 K and FeS (troilite) at 440 K. The 5C crystal was produced by annealing a 4C pyrrhotite crystal at 875 K to produce a change in the vacancy-ordering scheme that developed during cooling. The 5C structure is confirmed by single-crystal X-ray diffraction and the stoichiometry and homogeneity by electron microprobe and SEM BSE mapping. Resonant ultrasound spectroscopy (RUS), heat capacity, and magnetization measurements from room temperature down to 2 K are reported. The transition is marked by a steep change in elastic properties at the transition temperature, a peak in the heat capacity, and weak anomalies in measurements of magnetization. Magnetic hysteresis loops and comparison with the magnetic properties of 4C pyrrhotite suggest that the transition involves a change in orientation of moments between two different antiferromagnetic structures, perpendicular to the crystallographic c-axis at high temperatures and parallel to the crystal-lographic c-axis at low temperatures. The proposed structures are consistent with a group theoretical treatment that also predicts a first-order transition between the magnetic structures.

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