Y-Type Hexaferrites: Structural, Dielectric and Magnetic Properties

2012 ◽  
Vol 189 ◽  
pp. 209-232 ◽  
Author(s):  
Rajshree B. Jotania ◽  
Hardev Singh Virk
Keyword(s):  
Magnetic Properties ◽  
Quantum Interference ◽  
Room Temperature ◽  
Structural Changes ◽  
Ferromagnetic State ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Lcr Meter ◽  
Co Precipitation

This paper attempts to provide a historical survey of structure of various types of hexaferrites. It provides information about synthesis, characterization, structural, magnetic and dielectric properties of Y-type hexagonal ferrites using various chemical routes. We have prepared a series of cobalt doped Sr2Cu2-xCoxFe12O22(x = 0.0 to 1.0) hexaferrites using a wet chemical co-precipitation technique. The prepared hexaferrite precursors were calcined at 950 °C for 4 hours in a furnace and slowly cooled to room temperature. The crystal structure of Y-type hexaferrites is rather complicated. The chemical and structural changes were examined in detail by X-ray diffraction (XRD), Differential scanning calorimetry (DSC), Scanning electron microscopy (SEM), and Fourier transform infra-red (FTIR) spectroscopy. X-ray diffraction studies showed that sintering temperature as low as 950°C was sufficient to produce a single-phase Y-type hexaferrite material. The dielectric measurements were carried out over the frequency range of 100 Hz to 2 MHz at room temperature using an LCR meter to study the variation of dielectric constant and loss tangent with frequency. The magnetic properties of hexaferrite samples were investigated using a vibration sample magnetometer (VSM), and a superconducting quantum interference device (SQUID) magnetometer in the temperature range 30K to 200K. A change from ferromagnetic state to super paramagnetic state has been observed in Co doped Sr2Cu2-xCoxFe12O22(x= 0.6 to 1.0) hexaferrite. The novel applications of all types of hexaferrite materials have been described.

scholarly journals Size Effect on the Structural and Magnetic Properties of Nanosized PerovskiteLaFeO3Prepared by Different Methods

2012 ◽  
Vol 2012 ◽  
pp. 1-6 ◽  
Author(s):  
Nguyen Thi Thuy ◽  
Dang Le Minh
Keyword(s):  
Magnetic Properties ◽  
Electron Microscope ◽  
Room Temperature ◽  
High Energy ◽  
Ferromagnetic Behavior ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Transmission Electron ◽  
Co Precipitation

Nanosized LaFeO3material was prepared by 3 methods: high energy milling, citrate gel, and coprecipitation. The X-ray diffraction (XRD), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) show that the orthorhombic LaFeO3phase was well formed at a low sintering temperature of 500°C in the citrate-gel and co-precipitation methods. Scanning electron microscope (SEM) and transmission electron microscope (TEM) observations indicate that the particle size of the LaFeO3powder varies from 10 nm to 50 nm depending on the preparation method. The magnetic properties through magnetization versus temperatureM(T)and magnetization verses magnetic fieldM(H)characteristics show that the nano-LaFeO3exhibits a weak ferromagnetic behavior in the room temperature, and theM(H)curves are well fitted by Langevin functions.

Influence of Gd Addition on the Structure and Capability of Ni-Mn-In Metamagnetic Shape Memory Alloys

2012 ◽  
Vol 535-537 ◽  
pp. 950-953
Author(s):  
Li Na Bai ◽  
Gui Xing Zheng ◽  
Zhi Jian Duan ◽  
Jian Jun Zhang
Keyword(s):  
Differential Scanning Calorimetry ◽  
Magnetic Properties ◽  
Magnetic Property ◽  
Transition Temperature ◽  
Martensitic Transformation ◽  
Room Temperature ◽  
Vibrating Sample Magnetometry ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray

The influences of Gd concentration on martensitic transformation and magnetic properties of NiMnIn alloys were investigated by differential scanning calorimetry (DSC) , vibrating sample magnetometry (VSM), X-ray diffraction (XRD) and etc. It is Observed through the experiment: the addition of Gd enhances martensite transition temperature;X-ray diffraction analysis of experimental alloys is revealed that to the mixture is martensite and austenite at room temperature; content of Gd is not proportional to the improvement of magnetic property.

Adjusting Microstructure and Magnetic Properties of Ni-Mn-In Metamagnetic Shape Memory Alloys by Addition of Gd

2012 ◽  
Vol 535-537 ◽  
pp. 959-963
Author(s):  
Li Na Bai ◽  
Gui Xing Zheng ◽  
Jing Xin ◽  
Jian Jun Zhang
Keyword(s):  
Magnetic Field ◽  
Differential Scanning Calorimetry ◽  
Magnetic Properties ◽  
Shape Memory ◽  
Room Temperature ◽  
Vibrating Sample Magnetometry ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Microstructure And Magnetic Properties

The influences of Gd concentration on martensitic transformation and magnetic properties of NiMnIn alloys were investigated by differential scanning calorimetry (DSC) , vibrating sample magnetometry (VSM), X-ray diffraction (XRD) and etc. It shows that addition of Gd enhances martensite transition temperature and that X-ray diffraction analysis of experimental alloys is revealed which the mixture is martensite and austenite at room temperature. These alloys show promise as a metamagnetic shape memory alloy with magnetic-field-induced shape memory effect.

Microstructures, Electrical and Magnetic Properties of Zn Doped Co Nanoferrites

2012 ◽  
Vol 510-511 ◽  
pp. 221-226 ◽  
Author(s):  
M. Akram ◽  
M. Anis-ur-Rehman ◽  
M. Mubeen ◽  
M. Ali
Keyword(s):  
Magnetic Properties ◽  
Electrical Transport ◽  
Room Temperature ◽  
Precipitation Method ◽  
X Ray Diffraction ◽  
Electrical Transport Properties ◽  
X Ray ◽  
Electrical And Magnetic Properties ◽  
Crystallite Sizes ◽  
Co Precipitation

Non toxicity, bio compatibility and nanometer sizes regime which is comparable to the size of a cell, makes nanocrystalline Co ferrites particles very proficient. In the present research Zn doped cobalt ferrites were prepared by the chemical co-precipitation method and characterized by X-ray diffraction (XRD) at room temperature for structural analysis. X-ray diffraction patterns confirmed the FCC spinel structure of synthesized particles. Crystallite sizes were calculated from the most intense peak (311) using the Debye-Scherrer formula. The obtained crystallite sizes were in nanometer range for all the samples synthesized at reaction temperature of 70°C. Then samples were sintered at 550°C for 2 hours, characterized again by X-ray diffraction at room temperature. The crystallite sizes and lattice constants for all the samples were calculated again from the data obtained by XRD. DC electrical resistivity and AC electrical transport properties were analyzed. The magnetic properties such as coercivity (Hc) and remanence (Mr) of Co1-xZnxFe2O4for x = 0.0, 0.2, 0.4 were measured at room temperature by vibrating sample magnetometer. Coercivity and remanence were found maximum with minimum value of Zn in Co1-xZnxFe2O4.Observed structural and conduction properties of synthesized nanomaterials were correlated.

MICROSTRUCTURE AND MAGNETIC PROPERTIES CHANGE OF Fe3O4 NANOPARTICLES SYNTHESIZED UNDER MAGNETIC FIELDS AT ROOM TEMPERATURE

2009 ◽  
Vol 23 (23) ◽  
pp. 2723-2731 ◽  
Author(s):  
JUN WANG ◽  
SIHUA XIA ◽  
SHIHE CAO
Keyword(s):  
Magnetic Properties ◽  
Magnetic Fields ◽  
Room Temperature ◽  
Precipitation Method ◽  
X Ray Diffraction ◽  
Promising Technique ◽  
X Ray ◽  
Transmission Electron ◽  
Co Precipitation ◽  
Microstructure And Magnetic Properties

Magnetite nanoparticles have been synthesized by a co-precipitation method under magnetic fields (0~1 T) at room temperature. The as-prepared samples were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), vibrating sample magnetometer (VSM) and their microstructure analysis were evaluated on a Mössbauer spectrum. It was found that the Fe 3 O 4 samples produced under a magnetic field of 1 T had a much higher saturation magnetization (15.3 emu/g) than those produced under 0.6 T (7.56 emu/g) and 0 T magnetic fields (6.59 emu/g). This interesting result implies that magnetic fields can affect the growth of Fe 3 O 4 nanoparticles and further change the microstructure and crystallinity of Fe 3 O 4 nanoparticles. It is expected that this process could also be a promising technique to improve the magnetic properties of other magnetic materials.

scholarly journals Synthesis and Magnetic Properties of Hematite Particles in a “Nanomedusa” Morphology

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Jin Bae Lee ◽  
Hae Jin Kim ◽  
Janez Lužnik ◽  
Andreja Jelen ◽  
Damir Pajić ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Room Temperature ◽  
Magnetic Phase ◽  
Hydrothermal Process ◽  
Ferromagnetic State ◽  
X Ray Diffraction ◽  
Morin Transition ◽  
Preferential Direction ◽  
X Ray ◽  
Transmission Electron

We present the synthesis, characterization, and magnetic properties of hematite particles in a peculiar “nanomedusa” morphology. The particles were prepared from an iron-silica complex by a hydrothermal process in a solution consisting of ethyl acetate and ethanol. The particles’ morphology, structure, and chemical composition were investigated by transmission electron microscopy, powder X-ray diffraction, and scanning electron microscope equipped with an energy-dispersive X-ray spectrometer. The “hairy” particles consist of a spherical-like core of about 100 nm diameter and fibrous exterior composed of thin “legs” of 5 nm diameter grown along one preferential direction. The particles’ cores are crystalline and undergo a magnetic phase transition to a weakly ferromagnetic state at a temperature of 930 K that matches reasonably the Néel temperature of bulk hematite. However, unlike bulk hematite that undergoes Morin transition to an antiferromagnetic state around room temperature and small hematite nanoparticles that are superparamagnetic, the “nanomedusa” particles remain weakly ferromagnetic down to the lowest investigated temperature of 2 K. Each particle thus represents a nanodimensional “hairy” ferromagnet in a very broad temperature interval, extending much above the room temperature. Such high-temperature ferromagnetic nanoparticles are not frequently found among the nanomaterials.

Microstructure Evolution of a Fine Grain Al-50wt%Si Alloy Fabricated by High Energy Milling

2011 ◽  
Vol 479 ◽  
pp. 54-61 ◽  
Author(s):  
Fei Wang ◽  
Ya Ping Wang
Keyword(s):  
Grain Growth ◽  
Microstructure Evolution ◽  
Room Temperature ◽  
Milling Time ◽  
High Energy ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Laser Method ◽  
X Ray ◽  
Fine Grain

Microstructure evolution of high energy milled Al-50wt%Si alloy during heat treatment at different temperature was studied. Scanning electron microscope (SEM) and X-ray diffraction (XRD) results show that the size of the alloy powders decreased with increasing milling time. The observable coarsening of Si particles was not seen below 730°C in the high energy milled alloy, whereas, for the alloy prepared by mixed Al and Si powders, the grain growth occurred at 660°C. The activation energy for the grain growth of Si particles in the high energy milled alloy was determined as about 244 kJ/mol by the differential scanning calorimetry (DSC) data analysis. The size of Si particles in the hot pressed Al-50wt%Si alloy prepared by high energy milled powders was 5-30 m at 700°C, which was significantly reduced compared to that of the original Si powders. Thermal diffusivity of the hot pressed Al-50wt%Si alloy was 55 mm2/s at room temperature which was obtained by laser method.

scholarly journals Viability of the microencapsulation of a casein hydrolysate in lipid microparticles of cupuacu butter and stearic acid

2013 ◽  
Vol 2 (1) ◽  
Author(s):  
Samantha Cristina Pinho ◽  
Janaina Costa Da Silva
Keyword(s):  
Stearic Acid ◽  
Room Temperature ◽  
Casein Hydrolysate ◽  
Polysorbate 80 ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Initial Amount ◽  
X Ray ◽  
Lipid Mixtures ◽  
Lipid Microparticles

Solid lipid microparticles produced with a mixture of cupuacu butter and stearic acid were used to microencapsulate a commercial casein hydrolysate (Hyprol 8052). The composition of the lipid matrix used for the production of the lipid microparticles was chosen according to data on the wide angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC) of bulk lipid mixtures, which indicated that the presence of 10 % cupuacu butter was sufficient to significantly change the crystalline arrangement of pure stearic acid. Preliminary tests indicated that a minimum proportion of 4 % of surfactant (polysorbate 80) was necessary to produce empty spherical lipid particles with average diameters below 10 mm. The lipid microparticles were produced using 20 % cupuacu butter and 80 % stearic acid and then stabilized with 4 % of polysorbate 80, exhibiting an encapsulation efficiency of approximately 74 % of the casein hydrolysate. The melting temperature of the casein hydrolysate-loaded lipid microparticles was detected at 65.2 °C, demonstrating that the particles were solid at room temperature as expected and indicating that the incorporation of peptides had not affected their thermal behavior. After 25 days of storage, however, there was a release of approximately 30 % of the initial amount of encapsulated casein hydrolysate. This release was not thought to have been caused by the liberation of encapsulated casein hydrolysate. Instead, it was attributed to the possible desorption of the adsorbed peptides present on the surface of the lipid microparticles.

scholarly journals Structure and electric properties of cerium substituted SrBi1.8Ce0.2Nb2O9 and SrBi1.8Ce0.2Ta2O9 ceramics

2016 ◽  
Vol 10 (3) ◽  
pp. 183-188 ◽  
Author(s):  
Mohamed Afqir ◽  
Amina Tachafine ◽  
Didier Fasquelle ◽  
Mohamed Elaatmani ◽  
Jean-Claude Carru ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Solid State ◽  
Room Temperature ◽  
Single Phase ◽  
Solid State Reaction Method ◽  
X Ray Diffraction ◽  
Reaction Method ◽  
X Ray ◽  
Lcr Meter ◽  
Curie Temperature Tc

SrBi1.8Ce0.2Nb2O9 (SBCN) and SrBi1.8Ce0.2Ta2O9 (SBCT) powders were prepared via solid-state reaction method. X-ray diffraction analysis reveals that the SBCN and SBCT powders have the single phase orthorhom-bic Aurivillius structure at room temperature. The contribution of Raman scattering and FTIR spectroscopy of these samples were relatively smooth and resemble each other. The calcined powders were uniaxially pressed and sintered at 1250?C for 8 h to obtaine dense ceramics. Dielectric constant, loss tangent and AC conductivity of the sintered Ce-doped SrBi2Nb2O9 and SrBi2Ta2O9 ceramics were measured by LCR meter. The Ce-doped SBN (SBCN) ceramics have a higher Curie temperature (TC) and dielectric constant at TC (380?C and ?? ~3510) compared to the Ce-doped SBT (SBCT) ceramics (330?C and ?? ~115) when measured at 100Hz. However, the Ce-doped SBT (SBCT) ceramics have lower conductivity and dielectric loss.

scholarly journals Ferromagnetic Order in the Intermetallic Alloys laNi5-xMgx

2012 ◽  
Vol 29 (1) ◽  
pp. 50
Author(s):  
D.N Ba ◽  
L.T Tai ◽  
N.T Trung ◽  
N.T Huy
Keyword(s):  
Magnetic Properties ◽  
Curie Temperature ◽  
Room Temperature ◽  
Single Phase ◽  
Chemical Doping ◽  
Intermetallic Alloys ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ferromagnetic Order ◽  
Diffraction Patterns

The influences of the substitution of Ni with Mg on crystallographic and magnetic properties of the intermetallic alloys LaNi5-xMgx (x ≤ 0.4) were investigated. The X-ray diffraction patterns showed that all samples were of single phase, and the lattice parameters, a and c, decreased slightly upon chemical doping. LaNi5 is well known as an exchange-enhanced Pauli paramagnet. Interestingly, in LaNi5-xMgx, the ferromagnetic order existed even with a small amount of dopants; the Curie temperature reached the value of room temperature for x = 0.2, and enhanced with increasing x.

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