Physical and Dielectric Properties of MnFe2O4 Doped by Mo

2019 ◽  
Vol 4 (2) ◽  
pp. 125-136 ◽  
Author(s):  
F. Al-Mokdad ◽  
R. Sayed Hassan ◽  
R. Awad
Keyword(s):  
Dielectric Properties ◽  
Single Phase ◽  
Energy Gap ◽  
Magnetic Measurements ◽  
Magnetic Hysteresis ◽  
Spinel Ferrites ◽  
Ferromagnetic Behavior ◽  
X Ray ◽  
Mo Doping ◽  
Mnfe2o4 Nanoparticles

Background: The properties of spinel ferrites are known to be dependent on many various factors and mainly on the cations distribution among the tetrahedral and octahedral sites. Therefore, they are sensitive to the presence of doping cations, the type and the amount of these cations. Many researchers have focused on investigating the effect of doping on spinel ferrites nanoparticles with various types of dopants. Among the dopants, transition metal (TM) ions have shown significant effects and changes on the structural, optical, electric and magnetic properties of spinel ferrites nanoparticles. Objective: The goal of this work is to investigate the effect of the TM ions Mo5+ on the several properties of manganese ferrites nanoparticles. Methods: Mo-doped manganese ferrites nanoparticles with the general formula MnFe2-xMoxO4 (0≤x≤ 0.1) were prepared by co-precipitation technique using two different methods, depending on the molarity of NaOH and the annealing temperatures. The characterization of the prepared samples was conducted by X-ray powder diffraction (XRD), Energy-Dispersive X-ray (EDX), Transmission Electron Microscopy (TEM), ultraviolet-visible (UV-Vis) absorption spectroscopy and Fourier Transform Infrared (FTIR) spectroscopy in order to investigate the effect of Mo-doping on the structure, crystallite size, morphology, energy gap and functional groups of MnFe2O4 nanoparticles. Vibrating sample magnetometer (VSM) was used to study the magnetic hysteresis of the samples. Results: The XRD patterns show the segregation of MnFe2O4 phase into α-Fe2O3 and Mn2O3 for samples prepared at 4 M NaOH and annealing temperature of 873 K. Whereas, samples prepared at 2 M NaOH without annealing process, obtained a single phase of MnFe2O4. The Eg of both samples decreases with the increase in Mo-doping. FTIR confirms the presence of Fe-O bands corresponding to α-Fe2O3 for annealed samples, and the metal-O bands corresponding to octahedral and tetrahedral sites in non-annealed samples. Magnetic measurements show that annealed samples are antiferromagnetic whereas ferromagnetic behavior is observed in non-annealed samples. Dielectric measurements, for both samples, indicate that the dielectric parameters are strongly dependent on both Mo-concentrations and temperatures. Conclusion: In order to get a single phase of MnFe2O4 nanoparticles, thermal treatment at high temperature and high molarity of NaOH are not recommended. Mo-doping has significant influences on the optical, magnetic and dielectric properties and therefore future studies on the Mo-doping with different and new doping percentages are recommended.

scholarly journals Room Temperature Ferromagnetic and Optical Properties of Chrome Doped ZnS Nanorods Prepared by Hydrothermal Method

2017 ◽  
Vol 2017 ◽  
pp. 1-8 ◽  
Author(s):  
Wenhua Zhao ◽  
Zhiqiang Wei ◽  
Li Zhang ◽  
Xiaojuan Wu ◽  
Xuan Wang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Hydrothermal Method ◽  
Room Temperature ◽  
Single Phase ◽  
Diffuse Reflectance Spectroscopy ◽  
Magnetic Measurements ◽  
Ferromagnetic Behavior ◽  
X Ray ◽  
Pl Spectra ◽  
Cr Concentration

Cr doped Zn1-xCrxS nanorods with different concentration ratio (x=0, 0.01, 0.03, and 0.05) were successfully synthesized by hydrothermal method. The crystal microstructure, morphology, chemical composition, and optical and magnetic properties of the samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), X-ray energy dispersive spectrometry (XEDS), diffuse-reflectance spectroscopy (DRS), photoluminescence (PL) spectra, and the vibrating sample magnetometer (VSM). All the samples synthesized by this method exhibited single-phase wurtzite structure with good crystallization as demonstrated by XRD studies, which indicated that all Cr ions successfully substituted for the lattice site of Zn2+ and generated single-phase Zn1-xCrxS. DRS revealed the band gap of doped Zn1-xCrxS underwent blue shift compared to that of the bulk ZnS. PL spectra showed obvious ultraviolet emission peak at 375 nm and two blue emissions appear about 500 and 580 nm. The blue emissions intensity of doped samples improved with the increase of Cr concentration, comparing to pure ZnS. Magnetic measurements indicated that the undoped and doped ZnS nanorods exhibited well-defined ferromagnetic behavior at room temperature. The saturation magnetization weakened significantly with increasing Cr concentration comparing to pure ZnS and reached minimum for 3% Cr.

scholarly journals Morphological and magnetic features of columnar nanostructures CuO

2021 ◽  
Vol 2094 (2) ◽  
pp. 022002
Author(s):  
A V Ushakov ◽  
I V Karpov ◽  
L Yu Fedorov ◽  
V G Demin
Keyword(s):  
Magnetic Measurements ◽  
Magnetic Hysteresis ◽  
Coherent Scattering ◽  
Magnetic Hysteresis Loop ◽  
Ferromagnetic Behavior ◽  
X Ray Diffraction ◽  
Monoclinic Crystal ◽  
X Ray ◽  
Monoclinic Crystal Structure ◽  
Ionic Nature

Abstract Columnar nanostructures (CNS) were grown by plasma chemical synthesis at a gas mixture pressure of 90% He + 10% O2 200 Pa and substrate temperatures of 340K (sample 1) and 370K (sample 2). The effect of substrate temperature on the morphological, crystalline, magnetic, and impedance properties of CNS was studied. Scanning microscopy (SEM) showed that the morphology of CNS varies significantly from dendritic to wire structure. Energy dispersive X-ray spectroscopy (EDS) showed a change in the stoichiometry of the deficiency samples (Cu52O48) to an excess of oxygen (Cu42O58). X-ray diffraction analysis (XRD) and Rietveld fitting showed that samples 1 and 2 have a monoclinic crystal structure with a large proportion of the amorphous phase, the size of coherent scattering regions (CSR) was 26 nm (sample 1). Magnetic measurements showed that sample 1 exhibits ferromagnetic behavior, and at 6 K a magnetic hysteresis loop appears. Sample 2 from 250 K to room temperature exhibits diamagnetic behavior. A connection was found between the appearance of diamagnetism and a jump in the dielectric constant of sample 2. An assumption was made about the electron-ionic nature of the diamagnetism of sample 2.

scholarly journals Mn-Induced Thermal Stability of L10 Phase in Fept Magnetic Nanoscale Ribbons

Nanomaterials ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 1278
Author(s):  
Alina Daniela Crisan ◽  
Aurel Leca ◽  
Dan Pantelica ◽  
Ioan Dan ◽  
Ovidiu Crisan
Keyword(s):  
Rare Earth ◽  
Single Phase ◽  
Permanent Magnets ◽  
Magnetic Hysteresis ◽  
Ternary Alloys ◽  
Large Temperature ◽  
Nominal Composition ◽  
X Ray Diffraction ◽  
X Ray ◽  
Operation Conditions

Magnetic nanoscale materials exhibiting the L10 tetragonal phase such as FePt or ternary alloys derived from FePt show most promising magnetic properties as a novel class of rare earth free permanent magnets with high operating temperature. A granular alloy derived from binary FePt with low Pt content and the addition of Mn with the nominal composition Fe57Mn8Pt35 has been synthesized in the shape of melt-spun ribbons and subsequently annealed at 600 °C and 700 °C for promoting the formation of single phase, L10 tetragonal, hard magnetic phase. Proton-induced X-ray emission spectroscopy PIXE has been utilized for checking the compositional effect of Mn addition. Structural properties were analyzed using X-ray diffraction and diffractograms were analyzed using full profile Rietveld-type analysis with MAUD (Materials Analysis Using Diffraction) software. By using temperature-dependent synchrotron X-ray diffraction, the disorder–order phase transformation and the stability of the hard magnetic L10 phase were monitored over a large temperature range (50–800 °C). A large interval of structural stability of the L10 phase was observed and this stability was interpreted in terms of higher ordering of the L10 phase promoted by the Mn addition. It was moreover found that both crystal growth and unit cell expansion are inhibited, up to the highest temperature investigated (800 °C), proving thus that the Mn addition stabilizes the formed L10 structure further. Magnetic hysteresis loops confirmed structural data, revealing a strong coercive field for a sample wherein single phase, hard, magnetic tetragonal L10 exists. These findings open good perspectives for use as nanocomposite, rare earth free magnets, working in extreme operation conditions.

scholarly journals Sintering behaviour and microwave dielectric properties of MgO-2B2O3-xwt%BaCu(B2O5)-ywt%H3BO3 ceramics

2021 ◽  
Author(s):  
Haiquan Wang ◽  
Shixuan Li ◽  
Kangguo Wang ◽  
Xiuli Chen ◽  
Huanfu Zhou
Keyword(s):  
Dielectric Properties ◽  
Bulk Density ◽  
Single Phase ◽  
Sintering Temperature ◽  
Microwave Dielectric Properties ◽  
X Ray Diffraction ◽  
Microwave Dielectrics ◽  
X Ray ◽  
Microwave Dielectric ◽  
Sintering Behaviour

AbstractThis study investigates the bulk density, sintering behaviour, and microwave dielectric properties of the MgO-2B2O3 series ceramics synthesised by solid-state reaction. According to the X-ray diffraction and microstructural analyses, the as-prepared MgO-2B2O3 ceramics possess a single-phase structure with a rod-like morphology. The effects of different quantities of H3BO3 and BaCu(B2O5) (BCB) on the bulk density, sintering behaviour, and microwave dielectric properties of the MgO-2B2O3 ceramics were investigated. Accordingly, the optimal sintering temperature was obtained by adding 30 wt% H3BO3 and 8 wt% BCB. We also reduced the sintering temperature to 825 °C. Furthermore, the addition of 40 wt% H3BO3 and 4 wt% BCB increased the quality factor, permittivity, and temperature coefficient of resonance frequency of MgO-2B2O3 to 44,306 GHz (at 15 GHz), 5.1, and −32 ppm/°C, respectively. These properties make MgO-2B2O3 a viable low-temperature co-fired ceramic with broad applications in microwave dielectrics.

MAGNETOCALORIC EFFECT IN THE INTERMETALLIC COMPOUND Gd3Ni8Al

2012 ◽  
Vol 26 (25) ◽  
pp. 1250167 ◽  
Author(s):  
M. X. WANG ◽  
H. FU ◽  
Q. ZHENG ◽  
J. TANG
Keyword(s):  
Intermetallic Compound ◽  
Magnetocaloric Effect ◽  
Single Phase ◽  
Magnetic Entropy Change ◽  
Magnetic Measurements ◽  
Entropy Change ◽  
Magnetic Entropy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Refrigerant Capacity

The magnetic properties and magnetocaloric effect of the polycrystalline Gd 3 Ni 8 Al intermetallic compound are studied in this paper. Powder X-ray diffraction shows that the alloy is CeNi 3-type single-phase structure. The magnetic measurements indicate that the compound is ferromagnetic and undergoes a second-order phase transition at 62 K. The maximum of magnetic entropy change reaches 11 J/kg K for the field change from 0 to 50 kOe and the refrigerant capacity of the titled compound is found to be 4.8×102 J/kg.

Ferromagnetic Homogeneous Polycrystalline Zn1-xCoxO Oxides

2006 ◽  
Vol 45 ◽  
pp. 2520-2527
Author(s):  
Yue Bin Zhang ◽  
Sean Li
Keyword(s):  
Single Phase ◽  
Nearest Neighbor ◽  
Ferromagnetic Behavior ◽  
Additional Contribution ◽  
X Ray Diffraction ◽  
X Ray ◽  
Oxygen Ions ◽  
Random Manner ◽  
Single Phase Wurtzite Structure ◽  
Single Phase Wurtzite

In this work, the structural and magnetic properties of polycrystalline Zn1-xCoxO (x = 0, 0.02, 0.05, 0.0625, 0.10 and 0.15) oxides were studied in detail. Rietveld refinement of x-ray diffraction spectra indicates that a single-phase wurtzite structure was formed in Zn1-xCoxO samples for x up to 0.10. The magnetization for x = 0.02 can be fitted to a model with a paramagnetic Curie term and a diamagnetic constant which could arise from spins of isolated free Co ions and a diamagnetic background, respectively. For x > 0.02, however, an additional antiferromagnetic Curie-Weiss term needs to employ for fitting. This is due to an additional contribution from clustered Co ions that are in nearest neighbor positions through oxygen ions. Results show that the substitution of Co at the Zn site does not occur in a completely random manner but Co ions appear to have a tendency for clustering. In addition, the homogenous ZnO:Co thin film prepared by Pulsed Laser Deposition on SiO2/Si substrate shows ferromagnetic behavior at room temperature.

scholarly journals Effect of Fe Substitution on the Structural, Electrical and Dielectric Properties of La0.70Ca0.30MnO3 Cathode for SOFCs

2019 ◽  
Vol 9 (1) ◽  
pp. 324-328
Keyword(s):  
Dielectric Properties ◽  
Single Phase ◽  
Diffraction Method ◽  
X Ray Diffraction ◽  
Reaction Route ◽  
X Ray ◽  
Suitable Material ◽  
Density Values ◽  
Electrical And Dielectric Properties ◽  
Fe Substitution

Perovskite solid solutions (La0.70Ca0.30)(FexMn1-x)O3 where x = 0.01, 0.20, 0.30 and 0.40 ceramics were synthesized by solid state reaction route. The structural studies were carried by X-Ray diffraction method and the observed results have indicated that all the prepared samples were crystallized into single phase. The surface morphology was studied by Scanning Electron Microscopy and the images have revealed that grain size has increased with the increasing concentration of Fe. Archimedes principle was used to calculate the density of all the sintered samples and the density values were observed to be in increasing order. The impedance and dielectric properties have been characterized at different ranges of temperature and frequency. The value of electrical conductivity were found to be more than 100 S cm-1 , which indicate that the synthesized material is suitable material for cathode of Solid Oxide Fuel Cell.

scholarly journals High-temperature ferromagnetic semiconductor with a field-tunable green fluorescent effect

2020 ◽  
Vol 12 (1) ◽  
Author(s):  
Bowen Zhou ◽  
Qing Zhao ◽  
Zhehong Liu ◽  
Xudong Shen ◽  
Xubin Ye ◽  
...  
Keyword(s):  
Room Temperature ◽  
Energy Gap ◽  
Magnetic Measurements ◽  
Oxygen Deficiency ◽  
Perovskite Oxide ◽  
Ferromagnetic Behavior ◽  
Photoluminescence Intensity ◽  
Spin Ordering ◽  
Light Region ◽  
Green Fluorescent

Abstract Ferromagnetic semiconductors with luminescent effects provide a unique platform for studying magneto-electric-optical multifunctional devices. However, little is known about such materials with spin ordering well above room temperature. By using a unique high-pressure annealing method, a Cr and Fe disordered perovskite oxide SrCr0.5Fe0.5O2.875 (SCFO) with a simple cubic structure was prepared. Magnetic measurements demonstrated the ferromagnetic behavior with a spin ordering temperature as high as 600 K. In contrast to metallic SrCrO3 and SrFeO3, SCFO, with a moderate oxygen deficiency, is a direct bandgap semiconductor with an energy gap of 2.28 eV, which is within the visible light region. As a consequence, SCFO displays a green fluorescent effect arising from the d–p bonding and anti-bonding states. Moreover, the photoluminescence intensity can be tuned by a magnetic field. This work opens up a new avenue for research on room-temperature multifunctional materials with coupled magnetic, electrical, and optical performance.

Superparamagnetic Behavior of Granular Co-C Films Consisting of Nanocrystalline Cobalt Encapsulated in Carbon

2000 ◽  
Vol 614 ◽  
Author(s):  
Hao Wang ◽  
S.P. Wong ◽  
W.Y. Cheung ◽  
N. Ke ◽  
M.F. Chiah ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Rutherford Backscattering Spectrometry ◽  
Magnetic Measurements ◽  
Magnetic Hysteresis ◽  
Blocking Temperature ◽  
Vacuum Arc ◽  
Zero Field ◽  
X Ray Diffraction ◽  
X Ray ◽  
Force Microscopy

ABSTRACTNanocomposite Co-C thin films of about 15 nm thick were prepared by pulsed filtered vacuum arc deposition. The films were characterized by x-ray photoelectron spectroscopy, non-Rutherford backscattering spectrometry, x-ray diffraction, magnetic force microscopy and magnetic measurements. The as-deposited films were amorphous. After annealing at 350°C for one hour in vacuum (< 10−3 Pa), the films were found to consist of nanocrystalline Co grains encapsulated in carbon. The superparamagnetism of the annealed Co36C64 film was demonstrated by the measurement of DC susceptibility and magnetic hysteresis using a SQUID magnetometer. The superparamagnetic relaxation blocking temperature was marked to be about 12K by the peak of the zero-field-cooled magnetization under a field of 100 Oe. The magnetic properties of these annealed granular Co-C films transform from superparamagnetism to ferromagnetism when the Co concentration increases.

Preparation of Forsterite by Solid State Synthesis Process and its Dielectric Properties

2012 ◽  
Vol 534 ◽  
pp. 110-113 ◽  
Author(s):  
Fei Shi ◽  
Peng Cheng Du ◽  
Jing Xiao Liu ◽  
Ji Wei Wu ◽  
Chun Yuan Luo
Keyword(s):  
Dielectric Properties ◽  
Solid State ◽  
Single Phase ◽  
Raw Materials ◽  
Magnesium Carbonate ◽  
Solid State Synthesis ◽  
Molar Ratio ◽  
Synthesis Process ◽  
X Ray Diffraction ◽  
X Ray

Using basic magnesium carbonate (Mg(OH)2•4MgCO3•6H2O) and SiO2 as raw materials, forsterite (Mg2SiO4) was prepared by solid state synthesis process. The optimal process for synthesizing Mg2SiO4 was obtained by adjusting Mg/Si molar ratio and sintering temperature. The crystal phase of the obtained Mg2SiO4 powder was determined by X-ray diffraction (XRD). The results indicate that the single-phase Mg2SiO4 powder can be obtained when the mixtures with Mg/Si molar ratio of 2.05～2.01 were sintered at 1350°C for 3h in the air. The as-prepared Mg2SiO4 ceramic samples which were sintered at 1300～1360°C showed better dielectric properties with εr=7.4 and tanδ =7.5×10-4.

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