The Influence of Stoichiometry on the Index of Refraction of Cobalt Ferrite Samples at Terahertz Frequencies

MRS Advances ◽  
2017 ◽  
Vol 2 (58-59) ◽  
pp. 3663-3666
Author(s):  
Alan F. N. Boss ◽  
Antonio C. C. Migliano ◽  
Ingrid Wilke
Keyword(s):  
Cobalt Ferrite ◽  
State Of The Art ◽  
Secondary Phase ◽  
Index Of Refraction ◽  
Terahertz Frequency ◽  
Chemical Homogeneity ◽  
X Ray ◽  
Nickel Cobalt ◽  
Cobalt Ferrites ◽  
Terahertz Frequencies

ABSTRACT We report an experimental study on the terahertz frequency dielectric properties of manganese cobalt ferrites (MnxCo1−xFe2O4) and nickel cobalt ferrites (NixCo1-xFe2O4) with three different stoichiometry each, x=0.3, x=0.5 and 0.7. Particularly, we present a comparison and discussion of the terahertz frequency indices of refraction of these two ferrites compositions. MnxCo1−xFe2O4 and NixCo1-xFe2O4 pellets with different Mn/Co and Ni/Co ratios (x=0.3, x=0.5 and x=0.7) were prepared by state-of-the-art ceramic processing. The morphology and chemical homogeneity of these ferrites were characterized by energy dispersive x-ray spectroscopy. We observed that the indexes of refraction for manganese cobalt ferrites are 3.22, 3.71 and 3.67 for ratios of 0.3, 0.5 and 0.7, respectively. In the case of nickel cobalt ferrite, the indexes of refraction are 3.53, 3.57 and 3.47 for ratios of 0.3, 0.5 and 0.7 respectively. We notice a substantial difference in the index of refraction for the Mn0.3Co0.7Fe2O4. This difference may be correlated to a secondary phase formed in this sample.

M�ssbauer and x-ray spectroscopic investigation of high-magnetostriction nickel-cobalt ferrites

1972 ◽  
Vol 15 (3) ◽  
pp. 429-431
Author(s):  
P. P. Kirichok ◽  
G. S. Nodval'nykh ◽  
N. V. Kobrya ◽  
O. R. Borovskaya ◽  
L. M. Letyuk
Keyword(s):  
Spectroscopic Investigation ◽  
X Ray ◽  
Nickel Cobalt ◽  
Cobalt Ferrites

scholarly journals CoFe2O4 Nanomaterials: Effect of Annealing Temperature on Characterization, Magnetic, Photocatalytic, and Photo-Fenton Properties

Processes ◽  
2019 ◽  
Vol 7 (12) ◽  
pp. 885 ◽  
Author(s):  
Nguyen Thi To Loan ◽  
Nguyen Thi Hien Lan ◽  
Nguyen Thi Thuy Hang ◽  
Nguyen Quang Hai ◽  
Duong Thi Tu Anh ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Photocatalytic Activity ◽  
Rhodamine B ◽  
Cobalt Ferrite ◽  
Annealing Temperature ◽  
Xrd Analysis ◽  
Band Gap Energy ◽  
Cofe2o4 Nanoparticles ◽  
X Ray ◽  
Cobalt Ferrites

In this research, structural, magnetic properties and photocatalytic activity of cobalt ferrite spinel (CoFe2O4) nanoparticles were studied. The samples were characterized by X-ray powder diffraction (XRD), energy dispersive X-ray (EDX), scanning electron microscopy (SEM), transmission electronic microscopy (TEM), Brunauer–Emmett–Teller (BET), Fourier transform infrared spectroscopy (FTIR), and UV-visible diffused reflectance spectroscopy (DRS) analysis. The XRD analysis revealed the formation of the single-phase CoFe2O4 with a cubic structure that is annealed at 500–700 °C in 3 h. The optical band gap energy for CoFe2O4 was determined to be in the range of 1.57–2.03 eV. The effect on the magnetic properties of cobalt ferrites was analyzed by using a vibrating sample magnetometer (VSM). The particle size and the saturation magnetization of cobalt ferrite nanoparticles increased with increasing annealing temperature. The photocatalytic activity of CoFe2O4 nanoparticles was investigated by using rhodamine B dye under visible light. The decomposition of rhodamine B reached 90.6% after 270 min lighting with the presence of H2O2 and CF500 sample.

scholarly journals Magnetic Properties of Co0.5Zn0.5Fe2O4Nanoparticles Synthesized by a Template-Assisted Hydrothermal Method

2011 ◽  
Vol 2011 ◽  
pp. 1-5 ◽  
Author(s):  
H. Y. He
Keyword(s):  
Electron Microscopy ◽  
Saturation Magnetization ◽  
Hydrothermal Method ◽  
Cobalt Ferrite ◽  
Vibrating Sample Magnetometer ◽  
X Ray Diffraction ◽  
X Ray ◽  
Templating Agent ◽  
Nickel Cobalt ◽  
Scanning Electron

In the present paper, nickel cobalt ferrite (Co0.5Zn0.5Fe2O4) nanoparticles were synthesized using a template-assisted hydrothermal method. Carboxymethyl cellulose was used as the templating agent for controlling the morphology of the Co0.5Zn0.5Fe2O4nanoparticles. The synthesized nanoparticles were characterized using X-ray diffraction, scanning electron microscopy, and a vibrating sample magnetometer. The results indicated that the morphology of the nanoparticles changed from granular and superparamagnetic to platelike and ferromagnetic with the addition of the template. The Co0.5Zn0.5Fe2O4nanoparticles synthesized without the template exhibited a saturation magnetization and coercivity 2.81 T and 0.2 kA⋅m−1, while when the template was used, the saturation magnetization and coercivity increased to 3.13 T and 76.6 kA⋅m−1as the template proportion increased to 0.3.

scholarly journals Obtaining and X-ray Analysis of Cobalt Ferrite Powders Substituted by Nickel Cations

2015 ◽  
Vol 16 (2) ◽  
pp. 351-354
Author(s):  
V.S. Bushkova ◽  
I.P. Yaremiy ◽  
R.V. Ilnitsky ◽  
R.P. Lisovskiy ◽  
M.L. Mokhnatskyi
Keyword(s):  
Cobalt Ferrite ◽  
Sol Gel ◽  
Nickel Content ◽  
Coherent Scattering ◽  
Lattice Parameter ◽  
X Ray ◽  
Nickel Cobalt ◽  
Auto Combustion ◽  
Ray Density ◽  
Average Size

The aim of this work was to create and study of ferrite nickel-cobalt powders, using sol-gel technology with participation of auto-combustion. After completing the process autocombustion was obtained only one phase, which corresponded to  the cubic structure of spinel space group Fd3m. It was found that the average size of coherent scattering regions not exceeding 62 nm. The dependences of the lattice parameter, X-ray density and specific surface area of the ferrite powders from nickel content were found. It was shown that at substitution of cations cobalt on cations nickel latest give preference only B positions, thus displacing part of in the A positions.

SYNTHESIS AND CHARACTERIZATION OF COBALT FERRITES MAGNETIC NANOPARTICLES IN ALKANETHIOL SOLUTION

2004 ◽  
Vol 03 (04n05) ◽  
pp. 639-648
Author(s):  
W. T. KERK ◽  
J. M. LI ◽  
W. S. CHIN ◽  
A. C. H. HUAN
Keyword(s):  
Electron Microscopy ◽  
Magnetic Nanoparticles ◽  
Size Distribution ◽  
Room Temperature ◽  
Cobalt Ferrite ◽  
Homogeneous Solution ◽  
X Ray ◽  
Force Microscopy ◽  
Transmission Electron ◽  
Cobalt Ferrites

Magnetic nanoparticles of cobalt ferrite have been synthesized in a homogeneous solution containing dodecanethiol at room temperature. The alkanethiol molecules have provided a mean to control the particle size distribution. The uniformed size distribution, crystallinity and morphology of these nanoparticles are characterized with X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM). The stoichiometry of the cobalt ferrite is confirmed by both elemental analysis and Energy Dispersive X-ray (EDX). Fabrication of assembled arrays of these nanoparticles on Si (100) have been achieved by slow evaporation of the solution and studied by Atomic Force Microscopy (AFM). Magnetic properties of the nanoparticles are determined by Vibrating Sample Magnetometer (VSM) and show a magnetization (Ms) of 75.3 emu/g and a coercivity (Hc) of 1500 Oe at room temperature.

Effect of milling time on microstructure of cobalt ferrites synthesized by mechanical alloying

2021 ◽  
Vol 111 (1) ◽  
pp. 5-13
Author(s):  
A.E. Tomiczek
Keyword(s):  
Electron Microscopy ◽  
Mechanical Alloying ◽  
Cobalt Ferrite ◽  
Milling Time ◽  
Morphological Changes ◽  
Formation Rate ◽  
High Energy ◽  
Ferrite Powder ◽  
X Ray ◽  
Cobalt Ferrites

Purpose: of this paper is to determine the effect of manufacturing conditions, especially milling time, on the microstructure and phase composition of CoFe2O4 cobalt ferrite. Design/methodology/approach: Cobalt ferrite (CoFe2O4) has been synthesised from a stoichiometric mixture of CoCo3 and α-Fe2O3 powders in a high energy planetary mill. Annealing at 1000°C for 6 hours after milling was used to improve the solid-state reaction. Calcinated samples were analysed by X-ray diffraction (XRD), and transmission electron microscopy (TEM). The relationship between the milling time of powders, their microstructure, as well as their properties were evaluated. Particles size distribution and scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDX) examination were also made. Findings: CoFe2O4 ferrites were successfully synthesized by mechanical alloying of α-Fe2O3 and CoCO3 powders. The powder particles had undergone morphological changes with the increasing milling time. However, the milling time does not affect the ferrite formation rate. It is expected that the improvement of fabrication parameters can further enhance the properties of cobalt ferrite presented in this work. Research limitations/implications: Contribute to research on the structure and properties of cobalt ferrites manufactured by mechanical alloying. Practical implications: The reactive milling and subsequently annealing is an efficient route to synthesise cobalt ferrite powder. However, using steel milling equipment risks powder contamination with iron and chromium from the vials and balls. Originality/value: The results of the experimental research of the developed ferrite materials served as the basis for determining material properties and for further investigation.

Two-Terminal Active Devices for Terahertz Sources

2003 ◽  
Vol 13 (02) ◽  
pp. 395-427 ◽  
Author(s):  
G. I. Haddad ◽  
J. R. East ◽  
H. Eisele
Keyword(s):  
Power Generation ◽  
State Of The Art ◽  
Great Promise ◽  
Electromagnetic Spectrum ◽  
Terahertz Frequency ◽  
Frequency Range ◽  
Terahertz Frequency Range ◽  
Active Devices ◽  
New Device ◽  
Terahertz Frequencies

The terahertz frequency range of the electromagnetic spectrum holds great promise for many applications including sensing, imaging, and communications. However, the availability of solid-state sources with reasonable power levels is well recognized as one of the major obstacles for systems applications in this frequency range. Here, the state of the art of active two-terminal devices is reviewed and high-lighted with some exemplary experimental results. The potential, capabilities, and limitations of two-terminal devices regarding power generation at terahertz frequencies are discussed. Furthermore, a new device is described that has the potential of circumventing some of the limitations of existing devices.

Revisiting the High-Pressure Properties of the Metal-Organic Frameworks ZIF-8 and ZIF-67

2020 ◽  
Author(s):  
Pia Vervoorts ◽  
Stefan Burger ◽  
Karina Hemmer ◽  
Gregor Kieslich
Keyword(s):  
High Pressure ◽  
State Of The Art ◽  
Energy Landscape ◽  
Structural Flexibility ◽  
Zeolitic Imidazolate Frameworks ◽  
Stimuli Responsive ◽  
X Ray Diffraction ◽  
X Ray ◽  
Open Questions ◽  
Metal Organic

The zeolitic imidazolate frameworks ZIF-8 and ZIF-67 harbour a series of fascinating stimuli responsive properties. Looking at their responsitivity to hydrostatic pressure as stimulus, open questions exist regarding the isotropic compression with non-penetrating pressure transmitting media. By applying a state-of-the-art high-pressure powder X-ray diffraction setup, we revisit the high-pressure behaviour of ZIF-8 and ZIF-67 up to <i>p</i> = 0.4 GPa in small pressure increments. We observe a drastic, reversible change of high-pressure powder X-ray diffraction data at <i>p</i> = 0.3 GPa, discovering large volume structural flexibility in ZIF-8 and ZIF-67. Our results imply a shallow underlying energy landscape in ZIF-8 and ZIF-67, an observation that might point at rich polymorphism of ZIF-8 and ZIF-67, similar to ZIF-4(Zn).<br>

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