scholarly journals PHASE FORMATION AND SUPERCONDUCTIVITY OF Fe-TUBE ENCAPSULATED AND VACUUM-ANNEALED MgB2

2006 ◽  
Vol 20 (27) ◽  
pp. 1763-1769 ◽  
Author(s):  
K. P. SINGH ◽  
V. P. S. AWANA ◽  
MD. SHAHABUDDIN ◽  
M. HUSAIN ◽  
R. B. SAXENA ◽  
...  
Keyword(s):  
Room Temperature ◽  
Single Phase ◽  
Heating Temperature ◽  
Hold Time ◽  
Lattice Parameter ◽  
Hexagonal Structure ◽  
Synthesis Parameters ◽  
Phase Pure ◽  
The Right ◽  
Bell Shaped Curve

We report optimization of the synthesis parameters viz. heating temperature (TH), and hold time (t hold ) for vacuum-annealed (10-5 Torr) and LN 2 (liquid nitrogen) quenched MgB 2 compound. These are single-phase compounds crystallizing in the hexagonal structure (space group P 6/mmm ) at room temperature. Our XRD results indicated that for phase-pure MgB 2, the TH for 10-5 Torr annealed and LN 2-quenched samples is 750°C. The right stoichiometry i.e., MgB 2 of the compound corresponding to 10-5 Torr and TH of 750°C is found for the hold time (t hold ) of 2.30 hours. With varying t hold from 1–4 hours at fixed TH (750°C) and vacuum (10-5 Torr), the c-lattice parameter decreases first and later increases with t hold (hours) before a near saturation, while the a-lattice parameter first increases and later decreases beyond a t hold of 2.30 hours. The c/a ratio versus t hold plot showed an inverted bell-shaped curve, touching the lowest value of 1.141, which is the reported value for perfect stoichiometry of MgB 2. The optimized stoichimetric MgB 2 compound exhibited superconductivity at 39.2 K with a transition width of 0.6 K. In conclusion, the synthesis parameters for phase pure stoichimetric vacuum-annealed MgB 2 compound are optimized and are compared with widely-reported Ta tube encapsulated samples.

scholarly journals X-ray, IR and SEM studies on some Li-Cd ferrites

YMER Digital ◽  
2021 ◽  
Vol 20 (12) ◽  
pp. 333-340
Author(s):  
Sudhir Kulkarni ◽  
Keyword(s):  
Grain Size ◽  
Room Temperature ◽  
Single Phase ◽  
Lattice Parameter ◽  
Lithium Ferrite ◽  
Cadmium Content ◽  
X Ray Diffraction ◽  
Ceramic Method ◽  
X Ray ◽  
Single Phase Formation

Lithium-Cadmium ferrites with general formula Li0.5-x/2 Fe2.5-x/2 Cdx O4 (with x = 0,0.1,0.2....,0.7) were prepared by standard ceramic method. X-ray diffraction studies confirms single phase formation and lattice parameters were calculated. The crystal structure is cubic and lattice parameter increases with increasing Cd content. The infrared absorption (IR) spectra of all the samples were recorded in the range 200-800 cm-1 at room temperature in the KBr medium. Lithium ferrite shows four principal bands and some shoulders have been observed. The force constants Kt and Ko were calculated using Waldron's analysis. Scanning electron microscopy studies shows increase in grain size up to x = 0.1 and then the grain size decreases with increase in cadmium content.

scholarly journals Resistivity Enhancement of Sr-Hexaferrite Using Rare Earth Dopant to Minimize Energy Losses

2018 ◽  
Vol 778 ◽  
pp. 195-199 ◽  
Author(s):  
Nahall Niazi ◽  
Omer Farooq ◽  
Fatima Tuz Zahra ◽  
Muhammad Anis-ur-Rehman
Keyword(s):  
Room Temperature ◽  
Single Phase ◽  
Hexagonal Structure ◽  
Precipitation Method ◽  
Strontium Hexaferrite ◽  
Energy Losses ◽  
X Ray Diffraction ◽  
High Frequencies ◽  
X Ray ◽  
Co Precipitation

Strontium hexaferrite is a material of choice due its various magnetic applications. Energy losses are a prominent issue in these magnetic materials. To lower these energy losses, we need to improve the resistivity by reducing eddy current losses. In this work nanoparticles of Gadolinium (Gd) doped Sr-hexaferrite (SrFe12-xGdxO19 x =0 .0, 0.1) have been synthesized by co-precipitation method. Structural analysis was done by using X-ray diffraction technique (XRD). It was found that the formation of single phase i.e. hexagonal structure has been achieved when the samples were sintered at 920°C for 20 minutes. AC electrical properties such as conductivity (𝜎ac), dielectric constant (ε′), dielectric loss (tanδ) and impedance (Z); real (Z') and imaginary (Z") parts have been studied as a function of frequency at room temperature. Aim of the work was to enhance the resistivity and was successfully achieved. Gd doped sample is proposed as an energy efficient material to be used in devices working at high frequencies.

Substrate templated synthesis of single-phase and uniform Zr-porphyrin-based metal–organic frameworks

2020 ◽  
Vol 7 (1) ◽  
pp. 221-231
Author(s):  
Seong Won Hong ◽  
Ju Won Paik ◽  
Dongju Seo ◽  
Jae-Min Oh ◽  
Young Kyu Jeong ◽  
...  
Keyword(s):  
Chemical Bath Deposition ◽  
Single Phase ◽  
Metal Organic Frameworks ◽  
Templated Synthesis ◽  
Pore Structures ◽  
Phase Pure ◽  
Metal Organic ◽  
Cbd Method

We successfully demonstrate that the chemical bath deposition (CBD) method is a versatile method for synthesizing phase-pure and uniform MOFs by controlling their nucleation stages and pore structures.

Evaluation of 99mTc-Label led Vitamin K4 as an Agent for Testicular Imaging

1991 ◽  
Vol 30 (01) ◽  
pp. 35-39 ◽  
Author(s):  
H. S. Durak ◽  
M. Kitapgi ◽  
B. E. Caner ◽  
R. Senekowitsch ◽  
M. T. Ercan
Keyword(s):  
Soft Tissue ◽  
Room Temperature ◽  
Normal Subjects ◽  
Left Testis ◽  
Wide Range ◽  
Activity Ratios ◽  
The Right ◽  
Radioactivity Levels

Vitamin K4 was labelled with 99mTc with an efficiency higher than 97%. The compound was stable up to 24 h at room temperature, and its biodistribution in NMRI mice indicated its in vivo stability. Blood radioactivity levels were high over a wide range. 10% of the injected activity remained in blood after 24 h. Excretion was mostly via kidneys. Only the liver and kidneys concentrated appreciable amounts of radioactivity. Testis/soft tissue ratios were 1.4 and 1.57 at 6 and 24 h, respectively. Testis/blood ratios were lower than 1. In vitro studies with mouse blood indicated that 33.9 ±9.6% of the radioactivity was associated with RBCs; it was washed out almost completely with saline. Protein binding was 28.7 ±6.3% as determined by TCA precipitation. Blood clearance of 99mTc-l<4 in normal subjects showed a slow decrease of radioactivity, reaching a plateau after 16 h at 20% of the injected activity. In scintigraphic images in men the testes could be well visualized. The right/left testis ratio was 1.08 ±0.13. Testis/soft tissue and testis/blood activity ratios were highest at 3 h. These ratios were higher than those obtained with pertechnetate at 20 min post injection.99mTc-l<4 appears to be a promising radiopharmaceutical for the scintigraphic visualization of testes.

Structural and Magnetic Hysteresis Properties of Co-Zr Substituted Hexagonal Barium Ferrites

2015 ◽  
Vol 7 (1) ◽  
pp. 1346-1351
Author(s):  
Ch.Gopal Reddy ◽  
Ch. Venkateshwarlu ◽  
P. Vijaya Bhasker Reddy
Keyword(s):  
Magnetic Properties ◽  
Single Phase ◽  
Magnetic Hysteresis ◽  
Grain Morphology ◽  
Hexagonal Structure ◽  
Ion Composition ◽  
X Ray Diffraction ◽  
Ceramic Method ◽  
Barium Ferrites ◽  
Xrd Patterns

Co-Zr substituted M-type hexagonal barium ferrites, with chemical formula BaCoxZrxFe12-2xO19 (where x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0), have been synthesized by double sintering ceramic method. The crystallographic properties, grain morphology and magnetic properties of these ferrites have been investigated by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Vibrating Sample Magnetometer (VSM). The XRD patterns confirm the single phase with hexagonal structure of prepared ferrites. The magnetic properties have been investigated as a function of Co and Zr ion composition at an applied field in the range of 20 KOe. These studies indicate that the saturation magnetization (Ms) in the samples increases initially up to the Co-Zr composition of x=0.6 and decreases thereafter. On the other hand, the coercivity (Hc) and Remanent magnetization (Mr) are found to decrease continuously with increasing Co-Zr content. This property is most useful in permanent magnetic recording. The observed results are explained on the basis of site occupation of Co and Zr ions in the samples.

Photoluminescence Enhancement of CdS Nanocrystals Fabricated on Dithiocarbamate Functionalized PET Substrates

2012 ◽  
Vol 512-515 ◽  
pp. 1511-1515
Author(s):  
Chun Lin Zhao ◽  
Li Xing ◽  
Xiao Hong Liang ◽  
Jun Hui Xiang ◽  
Fu Shi Zhang ◽  
...  
Keyword(s):  
Room Temperature ◽  
Hexagonal Structure ◽  
Diffraction Measurement ◽  
X Ray Diffraction ◽  
Visible Absorption ◽  
X Ray ◽  
Cds Nanocrystals ◽  
Morphological Studies ◽  
Transmission Electron

Cadmium sulfide (CdS) nanocrystals (NCs) were self-assembled and in-situ immobilized on the dithiocarbamate (DTCs)-functionalized polyethylene glycol terephthalate (PET) substrates between the organic (carbon disulfide diffused in n-hexane) –aqueous (ethylenediamine and Cd2+ dissolved in water) interface at room temperature. Powder X-ray diffraction measurement revealed the hexagonal structure of CdS nanocrystals. Morphological studies performed by scanning electron microscopy (SEM) and high-resolution transmission electron microscope (HRTEM) showed the island-like structure of CdS nanocrystals on PET substrates, as well as energy-dispersive X-ray spectroscopy (EDS) confirmed the stoichiometries of CdS nanocrystals. The optical properties of DTCs modified CdS nanocrystals were thoroughly investigated by ultraviolet-visible absorption spectroscopy (UV-vis) and fluorescence spectroscopy. The as-prepared DTCs present intrinsic hydrophobicity and strong affinity for CdS nanocrystals.

scholarly journals MOVPE Growth of Quaternary (Al,Ga,In)N for UV Optoelectronics

2000 ◽  
Vol 5 (S1) ◽  
pp. 412-424
Author(s):  
Jung Han ◽  
Jeffrey J. Figiel ◽  
Gary A. Petersen ◽  
Samuel M. Myers ◽  
Mary H. Crawford ◽  
...  
Keyword(s):  
Room Temperature ◽  
Rutherford Backscattering Spectrometry ◽  
Optoelectronic Devices ◽  
Lattice Parameter ◽  
X Ray Diffraction ◽  
X Ray ◽  
Peak Energy ◽  
Movpe Growth ◽  
Pl Emission

We report the growth and characterization of quaternary AlGaInN. A combination of photoluminescence (PL), high-resolution x-ray diffraction (XRD), and Rutherford backscattering spectrometry (RBS) characterizations enables us to explore the contours of constant- PL peak energy and lattice parameter as functions of the quaternary compositions. The observation of room temperature PL emission at 351nm (with 20% Al and 5% In) renders initial evidence that the quaternary could be used to provide confinement for GaInN (and possibly GaN). AlGaInN/GaInN MQW heterostructures have been grown; both XRD and PL measurements suggest the possibility of incorporating this quaternary into optoelectronic devices.

On the occurrence of a metastable tetragonal t′-phase in a ZrO2−13.6 mole % MgO ceramic and its microscopic thermal evolution

1993 ◽  
Vol 8 (3) ◽  
pp. 605-610 ◽  
Author(s):  
M.C. Caracoche ◽  
P.C. Rivas ◽  
A.F. Pasquevich ◽  
A.R. López García ◽  
E. Aglietti ◽  
...  
Keyword(s):  
Thermal Behavior ◽  
Room Temperature ◽  
Oxygen Vacancies ◽  
Single Phase ◽  
Thermal Evolution ◽  
Hyperfine Interactions ◽  
Correlation Technique ◽  
Cubic Field ◽  
Time Differential ◽  
T Phase

The time-differential perturbed angular correlation technique has been used to investigate the thermal behavior of a ZrO2−13.6 mole % MgO ceramic between room temperature and 1423 K. Two different quadrupole hyperfine interactions corresponding to a tetragonal structure have been found to result on cooling the ceramic from the single-phase cubic field. One of them agrees with that depicting the pure t-ZrO2 tetragonal phase and the other one has been interpreted as describing a high-MgO-content nontransformable t'–ZrO2 phase. As temperature increases, the latter gives rise to a similar but fluctuating interaction related to the oxygen vacancies mobility and which shows a thermal behavior analogous to that already reported for the stabilized cubic ZrO2. Above 1100 K these dynamic t'-sites transform into pure tetragonal ones which behave ordinarily, suffering the t → m phase transition when cooling to room temperature. Differences found between TDPAC results and information drawn from other techniques are discussed.

Impedance Spectroscopy Study of LiTaO3 Powder Synthesized via Sol-Gel Method

2012 ◽  
Vol 545 ◽  
pp. 275-278 ◽  
Author(s):  
Lili Widarti Zainuddin ◽  
Norlida Kamarulzaman
Keyword(s):  
Room Temperature ◽  
Single Phase ◽  
Sol Gel ◽  
Rhombohedral Structure ◽  
Spectroscopy Study ◽  
X Ray Diffraction ◽  
Gel Method ◽  
X Ray ◽  
Sol Gel Method ◽  
Impedance Spectroscopy Study

A ceramics sample of LiTaO3 was prepared using a sol-gel method. The sample is annealed at 750 °C for 48 hours. X-ray diffraction analysis indicate the formation of single phase, rhombohedral structure. An ac impedance study was used to analyse the conductivity of LiTaO3 at room temperature and at various temperatures.

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