THE MICRO-REGION COMPOSITIONAL VARIATION OF Y1Ba2Cu3O9−x SINGLE PHASE SUPERCONDUCTOR

1987 ◽  
Vol 01 (02) ◽  
pp. 231-236 ◽  
Author(s):  
Zhenhong Mai ◽  
Liquan Chen ◽  
Xi Chu ◽  
Daoyang Dai ◽  
Yongming Ni ◽  
...  
Keyword(s):  
Single Phase ◽  
Structural Phase ◽  
Compositional Variation ◽  
Interfacial Region ◽  
X Ray Diffraction ◽  
X Ray ◽  
Compositional Distribution ◽  
New Superconductor ◽  
Phase Superconductor ◽  
The Ideal

We have investigated the microstructure and compositional distribution of the Y 1 Ba 2 Cu 3 O 9−x single phase superconductor with scanning electron microscopy, energy dispersion x-ray spectrometry and x-ray diffraction. It has been found that the micro-region compositions are far front the ideal values, especially the yttrium content is quite higher than the suspected amount in the interfacial region. between crystalline grains. We propose that there might be another structural phase co-existed with the Y 1 Ba 2 Cu 3 O 9−x compound and it can not be distinguished from the main phase with diffraction methods. This phase would influence the properties, in particular the critical current density jc of the new superconductor.

Studies on Internal Friction and Curie Temperature of NiMgCuZn Spinel Ferrites for Micro-Inductor Applications

2015 ◽  
Vol 241 ◽  
pp. 202-225
Author(s):  
N. Varalaxmi ◽  
K.V. Sivakumar ◽  
Hardev Singh Virk
Keyword(s):  
Internal Friction ◽  
Curie Temperature ◽  
Single Phase ◽  
Structural Phase ◽  
Structural Phase Transitions ◽  
X Ray Diffraction ◽  
Piezoelectric Resonator ◽  
X Ray ◽  
Compositional Changes ◽  
Single Stress

Three series of NiMgCuZn ferrites were prepared by conventional double sintering ceramic process. The formation of single phase in these ferrites was confirmed by X-ray diffraction. A brief review of the important investigations carried out on the internal friction behaviour of NiMgCuZnFe2O4, in the temperature range 40oC to 360oC, has been reported. In the present investigation, the composite piezoelectric resonator method has been used. The effect of compositional changes of ferrites on Curie temperature and internal friction are reported. Results and discussions on the temperature variation of internal friction of the three series of NiMgCuZnFe2O4samples are discussed. In all the series studied, only single stress induced relaxation peaks are observed. These studies were carried out to develop a ferrite composition for their use as core materials for microinductor applications. The results are explained in the light of structural phase transitions.

Powder X-ray diffraction and Rietveld analysis of La1−xCaxMnO3(0

2006 ◽  
Vol 21 (1) ◽  
pp. 40-44 ◽  
Author(s):  
P. R. Sagdeo ◽  
Shahid Anwar ◽  
N. P. Lalla
Keyword(s):  
Phase Transformation ◽  
Calcium Concentration ◽  
Single Phase ◽  
Structural Phase ◽  
Rietveld Analysis ◽  
Linear Variation ◽  
X Ray Diffraction ◽  
Structural Phase Transformation ◽  
Magnetic Phases ◽  
X Ray

Single-phase samples of La1−xCaxMnO3compounds have been synthesized by solid-state reaction. Detailed Rietveld analysis of powder X-ray diffraction data showed that La1−xCaxMnO3undergoes a structural phase transformation fromR-3ctoPnmaatX=0.05–0.075. There is a linear variation of lattice parameters as a function of calcium concentration. The slope of this linear variation changes atX=0.6. A correlation between observed Mn-O bond lengths, corresponding to different compositions, and possible magnetic phases is discussed.

Effects of Manganese Addition on Phase Formation Behavior and Dielectric Properties of ((K0.5Na0.5)0.935Li0.065)NbO3 Ceramics

2014 ◽  
Vol 608 ◽  
pp. 206-211
Author(s):  
Supattra Wongsaenmai ◽  
Santi Maensiri ◽  
Rattikorn Yimnirun
Keyword(s):  
Dielectric Properties ◽  
Phase Formation ◽  
Single Phase ◽  
Structural Phase ◽  
Tetragonal Symmetry ◽  
X Ray Diffraction ◽  
X Ray ◽  
Formation Behavior ◽  
Different Grain Size ◽  
Scanning Electron

In this study, ceramics in ((K0.5Na0.5)0.935Li0.065)NbO3+ xMnO2(mol%) ceramics (when x = 0.0025, 0.0050, 0.01 and 0.015) were successfully prepared by the conventional mixed-oxide technique. The structural phase formation and microstructure were characterized by x-ray diffraction technique (XRD) and scanning electron microscopy (SEM). The crystal structure was identified by XRD as a single-phase perovskite structure, with tetragonal symmetry. The microstructure shows different grain size with different composition x. This study clearly showed that the Mn has influence on the dielectric properties in ((K0.5Na0.5)0.935Li0.065)NbO3ceramics.

Fabrication of Li0.06(K0.5,Na0.5)0.94NbO3 Nanofibers by Electrospinning Technique

2019 ◽  
Vol 798 ◽  
pp. 218-222
Author(s):  
Supattra Wongsaenmai ◽  
Tawat Soitong
Keyword(s):  
Calcination Temperature ◽  
Single Phase ◽  
Sol Gel ◽  
Structural Phase ◽  
Orthorhombic Symmetry ◽  
X Ray Diffraction ◽  
Fiber Morphology ◽  
Electrospinning Technique ◽  
X Ray ◽  
Sol Gel Process

In this work, Li0.06(K0.5,Na0.5)0.94NbO3(KNNL) nanofibers were synthesized by sol–gel process and electrospinning technique. The thermal behaviour ofelectrospun fibers was characterized by thermogravimetric analysis (TG) to obtain the calcination temperature range. The structural phase formation and microstructure were characterized by X-ray diffraction technique (XRD) and scanning electron microscopy (SEM), respectively. The crystal structure was identified by XRD as a single-phase perovskite structure, with orthorhombic symmetry. The microstructure shows that the diameters are in the range of 80–160 nm. The electrospun fibers were calcined from 500°C to 900°C and observed the fiber morphology. With increasing calcination temperature, the fiber diameters decreased until the temperature up to 900 °C the morphology change from cylinder to square or rectangular shape grains.

SUPERCONDUCTIVITY IN Y-Ba-Cu(Cr)-O SYSTEM

1987 ◽  
Vol 01 (02) ◽  
pp. 281-284
Author(s):  
Z. Xianyu ◽  
R.J. Li ◽  
Q.H. Zhao ◽  
L.Q. Liu ◽  
Q.T. Wang ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Structural Analysis ◽  
Single Phase ◽  
Hexagonal Phase ◽  
Superconducting Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Phase Superconductor

We report the superconductor of Y-Ba-Cu-O system, with Tci= 100K , Tc=95K , Tcf=94.1K and Δ Tc=1K . The structural analysis by X-ray diffraction shows that single phase superconductor has order-disorder transformation around 220K and phase transformation takes place in the multiphase sample in the range of (123–173K). This indicates that the phase transformation related to the high Tci. With the substitution of Cr for Cu, with Cu:Cr=2:1 we have also obtained the superconductor with Tci=95.5 , Tc=91K , Tcf=86.3K and Tc=1K X-ray structural analysis shows that the major superconducting phase of this system is hexagonal phase.

Raman And Fluorescence Spectra Observed in Laser Microprobe Measurements of Several Compositions in the Ln-Ba-Cu-O System

1990 ◽  
Vol 48 (2) ◽  
pp. 278-279
Author(s):  
Edgar S. Etz ◽  
Thomas D. Schroeder ◽  
Winnie Wong-Ng
Keyword(s):  
Fluorescence Spectra ◽  
Single Phase ◽  
X Ray Diffraction ◽  
Ceramic Powders ◽  
Conventional Solid State Reaction ◽  
X Ray ◽  
Raman Microprobe ◽  
Methods Of Synthesis ◽  
Compositional Homogeneity ◽  
Processing Techniques

We are investigating by Raman microprobe measurements the superconducting and related phases in the LnBa2Cu3O7-x (for x=0 to 1) system where yttrium has been replaced by several of the lanthanide (Ln = Nd,Sm,Eu,Ho,Er) elements. The aim is to relate the observed optical spectra (Raman and fluorescence) to the compositional and structural properties of these solids as part of comprehensive materials characterization. The results are correlated with the methods of synthesis, the processing techniques of these materials, and their superconducting properties. Of relevance is the substitutional chemistry of these isostructural systems, the differences in the spectra, and their microanalytical usefulness for the detection of impurity phases, and the assessment of compositional homogeneity. The Raman spectra of most of these compounds are well understood from accounts in the literature.The materials examined here are mostly ceramic powders prepared by conventional solid state reaction techniques. The bulk samples are of nominally single-phase composition as determined by x-ray diffraction.

Observation of pseudo 10-fold symmetry in the ordered iron-zinc delta phase

1992 ◽  
Vol 50 (1) ◽  
pp. 36-37
Author(s):  
L. A. Giannuzzi ◽  
A. S. Ramani ◽  
P. R. Howell ◽  
H. W. Pickering ◽  
W. R. Bitler
Keyword(s):  
Single Phase ◽  
X Ray Diffraction ◽  
Rich Region ◽  
Average Cell ◽  
X Ray ◽  
Delta Phase ◽  
Cell Dimensions ◽  
Δ Phase ◽  
Morphological Differences ◽  
Concentration Discontinuity

The δ phase is a Zn-rich intermetallic, having a composition range of ∼ 86.5 - 92.0 atomic percent Zn, and is stable up to 665°C. The stoichiometry of the δ phase has been reported as FeZn7 and FeZn10 The deviation in stoichiometry can be attributed to variations in alloy composition used by each investigator. The structure of the δ phase, as determined by powder x-ray diffraction, is hexagonal (P63mc or P63/mmc) with cell dimensions a = 1.28 nm, c = 5.76 nm, and 555±8 atoms per unit cell. Later work suggested that the layer produced by hot-dip galvanizing should be considered as two distinct phases which are characterized by their morphological differences, namely: the iron-rich region with a compact appearance (δk) and the zinc-rich region with a columnar or palisade microstructure (δp). The sub-division of the δ phase was also based on differences in diffusion behavior, and a concentration discontinuity across the δp/δk boundary. However, work utilizing Weisenberg photographs on δ single crystals reported that the variation in lattice parameters with composition was small and hence, structurally, the δk phase and the δp phase were the same and should be thought of as a single phase, δ. Bastin et al. determined the average cell dimensions to be a = 1.28 nm and c = 5.71 nm, and suggested that perhaps some kind of ordering process, which would not be observed by x-ray diffraction, may be responsible for the morphological differences within the δ phase.

scholarly journals Preparation of high-entropy carbides by different sintering techniques

2021 ◽  
Vol 56 (19) ◽  
pp. 11237-11247 ◽  
Author(s):  
Johannes Pötschke ◽  
Manisha Dahal ◽  
Mathias Herrmann ◽  
Anne Vornberger ◽  
Björn Matthey ◽  
...  
Keyword(s):  
Grain Size ◽  
Single Phase ◽  
X Ray Diffraction ◽  
Vacuum Sintering ◽  
X Ray ◽  
High Entropy ◽  
Mean Grain Size ◽  
The Mean ◽  
Gas Pressure Sintering ◽  
Hardness Values

AbstractDense (Hf, Ta, Nb, Ti, V)C- and (Ta, Nb, Ti, V, W)C-based high-entropy carbides (HEC) were produced by three different sintering techniques: gas pressure sintering/sinter–HIP at 1900 °C and 100 bar Ar, vacuum sintering at 2250 °C and 0.001 bar as well as SPS/FAST at 2000 °C and 60 MPa pressure. The relative density varied from 97.9 to 100%, with SPS producing 100% dense samples with both compositions. Grain size measurements showed that the substitution of Hf with W leads to an increase in the mean grain size of 5–10 times the size of the (Hf, Ta, Nb, Ti, V,)C samples. Vacuum-sintered samples showed uniform grain size distribution regardless of composition. EDS mapping revealed the formation of a solid solution with no intermetallic phases or element clustering. X-ray diffraction analysis showed the structure of mostly single-phase cubic high-entropy carbides. Hardness measurements revealed that (Hf, Ta, Nb, Ti, V)C samples possess higher hardness values than (Ta, Nb, Ti, V, W)C samples.

Temperature-induced structural phase transitions in RERhSn (RE = Y, Gd-Tm, Lu)

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Simon Engelbert ◽  
Rolf-Dieter Hoffmann ◽  
Jutta Kösters ◽  
Steffen Klenner ◽  
Rainer Pöttgen
Keyword(s):  
Rare Earth ◽  
Phase Transitions ◽  
Driving Force ◽  
Room Temperature ◽  
Structural Phase ◽  
Structural Phase Transitions ◽  
Line Broadening ◽  
X Ray Diffraction ◽  
Temperature Dependent ◽  
X Ray

Abstract The structures of the equiatomic stannides RERhSn with the smaller rare earth elements Y, Gd-Tm and Lu were reinvestigated on the basis of temperature-dependent single crystal X-ray diffraction data. GdRhSn crystallizes with the aristotype ZrNiAl at 293 and 90 K. For RE = Y, Tb, Ho and Er the HP-CeRuSn type (approximant with space group R3m) is already formed at room temperature, while DyRhSn adopts the HP-CeRuSn type below 280 K. TmRhSn and LuRhSn show incommensurate modulated variants with superspace groups P31m(1/3; 1/3; γ) 000 (No. 157.1.23.1) (γ = 3/8 for TmRhSn and γ = 2/5 for LuRhSn). The driving force for superstructure formation (modulation) is a strengthening of Rh–Sn bonding. The modulation is expressed in a 119Sn Mössbauer spectrum of DyRhSn at 78 K through line broadening.

scholarly journals Influence of Li2CO3 addition on electrical and magnetic properties of Ni0.6Mg0.4Fe2O4

2020 ◽  
Vol 10 (03) ◽  
pp. 2050003
Author(s):  
M. R. Hassan ◽  
M. T. Islam ◽  
M. N. I. Khan
Keyword(s):  
Magnetic Properties ◽  
Single Phase ◽  
Low Frequency ◽  
Solid State Reaction Method ◽  
Charge Carriers ◽  
X Ray Diffraction ◽  
X Ray ◽  
Electrical And Magnetic Properties ◽  
Frequency Regime ◽  
Xrd Patterns

In this research, influence of adding Li2CO3 (at 0%, 2%, 4%, 6%) on electrical and magnetic properties of [Formula: see text][Formula: see text]Fe2O4 (with 60% Ni and 40% Mg) ferrite has been studied. The samples are prepared by solid state reaction method and sintered at 1300∘C for 6[Formula: see text]h. X-ray diffraction (XRD) patterns show the samples belong to single-phase cubic structure without any impurity phase. The magnetic properties (saturation magnetization and coercivity) of the samples have been investigated by VSM and found that the higher concentration of Li2CO3 reduces the hysteresis loss. DC resistivity increases with Li2CO3 contents whereas it decreases initially and then becomes constant at lower value with temperature which indicates that the studied samples are semiconductor. The dielectric dispersion occurs at a low-frequency regime and the loss peaks are formed in a higher frequency regime, which are due to the presence of resonance between applied frequency and hopping frequency of charge carriers. Notably, the loss peaks are shifted to the lower frequency with Li2CO3 additions.

Sign in / Sign up

Export Citation Format

Share Document