Superoonductivity in the R3CaBa3Cu7Oy System with R = Lanthanide

1992 ◽  
Vol 275 ◽  
Author(s):  
H. -C. I. Kao ◽  
J. L. Wang ◽  
R. J. Huang ◽  
C. M. Wang ◽  
M. K. Wu
Keyword(s):  
Single Phase ◽  
Perovskite Phase ◽  
Hole Concentration ◽  
Residual Resistivity ◽  
Lanthanide Ions ◽  
Similar Process ◽  
Oxygen Stoichiometry ◽  
Nominal Composition ◽  
Second Phase ◽  
Ionic Radii

ABSTRACTA series of samples with a nominal composition of R3CaBa3Cu7Oy (abbreviated as R3137), where R = Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er and Tm, was prepared by a similar process as for an 80-K superconductor, La3CaBa3Cu7Oy. Most of the R3137 (except for R = Ce, Tb) had a tetragonal triple-perovskite phase like La3137 identified from the XRD patterns, and they were superconducting except Pr3137. For R3+ radius larger than Dy3+ (0.908 Å), a single phase R3137 was observed, and their Tc(zero)' probably related to the rCu-o distance in the copper-oxygen layer, was spread from 85 to 76 K with a maximum for the Eu3137. Oxygen stoichiometry of these R3137 was slightly decreased with decreasing lanthanide radii. The hole concentration, (Cu-O), was found between 0.47 and 0.38/unit cell. For Smaller R3+ ions, residual resistivity was found in the superconducting samples due to the existence of second phase. From the structural study of La3137, it was known that part of the lanthanide ions had to be fitted into the bigger Ba-site. Because ionic radii of the heavy lanthanides (R3+ < Ho3+ = 0.894 Å) were too small to be located at the Ba-site, it was rather difficult to prepare these single phase R3137.

scholarly journals Plastic deformation and fracture behavior of a Fe-modified Al3Ti-base L12 intermetallic alloy

1991 ◽  
Vol 6 (5) ◽  
pp. 957-963 ◽  
Author(s):  
Hu Gengxiang ◽  
Chen Shipu ◽  
Wu Xiaohua ◽  
Chen Xiaofu
Keyword(s):  
Room Temperature ◽  
Single Phase ◽  
Deformation Mode ◽  
Intermetallic Alloy ◽  
Nominal Composition ◽  
Second Phase ◽  
Compression Tests ◽  
Transmission Electron ◽  
Deformation And Fracture ◽  
Ordered Intermetallic

The microstructure of the ordered intermetallic alloy with a nominal composition of Al66Fe9Ti24 is nearly single-phase L12 structure, with a few second phase agglomerates at some grain corners. Room temperature compression tests showed that this material exhibits a plastic strain of about 11% at fracture. Final fracture of the compression specimens occurred by a shear-off process along a surface oriented about 45 degrees to the compression axis. Fractographic analysis revealed that the fracture is transcrystalline and the fracture mode is mainly quasicleavage plus tearing. Transmission electron microscopy (TEM) was used to explore its deformation mechanisms. The dislocation density was low after homogenization, but is greatly increased during deformation. The deformation mode was found to be 〈110〉 {111} slip instead of twinning as in Al3Ti. The a〈110〉 superdislocations dissociated into two partials of a/3〈211〉-type, bounding a superlattice intrinsic stacking fault (SISF) on the {111} slip plane.

Microstructure and 90° domain assemblages of Pb(Zr, Ti)O3//RuO2 capacitors as a function of Zr-to-Ti stoichiometry

1996 ◽  
Vol 11 (9) ◽  
pp. 2309-2317 ◽  
Author(s):  
B. A. Tuttle ◽  
T. J. Headley ◽  
H.N. Al-Shareef ◽  
J. A. Voigt ◽  
M. Rodriguez ◽  
...  
Keyword(s):  
Single Phase ◽  
Perovskite Phase ◽  
Grain Morphology ◽  
Fluorite Structure ◽  
Second Phase ◽  
Cross Sectional ◽  
Thin Film Capacitors ◽  
Pzt Films ◽  
Granular Morphology ◽  
Phase Differences

Planar microstructure, 90° domain configurations, and cross-sectional perovskite grain morphology were characterized for a series of Pb(Zr, Ti)O3//RuO2 thin film capacitors. Perovskite grain size increased substantially with increasing Zr concentration of the Pb(Zr, Ti)O3 (PZT) films, being on the order of 0.15 μm for PZT 20/80 films and 2.5 μm for PZT 50/50 films. While PZT 20/80 and PZT 30/70 films were single phase perovskite, the PZT 40/60 and 50/50 films contained a second phase with fluorite structure. The second phase matrix consisted of two nanophases, one having fluorite structure while the other was amorphous. Both the amorphous nanophase and the fluorite nanophase were Pb deficient compared to the perovskite phase. Differences in cross-sectional perovskite grain morphology were substantial for these materials, with the PZT 40/60 film being almost entirely columnar and the PZT 20/80 film exhibiting almost entirely granular morphology. Differences in 90° domain wall density were essentially negligible among the films, suggesting that if 90° domains were responsible for the differences in electrical properties, it is not due to 90° domain population.

scholarly journals Fabrication and Characterization of Quinary High Entropy-Ultra-High Temperature Diborides

Ceramics ◽  
2021 ◽  
Vol 4 (2) ◽  
pp. 108-120
Author(s):  
Simone Barbarossa ◽  
Roberto Orrù ◽  
Valeria Cannillo ◽  
Antonio Iacomini ◽  
Sebastiano Garroni ◽  
...  
Keyword(s):  
High Temperature ◽  
Single Phase ◽  
Nominal Composition ◽  
High Entropy ◽  
Chemical Complexity ◽  
Alternative Processing ◽  
Plasma Sintering ◽  
High Temperature Synthesis ◽  
Spark Plasma

Due to their inherent chemical complexity and their refractory nature, the obtainment of highly dense and single-phase high entropy (HE) diborides represents a very hard target to achieve. In this framework, homogeneous (Hf0.2Nb0.2Ta0.2Mo0.2Ti0.2)B2, (Hf0.2Zr0.2Ta0.2Mo0.2Ti0.2)B2, and (Hf0.2Zr0.2Nb0.2Mo0.2Ti0.2)B2 ceramics with high relative densities (97.4, 96.5, and 98.2%, respectively) were successfully produced by spark plasma sintering (SPS) using powders prepared by self-propagating high-temperature synthesis (SHS). Although the latter technique did not lead to the complete conversion of initial precursors into the prescribed HE phases, such a goal was fully reached after SPS (1950 °C/20 min/20 MPa). The three HE products showed similar and, in some cases, even better mechanical properties compared to ceramics with the same nominal composition attained using alternative processing methods. Superior Vickers hardness and elastic modulus values were found for the (Hf0.2Nb0.2Ta0.2Mo0.2Ti0.2)B2 and the (Hf0.2Zr0.2Ta0.2Mo0.2Ti0.2)B2 systems, i.e., 28.1 GPa/538.5 GPa and 28.08 GPa/498.1 GPa, respectively, in spite of the correspondingly higher residual porosities (1.2 and 2.2 vol.%, respectively). In contrast, the third ceramic, not containing tantalum, displayed lower values of these two properties (25.1 GPa/404.5 GPa). However, the corresponding fracture toughness (8.84 MPa m1/2) was relatively higher. This fact can be likely ascribed to the smaller residual porosity (0.3 vol.%) of the sintered material.

scholarly journals Interactions of tervalent lanthanide ions with bacterial collagenase (clostridiopeptidase A)

1981 ◽  
Vol 195 (3) ◽  
pp. 677-684 ◽  
Author(s):  
Christopher H. Evans
Keyword(s):  
Ionic Radius ◽  
Substrate Inhibition ◽  
Volume Ratio ◽  
Binding Pocket ◽  
Lanthanide Ions ◽  
Ionic Radii ◽  
Apparent Dissociation Constant ◽  
Substrate Complex ◽  
Bacterial Collagenase ◽  
Hydrolysis Of

Tervalent cations of the lanthanide (rare-earth) elements reversibly inhibit bacterial collagenase (clostridiopeptidase A; EC 3.4.24.3). Sm3+, whose ionic radius is closest to that of Ca2+, is the most effective inhibitor, completely suppressing clostridiopeptidase activity at a concentration of 100μm in the presence of 5mm-Ca2+. Er3+ and Lu3+, which both have ionic radii smaller than either Ca2+ or Sm3+, inhibit less efficiently, and La3+, which is slightly larger than Ca2+ or Sm3+, inhibits only weakly. These findings indicate a closely fitting, stereospecific, Ca2+-binding pocket in clostridiopeptidase, which excludes ions that are only slightly larger than Ca2+ [ionic radius 0.099nm (0.99 Ȧ)]. By contrast, trypsin, an enzyme whose activity does not depend on Ca2+, requires lanthanide concentrations 50–100-fold greater for inhibition. Furthermore, the relative efficiency of inhibition of trypsin by lanthanides increases as the lanthanide ions become smaller and the charge/volume ratio increases. At a concentration of 50μm, Sm3+ lowers the apparent Km for the hydrolysis of Pz-peptide by clostridiopeptidase from 5.4mm to 0.37mm and the apparent Vmax. from 0.29 Wünsch–Heidrich unit to 0.018 unit. Thus Sm3+ enhances the affinity of this enzyme for its substrate; inhibition of hydrolysis of Pz-peptide may result from the excessive stability of the enzyme–Sm3+–substrate complex. Inhibition by Sm3+ is competitive with regard to Ca2+. The apparent dissociation constant, Kd, of Ca2+ is 0.27mm, where the Ki for Sm3+ is 12μm. Clostridiopeptidase is more thermolabile in the absence of Ca2+. With Sm3+, thermoinactivation of the enzyme at 53°C or 60°C is initially accelerated, but then becomes retarded as heating continues. Lanthanide ions bind to gelatin and collagen. In so doing, they appear to protect these substrates from lysis by clostridiopeptidase through mechanisms additional to supplanting Ca2+ at its binding site on the enzyme. Collagen and gelatin sequester sufficient lanthanide ions to gain partial protection from clostridiopeptidase in the absence of an extraneous source of these inhibitors.

Effects of Ce filling fraction and Fe content on the thermoelectric properties of Co-rich CeyFexCo4−xSb12

2001 ◽  
Vol 16 (3) ◽  
pp. 837-843 ◽  
Author(s):  
Xinfeng Tang ◽  
Lidong Chen ◽  
Takashi Goto ◽  
Toshio Hirai
Keyword(s):  
Thermal Conductivity ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Single Phase ◽  
Lattice Thermal Conductivity ◽  
Hole Concentration ◽  
Thermoelectric Figure Of Merit ◽  
Thermoelectric Figure ◽  
Filling Fraction ◽  
Fe Content

Single-phase filled skutterudite compounds, CeyFexCo4−xSb12 (x = 0 to 3.0, y = 0 to 0.74), were synthesized by a melting method. The effects of Fe content and Ce filling fraction on the thermoelectric properties of CeyFexCo4−xSb12 were investigated. The lattice thermal conductivity of Ce-saturated CeyFexCo4−xSb12, y being at the maximum corresponding to x, decreased with increasing Fe content (x) and reached its minimum at about x = 1.5. When x was 1.5, lattice thermal conductivity decreased with increasing Ce filling fraction till y = 0.3 and then began to increase after reaching the minimum at y = 0.3. Hole concentration and electrical conductivity of Cey Fe1.5Co2.5Sb12 decreased with increasing Ce filling fraction. The Seebeck coefficient increased with increasing Ce filling fraction. The greatest dimensionless thermoelectric figure of merit T value of 1.1 was obtained at 750 K for the composition of Ce0.28Fe1.52Co2.48Sb12.

Abstract 77: Ongoing Leakage Revealed by Second Phase Spot Sign Volume Expansion in Multi-Phase Computed Tomography Angiography Strongly Predicts Intracranial Hemorrhage Growth

Stroke ◽  
2020 ◽  
Vol 51 (Suppl_1) ◽  
Author(s):  
Abdulaziz Al Sultan ◽  
Ericka Teleg ◽  
MacKenzie Horn ◽  
Piyush Ojha ◽  
Linda Kasickova ◽  
...  
Keyword(s):  
Volume Expansion ◽  
Single Phase ◽  
Meta Analysis ◽  
Hematoma Expansion ◽  
Second Phase ◽  
Hematoma Volume ◽  
Spot Sign ◽  
Time Resolved ◽  
Multi Phase

Background: CTA spot sign is a predictor of intracerebral hemorrhage (ICH) expansion. This sign can fluctuate in appearance, volume, and timing. Multiphase CTA (mCTA) can identify spot sign through 3 time-resolved images. We sought to identify a novel predictor of follow up total hematoma expansion using mCTA. Methods: This cohort study included patients with ICH between 2012-2019. Quantomo software was used to measure total hematoma volume (ml) from baseline CT & follow-up CT/MRI blinded to spot sign in 3 mCTA phases. Spot sign expansion was calculated by subtracting 1 st phase spot sign volume from 2 nd phase spot sign volume measured in microliters. Results: 199 patients [63% male, mean age 69 years, median NIHSS 11, IQR 6-20] were included. Median baseline ICH volume was 16.1 ml (IQR 5-29.9 ml). Amongst all three mCTA phases, spot sign was best detected on the 2nd phase (23% vs 17.5% 1 st phase vs 22% 3 rd phase). In multivariable regression, spot sign expansion was significantly associated with follow up total hematoma expansion (OR: 1.03 per microliter of spot sign expansion, p=0.01). Figure 1 shows the predicted total hematoma expansion by spot sign expansion. mCTA spot sign had a higher sensitivity for predicting total hematoma volume expansion than single-phase CTA (reported in meta-analysis of 14 studies), 86% vs 53%, respectively, while both having similar specificity, 87% vs 88%, respectively. Conclusion: Spot sign expansion on mCTA is a novel predictor of total hematoma expansion and could be used to select patients for immediate therapeutic intervention in future clinical trials. Using mCTA improves sensitivity while preserving specificity over single-phase CTA.

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.

Synthesis and Luminescence Properties of Lanthanide (III)-Doped YF3 Nanoparticles

2006 ◽  
Vol 6 (3) ◽  
pp. 830-836 ◽  
Author(s):  
Yang Cui ◽  
Xianping Fan ◽  
Zhanglian Hong ◽  
Minquan Wang
Keyword(s):  
Upconversion Luminescence ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Lanthanide Ions ◽  
Luminescence Properties ◽  
Synthesis Process ◽  
Second Phase ◽  
Trivalent Lanthanide ◽  
Xrd Patterns ◽  
Luminescence Concentration Quenching

Synthesis process and luminescence properties of trivalent lanthanide ions (Ln3+) doped YF3 nanoparticles have been investigated. To synthesis Ln3+-doped YF3 nanoparticles, the mixture of (YCl3·nH2O + LnCl3·nH2O), and NH4F was hydrothermal treated at 180 °C in a Teflon-liner auto-clave or heated at higher temperatures (400 °C ∼ 600 °C) in a stove. The XRD patterns showed that the Ln3+-doped orthorhombic YF3 nanoparticles with no second phase have been prepared. The solid solution Y1−xEuxF3 (x = 0 ∼ 0.4) nanoparticles have been synthesized. The luminescence concentration quenching resulted from resonance energy transfer between neighboring Eu3+ ions occurred at higher Eu3+ concentrations (30 mol%). The upconversion luminescence of Er3+−Yb3+ codoped YF3 nanoparticles under 980 nm excitation has also been observed. With increase of heated temperature, the size of the Er3+−Yb3+ codoped YF3 nanoparticles increased gradually, and upconversion luminescence intensity increased significantly.

Nonstoichiometric Composition and Densification of CaRuO3 by SPS

2007 ◽  
Vol 352 ◽  
pp. 251-254 ◽  
Author(s):  
Nittaya Keawprak ◽  
Rong Tu ◽  
Takashi Goto
Keyword(s):  
Spark Plasma Sintering ◽  
Single Phase ◽  
Lattice Parameters ◽  
Second Phase ◽  
Nonstoichiometric Composition ◽  
Plasma Sintering ◽  
Spark Plasma

Calcium ruthenates were prepared in different ratios of Ru to Ca (RRu/Ca = 0.5～1.4) by spark plasma sintering. CaRuO3 in a single phase was obtained at RRu/Ca = 1.0. At RRu/Ca < 1.0, a mixture of CaRuO3 and CaO was obtained, whereas CaRuO3 with second phase of RuO2 was obtained at RRu/Ca > 1.0. The density at RRu/Ca < 1.0 were 80-85% and slightly increased with increasing RRu/Ca. The density significantly increased up to 95% with increasing RRu/Ca from 1.1 to 1.4, suggesting that the second phase of RuO2 was effective to densify CaRuO3. The density of CaRuO3 in a single phase was 82% at most. The lattice parameters of CaRuO3 decreased with increasing RRu/Ca from 0.7 to 1.0, showing a nonstoichiometric range of Ca1+δRuO3+δ.

Electrochemical Performance Research of Mg Ion Doped LiMnPO4/C

2012 ◽  
Vol 554-556 ◽  
pp. 365-368
Author(s):  
Zeng Fu Wei ◽  
Wei Su ◽  
Shi Nian Liu
Keyword(s):  
Single Phase ◽  
Phenolic Resin ◽  
Reversible Capacity ◽  
Electrochemical Kinetics ◽  
Cation Substitution ◽  
Rate Performance ◽  
Ionic Radii ◽  
Similar Morphology ◽  
Performance Research ◽  
Mg Substitution

LiMn1-xMgxPO4/C(x=0, 0.01, 0.04, 0.05, 0.1) were synthesized by using wet-ballmilling and solid-state calcining with phenolic resin as the carbon source. All samples are single phase with a similar morphology, but the cation substitution results in a crystal lattice shrink because of the smaller ionic radii of Mg2+, the particles are small and homogeneous. CV, EIS and charge/discharge measurement shows that the Mg substitution leads to a significantly increased reversible capacity due to the enhanced electrochemical kinetics. LiMn0.96Mg0.04PO4/C calcined at 600°C has a discharge capacity of 144mAh/g at 0.05C. When charging-discharging by CC-CV-CC mode at high rates, LiMn0.96Mg0.04PO4/C composite exhibits a good cycle and rate performance.

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