scholarly journals The Stability of Icosahedral Cd-Yb

2003 ◽  
Vol 805 ◽  
Author(s):  
Günter Krauss ◽  
Sofia Deloudi ◽  
Andrea Steiner ◽  
Walter Steurer ◽  
Amy R. Ross ◽  
...  
Keyword(s):  
Low Temperature ◽  
Ambient Temperature ◽  
Mechanical Stress ◽  
Single Crystals ◽  
High Temperatures ◽  
Low Temperatures ◽  
Ambient Pressure ◽  
X Ray Diffraction ◽  
X Ray ◽  
The Stability

ABSTRACTThe stability of single-crystalline icosahedral Cd-Yb was investigated using X-ray diffraction methods in the temperature range 20 K ≤ T ≤ 900 K at ambient pressure and from ambient temperature to 873 K at about 9 GPa. Single-crystals remain stable at low temperatures and in the investigated HP-HT-regime. At high temperatures and ambient pressure, the quasicrystal decomposes. The application of mechanical stress at low temperatures yields to the same decomposition, the formation of Cd. A reaction of icosahedral Cd-Yb with traces of oxygen or water causing the decomposition seems reasonable, but a low-temperature instability of this binary quasi-crystal cannot be ruled out totally.

Low temperature amorphization and superconductivity in FeSe single crystals at high pressures

2010 ◽  
Vol 25 (2) ◽  
pp. 396-400 ◽  
Author(s):  
Andrew K. Stemshorn ◽  
Georgiy Tsoi ◽  
Yogesh K. Vohra ◽  
Stanislav Sinogeiken ◽  
Phillip M. Wu ◽  
...  
Keyword(s):  
High Pressure ◽  
Low Temperature ◽  
Single Crystals ◽  
Amorphous Phase ◽  
Tetragonal Phase ◽  
Electrical Resistance ◽  
Low Temperatures ◽  
High Pressures ◽  
X Ray Diffraction ◽  
X Ray

In this study, we report low temperature x-ray diffraction studies combined with electrical resistance measurements on single crystals of iron-based layered superconductor FeSe to a temperature of 10 K and a pressure of 44 GPa. The low temperature high pressure x-ray diffraction studies were performed using a synchrotron source and superconductivity at high pressure was studied using designer diamond anvils. At ambient temperature, the FeSe sample shows a phase transformation from a PbO-type tetragonal phase to a NiAs-type hexagonal phase at 10 ± 2 GPa. On cooling, a structural distortion from a PbO-type tetragonal phase to an orthorhombic Cmma phase is observed below 100 K. At a low temperature of 10 K, compression of the orthorhombic Cmma phase results in a gradual transformation to an amorphous phase above 15 GPa. The transformation to the amorphous phase is completed by 40 GPa at 10 K. A loss of superconductivity is observed in the amorphous phase and a dramatic change in the temperature behavior of electrical resistance indicates formation of a semiconducting state at high pressures and low temperatures. The formation of the amorphous phase is attributed to a kinetic hindrance to the growth of a hexagonal NiAs phase under high pressures and low temperatures.

scholarly journals Thermal Analysis, Compressibility, and Decomposition of Synthetic Bastnäsite-(La) to Lanthanum Oxyfluoride

Minerals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 212
Author(s):  
Richard L. Rowland ◽  
Barbara Lavina ◽  
Kathleen E. Vander Kaaden ◽  
Lisa R. Danielson ◽  
Pamela C. Burnley
Keyword(s):  
High Temperature ◽  
Equation Of State ◽  
Ambient Temperature ◽  
Evolved Gas Analysis ◽  
Ambient Pressure ◽  
Basic Material ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Thermal Equation ◽  
X Ray

Understanding basic material properties of rare earth element (REE) bearing minerals such as their phase stability and equations of state can assist in understanding how economically viable deposits might form. Bastnäsite is the most commonly mined REE bearing mineral. We synthesized the lanthanum-fluoride end member, bastnäsite-(La) (LaCO3F), and investigated its thermal behavior and decomposition products from 298 K to 1173 K under ambient pressure conditions through thermogravimetric analysis, differential scanning calorimetry, evolved gas analysis, and high temperature powder X-ray diffraction. We also investigated the compressibility of bastnäsite-(La) via single crystal X-ray diffraction in diamond anvil cells at an ambient temperature up to 11.3 GPa and from 4.9 GPa to 7.7 GPa up to 673 K. At ambient pressure, bastnäsite-(La) was stable up to 598 K in air, where it decomposed into CO2 and tetragonal γ-LaOF. Above 948 K, cubic α-LaOF is stable. High temperature X-ray diffraction data were used to fit the Fei thermal equation of state and the thermal expansion coefficient α298 for all three materials. Bastnäsite-(La) was fit from 298 K to 723 K with V0 = 439.82 Å3, α298 = 4.32 × 10−5 K−1, a0 = −1.68 × 10−5 K−1, a1 = 8.34 × 10−8 K−1, and a2 = 3.126 K−1. Tetragonal γ-LaOF was fit from 723 K to 948 K with V0 = 96.51 Å3, α298 = 2.95×10−4 K−1, a0 = −2.41×10−5 K−1, a1 = 2.42×10−7 K−1, and a2 = 41.147 K−1. Cubic α-LaOF was fit from 973 K to 1123 K with V0 = 190.71 Å3, α298 = −1.12×10−5 K−1, a0 = 2.36×10−4 K−1, a1 = −1.73 × 10−7 K−1, and a2 = −17.362 K−1. An ambient temperature third order Birch–Murnaghan equation of state was fit with V0 = 439.82 Å3, K0 = 105 GPa, and K’ = 5.58.

X-Ray Structural Study of Li3N at High Pressure

1997 ◽  
Vol 499 ◽  
Author(s):  
Allen C. Ho ◽  
Maurice K. Granger ◽  
Arthur L. Ruoff
Keyword(s):  
High Pressure ◽  
Free Energy ◽  
Synchrotron Radiation ◽  
Equation Of State ◽  
Ambient Temperature ◽  
Structural Study ◽  
Ambient Pressure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Gibb’S Free Energy

ABSTRACTThe equation of state (EOS) of Li3N has been determined by energy-dispersive x-ray diffraction (EDXD) using synchrotron radiation up to 35 GPa at ambient temperature. Both the hexagonal D6h4(P63/mmc) and the hexagonal D6h1(P6/mmm) phases were present at ambient pressure. The D6h1 -structure completely transforms into the D6h4 -structure at modest pressure. The change in Gibb's free energy as a function of pressure for Li3N was calculated using the experimental EOS.

Application of X-ray diffraction topography for the study of Al single crystals plastically deformed at low temperatures

1975 ◽  
Vol 10 (3) ◽  
pp. 275-283 ◽  
Author(s):  
I. G. Novikova ◽  
V. I. Startsev ◽  
D. A. Didenko
Keyword(s):  
Single Crystals ◽  
Low Temperatures ◽  
X Ray Diffraction ◽  
X Ray

Low-Temperature (<300°C) Phosphate Ceramics from Reactive Aluminas

1989 ◽  
Vol 179 ◽  
Author(s):  
M. R. Silsbee ◽  
R. A. Steinke ◽  
D. M. Roy ◽  
D. K. Agrawal ◽  
R. Roy
Keyword(s):  
Mechanical Properties ◽  
Low Temperature ◽  
Low Temperatures ◽  
Ceramic Materials ◽  
X Ray Diffraction ◽  
X Ray ◽  
Characterization Techniques ◽  
Exciting Potential

AbstractReactive aluminas, including rapidly calcined gibbsites, offer exciting potential for forming ceramic materials at low temperatures. New x-ray amorphous aluminas will react with water at room temperatures to form compacts with 10–50 MPa tensile strengths, via viscous slurries. The cementious behavior of these materials has been examined. The results of TGA, x-ray diffraction, SEM, mechanical properties, and other characterization techniques, as applied to these systems, will be discussed.

scholarly journals In situlaser irradiation setup for a Bruker three-circle goniometer

2017 ◽  
Vol 50 (5) ◽  
pp. 1556-1558
Author(s):  
Dmitry S. Yufit
Keyword(s):  
Low Temperature ◽  
Single Crystals ◽  
Laser Irradiation ◽  
Diffraction Experiment ◽  
X Ray Diffraction ◽  
X Ray

A new design of a setup forin situlaser irradiation of single crystals during an X-ray diffraction experiment is presented. The system is designed for use with a Bruker three-circle goniometer in combination with a Helix ultra-low-temperature cryostat and consists of a laser mount and a set of three adjustable mirrors. The main advantages of the presented system include a stationary laser mount, the ability to irradiate a sample inside the Be nozzle and no impediments to the goniometer movements.

Chemistry of the S=O bond. 13. Structures of isomers 1 (I) and 2 (II) of 4-methyl-1,3,2-dioxathiane 2-oxide and 1,3,2-dioxathiepane 2-oxide (III) at 256, 240 and 228 K

1996 ◽  
Vol 52 (3) ◽  
pp. 505-508 ◽  
Author(s):  
D.G. Hellier ◽  
P. Luger ◽  
J. Buschmann
Keyword(s):  
Single Crystals ◽  
Low Temperatures ◽  
Chair Conformation ◽  
Equatorial Position ◽  
X Ray Diffraction ◽  
Compound I ◽  
Methyl Group ◽  
X Ray ◽  
Compound Ii ◽  
Axis Passing

The structures of the two isomers of 4-methyl-1,3,2-dioxathiane 2-oxide, C4H8SO3 (I, II), and 1,3,2-dioxathiepane 2-oxide, C4H8SO3 (III), have been determined by X-ray diffraction methods for single crystals that were grown in this case at low temperatures from the normally liquid compounds. Compound (I): orthorhombic, P212121, Mr = 136.17, a = 7.204 (6), b = 13.670 (11), c = 6.041 (6) Å, V = 594.91 Å3, Z= 4, Dx = 1.520 Mg m−3, Mo Kα (λ = 0.71068 Å), μ = 4.49 cm−1, F(000) = 288, T = 256 K, R = 0.042 for 778 unique reflections. Compound (II): orthorhombic, P212121, Mr = 136.17, a = 18.238 (6), b = 10.265 (3), c = 6.616 (2) Å, V = 1238.60 Å3, Z= 8, Dx = 1.460 Mg m−3, Mo Kα (λ = 0.71068 Å), μ = 4.31 cm−1, F(000) = 576, T = 240 K, R = 0.032 for 1597 unique reflections. Compound (III): monoclinic, P21/n, Mr = 136.17, a = 6.060 (3), b = 11.185 (8), c = 9.186 (4) Å, β = 101.32 (4)°, V = 610.52 Å3, Z = 4, Dx = 1.481 Mg m−3, Mo Kα (λ = 0.71068 Å), μ = 4.38 cm−1, F(000) = 288, T = 228 K, R = 0.037 for 1161 unique reflections. Compound (I) adopts a chair structure, which has a methyl group in an equatorial position and an axially oriented S=O group. Compound (II) is similar, except that the S=O group is equatorially oriented. Compound (III) adopts a twist-chair conformation with a local approximate endocyclic twofold axis passing through S(1) and the middle of the opposite bond, C(4)—C(5).

Kinetically asymmetric charge and discharge behavior of LiNi0.5Mn1.5O4 at low temperature observed by in situ X-ray diffraction

2014 ◽  
Vol 2 (37) ◽  
pp. 15414-15419 ◽  
Author(s):  
Ikuma Takahashi ◽  
Haruno Murayama ◽  
Kenji Sato ◽  
Takahiro Naka ◽  
Koji Kitada ◽  
...  
Keyword(s):  
Low Temperature ◽  
Low Temperatures ◽  
X Ray Diffraction ◽  
X Ray ◽  
Discharge Behavior

Thermodynamically reversible LiNi0.5Mn1.5O4 electrodes kinetically behave asymmetrically during charging and discharging at low temperatures.

scholarly journals Preparation of CoFe2O4/SiO2Nanocomposites at Low Temperatures Using Short Chain Diols

2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Thomas Dippong ◽  
Erika Andrea Levei ◽  
Oana Cadar
Keyword(s):  
Low Temperatures ◽  
Sol Gel ◽  
Silica Matrix ◽  
Short Chain ◽  
X Ray Diffraction ◽  
X Ray ◽  
Nanocrystallite Size ◽  
Methylene Groups ◽  
Diffraction Patterns ◽  
The Stability

The preparation of 70% CoFe2O4/30% SiO2(wt%) nanocomposites by sol-gel method using three short chain diols (1,2-ethanediol, 1,3-propanediol, and 1,4-butanediol) as chelators was studied. The Fourier transformed infrared spectra and X-ray diffraction patterns were used to confirm the formation of nanocomposites. The X-ray diffraction analysis showed that the chain length of the carboxylates embedded in the silica matrix influences the formation of crystallized cobalt ferrite as single phase at low temperatures. The influence of the methylene groups number in the precursors and annealing temperature on the nanocrystallite size was revealed. The stability of the obtained compounds was determined by calculation of thermodynamic parameters.

scholarly journals Structures and thermal stability of the α-LiNH4SO4 polytypes doped with Er3+ and Yb3+

2017 ◽  
Vol 73 (1) ◽  
pp. 122-133 ◽  
Author(s):  
N. P. Sabalisck ◽  
C. Guzmán-Afonso ◽  
C. González-Silgo ◽  
M. E. Torres ◽  
J. Pasán ◽  
...  
Keyword(s):  
Single Crystals ◽  
Slow Evaporation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Β Phase ◽  
Wide Range ◽  
Cyclic Temperature ◽  
Polymorphic Forms ◽  
The Stability ◽  
Thermal Stability Of

In order to clarify the polymorphism in the lithium sulfate family, LiRE x (NH4)1 − x SO4 (0.5 ≤ x ≤ 4.0 mol%, nominal value; RE = Er3+, Yb3+ and Dy3+) crystals were grown from aqueous solution by slow evaporation between 298 and 313 K. The doping of the samples allowed us to obtain two polymorphic forms, α and β, of LiNH4SO4 (LAS). By means of X-ray diffraction (XRD) in single crystals, we determined the crystal structures of two new α-polytypes, which we have named α1- and α2-LAS. They present the same space group P21/c and the following relation among their lattice parameters: a 2 = −c 1, b 2 = −b 1, c 2 = −2a 1 − c 1. In order to evaluate the stability of the new α-polytypes, we performed thermal analysis, X-ray diffraction and dielectric spectroscopy on single crystals and polycrystalline samples over the cyclic temperature range: 190 → 575  → 190 K. The results obtained by all the techniques used in this study demonstrate that α-polytypes are stable across a wide range of temperatures and they show an irreversible phase transition to the paraelectric β-phase above 500 K. In addition, a comparative study of α- and β-polytypes shows that both polymorphic structures have a common axis, with a possible intergrowth that facilitates their coexistence and promotes the reconstructive α → β transition. This intergrowth was related to small anomalies detected between 240 and 260 K, in crystals with an α-habit.

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