Diffraction Study of The Transformation of an Al-Cu-Fe Atomized Powder Upon Annealing at 500°C

2000 ◽  
Vol 643 ◽  
Author(s):  
P. Weisbecker ◽  
G. Bonhomme ◽  
A. Cael ◽  
L. Zhang ◽  
J.M. Dubois
Keyword(s):  
Diffraction Study ◽  
Initial Mixture ◽  
Heat Treatments ◽  
Cubic Phase ◽  
Nominal Composition ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cubic Phases ◽  
Cscl Type ◽  
Oxygen Atoms

AbstractUsing powder X-ray diffraction, we have studied the transformation of an atomized powder of nominal composition Al62Cu25.5Fe12.5 upon annealing at 500°C in air or in vacuum. The initial mixture of icosahedral and B2 cubic phases transforms within 2 hours into a nearly pure icosahedral compound. We observe however that a small amount of residual cubic phase is still present after annealings as long as 65 hours. Furthermore, the initial cubic phase splits in two components, a CsCl-type and a disordered bcc cubic phase. By comparison of the heat treatments in air and in vacuum, we point out that oxygen atoms diffuse into the icosahedral lattice.

TETRAGONAL-ORTHORHOMBIC UNIT CELL TRANSFORMATION IN THE HYDROGEN-DOPED Y–Ba–Cu–OXIDE

1990 ◽  
Vol 04 (04) ◽  
pp. 289-292 ◽  
Author(s):  
H. DRULIS ◽  
J. KLAMUT ◽  
Z. BUKOWSKI
Keyword(s):  
Phase Transition ◽  
Diffraction Study ◽  
Cell Transformation ◽  
Unit Cell ◽  
Nominal Composition ◽  
X Ray Diffraction ◽  
Orthorhombic Unit Cell ◽  
X Ray ◽  
Orthorhombic Cell ◽  
Oxygen Atoms

A hydride sample with nominal composition H 0.7 YBa 2 Cu 3 O 6.1 was synthesized. An X-ray diffraction study showed a phase transition from the tetragonal to orthorhombic cell. It is the first example of such transition among Y–Ba–Cu–O ceramics induced by non-oxygen atoms.

In Situ Synchrotron X-Ray Diffraction Study of the Rhombohedral-to-HT-Cubic Phase Transformation in Ln6 WO12 (Ln = Y, Ho, Er, Yb)

2013 ◽  
Vol 97 (4) ◽  
pp. 1256-1263 ◽  
Author(s):  
Zlatomir D. Apostolov ◽  
Pankaj Sarin ◽  
Robert W. Hughes ◽  
Waltraud M. Kriven
Keyword(s):  
Phase Transformation ◽  
Diffraction Study ◽  
Cubic Phase ◽  
X Ray Diffraction ◽  
X Ray

Temperature-Jump Time-Resolved X-ray Diffraction Study of Cubic−Cubic Phase-Transition Kinetics in Thermotropic Cubic Mesogen 1,2-Bis(4′-n-alkoxybenzoyl)hydrazines (BABH-n)

Langmuir ◽  
2010 ◽  
Vol 26 (14) ◽  
pp. 11605-11608 ◽  
Author(s):  
Hiroyuki Mori ◽  
Shoichi Kutsumizu ◽  
Kazuya Saito ◽  
Katsuhiro Yamamoto ◽  
Shinichi Sakurai ◽  
...  
Keyword(s):  
Phase Transition ◽  
Diffraction Study ◽  
Temperature Jump ◽  
Cubic Phase ◽  
X Ray Diffraction ◽  
Time Resolved ◽  
X Ray ◽  
Jump Time ◽  
Phase Transition Kinetics

Variable-temperature single-crystal X-ray diffraction study of tetragonal and cubic perovskite-type barium titanate phases

2016 ◽  
Vol 72 (1) ◽  
pp. 151-159 ◽  
Author(s):  
Tomotaka Nakatani ◽  
Akira Yoshiasa ◽  
Akihiko Nakatsuka ◽  
Tatsuya Hiratoko ◽  
Tsutomu Mashimo ◽  
...  
Keyword(s):  
Single Crystal ◽  
Diffraction Study ◽  
Variable Temperature ◽  
Cubic Phase ◽  
X Ray Diffraction ◽  
Temperature Dependent ◽  
X Ray ◽  
M Phase ◽  
The Mean ◽  
Perovskite Type

A variable-temperature single-crystal X-ray diffraction study of a synthetic BaTiO3perovskite has been performed over the temperature range 298–778 K. A transition from a tetragonal (P4mm) to a cubic (Pm \overline 3 m) phase has been revealed near 413 K. In the non-centrosymmetricP4mmsymmetry group, both Ti and O atoms are displaced along thec-axis in opposite directions with regard to the Ba position fixed at the origin, so that Ti4+and Ba2+cations occupy off-center positions in the TiO6and BaO12polyhedra, respectively. Smooth temperature-dependent changes of the atomic coordinates become discontinuous with the phase transition. Our observations imply that the cations remain off-center even in the high-temperature cubic phase. The temperature dependence of the mean-square displacements of Ti in the cubic phase includes a significant static component which means that Ti atoms are statistically distributed in the off-center positions.

scholarly journals X-Ray Diffraction Study of Oxygen-Conducting Compounds Ln2Mo2O9(Ln = La, Pr)

2014 ◽  
Vol 70 (a1) ◽  
pp. C48-C48
Author(s):  
Alexander Antipin ◽  
Olga Alekseeva ◽  
Natalya Sorokina ◽  
Alexandra Kuskova ◽  
Michail Presniakov ◽  
...  
Keyword(s):  
High Temperature ◽  
Single Crystals ◽  
Basic Research ◽  
Cubic Phase ◽  
X Ray Diffraction ◽  
Oxide Systems ◽  
Transmission Microscopy ◽  
X Ray ◽  
Oxygen Conductivity ◽  
Oxygen Atoms

Lanthanum molibdate La2Mo2O9(LM) and the compounds on its basis (LAMOX) attract much attention because of the high oxygen conductivity (6x10-2Sm/cm), which were found by Lacorre group. LM has the first-order phase transition at about 5800C and two phases: low-temperature monoclinic α-phase (P21) and high-temperature β-phase (P213) [1]. In the present work single crystals Ln2Mo2O9(Ln = La, Pr) were obtained by spontaneous flux crystallization in the Ln2O3–MoO3oxide systems. The LM and PM single crystals are studied by precision X-ray diffraction and high-resolution transmission microscopy. A cubic cell with a = 7.155(1) and 7.155(1) Å was chosen for two LM samples (LM_I and LM_II, respectively). More than 90% (LM_I) and 60% (LM_II) of the reflections measured were indexed in this cell. The unit cell parameter of the PM compound is slightly shorter: a = 7.087(1) and 7.089(1) Å for the PM_I and PM_II samples, respectively. More than 90% of the reflections measured were indexed for both PM crystals. It was found that the LM_II crystal consists of two cubic components grown together; a ≍ 7.155 Å for both components. The crystal structures for two LM and two PM samples are determined in space group P213. It is found that La and Pr atoms, as well as Mo1 and O1 atoms, are located in the vicinity of 3-fold axes rather than on the axes like in the high-temperature cubic phase. In both structures, the O2 and O3 positions are partially occupied. The coexistence of different configurations of the Mo coordination environment facilitates the oxygen ion migration in the structure. Based on the X-ray data, activation energies of oxygen atoms are calculated and migration paths of oxygen ions in the structures are analyzed. The conductivity of PM crystals is close to that of LM crystals. Oxygen atoms O2 and O3 make main contributions to ion conductivity of LM and PM. This study was supported in part by part by the Russian Foundation for Basic Research (project no. 14-02-00531).

High-temperature single-crystal X-ray diffraction study of tetragonal and cubic perovskite-type PbTiO3phases

2016 ◽  
Vol 72 (3) ◽  
pp. 381-388 ◽  
Author(s):  
Akira Yoshiasa ◽  
Tomotaka Nakatani ◽  
Akihiko Nakatsuka ◽  
Maki Okube ◽  
Kazumasa Sugiyama ◽  
...  
Keyword(s):  
Phase Transition ◽  
High Temperature ◽  
Single Crystal ◽  
Diffraction Study ◽  
Relative Displacement ◽  
High Temperature Phase ◽  
Cubic Phase ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
X Ray

A high-temperature single-crystal X-ray diffraction study of a synthetic PbTiO3perovskite was carried out over the wide temperature range 298–928 K. A transition from a tetragonal (P4mm) to a cubic (Pm \bar 3 m) phase has been revealed near 753 K. In the non-centrosymmetricP4mmsymmetry group, the difference in relative displacement between Pb and O along thec-axis is much larger than that between Ti and O. The Pb and Ti cations contribute sufficiently to polarization being shifted in the opposite direction compared with the shift of O atoms. Deviation from the linear changes in Debye–Waller factors and bonding distances in the tetragonal phases can be interpreted as a precursor phenomenon before the phase transition. Disturbance of the temperature factorUeqfor O is observed in the vicinity of the transition point, whileUeqvalues for Pb and Ti are continuously changing with increasing temperature. The O site includes the clear configurational disorder in the cubic phase. The polar local positional distortions remain in the cubic phase and are regarded as the cause of the paraelectricity. Estimated values of the Debye temperature ΘDfor Pb and Ti are 154 and 467 K in the tetragonal phase and decrease 22% in the high-temperature phase. Effective potentials for Pb and Ti change significantly and become soft after the phase transition.

scholarly journals Fusion Peptides Promote Formation of Bilayer Cubic Phases in Lipid Dispersions. An X-Ray Diffraction Study

2013 ◽  
Vol 104 (5) ◽  
pp. 1029-1037 ◽  
Author(s):  
Boris G. Tenchov ◽  
Robert C. MacDonald ◽  
Barry R. Lentz
Keyword(s):  
Diffraction Study ◽  
Fusion Peptides ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cubic Phases

Distortions in tetrahedral copper(I)–phosphine complexes: bis(triphenylphosphine)copper(I) nitrate

1969 ◽  
Vol 47 (8) ◽  
pp. 1440-1441 ◽  
Author(s):  
G. G. Messmer ◽  
Gus J. Palenik
Keyword(s):  
Crystal Structure ◽  
Diffraction Study ◽  
Three Dimensional ◽  
Nitrate Group ◽  
X Ray Diffraction ◽  
X Ray ◽  
Phosphine Complexes ◽  
Ideal Tetrahedron ◽  
Oxygen Atoms

The crystal structure of bis(triphenylphosphine)copper(I) nitrate has been determined by a three-dimensional X-ray diffraction study. The copper(I) atom is bonded to the two phosphines and two oxygen atoms of the nitrate group. However, the molecule is distorted from that of an ideal tetrahedron, with the P—Cu—P angle being 131.1°.

scholarly journals A Neutron and X-ray Diffraction Study of the Structure of Nd Phosphate Glasses

2001 ◽  
Vol 56 (3-4) ◽  
pp. 237-243 ◽  
Author(s):  
Uwe Hoppe ◽  
Heike Ebendorff-Heidepriem ◽  
Jörg Neuefeind ◽  
Daniel T. Bowron
Keyword(s):  
Neutron Diffraction ◽  
Diffraction Study ◽  
Coordination Number ◽  
Diffraction Data ◽  
Phosphate Glasses ◽  
Neutron Diffraction Data ◽  
X Ray Diffraction ◽  
X Ray ◽  
Oxygen Atoms

Abstract Diffraction experiments were performed on two (Nd2O3)x(P2O5)1- x glasses for studying the en­ vironmental order of the Nd3+ cations. In case of the metaphosphate glass (x = 0.25) a combination of X-ray and neutron diffraction data was used to separate the Nd-O and O-O first neighbor peaks. An Nd-O coordination number of 6.6±0.3 and a mean Nd-O distance of (0.239±0.001) nm were determined. In the ultraphosphate glass studied (x = 0.20) these values increase to 6.9±0.3 and (0.240±0.001) nm where the Nd-0 coordination number is equal to the number of terminal oxygen atoms (OT) which are available for coordination of each Nd3+ cation. This indicates the formation of NdOn polyhedra not sharing any O atom where also all OT's are in N d-OT-P positions. In the metaphosphate glass the NdOn polyhedra have to share some OT sites.

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