The Crystal Structure of Pressure-Induced Phases of In2Te3and Ga2Te3

1992 ◽  
Vol 7 (2) ◽  
pp. 99-102 ◽  
Author(s):  
N.R. Serebryanaya
Keyword(s):  
Crystal Structure ◽  
Metastable Phase ◽  
Face Centered Cubic ◽  
Volume Changes ◽  
X Ray ◽  
The Face ◽  
Crystal Structure Transformation ◽  
Face Centered ◽  
Heating Up

AbstractPhase transitions were found with use of an in situX-ray anvil-type of apparatus with a boron annulus at pressures up to 12 GPa. The disordering of vacancies in the In sub-structure, or α→βtransition, was found in In2Te3at p > 1.9 GPa. The next transformation from the β-form into the Bi2Te3type of structure was observed in both sesquitellurides at 2.0 GPa and 5.0 GPa for In2TGe3and Ga2Te3respectively. The In2Te3metastable phase of the Bi2Te3resulted from heating up to 200° C at p > 4.0 GPa, and it remained in a normal condition on release of the pressure. The X-ray powder diffraction data of pressure-induced phases, volume changes and bulk modulus of both sesquitellurides are given. The compressibility anisotropy of the layer pressure-induced phase was observed. The mechanism of the crystal structure transformation from the face-centered cubic structure into the Bi2Te3type is proposed to be due to the displacement of atoms from the space diagonal of the cube [111] into [112]-cubic direction and the rhombohedral distortion of the angle between these directions.

A partly disordered 2 × 2 × 2 – superstructure of γ-brass related phase in Mn–Ni–Zn system

2021 ◽  
Vol 236 (3-4) ◽  
pp. 71-80
Author(s):  
Sivaprasad Ghanta ◽  
Anustoop Das ◽  
Rajat Kamboj ◽  
Partha P. Jana
Keyword(s):  
Crystal Structure ◽  
High Symmetry ◽  
Face Centered Cubic ◽  
X Ray Diffraction ◽  
X Ray ◽  
Lattice Constants ◽  
Cubic Lattice ◽  
The Face ◽  
Face Centered ◽  
Related Phase

Abstract The T phase in the Mn–Ni–Zn system was obtained as a product of high-temperature solid-state syntheses from the loaded composition of MnxNi2−xZn11 (x = 0.2–1.5)/MnxNi15.38−xZn84.62 (x = 1.54–11.54). The crystal structure of the T phase has been explored by means of X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS). The structures were solved in the face-centered cubic space group F 4 ‾ 3 m $F‾{4}3m$ (216) and contain 409–410 atoms/unit cell. The lattice constants were found to be a = 18.1727(2) and 18.1954(1) Å for crystals C1 and C2, respectively. The crystal structure denoted the T phase is a (2aγ)3-superstructure of the ordinary cubic γ-brass-type phase. The phase is isostructural to (Fe, Ni)Zn6.5. A “cluster” description has been used to visualize the crystal structure of the title phase. The structures have been constructed by the five distinct clusters and they are situated about the high symmetry sites of the face-centered cubic lattice. The T phase is stabilized at a valance electron concentration of 1.78, which is slightly higher than those expected for typical γ-brass Hume‐Rothery compounds.

Controlling Aspect Ratio of Copper Group Nanowire Arrays by Electrochemical Deposition in the Nanopores of AAO

2011 ◽  
Vol 335-336 ◽  
pp. 429-432 ◽  
Author(s):  
Xiu Yu Sun ◽  
Fa Qiang Xu
Keyword(s):  
Aspect Ratio ◽  
Nanowire Arrays ◽  
Face Centered Cubic ◽  
X Ray Diffraction ◽  
X Ray ◽  
Anodic Aluminum ◽  
Au Nanowire ◽  
The Face ◽  
Face Centered ◽  
Xrd Patterns

Highly ordered Cu, Ag and Au nanowire arrays with high aspect ratio and highly dense self-supporting nanowire patterns of copper group were successfully prepared using cyclic voltammetry with the assistance of anodic aluminum oxide (AAO) template. The X-ray diffraction (XRD) patterns of the metal nanowries were indexed to the face-centered cubic structure. The field emission scanning electron microscope (FE-SEM) results demonstrated that the length of nanowire could be controlled by changing the electrodepositon conditions. The aspect ratio of nanowire arrays can be tuned.

Novel Nanohybrids Derived from the Attachment of FePt Nanoparticles on Carbon Nanotubes

2008 ◽  
Vol 8 (11) ◽  
pp. 5942-5951 ◽  
Author(s):  
Theodoros Tsoufis ◽  
Aphrodite Tomou ◽  
Dimitrios Gournis ◽  
Alexios P. Douvalis ◽  
Ioannis Panagiotopoulos ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Carbon Nanotubes ◽  
Particle Size ◽  
Fept Nanoparticles ◽  
Face Centered Cubic ◽  
Magnetization Measurements ◽  
Hybrid Sample ◽  
The Face ◽  
Face Centered ◽  
Mwcnts Surface

Multiwalled carbon nanotubes (MWCNTs) were used as nanotemplates for the dispersion and stabilization of FePt nanoparticles (NPs). Pre-formed capped FePt NPs were connected to the MWCNTs external surface via covalent binding through organic linkers. Free FePt NPs and MWCNTs-FePt hybrids were annealed in vacuum at 700 °C in order to achieve the L10 ordering of the FePt phase. Both as prepared and annealed samples were characterized and studied using a combination of experimental techniques, such as Raman and Mössbauer spectroscopies, powder X-ray Diffraction (XRD), magnetization and transmittion electron microscopy (TEM) measurements. TEM measurements of the hybrid sample before annealing show that a fine dispersion of NPs along the MWCNTs surface is achieved, while a certain amount of free particles attached to each other in well connected dense assemblies of periodical or non-periodical particle arrangements is also observed. XRD measurements reveal that the FePt phase has the face-centered cubic (fcc) disordered crystal structure in the as prepared samples, which is transformed to the face-centered tetragonal (fct) L10 ordered crystal structure after annealing. An increase in the average particle size is observed after annealing, which is higher for the free NPs sample. Superparamagnetic phenomena due to the small FePt particle size are observed in the Mössbauer spectra of the as prepared samples. Mössbauer and magnetization measurements of the MWCNTs-FePt hybrids sample reveal that the part of the FePt particles attached to the MWCNTs surface shows superparamagnetic phenomena at RT even after the annealing process. The hard magnetic L10 phase characteristics are evident in the magnetization measurements of both samples after annealing, with the coercivity of the hybrid sample over-scaling that of the free NPs sample by a factor of 1.25.

Optical and Structural Properties of InAs/GaSb Nanostructures

2003 ◽  
Vol 794 ◽  
Author(s):  
D.W. Stokes ◽  
J.H Li ◽  
R.L. Forrest ◽  
S.L. Ammu ◽  
J.C. Lenzi ◽  
...  
Keyword(s):  
Quantum Well ◽  
Infrared Absorption ◽  
Optoelectronic Device ◽  
Face Centered Cubic ◽  
X Ray ◽  
Composition Modulation ◽  
Modulated Structures ◽  
Two Samples ◽  
The Face ◽  
Face Centered

ABSTRACTThe nanostructures self-organized via lateral composition modulation in 140 period (InAs)13/(GaSb)13 superlattices grown by molecular beam epitaxy have been studied by highresolution x-ray diffraction and infrared absorption. Three samples were analyzed in this study; two with lateral composition modulation and one without. X-ray reciprocal space map scans were taken to determine the average morphology of the modulated structures. Both vertical and lateral satellite peaks were observed for the samples with composition modulation, indicating the formation of two-dimensional nanowire arrays. The vertical wavelength measured for the two samples was twice the period intended by the growers. This is due to the face-centered cubic type stacking of the nanowires. Infrared absorption spectra of these two samples were compared to the spectra of the sample with no lateral composition modulation. Transitions involving the heavy- and light-hole bands in the GaSb hole quantum well and the electron subbands of the InAs electron quantum well were not evident for the samples with lateral composition modulation, indicating that the nanostructure of the lateral composition modulation affects the optical response of the sample, which is important for optoelectronic device applications.

In situ high-temperature X-ray diffraction characterization of silver sulfide, Ag2S

2011 ◽  
Vol 26 (2) ◽  
pp. 114-118 ◽  
Author(s):  
Thomas Blanton ◽  
Scott Misture ◽  
Narasimharao Dontula ◽  
Swavek Zdzieszynski
Keyword(s):  
High Temperature ◽  
Structure Refinement ◽  
Silver Sulfide ◽  
Rietveld Analysis ◽  
Face Centered Cubic ◽  
X Ray Diffraction ◽  
X Ray ◽  
Face Centered ◽  
Fcc Phase

Silver sulfide, Ag2S, is most commonly known as the tarnish that forms on silver surfaces due to the exposure of silver to hydrogen sulfide. The mineral acanthite is a monoclinic crystalline form of Ag2S that is stable to 176°C. Upon heating above 176°C, there is a phase conversion to a body-centered cubic (bcc) form referred to as argentite. Further heating above 586°C results in conversion of the bcc phase to a face-centered cubic (fcc) phase polymorph. Both high-temperature cubic phases are solid-state silver ion conductors. In situ high-temperature X-ray diffraction was used to better understand the polymorphs of Ag2S on heating. The existing powder diffraction file (PDF) entries for the high-temperature fcc polymorph are of questionable reliability, prompting a full Rietveld structure refinement of the bcc and fcc polymorphs. Rietveld analysis was useful to show that the silver atoms are largely disordered and can only be described by unreasonably large isotropic displacement parameters or split site models.

Formation of face-centered cubic titanium on a Ni single crystal and in Ni/Ti multilayers

1994 ◽  
Vol 9 (1) ◽  
pp. 31-38 ◽  
Author(s):  
Alan F. Jankowski ◽  
Mark A. Wall
Keyword(s):  
Structural Characteristics ◽  
Single Layer ◽  
High Resolution Electron Microscopy ◽  
Cubic Phase ◽  
Face Centered Cubic ◽  
X Ray Diffraction ◽  
X Ray ◽  
Resolution Electron ◽  
The Face ◽  
Face Centered

The artificial layering of metals can change both physical and structural characteristics from the bulk. The stabilization of polymorphic metallic phases can occur on a dimensional scale that ranges from single overgrowth layers to repetitive layering at the nanoscale. The sputter deposition of crystalline titanium on nickel, as both a single layer and in multilayer form, has produced a face-centered cubic phase of titanium. The atomic structure of the face-centered cubic titanium phase is examined using high resolution electron microscopy in combination with electron and x-ray diffraction.

CHALKOGENIDES OF THE TRANSITION ELEMENTS: II. EXISTENCE OF THE π PHASE IN THE M9S8 SECTION OF THE SYSTEM Fe–Co–Ni–S

1961 ◽  
Vol 39 (2) ◽  
pp. 297-317 ◽  
Author(s):  
Osvald Knop ◽  
Mohammad Anwar Ibrahim
Keyword(s):  
Crystal Structure ◽  
Cobalt Content ◽  
Cubic Phase ◽  
Face Centered Cubic ◽  
Transition Elements ◽  
Maximum Increase ◽  
The Face ◽  
Face Centered ◽  
The Stability ◽  
Stability Limits

The face-centered cubic phase π(Fe,Co,Ni,S) has been shown to exist, at room temperature, within wide composition limits in or close to the M9S8 section of the quaternary system Fe–Co–Ni–S. The M:S ratio of the binary phase π (Co,S) is 9:8 with very narrow homogeneity ranges on both sides of Co9S8, but in π (Fe,Co,Ni,S) the ratio is somewhat higher and appears to increase with decreasing cobalt content. Stoichiometric Co9S8 probably contains a small number of vacancies in both sublattices. It is quite lilcely that the sulphur sublattice is nearly fully occupied and that departures from stoichiometry are caused by the varying degree of occupancy of the metal sublattice.The crystal structure, which was proposed for Co9S8 and for the mineral pentlandite by Lindqvist etal., has been confirmed for these two substances and for π (Fe,Co,Ni,S) in general by X-ray and neutron powder diffraction. The present evidence does not support the crystal structure suggested for natural pentlandite by Eliseev; Eliseev's model does not, in fact, account for the diffraction data of any of the substances examined in this work.Replacement of cobalt in π (Co,S) by iron or nickel or both results in an expansion of the unit cell, the maximum increase in a(π) amounting to about 3%. Cobalt in π (Co,S) cannot be replaced completely by iron or by nickel in samples prepared by dry synthesis, but if the substitution is simultaneous, the π structure will be preserved over a considerable range of compositions even on total replacement. The stability limits of π (Fe,Ni,S) have been found somewhat wider than those stated by Lundqvist.In π phases with the compositions Co8MS8 the metal atoms can conceivably be present in ordered sublattices. This possibility was explored by neutron diffraction in slowly cooled Co8NiS8. Unlike in spinels, where nickel shows a strong preference for octahedral co-ordination, the cobalt and nickel atoms were found to be distributed at random.

Highly Oriented Co Soft Magnetic Films on Si Substrates

1999 ◽  
Vol 562 ◽  
Author(s):  
Heng Gong ◽  
Wei Yang ◽  
Maithri Rao ◽  
David E. Laughlin ◽  
David N. Lambeth
Keyword(s):  
Magnetic Properties ◽  
Magnetic Films ◽  
Face Centered Cubic ◽  
X Ray Diffraction ◽  
Orientation Relationships ◽  
Soft Magnetic ◽  
X Ray ◽  
Si Substrates ◽  
The Face ◽  
Face Centered

ABSTRACTThin Co and Co based alloy films with the face centered cubic (FCC) structure have been epitaxially grown on single crystal Si wafers by sputter deposition. Epitaxial orientation relationships have been determined by x-ray diffraction, x-ray pole figure scans and TEM. Magnetic properties have been characterized using vibrating sampling magnetometer (VSM), torque magnetometer and BH loop tracer. Soft magnetic properties have been observed for the pure Co films.

Prediction of metastable phase formation in an immiscible Cu–Cr system from interatomic potential and ab initio calculation

2003 ◽  
Vol 18 (10) ◽  
pp. 2300-2303 ◽  
Author(s):  
H. R. Gong ◽  
L. T. Kong ◽  
B. X. Liu
Keyword(s):  
Ab Initio ◽  
Interatomic Potential ◽  
Metastable Phase ◽  
The Body ◽  
Face Centered Cubic ◽  
The Face ◽  
Bcc Structure ◽  
Face Centered ◽  
Dynamics Simulations ◽  
Cr System

Ab initio calculation was performed to predict the structures, lattice constants, and cohesive energies of metastable Cu75Cr25 and Cu50Cr50 phases. An n-body Cu–Cr potential was derived through fitting to some ab initio calculated results and was capable of reproducing some intrinsic properties of the Cu–Cr system. Based on the derived potential, molecular dynamics simulations predicted that for a Cu100−xCrx alloy, the face-centered-cubic structure is more stable than the body-centered-cubic (bcc) one when 0 ≤ x ≤ 25, while the bcc structure becomes energetically favored when 25 < x ≤ 100. Interestingly, the predictions match well with the experimental observations.

Powder data for buckminsterfullerene, C60

1994 ◽  
Vol 9 (2) ◽  
pp. 93-95 ◽  
Author(s):  
David E. McCready ◽  
Mikhail S. Alnajjar
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Intensity Ratio ◽  
Unit Cell ◽  
Face Centered Cubic ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Face Centered ◽  
Buckminsterfullerene C60

X-ray powder diffraction data for buckminsterfullerene, C60 are reported. The crystal structure is a face-centered cubic unit cell with a = 14.165 (1) Å. The reference intensity ratio (I/Icor) is 2.20.

Sign in / Sign up

Export Citation Format

Share Document