Pressure Tuning of Crystalline As2Te3

2004 ◽  
Vol 848 ◽  
Author(s):  
T. J. Scheidemantel ◽  
J. F. Meng ◽  
J. V. Badding

ABSTRACTWe report the pressure dependence of the thermoelectric power of As2Te3. Pressures up to 10 GPa were induced using a Mao-Bell diamond anvil cell. The absolute value of the thermoelectric power dropped from S ≈ 230μV/K at ambient pressure to S ≈ 75 GPa near 5 GPa. At 6 GPa it then increased rapidly to S ≈ 220βV/K. This behavior is indicative of a structural phase transition as suggested by previously published high pressure phase diagrams.

2007 ◽  
Vol 102 (10) ◽  
pp. 106104 ◽  
Author(s):  
N. Nissim ◽  
S. Eliezer ◽  
L. Bakshi ◽  
L. Perelmutter ◽  
D. Moreno ◽  
...  

Author(s):  
Andrzej Katrusiak

The diamond-anvil cell (DAC) was invented 60 years ago, ushering in a new era for material sciences, extending research into the dimension of pressure. Most structural determinations and chemical research have been conducted at ambient pressure, i.e. the atmospheric pressure on Earth. However, modern experimental techniques are capable of generating pressure and temperature higher than those at the centre of Earth. Such extreme conditions can be used for obtaining unprecedented chemical compounds, but, most importantly, all fundamental phenomena can be viewed and understood from a broader perspective. This knowledge, in turn, is necessary for designing new generations of materials and applications, for example in the pharmaceutical industry or for obtaining super-hard materials. The high-pressure chambers in the DAC are already used for a considerable variety of experiments, such as chemical reactions, crystallizations, measurements of electric, dielectric and magnetic properties, transformations of biological materials as well as experiments on living tissue. Undoubtedly, more applications involving elevated pressure will follow. High-pressure methods become increasingly attractive, because they can reduce the sample volume and compress the intermolecular contacts to values unattainable by other methods, many times stronger than at low temperature. The compressed materials reveal new information about intermolecular interactions and new phases of single- and multi-component compounds can be obtained. At the same time, high-pressure techniques, and particularly those of X-ray diffraction using the DAC, have been considerably improved and many innovative developments implemented. Increasingly more equipment of in-house laboratories, as well as the instrumentation of beamlines at synchrotrons and thermal neutron sources are dedicated to high-pressure research.


2009 ◽  
Vol 478 (1-2) ◽  
pp. 392-397 ◽  
Author(s):  
Björn Winkler ◽  
Erick A. Juarez-Arellano ◽  
Alexandra Friedrich ◽  
Lkhamsuren Bayarjargal ◽  
Jinyuan Yan ◽  
...  

Crystals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 75 ◽  
Author(s):  
Linfei Yang ◽  
Lidong Dai ◽  
Heping Li ◽  
Haiying Hu ◽  
Meiling Hong ◽  
...  

The phase stability of epsomite under a high temperature and high pressure were explored through Raman spectroscopy and electrical conductivity measurements in a diamond anvil cell up to ~623 K and ~12.8 GPa. Our results verified that the epsomite underwent a pressure-induced phase transition at ~5.1 GPa and room temperature, which was well characterized by the change in the pressure dependence of Raman vibrational modes and electrical conductivity. The dehydration process of the epsomite under high pressure was monitored by the variation in the sulfate tetrahedra and hydroxyl modes. At a representative pressure point of ~1.3 GPa, it was found the epsomite (MgSO4·7H2O) started to dehydrate at ~343 K, by forming hexahydrite (MgSO4·6H2O), and then further transformed into magnesium sulfate trihydrate (MgSO4·3H2O) and anhydrous magnesium sulfate (MgSO4) at higher temperatures of 373 and 473 K, respectively. Furthermore, the established P-T phase diagram revealed a positive relationship between the dehydration temperature and the pressure for epsomite.


2013 ◽  
Vol 22 ◽  
pp. 612-618 ◽  
Author(s):  
DINESH C. GUPTA ◽  
IDRIS HAMID

ab-initio calculations using fully relativistic pseudo-potential have been performed to investigate the high pressure phase transition, elastic and electronic properties of lead-chalcogenides including the less known lead polonium. The calculated ground state parameters, for the rock-salt structure show good agreement with the experimental data. The enthalpy calculations show that these materials undergo a first-order phase transition from rock-salt to CsCl structure at 19.4, 15.5, 11.5 and 7.3 GPa for PbS, PbSe, PbTe and PbPo, respectively. Present calculations successfully predicted the location of the band gap at L-point of Brillouin zone as well as the value of the band gap in every case at ambient pressure. It is observed that unlike other lead-chalcogenides, PbPo is semi-metal at ambient pressure. The pressure variation of the energy gap indicates that these materials metalized under high pressures. For this purpose, the electronic structure of these materials has also been computed in parent as well as in high pressure phase.


2000 ◽  
Vol 56 (2) ◽  
pp. 189-196 ◽  
Author(s):  
Stefan Carlson ◽  
Ann-Kristin Larsson ◽  
Franziska E. Rohrer

The ReO3-type structure NbO2F, niobium dioxyfluoride, has been studied at high pressures using diamond anvil cells and synchrotron X-ray radiation. High-pressure powder diffraction measurements have been performed up to 40.1 GPa. A phase transition from the cubic (Pm3¯m) ambient pressure structure to a rhombohedral (R3¯c) structure at 0.47 GPa has been observed. Rietveld refinements at 1.38, 1.96, 3.20, 6.23, 9.00 and 10.5 GPa showed that the transition involves an a − a − a − tilting of the cation–anion coordination octahedra and a change of the anion–anion arrangement to approach hexagonal close packing. Compression and distortion of the Nb(O/F)6 octahedra is also revealed by the Rietveld refinements. At 17–18 GPa, the diffraction pattern disappears and the structure becomes X-ray amorphous.


Author(s):  
Saheli Banerjee ◽  
Alka B Garg ◽  
H. K. Poswal

Abstract In this article we report the synthesis, characterization and high pressure investigation on technologically important, rare earth orthotantalate, EuTaO4. Single phase polycrystalline sample of EuTaO4 has been synthesized by solid state reaction method adopting monoclinic M'-type fergusonite phase with space group P2/c. Structural and vibrational properties of synthesized compound are investigated using synchrotron based x-ray powder diffraction, and Raman spectroscopic techniques respectively. Both the techniques show presence of an isostructural, first order, reversible phase transition near 17 GPa. Bulk modulus obtained by fitting the experimental pressure volume data for low pressure and high pressure phase is 136.0(3) and 162.8(21) GPa. High pressure phase is accompanied by an increase in coordination number around Ta atom from 6 to 8. First principles calculations under the frame work of density functional theory (DFT) also predicts the isostructural phase transition and change in coordination around Ta atom, corroborating the experimental findings.


Author(s):  
Valeri Brouskov ◽  
Michael Hanfland ◽  
Rainer Pöttgen ◽  
Ulrich Schwarz

AbstractStructural properties of the ternary intermetallic compound CeAuGe were investigated at hydrostatic pressures up to 15 GPa with high-resolution angle dispersive X-ray powder diffraction using synchrotron radiation and the diamond anvil cell technique. At 8.7(7) GPa a first order phase transition is observed from a hexagonal NdPtSb-type arrangement into an orthorhombic high-pressure modification with a TiNiSi-type crystal structure. The transformation is associated with a 3% shortening of the lattice parameter perpendicular to the puckered layers [AuGe]


1989 ◽  
Vol 22 (1) ◽  
pp. 61-63 ◽  
Author(s):  
J. S. Olsen ◽  
L. Gerward ◽  
U. Benedict ◽  
H. Luo ◽  
O. Vogt

High-pressure X-ray diffraction studies have been performed on ThP using synchrotron radiation and a diamond-anvil cell. The bulk modulus B 0 and its pressure derivative B′0 have been determined (B 0 = 137 GPa; B′0 = 5.1). A phase transition from the NaCl structure to the CsCl structure was observed at about 30 GPa.


2005 ◽  
Vol 22 (6) ◽  
pp. 1347-1349 ◽  
Author(s):  
Han Yong-Hao ◽  
Luo Ji-Feng ◽  
Gao Chun-Xiao ◽  
Ma Hong-An ◽  
Hao Ai-Min ◽  
...  

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