Experimental and theoretical study of β-AsTe under hydrostatic pressure
We report a joint experimental and theoretical high-pressure study of the structural and vibrational properties of tetradymite-like ( R 3&cmb.macr; m ) β-As 2 Te 3 . Two samples have been characterized by angle-dispersive synchrotron powder X-ray diffraction and Raman scattering measurements und...
Saved in:
| Published in | Journal of materials chemistry. C, Materials for optical and electronic devices Vol. 11; no. 3; pp. 137 - 155 |
|---|---|
| Main Authors | , , , , , , , , , , , |
| Format | Journal Article |
| Published |
19.01.2023
|
| Online Access | Get full text |
Cover
Loading…
| Summary: | We report a joint experimental and theoretical high-pressure study of the structural and vibrational properties of tetradymite-like (
R
3&cmb.macr;
m
) β-As
2
Te
3
. Two samples have been characterized by angle-dispersive synchrotron powder X-ray diffraction and Raman scattering measurements under hydrostatic conditions with the help of
ab initio
calculations. One sample was synthesized at high pressure and high-temperature conditions with a Paris-Edinburg cell and the other by the melt-quenching technique. Both β-As
2
Te
3
samples show the same properties and exhibit two isostructural phase transitions of order higher than 2,
i.e.
of electronic origin, near 2.0(2) and 6.0(5) GPa that are compatible with the changes predicted by recent electronic band structure calculations. The first isostructural phase transition can be attributed to the topological quantum phase transition from a trivial insulator to a topological insulator, passing through a 3D Dirac topological semimetal. This topological transition, specific to β-As
2
Te
3
, is not observed in isostructural Te-based sesquichalcogenides α-Sb
2
Te
3
and α-Bi
2
Te
3
that are topological insulators at room conditions. The second isostructural phase transition is likely related to an insulator-metal transition. Additionally, we have observed two partially reversible first-order phase transitions in β-As
2
Te
3
above 10 and 17 GPa. We have found a high anharmonic behavior of the two Raman-active modes with the lowest frequencies in β-As
2
Te
3
that explains the already reported ultra-low lattice thermal conductivity of β-As
2
Te
3
. Moreover, we have studied the similarities of β-As
2
Te
3
with α-Sb
2
Te
3
and α-Bi
2
Te
3
(two of the best thermoelectric materials), thus providing insights into the origin of the ultra-low lattice thermal conductivity values in these compounds related to unconventional chemical bonds present in these isostructural materials.
Schematic view of the β-As
2
Te
3
polymorph (S. G.
R
3&cmb.macr;
m
) including the polyhedral units (AsTe6, TeAS6, and Te2 antiprism of β-As
2
Te
3
) of the hexagonal unit cell. Images of the experimental and theoretical techniques used are shown as well as the main results reported. |
|---|---|
| Bibliography: | PACS: 31.15.A-, 61.05.cp, 62.50.-p, 64.30.Jk, 71.15.Mb and α-As Electronic supplementary information (ESI) available: Rietveld refinements of sample #2 at ambient pressure; experimental HP-XRD patterns of sample #2 at selected pressures; Rietveld refinements similar pressure of sample #1 and #2; sequences of experimental HP-XRD patterns of sample #1 and #2; relaxed XRD pattern of sample #1; comparative of experimental XRD patterns of β-As α-Sb https://doi.org/10.1039/d2tc03357g including SOC; theoretical (PBE + D3) dielectric constants and average born effective charges of As and Te atoms; schematic view of the crystalline structure of α-As vs. of As Te 2 3 pressure; theoretical (PBE + D3) interlayer and intralayer distances for isostructural β-As pressure; theortical bond angle variance, quadratic elongation, and effective coordination number of some octahedrons; bader charges in β-As and α-Bi at about 14 GPa. See DOI with β-Bi at about 17.6 GPa; theoretical (PBE + D3) axial compressibilities and bulk modulus for isostructural β-As |
| ISSN: | 2050-7526 2050-7534 |
| DOI: | 10.1039/d2tc03357g |