Extremely long period-stacking structure in the Sb–Te binary system

Kifune, Kouichi; Kubota, Yoshiki; Matsunaga, Toshiyuki; Yamada, Noboru

doi:10.1107/s0108768105017714

Cited by 96 publications

(81 citation statements)

References 8 publications

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“…Since it has limited solubility to Sb with relatively moderate slope of Sb-solvus, it is likely to decompose to δ+Sb 2 Te 3 phase mixture [28,29,[100][101][102][103], whereas Sb 2 Te 3 is equilibrium phase and may appear as diferent homologous forms [72,73,[104][105][106][107]. Precipitation of antimony-telluride second phase in δ-matrix is expected to afect TE performance due to contributions from both matrix and precipitate phases or variation of the average matrix composition.…”

Section: Formation Of Sb 2 Te 3 and Sb 8 Te 3 (R-3m) Phasesmentioning

confidence: 99%

Silver-Antimony-Telluride: From First-Principles Calculations to Thermoelectric Applications

Amouyal¹

2016

Thermoelectrics for Power Generation - A Look at Trends in the Technology

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Silver-antimony-telluride (AgSbTe 2 ) based compounds have emerged as a promising class of materials for thermoelectric (TE) power generation at the mid-temperature range. This Chapter demonstrates utilization of irst-principles calculations for predicting TE properties of AgSbTe 2 -based compounds and experimental validations. Predictive calculations of the efects of La-doping on vibrational and electronic properties of AgSbTe 2 compounds are performed applying the density functional theory (DFT), and temperature-dependent TE transport coeicients are evaluated applying the Bolzmann transport theory (BTE). Experimentally, model ternary (AgSbTe 2 ) and quaternary (3 at. % La-AgSbTe 2 ) compounds were synthesized, for which TE transport coeicients were measured, indicating that thermal conductivity decreases due to La-alloying. The later also reduces electrical conductivity and increases Seebeck coeicients. All trends correspond with those predicted from irst-principles. Thermal stability issues are essential for TE device operation at service conditions, e.g. changes of matrix composition and second-phase precipitation, and are also addressed in this study on both computational and experimental aspects. It is shown that La-alloying afects TE igure-of-merit positively, e.g., improving from 0.35 up to 0.50 at 260 °C. We highlight the universal aspects of this approach that can be applied for other TE compounds. This enables us screening their performance prior to synthesis in laboratory.Keywords: silver-antimony-telluride, irst-principles calculations, thermoelectric transport properties, Bolzmann transport theory, latice dynamics, thermal stability IntroductionIt is of utmost technological importance to develop predictive tools that will provide us with information about design of materials' functional properties. In this context, density functional theory (DFT) irst-principle calculations ofer us such possibilities [1][2][3][4] Despite of relatively high ZT values of AgSbTe 2 phase, it is still challenging to increase them to the range of 2-3. Reaching at this limit will enable us employing this material for energy conversion at power levels >500 W [34]. Reduction in latice thermal conductivity is a conventional way to enhance TE performance and is achieved by either doping with solute elements [35] or formation of second phases to stimulate phonon scatering [36][37][38]. These latice defects afect, of course, electronic properties, mainly electrical conductivity and Seebeck coeicient. Atempts to improve TE properties of AgSbTe 2 -based alloys by doping with diferent elements [19,25,[39][40][41][42][43][44][45][46][47] Notwithstanding the aforementioned successful experimental and computational atempts, a set of experimental routines, that is initiated and directed by predictions from irst principles for complete TE performance or any other computational procedure, is missing. Thermoelectrics for Power Generation -A Look at Trends in the Technology 148A signiicant step in this direction is introduced by o...

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Section: Formation Of Sb 2 Te 3 and Sb 8 Te 3 (R-3m) Phasesmentioning

confidence: 99%

Silver-Antimony-Telluride: From First-Principles Calculations to Thermoelectric Applications

Amouyal¹

2016

Thermoelectrics for Power Generation - A Look at Trends in the Technology

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“…The investigated compounds had a very similar in-plane lattice parameter a, but the c parameter varied strongly with the amount of Sb and c values up to 100Å have been found. 11 In particular, the Sb 2 Te structure of the δ phase has a hexagonal unit cell containing 9 layers: Sb 4 (Sb 2 Te 3 ), with a = 4.272Å and c = 17.633Å, 15 shown in the middle in Fig. 1, and the SbTe structure of the γ phase has a hexagonal unit cell containing 12 layers: Sb 2 (Sb 2 Te 3 ) 2 , with a = 4.26Å and c = 23.9Å, 8 shown on the right in Fig.…”

Section: Introductionmentioning

confidence: 99%

“…In the past decades [8][9][10][11][12][13][14] several Sb-rich compounds (mainly in the δ phase) have been studied and characterized and it turns out that all known Sb-Te compounds with an Sb concentration above 40 at. % are composed of bilayers of Sb and Sb 2 Te 3 units and can be represented by the general formula (Sb 2 ) n (Sb 2 Te 3 ) m .…”

Section: Introductionmentioning

confidence: 99%

Stability of Sb-Te layered structures: First-principles study

Govaerts¹,

Sluiter²,

Partoens³

et al. 2012

Phys. Rev. B

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Using an effective one-dimensional cluster expansion in combination with first-principles electronic structure calculations we have studied the energetics and electronic properties of Sb-Te layered systems. For a Te concentration between 0 and 60 at. % an almost continuous series of metastable structures is obtained consisting of consecutive Sb bilayers next to consecutive Sb 2 Te 3 units, with the general formula (Sb 2 ) n (Sb 2 Te 3 ) m (n,m = 1,2, . . .). Between 60 and 100 at. % no stable structures are found. We account explicitly for the weak van der Waals bonding between Sb bilayers and Sb 2 Te 3 units by using a recently developed functional, which strongly improves the interlayer bonding distances. At T = 0 K, no evidence is found for the existence of two separate single-phase regions δ and γ and a two-phase region δ + γ . Metastable compounds with a Te concentration between 0 and 40 at. % are semimetallic, whereas compounds with a Te concentration between 50 and 60 at. % are semiconducting. Compounds with an odd number of Sb layers are metallic and have a much higher formation energy than those with an even number of consecutive Sb layers, thereby favoring the formation of Sb bilayers.

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“…These procedures resulted in silver-colored single crystals of ∼5 mm size. We note here that several other compositions of the (Sb 2 ) m -(Sb 2 Te 3 ) n family have been synthesized in crystalline form as small grains [19]. Their microscopic size, however, impedes access to the electronic structure by ARPES.…”

mentioning

confidence: 99%

“…This provides for an "infinitely adaptive series" of * marco.grioni@epfl.ch distinct compounds between the end member compositions Sb 2 Te 3 (m = 0) and Sb (n = 0) [17][18][19][20] that are known to be a TI and a topological semimetal, respectively [21][22][23][24][25][26][27]. Early experiments assessed the topological nature of bulk Sb and Sb-Bi alloys [21,22].…”

mentioning

confidence: 99%

Engineering the topological surface states in the(Sb2)m−Sb2Te3(m=0
Johannsen
¹
,
Autès
²
,
Crepaldi
³

et al. 2015
Phys. Rev. B
20
1
20
0
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We investigate the evolution of both the occupied and unoccupied electronic structure in representative compounds of the infinitely adaptive superlattice series (Sb 2 ) m -Sb 2 Te 3 (m = 0-3) by means of angle-resolved photoemission spectroscopy and time-delayed two-photon photoemission, combined with first-principles band-structure calculations. We discover that the topological nature of the surface states and their spin texture are robust, with dispersions evolving from linear (Dirac-like) to parabolic (Rashba-like) along the series, as the materials evolve from semiconductors to semimetals. Our findings provide a promising strategy for engineering the topological states with the desired flexibility needed for realizing different quantum phenomena and spintronics applications. Three-dimensional topological insulators (TIs) are materials where the topological properties of the insulating bulk band structure guarantee the existence of metallic surface states [1,2]. These topological surface states (TSS) are characterized by a Dirac-like energy-momentum dispersion and by a helical spin-momentum texture [3,4] that protects them against backscattering and localization [5,6]. TIs are promising materials for spintronics and provide an exceptional playground to study novel physical phenomena [7,8]. Possible applications depend on the ability to control the electronic properties of the TSS. Common strategies for achieving such a control involve chemical substitution and adsorbate doping [9][10][11][12][13]. Alternatively, it has been proposed that multilayer heterostructures could be used to obtain artificial TIs with tunable properties defined by the stacking sequences of the constituent two-dimensional building blocks [14][15][16].In this Rapid Communication, we demonstrate the possibility of TSS band-structure engineering in the naturally occurring homologous series of topological superlattices (Sb 2 ) m -(Sb 2 Te 3 ) n composed of Sb 2 bilayers (BLs) and Sb 2 Te 3 quintuple layers (QLs) [17,18]. This series enables a systematic investigation of the evolution of topological properties as a function of the stacking sequence of the constituent building blocks. Our results show that the topological states are remarkably robust and that their dispersion can be tuned in the explored range (m = 0-3; n = 1), and in bulk Sb, with an unchanging strong Z 2 index ν 0 = 1.All (Sb 2 ) m -(Sb 2 Te 3 ) n compounds display layered crystal structures produced by ordered stacking of Sb 2 Te 3 QLs and antimony BLs along the c axis of the hexagonal unit cell. This provides for an "infinitely adaptive series" of * marco.grioni@epfl.ch distinct compounds between the end member compositions Sb 2 Te 3 (m = 0) and Sb (n = 0) [17][18][19][20] that are known to be a TI and a topological semimetal, respectively [21][22][23][24][25][26][27]. Early experiments assessed the topological nature of bulk Sb and Sb-Bi alloys [21,22]. By contrast, the experimental observation of the predicted TSS in Sb 2 Te 3 has been delayed by the intrinsic p doping ...

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Extremely long period-stacking structure in the Sb–Te binary system

Cited by 96 publications

References 8 publications

Silver-Antimony-Telluride: From First-Principles Calculations to Thermoelectric Applications

Silver-Antimony-Telluride: From First-Principles Calculations to Thermoelectric Applications

Stability of Sb-Te layered structures: First-principles study

Engineering the topological surface states in the(Sb2)m−Sb2Te3(m=0
Johannsen
¹
,
Autès
²
,
Crepaldi
³

et al. 2015
Phys. Rev. B
20
1
20
0
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Extremely long period-stacking structure in the Sb–Te binary system

Cited by 96 publications

References 8 publications

Silver-Antimony-Telluride: From First-Principles Calculations to Thermoelectric Applications

Silver-Antimony-Telluride: From First-Principles Calculations to Thermoelectric Applications

Stability of Sb-Te layered structures: First-principles study

Engineering the topological surface states in the(Sb2)m−Sb2Te3(m=0Johannsen1, Autès2, Crepaldi3 et al. 2015Phys. Rev. B201200View full textAdd to dashboardCite

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Engineering the topological surface states in the(Sb2)m−Sb2Te3(m=0
Johannsen
¹
,
Autès
²
,
Crepaldi
³

et al. 2015
Phys. Rev. B
20
1
20
0
View full text Add to dashboard Cite