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Title: Structures and thermoelectric properties of the infinitely adaptive series (Bi{sub 2}){sub m}(Bi{sub 2}Te{sub 3}){sub n}

Abstract

The structures and thermoelectric properties of the (Bi{sub 2}){sub m}(Bi{sub 2}Te{sub 3}){sub n} homologous series, derived from stacking hexagonal Bi{sub 2} and Bi{sub 2}Te{sub 3} blocks, are reported. The end members of this series are metallic Bi and semiconducting Bi{sub 2}Te{sub 3}; nine members of the series have been studied. The structures form an infinitely adaptive series and a unified structural description based on a modulated structure approach is presented. The as-synthesized samples have thermopowers (S) that vary from n type for Bi{sub 2}Te{sub 3} to p type for phases rich in Bi{sub 2} blocks but with some Bi{sub 2}Te{sub 3} blocks present, to n type again for Bi metal. The thermoelectric power factor (S{sup 2}/{rho}) is highest for Bi metal (43 {mu}W/K{sup 2} cm at 130 K), followed by Bi{sub 2}Te{sub 3} (20 {mu}W/K{sup 2} cm at 270 K), while Bi{sub 2}Te (m:n=5:2) and Bi{sub 7}Te{sub 3} (m:n=15:6) have 9 {mu}W/K{sup 2} cm (at 240 K) and 11 {mu}W/K{sup 2} cm (at 270 K), respectively. The results of doping studies with Sb and Se into Bi{sub 2}Te are reported.

Authors:
;  [1];  [2]; ;  [3]
  1. Department of Chemistry, Princeton University, Princeton, New Jersey 08544 (United States)
  2. National Centre for High Resolution Electron Microscopy, Department of Nanoscience, Delft Institute of Technology, 2628 CJ, Delft (Netherlands)
  3. Department of Physics, Princeton University, Princeton, New Jersey 08544 (United States)
Publication Date:
OSTI Identifier:
20951429
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. B, Condensed Matter and Materials Physics; Journal Volume: 75; Journal Issue: 19; Other Information: DOI: 10.1103/PhysRevB.75.195203; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ANTIMONY; BISMUTH; BISMUTH TELLURIDES; COMPARATIVE EVALUATIONS; CRYSTAL STRUCTURE; HEXAGONAL CONFIGURATION; POWER FACTOR; SELENIUM; SEMICONDUCTOR MATERIALS; TEMPERATURE DEPENDENCE; TEMPERATURE RANGE 0065-0273 K; THERMOELECTRIC PROPERTIES

Citation Formats

Bos, J. W. G., Cava, R. J., Zandbergen, H. W., Lee, M.-H., and Ong, N. P.. Structures and thermoelectric properties of the infinitely adaptive series (Bi{sub 2}){sub m}(Bi{sub 2}Te{sub 3}){sub n}. United States: N. p., 2007. Web. doi:10.1103/PHYSREVB.75.195203.
Bos, J. W. G., Cava, R. J., Zandbergen, H. W., Lee, M.-H., & Ong, N. P.. Structures and thermoelectric properties of the infinitely adaptive series (Bi{sub 2}){sub m}(Bi{sub 2}Te{sub 3}){sub n}. United States. doi:10.1103/PHYSREVB.75.195203.
Bos, J. W. G., Cava, R. J., Zandbergen, H. W., Lee, M.-H., and Ong, N. P.. Tue . "Structures and thermoelectric properties of the infinitely adaptive series (Bi{sub 2}){sub m}(Bi{sub 2}Te{sub 3}){sub n}". United States. doi:10.1103/PHYSREVB.75.195203.
@article{osti_20951429,
title = {Structures and thermoelectric properties of the infinitely adaptive series (Bi{sub 2}){sub m}(Bi{sub 2}Te{sub 3}){sub n}},
author = {Bos, J. W. G. and Cava, R. J. and Zandbergen, H. W. and Lee, M.-H. and Ong, N. P.},
abstractNote = {The structures and thermoelectric properties of the (Bi{sub 2}){sub m}(Bi{sub 2}Te{sub 3}){sub n} homologous series, derived from stacking hexagonal Bi{sub 2} and Bi{sub 2}Te{sub 3} blocks, are reported. The end members of this series are metallic Bi and semiconducting Bi{sub 2}Te{sub 3}; nine members of the series have been studied. The structures form an infinitely adaptive series and a unified structural description based on a modulated structure approach is presented. The as-synthesized samples have thermopowers (S) that vary from n type for Bi{sub 2}Te{sub 3} to p type for phases rich in Bi{sub 2} blocks but with some Bi{sub 2}Te{sub 3} blocks present, to n type again for Bi metal. The thermoelectric power factor (S{sup 2}/{rho}) is highest for Bi metal (43 {mu}W/K{sup 2} cm at 130 K), followed by Bi{sub 2}Te{sub 3} (20 {mu}W/K{sup 2} cm at 270 K), while Bi{sub 2}Te (m:n=5:2) and Bi{sub 7}Te{sub 3} (m:n=15:6) have 9 {mu}W/K{sup 2} cm (at 240 K) and 11 {mu}W/K{sup 2} cm (at 270 K), respectively. The results of doping studies with Sb and Se into Bi{sub 2}Te are reported.},
doi = {10.1103/PHYSREVB.75.195203},
journal = {Physical Review. B, Condensed Matter and Materials Physics},
number = 19,
volume = 75,
place = {United States},
year = {Tue May 15 00:00:00 EDT 2007},
month = {Tue May 15 00:00:00 EDT 2007}
}
  • The dependence of the electrical conductivity, thermoelectric power and figure of merit on the grain size in cold pressed Bi{sub 1.8}Sb{sub 0.2{minus}{ital x}}In{sub {ital x}}Te{sub 2.85}Se{sub 0.15}, where {ital x}=0, 0.01, 0.02 was measured. The influence of the indium content and grain size on the thermoelectric properties is discussed. In this materials the changes of the free carrier concentration are due to the interaction between antisite-defects and vacancies during the sintering. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.
  • Using high-pressure magnetotransport techniques we have discovered superconductivity in Bi 2Te, a member of the infinitely adaptive (Bi 2)m(Bi 2Te 3)n series, whose end members, Bi and Bi 2Te 3, can be tuned to display topological surface states or superconductivity. Bi 2Te has a maximum T c = 8.6 K at P = 14.5 GPa and goes through multiple high pressure phase transitions, ultimately collapsing into a bcc structure that suggests a universal behavior across the series. High-pressure magnetoresistance and Hall measurements suggest a semi-metal to metal transition near 5.4 GPa, which accompanies the hexagonal to intermediate phase transition seenmore » via x-ray diffraction measurements. In addition, the linearity of H c2 (T) exceeds the Werthamer-Helfand-Hohenberg limit, even in the extreme spin-orbit scattering limit, yet is consistent with other strong spin-orbit materials. Furthermore, considering these results in combination with similar reports on strong spin-orbit scattering materials seen in the literature, we suggest the need for a new theory that can address the unconventional nature of their superconducting states.« less
  • The phase stability of the (Bi{sub 2}){sub m} (Bi{sub 2}Te{sub 3}){sub n} natural superlattices has been investigated through the low temperature solid state synthesis of a number of new binary Bi{sub x}Te{sub 1-x} compositions. Powder X-ray diffraction revealed that an infinitely adaptive series forms for 0.44{<=}x{<=}0.70, while an unusual 2-phase region with continuously changing compositions is observed for 0.41{<=}x{<=}0.43. For x>0.70, mixtures of elemental Bi and an almost constant composition (Bi{sub 2}){sub m} (Bi{sub 2}Te{sub 3}){sub n} phase are observed. Rietveld analysis of synchrotron X-ray powder diffraction data collected on Bi{sub 2}Te (m=2, n=1) revealed substantial interchange of Bi andmore » Te between Bi{sub 2} and Bi{sub 2}Te{sub 3} blocks, demonstrating that the block compositions are variable. All investigated phase pure compositions are degenerate semiconductors with low residual resistivity ratios and moderate positive magnetoresistances (R/R{sub 0}=1.05 in 9 T). The maximum Seebeck coefficient is +80 {mu}V K{sup -1} for x=0.63, leading to an estimated thermoelectric figure of merit, zT=0.2 at 250 K. - Graphical abstract: An infinite number of possible (Bi{sub 2}){sub m} (Bi{sub 2}Te{sub 3}){sub n} structures exist for Bi{sub x}Te{sub 1-x} compositions between x=0.44 and x=0.70. Compositions near x=2/3 are promising p-type thermoelectrics. Highlights: Black-Right-Pointing-Pointer Phase Stability of the (Bi{sub 2}){sub m}{center_dot}(Bi{sub 2}Te{sub 3}){sub n} Natural Superlattices. Black-Right-Pointing-Pointer Thermoelectric Properties in the Bi{sub x}Te{sub 1-x} Phase Diagram. Black-Right-Pointing-Pointer Crystal Structure of Bi{sub 2}Te from Synchrotron X-ray Powder Diffraction.« less
  • Ag-doped n-type (Bi{sub 2}Te{sub 3}){sub 0.9}-(Bi{sub 2-} {sub x} Ag {sub x} Se{sub 3}){sub 0.1} (x=0-0.4) alloys were prepared by spark plasma sintering and their physical properties evaluated. When at low Ag content (x=0.05), the temperature dependence of the lattice thermal conductivity follows the trend of (Bi{sub 2}Te{sub 3}){sub 0.9}-(Bi{sub 2}Se{sub 3}){sub 0.1}; while at higher Ag content, a relatively rapid reduction above 400 K can be observed due possibly to the enhancement of scattering of phonons by the increased defects. The Seebeck coefficient increases with Ag content, with some loss of electrical conductivity, but the maximum dimensionless figure ofmore » merit ZT can be obtained to be 0.86 for the alloy with x=0.4 at 505 K, about 0.2 higher than that of the alloy (Bi{sub 2}Te{sub 3}){sub 0.9}-(Bi{sub 2}Se{sub 3}){sub 0.1} without Ag-doping. - Graphical abstract: The temperature dependence of dimensionless thermoelectric figure of merit ZT for different (Bi{sub 2}Te{sub 3}){sub 0.9}-(Bi{sub 2-} {sub x} Ag {sub x} Se{sub 3}){sub 0.1} (x=0-0.4) alloys prepared by spark plasma sintering.« less
  • n-Type (Bi{sub 2}Te{sub 3}){sub 0.9}-(Bi{sub 2-x}Cu{sub x}Se{sub 3}){sub 0.1} (x=0-0.2) alloys with Cu substitution for Bi were prepared by spark plasma-sintering technique and their structural and thermoelectric properties were evaluated. Rietveld analysis reveals that approximate 9.0% of Bi atomic sites are occupied by Cu atoms and less than 4.0 wt% second phase Cu{sub 2.86}Te{sub 2} precipitated in the Cu-doped parent alloys. Measurements show that an introduction of a small amount of Cu (x{<=}0.1) can reduce the lattice thermal conductivity ({kappa}{sub L}), and improve the electrical conductivity and Seebeck coefficient. An optimal dimensionless figure of merit (ZT) value of 0.98 ismore » obtained for x=0.1 at 417 K, which is obviously higher than those of Cu-free Bi{sub 2}Se{sub 0.3}Te{sub 2.7} (ZT=0.66) and Ag-doped alloys (ZT=0.86) prepared by the same technologies. - Graphical abstract: After Cu-doping with x=0.1, the highest ZT value of 0.98 is obtained at 417 K, which is about 0.32 and 0.12 higher than those of Cu-free Bi{sub 2}Se{sub 0.3}Te{sub 2.7} and the Ag-doped alloys (Bi{sub 2}Te{sub 3}){sub 0.9}-(Bi{sub 2-x}Ag{sub x}Se{sub 3}){sub 0.1} (x=0.4), respectively.« less