The Thermoelectric Properties of n-Type Bismuth Telluride: Bismuth Selenide Alloys Bi2Te3−xSex

Abstract

<jats:p>Alloying bismuth telluride with antimony telluride and bismuth selenide for <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M3"><mml:mi>p</mml:mi></mml:math>- and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M4"><mml:mi>n</mml:mi></mml:math>-type materials, respectively, improves the thermoelectric quality factor for use in room temperature modules. As the electronic and thermal transports can vary substantially, the alloy composition is a key engineering parameter. The <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M5"><mml:mi>n</mml:mi></mml:math>-type Bi<jats:sub>2</jats:sub>Te<jats:sub>3-</jats:sub><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M6"><mml:msub><mml:mrow /><mml:mrow><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:math>Se<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M7"><mml:msub><mml:mrow /><mml:mrow><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:math> alloy lags its <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M8"><mml:mi>p</mml:mi></mml:math>-type counterpart in thermoelectric performance and does not lend itself as readily to simple transport modeling which complicates engineering. Combining literature data with recent results across the entire alloy composition range, the complex electronic structure dynamics and trends in lattice thermal conductivity are explored. Spin-orbit interaction plays a critical role in determining the position and degeneracy of the various conduction band minima. This behavior is incorporated into a two-band effective mass model to estimate the transport parameters in each band. An alloy scattering model is utilized to demonstrate how phonon scattering behaves differently on either side of the intermediate ordered compound Bi<jats:sub>2</jats:sub>Te<jats:sub>2</jats:sub>Se due to chalcogen site occupancy preference. The parametrization of the electronic and thermal transports presented can be used in future optimization efforts.</jats:p>

Discovery of multivalley Fermi surface responsible for the high thermoelectric performance in Yb 14 MnSb 11 and Yb 14 MgSb 11

“…Many well-known thermoelectric systems [Bi 2− x Sb x Te 3 ( 16 ), Bi 2 Te 3− x Se x ( 17 ), PbTe 1− x Se x ( 18 ), La 3− x Te 4 ( 19 ), CoSb 3 ( 20 ), and Mg 2 Si 1− x Sn x ( 21 )] have multiple electronic bands and have Fermi surfaces with high valley degeneracy and low band effective mass. This is because the maximum zT achievable by a thermoelectric material is generally determined by its quality factor where N v is the valley degeneracy or number of Fermi surface pockets, m b * is the band effective mass of one valley, and κ L is the lattice thermal conductivity ( 22 ).…”

Tuning Valley Degeneracy with Band Inversion

“…[8][9][10][11][12][13] Recently, nontrivial electronic structure topologies have also attracted interest as a strategy for increasing the valley degeneracy in materials such as rock-salt SnSe, 14,15 PbTe-SnTe-GeTe alloys, 16 and Bi 2 Te 3 . [17][18][19] In these systems, it is often discussed that band inversion leads to highly-corrugated Fermi surfaces with multiple carrier pockets near the band edge. It is curious however that band inversion leads to high valley degeneracy in some materials while it does not in others; for example, Bi 2 Te 3 has inverted bands and exhibits high valley degeneracy (N V = 6), 20 whereas the chemically similar Bi 2 Se 3 also has inverted bands but exhibits a single carrier pocket at the Γ-point (N V = 1).…”

“…It is curious however that band inversion leads to high valley degeneracy in some materials while it does not in others; for example, Bi 2 Te 3 has inverted bands and exhibits high valley degeneracy (N V = 6), 20 whereas the chemically similar Bi 2 Se 3 also has inverted bands but exhibits a single carrier pocket at the Γ-point (N V = 1). 18,19 While band inversion is a key characteristic of topological insulators in the context of surface/edge states, [21][22][23][24][25] comparatively little is discussed regarding the consequent electronic structure in the bulk.…”

Achieving High Thermoelectric Performance in Rare-Earth Element-Free CaMg 2 Bi 2 with High Carrier Mobility and Ultralow Lattice Thermal Conductivity

“…Recently, solid-state thermoelectric (TE) technology has received a great deal of attention because of its ability to directly convert the waste heat into desirable electricity [3]. The conversion efficiency of thermoelectric device is determined by the dimensionless figure-of-merit ZT = S 2 σT/ðκ E + κ L Þ, in which S, T, σ, κ E , and κ L are Seebeck coefficient, absolute temperature, electrical conductivity, electronic thermal conductivity, and lattice thermal conductivity, respectively [4]. However, the intertwined correlation among the S, σ, and κ E hinders the further enhancement of ZT value.…”