Twin-driven thermoelectric figure-of-merit enhancement of Bi₂Te₃ nanowires

Abstract

Thermoelectric figure-of-merits (ZT) are enhanced or degraded by crystal defects such as twins and excess atoms that are correlated with thermal conductivity (k) and carrier concentration (n). For Bi2Te3, it is unclear whether the crystal defects can enhance ZT without a degradation in the thermopower factor. In the present study, n-type Bi2Te3 nanowires (NWs) are electrochemically synthesized to have twin-free (TF) or twin-containing (TC) microstructures with a ZT of 0.10 and 0.08, respectively, at 300 K. The ZTs of TF and TC NWs remarkably increase up to 0.21 and 0.31, when heat-treatments cause n-reduction and twins induce phonon scattering, as follows: first, the enhancement of the Seebeck coefficient from -70 to -98 μV K(-1) for TF NWs and from -57 to -143 μV K(-1) for TC NWs, by virtue of n-reduction; secondly, twin-driven k-reduction from 1.9 to 1.4 W m(-1) K(-1) of TC NWs, while the k of TF NWs increases from 2.3 to 2.6 W m(-1) K(-1) due to the enhanced carrier mobility. The lattice thermal conductivities of TC NW are lowered from 1.1 to 0.8 W m(-1) K(-1) by phonon scattering at twins. Density functional theory calculations indicate that twins do not significantly influence the Seebeck coefficient of Bi2Te3. It is strongly recommended that twins be incorporated with an optimum carrier concentration to enhance the ZT of Bi2Te3.

Quantum electrical transport properties of topological insulator Bi 2 Te 3 nanowires

“…Bi 2 Te 3 nanowires were grown by electrochemical deposition by using porous anodic aluminum oxide membrane nanotemplates. [28] The cylindrical nanowires had a typical diameter and length of ~60 nm and 810 μm, respectively ( Fig. 1(a)).…”

Dramatically reduced lattice thermal conductivity of Mg2Si thermoelectric material from nanotwinning

“…Twin boundaries (TBs), a thermodynamically stable planar defect, could provide another phonon scattering source to effectively suppress κ L [36][37][38] [38]. These findings suggest that TBs play significant roles in phonon scattering and κ L reduction without degrading electronic transport properties.…”

Effect of SrTiO3 Nanoparticles in Conductive Polymer on the Thermoelectric Performance for Efficient Thermoelectrics

“…On the other hand, the SrTiO 3 /PANI composites showed negative S values due to the N-type semiconducting behavior of SrTiO 3 ; furthermore, the absolute S value increased along with the SrTiO 3 content because of the high S of SrTiO 3 at room temperature (~−300 µV/K) [40]. The Sebeck coefficient of a material is generally inversely proportional to µ and this trend is described by the following model [41,42]:…”