Improvement of thermoelectric performance in Sb2Te3/Te composites

Abstract

Te-impurity-incorporated Sb 2 Te 3 , i.e., Sb 2 Te 3 + x mol % Te (x = 0, 4, 6, and 9) composites were synthesized by solid-state reaction technique. Analysis of x-ray diffraction indicates not only Te impurity as a second phase but also doping of Te via suppression of inherent Te vacancies in the Sb 2 Te 3 matrix. As a result of this doping and of the change in formation energy of different types of native defects in Sb 2 Te 3 due to synthesis in a Te-rich condition, carrier concentration (n H ) lower than the pristine sample was observed. Low n H along with gradual convergence of valence bands due to progressive suppression of Te vacancies increases the Seebeck coefficient (S) in Te-incorporated samples. Even though Te impurities increase electrical resistivity (ρ), enhanced texturing of lattice planes ensures that charge carrier mobility does not degrade due to Te addition. As a result, a maximum power factor = 17 μW cm −1 K −2 at T = 480 K for x = 6 has been achieved. In addition, Te addition strengthens phonon scattering via an increase of phonon-phonon Umklapp scattering and point-defect-induced scattering of phonons. Due to such a strong phonon scattering, thermal conductivity (κ) decreases, and a reduced lattice thermal conductivity (κ L ), as low as 0.28 W m −1 K −1 at 500 K for x = 6, has been achieved. As a result of simultaneous increase of S and decrease of κ, a high ZT ∼0.87 at 480 K, almost 33% higher than that of the host material, has been achieved.

Enhancing Thermoelectric Performance in P‐Type Sb2Te3‐Based Compounds Through Nb─Ag Co‐Doping with Donor‐Like Effect

“…It will dramatically reduce the hole concentrations in Sb 2 Te 3 . As shown in Equation ( 1): [24] V…”

“…It will dramatically reduce the hole concentrations in Sb 2 Te 3 . As shown in Equation (): [ 24 ] $$$$\begin{equation}{{\mathrm{V^{\prime\prime\prime}}}}_{{\mathrm{Sb}}} + {\mathrm{S}}{{\mathrm{b^{\prime}}}}_{{\mathrm{Te}}} \to {\mathrm{V}}_{{\mathrm{Te}}}^{\centerdot \centerdot } + {\mathrm{Sb}}_{{\mathrm{Sb}}}^ \times + 6{\mathrm{e^{\prime}}}\end{equation}$$$$…”

“…a) Schematic diagram of the donor‐like effect of Sb 2 Te 3 , b) the carrier concentration, Seebeck coefficient and power factor of Sb 2 Te 3 in this study compared with those obtained using other preparation methods at 300 K. [ 16,23,24,29,30 ] …”

“…For instance, Sun et al designed In-Cu co-doping to optimize the transport properties of carriers and phonons in Sb 1.82 In 0.15 Cu 0.03 Te 2.98 , leading to a peak ZT value approach unit at 623 K. [22] However, the quest remains for a high ZT avg within the 300-600 K range, a parameter more important than the peak ZT value in practice. [24,25] Overcoming this challenge is intricate due to the difficulty in enhancing ZT values near room temperature (<400 K).…”

Tuning of thermoelectric performance by modulating vibrational properties in Ni-doped Sb2Te3

“…Sb 2 Te 3 is one of the most popular 3D TIs, and it has potential for TE application in the vicinity of room temperature [7,27]. Sb 2 Te 3 possesses a narrow band gap (∼0.2 eV) [27].…”