Multiscale Defects as Strong Phonon Scatters to Enhance Thermoelectric Performance in Mg₂Sn_1–xSb_x Solid Solutions

Abstract

Mg2Sn based solid solutions have attracted much research interest due to their high thermoelectric (TE) performance in the mid‐temperature region and abundant constituent elements. Further enhancement of the figure of merit zT lies in the effective reduction of the relatively high lattice thermal conductivity. It has been demonstrated that alloying high content of aliovalent Sb (>10%) in Mg2Si analogue can induce Mg vacancies and dense dislocations to greatly suppress the lattice thermal conductivity. In this work, the strategy is extended to the Sb alloyed Mg2Sn to enhance zT. Detailed microstructure investigations reveal the existence of high density of interstitial clusters. By introducing these nanostructures as the additional phonon scattering sources, the theoretical calculation well match the low experimental lattice thermal conductivity. Superior to the Sb alloyed Mg2Si, relatively high power factor is maintained in the Sb alloyed Mg2Sn and the maximum zT of 0.9 at 750 K is obtained. With simpler chemical composition though, the Mg2Sn1–xSbx (x > 0.1) has comparable TE performance with the Sb alloyed Mg2Si0.4Sn0.6 solid solutions, exhibiting promising potential for practical applications. The present work offers a comprehensive understanding of the effect of aliovalent alloying and concomitant complex microstructure in reducing thermal conductivity and enhancing zT.

Adaptable sublattice stabilized high-entropy materials with superior thermoelectric performance

“…, δ ≈ 0.5 x . Such a self-compensation effect has been also observed in other materials like skutterudites, 52 Mg 2− δ Sn 1− x Sb x 53 and Cu 2− δ Te 0.9− y I 0.1 S y . 18,22 The calculated configuration entropy Δ S for Mg 2− δ Si 0.12 Ge 0.13 Sn 0.55 Bi 0.20 is as large as 9.74 J mol −1 K −1 , which is furtherly increased to 11.28 J mol −1 K −1 when considering the extra entropy introduced by the Mg vacancies.…”

“…The data from other studies are included for comparison[42][43][44]54 (the dashed line is a guide to the eye). (d) Temperature dependence of lattice thermal conductivity k L of x = 0.15 and 0.20 samples, in comparison with the data from other studies 7,44,48,50,53.…”

“…(d) Temperature dependence of lattice thermal conductivity k L of x = 0.15 and 0.20 samples, in comparison with the data from other studies. 7,44,48,50,53 Energy & Environmental Science Paper distributed after heat treatments, and no obvious phase separation and spinodal decomposition are observed.…”

Interface Engineering Boosting High Power Density and Conversion Efficiency in Mg2Sn0.75Ge0.25‐Based Thermoelectric Devices

“…[ 14 ] Tremendous subsequent efforts have gravitated toward pursuing much higher PF and ZT . For example, solid solution [ 15–18 ] and doping [ 16,19–21 ] strategies were employed to optimize PF and ZT values via band convergence and strengthening phonon scattering. Additionally, Mg over‐compensation, [ 22,23 ] heat treatment [ 24 ] and surface protection utilizing BN, [ 25 ] Al 2 O 3 , [ 26 ] or aerogel [ 27 ] have brought further stability to the Mg 2 (Si, Sn)‐based TE materials.…”

Enhanced thermoelectric performance of p-type Mg2Sn single crystals via multi-scale defect engineering

“…Among the considered materials, Mg 2 Sn and its derivatives Mg 2 (Si,Ge,Sn) are potential TE materials for operation at moderate temperatures between 400 K and 800 K. 5–34 Good TE performances ( zT ∼ 0.9 at 750 K) have been reported for n-type Mg 2 Sn utilizing point defects and carrier optimization. 26,27 Among the n-type Mg 2 Sn samples, undoped, B-doped, and Sb-doped Mg 2 Sn single crystals (SCs), 22–24,34 Bi-doped Mg 2 Sn polycrystals (PCs), 26 and Sb-doped Mg 2 Sn PCs 27 prepared by applying physical and chemical pressure were found to contain Mg vacancy (V Mg ) as a point defect.…”