Beneficial Contribution of Alloy Disorder to Electron and Phonon Transport in Half‐Heusler Thermoelectric Materials

Abstract

Electron and phonon transport characteristics determines the potential of thermoelectric materials for power generation or refrigeration. This work shows that, different from most of high performance thermoelectric materials with dominant acoustic phonon scattering, the promising ZrNiSn based half‐Heusler thermoelectric solid solutions exhibit an alloy scattering dominated charge transport. A low deformation potential and a low alloy scattering potential are found for the solid solutions, which is beneficial to maintain a relatively high electron mobility despite of the large effective mass, and can be intrinsic favorable features contributing to the noticeably high power factors of ZrNiSn based alloys. A quantitive description of the different phonon scattering mechanisms suggests that the point defect scattering is the most important mechanism that determines the phonon transport process of the solid solutions. The present results indicate that alloying can be an effective approach for such materials systems to enhance thermoelectric figure of merit ZT by reducing phonon thermal conductivity, while minimizing the deterioration of charge mobility due to the low alloy scatteirng potential.

Electronic origin of the high thermoelectric performance of GeTe among the p-type group IV monotellurides

“…Effective approaches include nanostructuring, 2-7 lattice anharmonicity, 8,9 liquid phonons, 10,11 vacancy [12][13][14] or interstitial 15 point defects and a low sound velocity. 16 Band engineering concepts including a large number of degenerated bands, [17][18][19][20][21][22][23][24][25] a low band effective mass 26 and weak carrier scattering 27 have also proven to be successful in enhancing the TE performance. The knowledge of the band structure is thus critical for band engineering and optimizing the electrical transport of TE materials.…”

Uncovering high thermoelectric figure of merit in (Hf,Zr)NiSn half-Heusler alloys

“…On the other hand, the study of the effect of intrinsic disorder on TE properties of HH phases has recently gained attention. [7][8][9][10] HH phases are prone to antisite disorder, as shown in the inset of Figure 1. [11][12][13] This intrinsic disorder can adversely influence the PF and thus ZT.…”

Attaining high mid-temperature performance in (Bi,Sb)2Te3 thermoelectric materials via synergistic optimization

“…It is useful to compare the optimal operation temperature ('service temperature') of state-of-the-art TE materials and the temperature range in which most of the waste heat is produced. State-of-the-art TE materials have their best zT values (those between 1 and 2) in different temperature regimes; for example, Bi 2 Te 3 works best near room temperature, 3,4 whereas PbTe, Mg 2 Si 1-x Sn x , Half-Heusler compounds and filled skutterudites generally reach their best performance above 600 K. [5][6][7][8][9][10][11][12][13][14] There is a conspicuous lack of high-performance TE materials between 400 and 600 K, the mid-temperature range. Meanwhile, most of the waste heat produced (including various industrial sectors and automobile exhausts) is in the temperature range of 400-900 K, and hence it is unharvested.…”