Physical Insights on the Lattice Softening Driven Mid‐Temperature Range Thermoelectrics of Ti/Zr‐Inserted SnTe—An Outlook Beyond the Horizons of Conventional Phonon Scattering and Excavation of Heikes’ Equation for Estimating Carrier Properties

Abstract

Most of the best known SnTe‐based materials exhibit an attractive thermoelectric figure of merit (zT) only at the high‐temperature regime, but their performance at the low‐mid temperature ranges is quite uninspiring, and this discordance necessitates a large temperature gradient (∆T ≥ 550 K) to effectuate a reasonable efficiency, η. Here, the transition elements, Ti and Zr, that have not been used in the past are tried as dopants for SnTe and an enhanced device/average zT and/or η are reported with a lower ∆T ≈ 400 K and without the requisite for a stupendous peak/maximum zT. This notable performance emanates from—i) improved weighted mobility by optimally balancing between effective mass, carrier concentration, and mobility, ii) coupling of charge carriers with magnetic entropy, and the paramount factor being the iii) weakening of the chemical bonds (lattice softening). The thermal damping caused by lattice softening affects the phonon group velocity and the elastic properties, and the resultant increase in the degree of anharmonicity and the high density of internal strain‐fields, along with the phonon scattering effects, play an active role in tuning the overall thermoelectric performance. This work also excavates/opens up the discussion of applying the Heikes’ equation to qualitatively compare the trend of charge carriers for a given thermoelectric material system.

Effect of Nanostructuring on the Thermoelectric Properties of β-FeSi2

“…The efficiency of a thermoelectric module is proportional to the figure of merit, consequently, it is expected to reach a high ZT to obtain high performances. However, the efficiency is still limited for the thermogeneration of electricity compared to electricity produced by turbines [2], and most of the new thermoelectric materials, as well as the conventional materials, are made of rare, expensive and toxic elements such as chalcogen or pnictogen atoms or have stability problems [3][4][5]. To overwhelm these last problems, silicide intermetallics such as Mg 2 Si 1-x Sn x , higher manganese silicides or β-FeSi 2 were developed [6].…”

Potential of Recycled Silicon and Silicon-Based Thermoelectrics for Power Generation

“…For instance, thermal conductivity comprises lattice (κ lat ), bipolar (κ bi ), and electrical (κ ele ) components [12][13][14][15][16][17][18][19][20][21]. Much of the work in decreasing thermal conductivity is aimed towards κ lat , utilizing strategies such as downscaling and isovalent substitution, which hinder the transport of heat-carrying acoustic phonons [22][23][24][25][26][27][28][29][30][31][32][33][34]. More recently, machine learning has been popularly used in conjunction with materials science discovery and air materials development [35][36][37][38].…”

Physical Intuition to Improve Electronic Properties of Thermoelectrics

“…The absence of lone pairs in Mg/Mn weakens the quenching of lone pairs in PbTe, resulting in lower L band energy [36]. In addition, band convergence in PbTe and SnTe can be achieved by doping of Zn, Cd, Mg, Mn, or Ca, all of which are without s 2 lone pair [37][38][39][40][41][42][43][44]. A very useful reference for designing band convergence and resonant doping in binary chalcogenides can be found in Ref.…”