Role of sintering temperature on electronic and mechanical properties of thermoelectric material: A theoretical and experimental study of TiCoSb half-Heusler alloy

Realization of Band Convergence in p-Type TiCoSb Half-Heusler Alloys Significantly Enhances the Thermoelectric Performance

“…The substitution of Sn for Sb does not significantly affect the mechanical properties. For all of the samples, the microhardness remains in the range 7.9 - 8.8 GPa, which is comparable to the values measured in prior reports on TiCoSb. , The observed microhardness values are much higher than those of the commercial materials (Bi 2 Te 3 , PbTe) and are close to the values reported for other HH alloys. , Similarly, the fracture toughness of all samples was found to be in the range 1.7 - 2.2 MPa·m –1/2 , which are very close to those reported for HH alloys. , …”

“…To further confirm band convergence and better explain the electronic transport properties, electronic band structure calculations have been performed for pristine TiCoSb, TiCo 0.85 Fe 0.15 Sb, and TiCo 0.85 Fe 0.15 Sb 0.97 Sn 0.03 (Figure ). For TiCoSb, our previously predicted crystal structure was used . Our first-principles calculations predict that pure TiCoSb has an indirect band gap of 1.05 eV (Figure a,d).…”

“…For TiCoSb, our previously predicted crystal structure was used. 49 Our first-principles calculations predict that pure TiCoSb has an indirect band gap of 1.05 eV (Figure The valence band maximum (VBM) and conduction band minimum (CBM) are located at the and X points of the BZ, respectively. The has a small energy difference of 51 meV with the band edge at the L point, which is very close to that found in prior reports on TiCoSb.…”

“…Several families of TE materials have been investigated over the last few decades for power generation applications at high temperatures, such as chalcogenides, skutterudites, silicides, and clathrates . Among them, half-Heuslers (HHs) ,, are promising compounds for mid- to high-temperature applications due to their excellent mechanical robustness, high thermal stability, and environmentally friendly and low-cost constituting elements in addition to their good TE performance. ,− HH compounds crystallize in the cubic MgAgAs structure type described in the F 4̅3 m space group (space group no. 216).…”

“…216). The face-centered cubic (fcc) lattice can be viewed as three interpenetrated sublattices of equal unit cell size. , This family offers a wide range of chemical compositions, even though compounds with 18 valence-electron count (VEC) are the most promising for thermoelectric applications due to their narrow band gap and sharp slope in the density of states near the Fermi level. , Among HH compounds, XNiSn and XCoSb (X = Ti, Zr, Hf) have been widely explored, notably leading to n-type compositions (with X = Zr) with high thermoelectric performance. − ,− In comparison, p-type analogues based on TiCoSb exhibit lower TE performance despite various approaches employed such as doping, ,− nanostructuring, and nanocomposite …”