Realizing p-type NbCoSn half-Heusler compounds with enhanced thermoelectric performance via Sc substitution

Abstract

N-type half-Heusler NbCoSn is a promising thermoelectric material due to favourable electronic properties. It has attracted much attention for thermoelectric applications while the desired p-type NbCoSn counterpart shows poor thermoelectric performance. In this work, p-type NbCoSn has been obtained using Sc substitution at the Nb site, and their thermoelectric properties were investigated. Of all samples, Nb 0.95 Sc 0.05 CoSn compound shows a maximum power factor of 0.54 mW/mK 2 which is the highest among the previously reported values of p-type NbCoSn. With the suppression of thermal conductivity, p-type Nb 0.95 Sc 0.05 CoSn compound shows the highest measured figure of merit ZT = 0.13 at 879 K.

Thermoelectric properties of n-type half-Heusler NbCoSn with heavy-element Pt substitution

“…Ti, Mo, and Hf were initially described as weak p-type acceptors for NbCoSn by Kawaharada et al 31,32 Later, Ferluccio et al 33 reported Zr-and Tidoped NbCoSn with a positive Seebeck coefficient. Sc was also used as an acceptor for NbCoSn by Yan et al 34 However, the low electrical conductivities in these p-type NbCoSn samples suggested that the electrical power factors were not yet optimal, preventing the attainment of the predicted high performance. The interstitial Co, predicted to be the most stable intrinsic defect in NbCoSn by Bhattacharya and Madsen, 29 was thought to be the possible 'killer-defect', hindering the realization of heavily hole-doped NbCoSn.…”

The structural stability, lattice dynamics, electronic, thermophysical, and mechanical properties of the inverse perovskites A 3 OX: A comparative first‐principles study

“…A combination of high S , σ , and low κ is requisite for high‐power conversion efficiency, ZT. The inter‐dependencies of all thermodynamic parameters require to accommodate one single parameter by improving others to develop highly efficient thermoelectric material 69 . To approximate ZT value, the power factor ( S 2 σ ) is calculated for all the A 3 OX alloys which present a linear increase in temperature as displayed in Figure 5J‐L.…”

“…The interdependencies of all thermodynamic parameters require to accommodate one single parameter by improving others to develop highly efficient thermoelectric material. 69 To approximate ZT value, the power factor (S 2 σ) is calculated for all the A 3 OX alloys which present a linear increase in temperature as displayed in Figure 5J-L. Power factor rises gradually at cost of coordinated higher electrical conductivity and Seebeck coefficient, and reduced lattice thermal conductivity, fulfilling the precondition for the higher power factor. This estimate all A 3 OX alloys being optimized as a better ZT value owning HH alloys delivering a remarkable performance as a thermoelectric material.…”

Improved Thermoelectric Performance in N-Type Half-Heusler NbCoSn by Heavy-Element Pt Doping

“…A possible hindrance in the realization of the heavily hole-doped NbCoSn could be the presence of interstitial Co, predicted to be the most stable intrinsic defect in NbCoSn by Bhattacharya and Madsen 29 , which could act as a 'killerdefect'. Excess Co was found in the synthesized NbCoSn samples, despite being designed to have the nominal composition 34,35 . A similar phenomenon was also observed in the ZrNiSn system, in which excess Ni significantly changes the electronic structure and transport properties 36,37 .…”

“…Ti, Mo, and Hf were initially described as weak p-type acceptors for NbCoSn by Kawaharada et al 31,32 Later, Ferluccio et al 33 reported Zr-and Ti-doped NbCoSn with a positive Seebeck coefficient. Sc was also used as an acceptor for NbCoSn by Yan et al 34 However, the low electrical conductivities in these p-type NbCoSn samples suggested that the electrical power factors were not yet optimal, preventing the attainment of the predicted high performance. A possible hindrance in the realization of the heavily hole-doped NbCoSn could be the presence of interstitial Co, predicted to be the most stable intrinsic defect in NbCoSn by Bhattacharya and Madsen 29 , which could act as a 'killerdefect'.…”