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<p>Half-Heusler compounds based on TiCoSb have attracted considerable interest in thermoelectric applications, with most prior efforts relying on single-element substitution (Nb, Ta, or Hf) to improve either electronic or phonon transport. However, the low/moderate thermoelectric figure of merit hinders its applications in many industrial fields. In this work, we demonstrate a dual Nb–Hf substitution strategy at the Ti site, designed to simultaneously optimize carrier transport and enhance phonon scattering within a single compositional framework. Unlike earlier Nb-, Ta-, or Hf-doped TiCoSb systems that primarily target isolated transport channels, the present approach enables cooperative modulation of electrical and thermal properties, resulting in an overall improvement in thermoelectric performance. Substitution has led to the presence of phonon scattering centers and consequently smaller thermal conductivity could be achieved. Promising power factor has been recorded at 9.3 µW cm<sup>− 1</sup> K<sup>− 2</sup> for the double doped Ti<sub>0.6</sub>Hf<sub>0.2</sub>Nb<sub>0.2</sub>CoSb alloy at 700&#xa0;K. Improved thermoelectric figure of merit (<i>zT</i>) has been achieved as a result. The maximum <i>zT</i> value was recorded for the double doped Ti<sub>0.6</sub>Hf<sub>0.2</sub>Nb<sub>0.2</sub>CoSb alloy at 0.17, observed at 700&#xa0;K. Although dual Nb–Hf substitution effectively suppresses lattice thermal conductivity, the associated increase in alloy and defect scattering also limits carrier mobility, preventing a proportional increase in the power factor. This intrinsic trade-off represents the primary factor constraining zT in the present system.</p>

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Heavy Nb and hf doping for enhanced thermoelectric properties in n-Type TiCoSb half-Heusler compounds

  • 期刊论文

  • 发表日期：

    2026年3月9日

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  • A. El-Khouly,
  • V. Khovaylo,
  • S. M. Amer,
  • M. Ataalla,
  • A. M. Adam

摘要

Half-Heusler compounds based on TiCoSb have attracted considerable interest in thermoelectric applications, with most prior efforts relying on single-element substitution (Nb, Ta, or Hf) to improve either electronic or phonon transport. However, the low/moderate thermoelectric figure of merit hinders its applications in many industrial fields. In this work, we demonstrate a dual Nb–Hf substitution strategy at the Ti site, designed to simultaneously optimize carrier transport and enhance phonon scattering within a single compositional framework. Unlike earlier Nb-, Ta-, or Hf-doped TiCoSb systems that primarily target isolated transport channels, the present approach enables cooperative modulation of electrical and thermal properties, resulting in an overall improvement in thermoelectric performance. Substitution has led to the presence of phonon scattering centers and consequently smaller thermal conductivity could be achieved. Promising power factor has been recorded at 9.3 µW cm− 1 K− 2 for the double doped Ti0.6Hf0.2Nb0.2CoSb alloy at 700 K. Improved thermoelectric figure of merit (zT) has been achieved as a result. The maximum zT value was recorded for the double doped Ti0.6Hf0.2Nb0.2CoSb alloy at 0.17, observed at 700 K. Although dual Nb–Hf substitution effectively suppresses lattice thermal conductivity, the associated increase in alloy and defect scattering also limits carrier mobility, preventing a proportional increase in the power factor. This intrinsic trade-off represents the primary factor constraining zT in the present system.