Tohoku University · Materials Science
Professor Nagendra S. Chauhan's research lab specializes in advanced thermoelectric materials, focusing on defect engineering, compositional tuning, and nanostructuring of half-Heusler alloys to enhance their thermoelectric performance. The lab explores Hf-free and cost-effective n- and p-type half-Heusler materials, particularly Zr-based systems, to achieve high figure-of-merit (ZT > 1) and improved energy conversion efficiency. Key research directions include lattice thermal conductivity reduction through atomic-scale disorder, defect modulation (e.g., Ni-vacancies and interstitials), and grain-scale compositional variations to simultaneously optimize electrical and thermal transport properties.
Figures are computed from collected data and may differ slightly.
Despite Hf-free half-Heusler (HH) alloys being currently explored as an important class of cost-effective thermoelectric materials for power generation, owing to their thermal stability coupled with high cost of Hf, their figure-of-merit (ZT) still remains far below unity. We report a state-of-the-art figure-of-merit (ZT) ∼ 1 at 873 K in Hf-free n-type V-doped Zr1–xVxNiSn HH alloy, synthesized employing arc-melting followed by spark plasma sintering. The efficacy of V as a dopant on the Zr-site
ZrCoSb based half-Heusler (HH) alloys have been widely studied as a p-type thermoelectric (TE) material for power generation applications in the mid-temperature regime. However, their intrinsically high thermal conductivity has been found to be detrimental for the improvement in their thermoelectric figure-of-merit (ZT), which presently is far below unity. In the current work, a state-of-the-art ZT ∼1.1 at 873 K was realized in an optimized composition of nanostructured Zr1-xHfxCoSb0.9Sn0.1 HH a
Compositional tailoring enables fine-tuning of thermoelectric (TE) transport parameters by synergistic modulation of electronic and vibrational properties. In the present work, the aspects of compositionally tailored defects have been explored in ZrNiSn-based half-Heusler (HH) TE materials to achieve high TE performance and cost effectiveness in n-type Hf-free HH alloys. In off-stoichiometric Ni-rich ZrNi<sub>1+<i>x</i></sub>Sn alloys in a low Ni doping limit (<i>x</i> < 0.1), excess Ni induces
Defect engineering of thermoelectric (TE) materials enables the alteration of their crystal lattice by creating an atomic-scale disorder, which can facilitate a synergistic modulation of the electrical and phonon transport, leading to the enhancement of their TE properties. This work employs a compositional nonstoichiometry strategy for manipulation of Ni-vacancies and Ni-interstitials through Ni-deficient and Ni-excess compositions of (Zr, Hf)Ni1±xSn-based half-Heusler (HH) alloys to realize a
<italic>In situ</italic>synthesis of composites employing ASSET in combination with panoscopic approach has been demonstrated in p-type ZrCoSb-based half-Heusler thermoelectric materials for significant enhancement in thermoelectric figure of merit.
Reducing the lattice thermal conductivity (κL) comprises one of the crucial aspects of thermoelectric research. Ternary intermetallic half Heusler compounds have revealed properties promising for thermoelectric applications. Studies have shown that self doping with Ni in Ni based half Heuslers leads to unprecedented lowering in the κL. Although the underlying physical mechanisms have not been explored in detail, with ZrNiSn as a case study, we experimentally investigate the change in κL with inc
Half-Heuslers (HH) represent an emerging family of thermoelectric (TE) materials, wherein intrinsic doping enables a wide range of electronic functionalities. In recent years, the solid-state transformation phenomenonon of spinodal decomposition has been actively explored as an effective paradigm to attain bulk nanostructured TE materials via induced phase separation. In the present work, the implication of intrinsic doping and spinodal decomposition on the thermal and electrical transport param
A high thermoelectric figure of merit (ZT) in state-of-the-art bismuth antimony telluride (BST) composites was attained by an excess tellurium-assisted liquid-phase compaction approach. Herein, we report a maximum ZT of ≈ 1.4 at 500 K attained for BST bulk nanocomposites fabricated by spark plasma sintering of colloidally synthesized (Bi,Sb)2Te3 platelets and Te-rich rods. The Te-rich nanodomains and antimony precipitation during sintering result in compositional fluctuations and atomic ordering
Intrinsically high lattice thermal conductivity has remained a major bottleneck for achieving a high thermoelectric figure of merit (<i>zT</i>) in state-of-the-art ternary half-Heusler (HH) alloys. In this work, we report a stable n-type biphasic-quaternary (Ti,V)CoSb HH alloy with a low lattice thermal conductivity κ<sub>L</sub> ≈ 2 W m<sup>-1</sup> K<sup>-1</sup> within a wide temperature range (300-873 K), which is comparable to the reported nanostructured HH alloys. A solid-state transformat
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