Year-end Sale % OFF 
Abstract
Half-Heusler phases (space group F 4 ¯ 3 m , C1b) have recently captured much attention as promising thermoelectric materials for heat-to-electric power conversion in the mid-to-high temperature range. The most studied ones are the RNiSn-type half-Heusler compounds, where R represents refractory metals Hf, Zr, and Ti. These compounds have shown a high-power factor and high-power density, as well as good material stability and scalability. Due to their high thermal conductivity, however, the dimensionless figure of merit (zT) of these materials has stagnated near 1 for a long time. Since 2013, the verifiable zT of half-Heusler compounds has risen from 1 to near 1.5 for both n- and p-type compounds in the temperature range of 500–900 °C. In this brief review, we summarize recent advances as well as approaches in achieving the high zT reported. In particular, we discuss the less-exploited strain-relief effect and dopant resonant state effect studied by the author and his collaborators in more detail. Finally, we point out directions for further development.
Highlights
Thermoelectric energy conversion is an important component of renewable-energy technology.Among many thermoelectric (TE) materials, half-Heusler compounds, principally with the composition XYZ, where X and Y are transition or rare earth elements andZ is a main group element, are the most studied ones
The dimensionless figure of merit, zT, for TE materials is defined as zT = S2 σ/k T, where σ is the electrical conductivity, S is the Seebeck coefficient, and k is thermal conductivity. zT can be written as zT = ( PF · T )/k where
Hybridization between localized dopant states and extended host band states led to band anticrossing in electronegativity-mismatched semiconductor, producing resonant states in some cases [31,32]
Summary
Thermoelectric energy conversion is an important component of renewable-energy technology. There are two basic approaches to enhancing the zT of half-Heusler compounds: (1) lowering thermal conductivity, and (2) raising the power factor. These two TE properties are inter-related and it is nontrivial to simultaneously improve them. By employing different approaches, several groups have been successful in overcoming the barrier to high zT in HH compounds. In this brief review, we first summarize the notable results in half-Heusler compounds since 2013, namely, zT > 1, and the origin of high thermoelectric performance.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
