Abstract
Thermoelectric materials, which directly convert thermal energy to electricity and vice versa, are considered a viable source of renewable energy. However, the enhancement of conversion efficiency in these materials is very challenging. Recently, multiphase thermoelectric materials have presented themselves as the most promising materials to achieve higher thermoelectric efficiencies than single-phase compounds. These materials provide higher degrees of freedom to design new compounds and adopt new approaches to enhance the electronic transport properties of thermoelectric materials. Here, we have summarised the current developments in multiphase thermoelectric materials, exploiting the beneficial effects of secondary phases, and reviewed the principal mechanisms explaining the enhanced conversion efficiency in these materials. This includes energy filtering, modulation doping, phonon scattering, and magnetic effects. This work assists researchers to design new high-performance thermoelectric materials by providing common concepts.
Highlights
Thermoelectric (TE) materials have been attracting a great deal of interest because of their applications in energy recovery from industrial waste heat and high-efficiency cooling of next-generation integrated circuits [1]
Most thermoelectric materials used in commercial applications have a zT of around 1 [2], which corresponds to an efficiency of roughly 10% in the medium temperature range [3]
We summarise the main strategies discovered to date to increase the thermoelectric efficiency in multiphase materials. This includes: (1) energy filtering, creating potential barriers in the electronic band structure of the main phase through interfaces with the secondary phases. This results in an increase in the overall Seebeck coefficient [33,34,35]; (2) modulation doping, where the heterojunctions between secondary phases with larger bandgaps and higher carrier concentrations than the matrix are used to greatly increase the electrical conductivity of the multiphase compounds [36,37,38]; (3) phonon scattering by interfaces, grain boundaries, and defects to reduce the lattice thermal conductivity [39,40,41,42]; and (4) magnetic effects, which utilises the magnon-drag mechanism in magnetic materials [43,44,45], semiconductors doped with magnetic elements [46,47,48], or semiconductors containing secondary magnetic phases [49,50] to improve the thermoelectric efficiency [51,52]
Summary
Thermoelectric (TE) materials have been attracting a great deal of interest because of their applications in energy recovery from industrial waste heat and high-efficiency cooling of next-generation integrated circuits [1]. This includes: (1) energy filtering, creating potential barriers in the electronic band structure of the main phase through interfaces with the secondary phases This results in an increase in the overall Seebeck coefficient [33,34,35]; (2) modulation doping, where the heterojunctions between secondary phases with larger bandgaps and higher carrier concentrations than the matrix are used to greatly increase the electrical conductivity of the multiphase compounds [36,37,38]; (3) phonon scattering by interfaces, grain boundaries, and defects to reduce the lattice thermal conductivity [39,40,41,42]; and (4) magnetic effects, which utilises the magnon-drag mechanism in magnetic materials [43,44,45], semiconductors doped with magnetic elements [46,47,48], or semiconductors containing secondary magnetic phases [49,50] to improve the thermoelectric efficiency [51,52]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
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.
