Low-thermal-conductivity group 13 chalcogenides as high-efficiency thermoelectric materials

• Published in: Physica status solidi. A, Applications and materials science Applications and materials science, 2013-01, Vol.210 (1), p.82-88
• Main Authors: Kurosaki, Ken, Yamanaka, Shinsuke
• Format: Article
• Language: English
• Subjects: Conductivity; Efficiency; Energy management; group 13 elements; telluride; thermal conductivity; thermoelectric
• ISSN: 1862-6300; 1862-6319
• DOI: 10.1002/pssa.201228680

Thermoelectric (TE) generators can directly generate electrical power from waste heat and are promising for use in power supplies and for realizing sustainable energy management. However, the low efficiencies of TE materials in converting heat to electricity is the main impediment to applying TE generators in many industries including exhaust heat recovery in automobiles. The efficiency of TE materials is quantified by a dimensionless figure of merit ZT. To enhance ZT, it is important to reduce the lattice thermal conductivity (κlat) of a material while maintaining a high electrical conductivity. Here, we review the TE properties of thallium‐based compounds, mainly tellurides. Many thallium tellurides exhibit extremely low κlat below 0.5 W m−1 K−1, which is almost one third that of Bi2Te3 used in current TE devices. Of the thallium tellurides, Ag9TlTe5 has the highest ZT value of 1.2, which is higher than typical ZT values 0.8 of Bi2Te3; this is primarily due to the extremely low κlat of Ag9TlTe5. In addition, we briefly review the TE properties of tellurides of other group 13 elements that contain structural vacancies such as Ga2Te3. Tellurides exhibit various vacancy distributions and hence have interesting TE properties. Based on the results of the TE properties of these tellurides, we propose a strategy for improving TE materials. Chalcogenides containing elements from group 13 have attracted attention as thermoelectric materials, particularly compounds with crystal structures derived from the diamond structure, such as the zinc‐blende structure and the chalcopyrite structure. Specifically, a series of compounds that include CuGaTe2, CuInTe2, and AgGaTe2 has been found to exhibit high thermoelectric figure of merit (ZT) values at high temperatures. These chalcogenides are expected to attract increasing attention as novel thermoelectric materials in the future and to be the subject of much research aiming to determine the mechanism responsible for the high ZT and to further enhance the performance.