Bulk and Surface Structure and High-Temperature Thermoelectric Properties of Inverse Clathrate-III in the Si-P-Te System

• Published in: Chemistry : a European journal Vol. 16; no. 42; pp. 12582 - 12589
• Main Authors: Zaikina, Julia V., Mori, Takao, Kovnir, Kirill, Teschner, Detre, Senyshyn, Anatoliy, Schwarz, Ulrich, Grin, Yuri, Shevelkov, Andrei V.
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 08.11.2010; WILEY‐VCH Verlag; Wiley Subscription Services, Inc
• Subjects: Cationic; Chemistry; Clathrates; Corrosion resistance; Degradation; Nanostructure; neutron diffraction; Tellurium; Temperature; thermal stability; Thermoelectric materials; Thermoelectricity; Zintl phases
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201001990

The creation of thermoelectric materials for waste heat recovery and direct solar energy conversion is a challenge that forces the development of compounds that combine appreciable thermoelectric figure‐of‐merit with high thermal and chemical stability. Here we propose a new candidate for high‐temperature thermoelectric materials, the type‐III Si172−xPxTey cationic clathrate, in which the framework is composed of partially ordered silicon and phosphorus atoms, whereas tellurium atoms occupy guest positions. We show that the utmost stability of this clathrate (up to 1500 K) in air is ensured by the formation of a nanosized layer of phosphorus‐doped silica on the surface, which prevents further oxidation and degradation. As‐cast (non‐optimized) Si‐P‐Te clathrates display rather high values of the thermoelectric figure‐of‐merit (ZT=0.24–0.36) in the temperature range of 700–1100 K. These ZT values are comparable to the best values achieved for the properly doped transition‐metal‐oxide materials. The methods of the thermoelectric efficiency optimization are discussed. Thermoelectric Si‐P‐Te clathrate‐III: Si‐P‐Te clathrate‐III has been developed as a new high‐temperature thermoelectric material. Its utmost stability (up to 1500 K) in air is the result of the formation of a nanosized surface layer of phosphorus‐doped silica. The as‐prepared Si‐P‐Te clathrate displays high values of the thermoelectric figure‐of‐merit at temperatures up to 1100 K (see figure). Further methods of thermoelectric efficiency optimization for Si‐P‐Te clathrates are discussed.