Nanostructured rocksalt-type solid solution series (Ge{sub 1−x}Sn{sub x}Te){sub n}Sb{sub 2}Te{sub 3} (n=4, 7, 12; 0≤x≤1): Thermal behavior and thermoelectric properties
- Department of Chemistry, Ludwig Maximilian University, Butenandtstraße 5-13, 81377 Munich (Germany)
- German Aerospace Center, Linder Höhe, 51147 Cologne (Germany)
- Institute for Mineralogy, Crystallography and Materials Science, Leipzig University, Scharnhorststraße 20, 04275 Leipzig (Germany)
Solid solutions (Ge{sub 1−x}Sn{sub x}Te){sub n}Sb{sub 2}Te{sub 3} (n=4, 7, 12; 0≤x≤1) represent stable high-temperature phases and can be obtained as metastable compounds by quenching. High-resolution transmission electron microscopy reveals that the quenched (pseudo-)cubic materials exhibit parquet-like nanostructures comparable to, but especially for n=4 more pronounced than in (GeTe){sub n}Sb{sub 2}Te{sub 3} (GST materials). The temperature-dependent phase transitions are comparable; however, substitution with Sn significantly lowers the transition temperatures between cubic high-temperature phase and the long range ordered layered phases that are stable at ambient conditions. In addition, the metrics of the quenched Sn-containing materials remains closer to cubic, especially for samples with n=7 or 12. For samples with high defect concentrations (n=4, 7), Sn-substituted samples exhibit electrical conductivities up to 3 times higher than those of corresponding GST materials. Since the difference in thermal conductivity is much less pronounced, this results in a doubling of the thermoelectric figure of merit (ZT) at high temperatures for (Ge{sub 0.5}Sn{sub 0.5}Te){sub 4}Sb{sub 2}Te{sub 3} as compared to (GeTe){sub 4}Sb{sub 2}Te{sub 3}. Sn doping in (GeTe){sub 7}Sb{sub 2}Te{sub 3} increases the ZT value by a factor of up to 4 which is also due to an increased Seebeck coefficient. - Graphical abstract: High-resolution transmission electron micrographs of (GeTe){sub 4}Sb{sub 2}Te{sub 3} (top) and (Ge{sub 0.5}Sn{sub 0.5}Te){sub 4}Sb{sub 2}Te{sub 3} (bottom) with different nanostructures and thermoelectric figures of merit (ZT) of these samples. - Highlights: • Representative samples of solid solutions of (Ge{sub 1−x}Sn{sub x}Te){sub n}Sb{sub 2}Te{sub 3} were synthesized. • Sn substitution leads to more pronounced nanostructures in defect-rich compounds. • Phase transitions are comparable to (GeTe){sub n}Sb{sub 2}Te{sub 3} but occur at lower temperatures. • Sn substitution tends to increase electrical conductivity and Seebeck coefficient. • ZT of (GeTe){sub 7}Sb{sub 2}Te{sub 3} increases from 0.2 to 0.7 (at 400 °C) upon Sn substitution.
- OSTI ID:
- 22334287
- Journal Information:
- Journal of Solid State Chemistry, Vol. 215; Other Information: Copyright (c) 2014 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- English
Similar Records
Novel superstructure of the rocksalt type and element distribution in germanium tin antimony tellurides
Acceleration of Crystallization Kinetics in Ge‐Sb‐Te‐Based Phase‐Change Materials by Substitution of Ge by Sn