Phase stability and thermoelectric properties of semiconductor-like tetragonal FeAl2
| Autor: | Kazuki Tobita, Koichi Kitahara, Yukari Katsura, Naoki Sato, Daisuke Nishio-Hamane, Hirotada Gotou, Kaoru Kimura |
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| Jazyk: | angličtina |
| Rok vydání: | 2019 |
| Předmět: | |
| Zdroj: | Science and Technology of Advanced Materials, Vol 20, Iss 1, Pp 937-948 (2019) |
| Druh dokumentu: | article |
| ISSN: | 1468-6996 1878-5514 14686996 |
| DOI: | 10.1080/14686996.2019.1662272 |
| Popis: | Tetragonal FeAl2 is a high-pressure phase and is predicted to exhibit semiconductor-like behavior. We investigated the pressure and temperature synthesizing conditions of tetragonal FeAl2, supported by in situ X-ray diffractions, using synchrotron radiation during heating the sample under a pressure of 20 GPa. Based on the determined optimal conditions, we synthesized the bulk polycrystalline samples of tetragonal FeAl2 at 7.5 GPa and 873 K, using a multi-anvil press and measured its thermoelectric properties. The Seebeck coefficient of tetragonal FeAl2 showed a large negative value of – 105 μV/K at 155 K and rapidly changed to a positive value of 75 μV/K at 400 K. Although these values are the largest among those of Fe–Al alloys, the maximum power factor remained at 0.41 mW/mK2 because the carrier concentration was not tuned. A comparison of the Gibbs free energy of tetragonal FeAl2, triclinic FeAl2 and FeAl+Fe2Al5 revealed that tetragonal FeAl2 became unstable as the temperature increased, because of its smaller contribution of vibrational entropy. |
| Databáze: | Directory of Open Access Journals |
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