Features of the High-Temperature Structural Evolution of GeTe Thermoelectric Probed by Neutron and Synchrotron Powder Diffraction
Among other chalcogenide thermoelectric materials, GeTe and derivative alloys are good candidates for intermediate temperature applications, as a replacement for toxic PbTe. We have prepared pure polycrystalline GeTe by using arc-melting, and investigated its structural evolution by using neutron po...
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MDPI AG
2019-12-01
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| Online Access: | https://www.mdpi.com/2075-4701/10/1/48 |
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| author | Javier Gainza Federico Serrano-Sánchez Norbert Marcel Nemes José Luis Martínez María Teresa Fernández-Díaz José Antonio Alonso |
| author_facet | Javier Gainza Federico Serrano-Sánchez Norbert Marcel Nemes José Luis Martínez María Teresa Fernández-Díaz José Antonio Alonso |
| author_sort | Javier Gainza |
| collection | DOAJ |
| description | Among other chalcogenide thermoelectric materials, GeTe and derivative alloys are good candidates for intermediate temperature applications, as a replacement for toxic PbTe. We have prepared pure polycrystalline GeTe by using arc-melting, and investigated its structural evolution by using neutron powder diffraction (NPD) and synchrotron X-ray diffraction (SXRD), as well as its correlation with the thermal variation of the Seebeck coefficient. Besides a significant Ge deficiency (~7% Ge vacancies), the thermal evolution of the unit-cell volume and Ge-Te bond lengths in the rhombohedral phase (space group <i>R3m</i>), below 700 K, show unexpected anomalies involving the abrupt Ge-Te bond lengthening accompanied by increased Te thermal displacements. Above 700 K, the sample is cubic (space group <i>Fm-3m</i>) and shows considerably larger displacement parameters for Ge than for Te, as a consequence of the random distribution of the lone pair lobes of Ge<sup>2+</sup>. The Seebeck coefficient, reaching 120 μV K<sup>−1</sup> at 775 K, shows a shoulder in the 500−570 K region that can be correlated to the structural anomaly, modifying the electron-phonon scattering in this temperature range. |
| first_indexed | 2024-12-10T15:00:37Z |
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| id | doaj.art-66c02eac6be44fe9ad07f6412aa7859a |
| institution | Directory Open Access Journal |
| issn | 2075-4701 |
| language | English |
| last_indexed | 2024-12-10T15:00:37Z |
| publishDate | 2019-12-01 |
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| series | Metals |
| spelling | doaj.art-66c02eac6be44fe9ad07f6412aa7859a2022-12-22T01:44:10ZengMDPI AGMetals2075-47012019-12-011014810.3390/met10010048met10010048Features of the High-Temperature Structural Evolution of GeTe Thermoelectric Probed by Neutron and Synchrotron Powder DiffractionJavier Gainza0Federico Serrano-Sánchez1Norbert Marcel Nemes2José Luis Martínez3María Teresa Fernández-Díaz4José Antonio Alonso5Instituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Científicas (CSIC), Sor Juana Inés de la Cruz 3, 28049 Madrid, SpainInstituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Científicas (CSIC), Sor Juana Inés de la Cruz 3, 28049 Madrid, SpainDepartamento de Física de Materiales, Universidad Complutense de Madrid, E-28040 Madrid, SpainInstituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Científicas (CSIC), Sor Juana Inés de la Cruz 3, 28049 Madrid, SpainInstitut Laue Langevin, BP 156X, Grenoble F-38042, FranceInstituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Científicas (CSIC), Sor Juana Inés de la Cruz 3, 28049 Madrid, SpainAmong other chalcogenide thermoelectric materials, GeTe and derivative alloys are good candidates for intermediate temperature applications, as a replacement for toxic PbTe. We have prepared pure polycrystalline GeTe by using arc-melting, and investigated its structural evolution by using neutron powder diffraction (NPD) and synchrotron X-ray diffraction (SXRD), as well as its correlation with the thermal variation of the Seebeck coefficient. Besides a significant Ge deficiency (~7% Ge vacancies), the thermal evolution of the unit-cell volume and Ge-Te bond lengths in the rhombohedral phase (space group <i>R3m</i>), below 700 K, show unexpected anomalies involving the abrupt Ge-Te bond lengthening accompanied by increased Te thermal displacements. Above 700 K, the sample is cubic (space group <i>Fm-3m</i>) and shows considerably larger displacement parameters for Ge than for Te, as a consequence of the random distribution of the lone pair lobes of Ge<sup>2+</sup>. The Seebeck coefficient, reaching 120 μV K<sup>−1</sup> at 775 K, shows a shoulder in the 500−570 K region that can be correlated to the structural anomaly, modifying the electron-phonon scattering in this temperature range.https://www.mdpi.com/2075-4701/10/1/48thermoelectricsneutron powder diffractionge deficiencystructural phase transition |
| spellingShingle | Javier Gainza Federico Serrano-Sánchez Norbert Marcel Nemes José Luis Martínez María Teresa Fernández-Díaz José Antonio Alonso Features of the High-Temperature Structural Evolution of GeTe Thermoelectric Probed by Neutron and Synchrotron Powder Diffraction Metals thermoelectrics neutron powder diffraction ge deficiency structural phase transition |
| title | Features of the High-Temperature Structural Evolution of GeTe Thermoelectric Probed by Neutron and Synchrotron Powder Diffraction |
| title_full | Features of the High-Temperature Structural Evolution of GeTe Thermoelectric Probed by Neutron and Synchrotron Powder Diffraction |
| title_fullStr | Features of the High-Temperature Structural Evolution of GeTe Thermoelectric Probed by Neutron and Synchrotron Powder Diffraction |
| title_full_unstemmed | Features of the High-Temperature Structural Evolution of GeTe Thermoelectric Probed by Neutron and Synchrotron Powder Diffraction |
| title_short | Features of the High-Temperature Structural Evolution of GeTe Thermoelectric Probed by Neutron and Synchrotron Powder Diffraction |
| title_sort | features of the high temperature structural evolution of gete thermoelectric probed by neutron and synchrotron powder diffraction |
| topic | thermoelectrics neutron powder diffraction ge deficiency structural phase transition |
| url | https://www.mdpi.com/2075-4701/10/1/48 |
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