Oxygen Vacancy in Magnéli Phases and Its Effect on Thermoelectric Performances

Oxygen Vacancy in Magnéli Phases and Its Effect on Thermoelectric Performances

Magnéli phases exhibit significant potential for applications in electronic materials in energy conversion due to their high electrical conductivity and excellent thermal stability. In this study, single-phase Ti<sub>n</sub>O<sub>2n−1</sub> (<i>n</i> = 4, 5, 6) bu...

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Bibliographic Details
Main Authors: Zhou Guan, Chuangshi Feng, Hongquan Song, Lingxu Yang, Xin Wang, Huijun Liu, Jiawei Zhang, Fanqian Wei, Xin Yuan, Hengyong Yang, Yu Tang, Fuxiang Zhang
Format: Article
Language:English
Published: MDPI AG 2025-04-01
Series:Nanomaterials
Subjects:
Magnéli phase
oxygen vacancy
thermoelectric performance
single parabolic band
Online Access:https://www.mdpi.com/2079-4991/15/9/684
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Summary:Magnéli phases exhibit significant potential for applications in electronic materials in energy conversion due to their high electrical conductivity and excellent thermal stability. In this study, single-phase Ti<sub>n</sub>O<sub>2n−1</sub> (<i>n</i> = 4, 5, 6) bulk materials were successfully prepared by a combination of the carbothermal reduction of nano-sized rutile TiO<sub>2</sub> and hot-press sintering methods. The relationships between the phase evolution, microstructural features, and thermoelectric performance were investigated systematically. Synchrotron X-ray diffraction (SXRD) and scanning electron microscopy (SEM) analyses revealed that the Ti<sub>4</sub>O<sub>7</sub> and Ti<sub>5</sub>O<sub>9</sub> materials had single-phase structures with high densities (relative density > 97%) and no obvious grain boundary holes or microcracks. We tested the thermoelectric properties of the Magnéli phases in the temperature range of 300–1100 K. The Magnéli phases exhibited a significant temperature dependence, with peak zT values of 0.17, 0.18, and 0.14 for Ti<sub>4</sub>O<sub>7</sub>, Ti<sub>5</sub>O<sub>9</sub>, and Ti<sub>6</sub>O<sub>11</sub>, respectively, at 1100 K. This variation in thermoelectric performance was mainly attributed to the synergistic effect of the oxygen vacancy concentration and the shear surface density on the carrier concentration and lattice thermal conductivity. Furthermore, the Fermi energy levels and electronic thermal conductivity of the Magnéli phases were calculated using the single parabolic band (SPB) model.
ISSN:2079-4991

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