【摘 要】
：
Normal titanium oxycarbide exhibits an excellent electrical conductivity and a high carrier concentration of approximately 1021 cm?3;however, the low Seebeck coefficient limits the thermoelectric application. In this study, first-principle calculations de
【机 构】
：
State Key Laboratory of Advanced Metallurgy,University of Science and Technology Beijing,Beijing 100
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Normal titanium oxycarbide exhibits an excellent electrical conductivity and a high carrier concentration of approximately 1021 cm?3;however, the low Seebeck coefficient limits the thermoelectric application. In this study, first-principle calculations demonstrate that the metal vacancy of titanium oxycarbide weakens the density of state passing through the valence band at the Fermi level, impairing the carrier concen-tration and enhancing carrier mobility. Thermodynamic analysis justifies the formation of titanium oxycarbide with metal vacancy through sol-id-state reaction. Transmission electron microscopic images demonstrate the segregation of metal vacancy based on the observation of the de-fect-rich and single-crystal face-centered cubic regions. Metal vacancy triggers the formation of vacancy-rich and single-crystal face-centered cubic regions. The aggregation of metal vacancy leads to the formation of the vacancy-rich region and other regions with a semi-coherent inter-face, suppressing the carrier concentration from 1.71 × 1021 to 4.5 × 1020 cm?3 and resulting in the Seebeck coefficient from ?11 μV/K of TiC0.5O0.5 to ?64 μV/K at 1073 K. Meanwhile, vacancies accelerate electron migration from 1.65 to 4.22 cm?2·V?1·s?1, maintaining high con-ductivity. The figure of merit (ZT) increases more than five orders of magnitude via the introduction of metal vacancy, with the maximum figure of 2.11 × 10?2 at 1073 K. These results indicate the potential thermoelectric application of metal-oxycarbide materials through vacancy engineering.
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