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Role of cobalt for titanium substitution on the thermoelectric properties of the thiospinel CuTi2S4

Abstract : A complete thiospinel solid solution CuCoxTi2-xS4 (0 ≤ x < 1) has been synthesized by conventional sealed tube synthesis followed by Spark Plasma Sintering, whereas, for x = 1, the presence of secondary phases is observed. The compounds exhibit a semi-metallic behavior in the whole composition range in spite of the existence of two subdomains characterized by different major redox species: (I) involving Cu+, Ti3+, Ti4+, Co2+ for 0 ≤ x ≤ 0.5 and (II) involving Cu+, Cu2+, Ti4+, Co2+for 0.5 < x ≤ 1. The thermoelectric properties show that, in the compositional range x = 0.3–0.8, the figure of merit does not depend significantly on x, ZT ranging from 0.13 to 0.18 at 675 K, whereas for the limit x = 0, it drops down to 0.04. This behavior is interpreted in terms of the predominant influence of the redox couple Ti3+/Ti4+ on the transport properties, as long as Cu+ is present, according to the equilibrium Cu+ + Ti4+⇌ Cu2+ + Ti3+. The thiospinel CuCo0.6Ti1.4S4, which exhibits the higher ZT of 0.18 at 675 K, opens the route to the research of new “Ti4+-Cu+” based thermoelectric sulfides with different structures.
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https://hal-normandie-univ.archives-ouvertes.fr/hal-02274130
Contributor : Emmanuel Guilmeau <>
Submitted on : Thursday, August 29, 2019 - 3:32:14 PM
Last modification on : Tuesday, September 3, 2019 - 2:33:07 PM

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Cédric Bourgés, Ventrapati Pavan Kumar, Hiroki Nagai, Yuzuru Miyazaki, Bernard Raveau, et al.. Role of cobalt for titanium substitution on the thermoelectric properties of the thiospinel CuTi2S4. Journal of Alloys and Compounds, Elsevier, 2019, 781 (1), pp.1169-1174. ⟨10.1016/j.jallcom.2018.12.102⟩. ⟨hal-02274130⟩

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