Enhanced Thermoelectric Performance in Cu ₇ Sn ₃ S ₁₀ ‐based Hybrid Materials with Highly Dispersed Multiwalled Carbon Nanotubes

Abstract Ternary copper chalcogenide Cu 7 Sn 3 S 10 has attracted great attention due to its complex and tunable crystal structure, good thermoelectric performance, and earth‐abundant and eco‐friendly elements. However, the optimization of thermoelectric performance in Cu 7 Sn 3 S 10 is greatly restricted because the strategy of element doping to tune electrical and thermal transports is only limited by halogen elements. Here, highly dispersed multiwalled carbon nanotubes (MCNTs) are introduced into Cu 7 Sn 3 S 10 to realize hybrid materials with enhanced thermoelectric performance. A series of Cu 7+ y Sn 3 S 10 / x wt.% MCNTs hybrid materials are successfully fabricated by ball milling combined with spark plasma sintering. The high‐purity Cu 7 Sn 3 S 10 /MCNTs hybrid materials are identified as polymorphs simultaneously crystalizing in tetragonal, primitive cubic, and face‐centered cubic structures. Such complex phase structures can produce lots of intrinsic cation‐disorders, phase interfaces, grain boundaries, and Cu 7 Sn 3 S 10 /MCNTs heterointerfaces, which can strengthen phonon and carrier scattering, while the heterointerfaces can serve as carrier reservoirs to trap holes to reduce the carrier concentration toward the optimal range. Combining these effects, both lattice thermal conductivity and carrier thermal conductivity are significantly reduced. Correspondingly, a maximum figure of merit zT of 0.65 is achieved in Cu 7.05 Sn 3 S 10 /2wt.% MCNTs at 750 K, about twice as compared with the MCNTs‐free Cu 7 Sn 3 S 10 . This work suggests that hybrid materials with well dispersed MCNTs can greatly enhance the material's thermoelectric performance.