Mechanically exfoliated MoS2 nanoflakes for optimizing the thermoelectric performance of SrTiO3-based ceramic composites

As a semiconducting material with relatively low thermal conductivity, MoS2 nanoflake has the potential to serve as a modulator for optimizing the performance of thermoelectric (TE) materials. However, the low yield of MoS2 nanoflakes prepared by conventional methods has constrained the development of MoS2 optimized TE materials. We propose a mechanical exfoliation method for mass production of MoS2 nanoflakes using attrition mill. After mixed with La and Nb co-doped SrTiO3 (SLNT) powder, the MoS2/SLNT composites are fabricated by spark plasma sintering. It is found that the heterojunctions formed at MoS2/SLNT interfaces with proper band offset can effectively scatter the low-energy electrons, resulting in enhanced Seebeck coefficient without significantly undermining the electrical conductivity. The power factor of composites is improved when the MoS2 content is lower than 1.5 vol%. Meanwhile, the thermal conductivity of composites is significantly decreased due to the phonon scattering induced large thermal resistance at MoS2/SLNT interfaces, which is much higher than that in graphene embedded SrTiO3 composites. Consequently, a maximum ZT = 0.24 is obtained at 800 K in 1.5 vol% MoS2/SLNT composite, which is ∼26 % higher compared with pristine matrix. This work paves the way for application of TE materials modulated by transition metal dichalcogenides.