Enhancing thermoelectric properties of higher manganese silicide through facilitated non-equilibrium reactions via the introduction of additional Carbon nano-dots

Higher manganese silicide (HMS) has gained significant attention as a compelling choice for thermoelectric (TE) applications at medium temperatures due to its abundance, environmental friendliness, and impact resistance properties. Recent achievement in HMS involves leveraging the synergistic effect of energy filtering, modulation doping, and boundary scattering to enhance the TE performance. However, excellent TE properties on HMS usually demands extreme preparation processes such as shock compression, melt spinning technique, or chemical vapor transport approach, as well as the use of rare and expensive elements or nano-dots (NDs), such as Re, Ge, Ag/Pt alloy, or CsPbBr3 quantum dots. In this study, a facile wet ball milling combing with spark plasma sintering is used to streamline the synthesis processes. Relatively green, cost-effective, and accessible C NDs are used to facilitated non-equilibrium reactions and enhance TE properties of HMS. Due to the C-doped effect, the PF increased from 1.42 to 1.62 mW m−1 K−2 at 723 K, representing an approximately 14 % improvement compared to the pristine HMS. The introduction of C, derived SiC and Mn NDs result in the enhancing phonon scattering, and leading to a reduction in lattice thermal conductivity from 2.21 to 1.81 W m−1 K−1. Consequently, the figure of merit (zT) increases from 0.42 to 0.55 at 823 K, representing an enhancement of approximately ∼ 31 %. Predictably, the incorporation of C NDs into semiconductors stands as one of the effective strategies for enhancing the TE properties. •Incorporating C NDs enhances non-equilibrium reactions and facilitates the formation of C-Si bonds in HMS.•C-doping optimizes the carrier concentration, leading to a ~14% increase in the PF at 723 K.•C NDs, Mn, and SiC precipitates enhance phonon scattering and reduce the lattice thermal conductivity ~18%.•High zT value of 0.55 (increase of ~31%) at 823 K is achieved in HMS/C NDs composites.