Creating high-dense stacking faults and endo-grown nanoneedles to enhance phonon scattering and improve thermoelectric performance of Cu2SnSe3

Since mid- and low frequency phonons (MLFPs) dominate heat transport in multi-component alloys/compounds, it is vital to block MLFPs to reduce lattice thermal conductivity k(L). Here we show that through creating high-dense stacking faults (SFs) via lowing SFs energy and endo-grown AgInSnSe4 nanoneedles via solid-state reaction in (Ag, Fe, In)-doped Cu2SnSe3 thermoelectric compound its k(L) is reduced to theoretical minimum ~0.2 WK-1 m(-1) (at 848 K). Theoretical analysis reveals that aspect ratio xi of nanoneedles works as an extra degree of freedom and similar to SFs strong scattering of MLFPs occurs as xi=10= 10 (radius a=50 nm). Besides, the intrinsic cause of AgInSnSe4 nanoneedle growth is found to be its large surface energy in [112] direction. In addition, Fe and Ag (In) doping can simultaneously enhance electronic density of states, with the former bringing extra hole conduction paths, resulting in 3-fold increase in power factor (12 mu Wcm(-1) K-2 at ~800 K). At last, a large figure of merit ZT= 1.61 is achieved at 848 K, demonstrating that synergetic phonon-scattering by both high dense SFs and nanoneedles with large xi combined with regulation of electronic structures is an effective way to improve its thermoelectric performance.

Automated summary

By reducing stacking fault energy and using nanoneedles, the lattice thermal conductivity of Cu2SnSe3 thermoelectric compound is successfully reduced. The aspect ratio of the nanoneedles and stacking faults play important roles in scattering low frequency phonons in multi-component alloys/compounds.