High performance GeTe thermoelectrics enabled by lattice strain construction

Numerous intrinsic Ge vacancies in thermoelectric GeTe not only lead to overhigh carrier concentration but also seriously deteriorate carrier mobility, which shackles its thermoelectric performance. The efficient strategy and the related underlying mechanism in suppressing intrinsic Ge vacancy, however, are rarely researched yet. Herein, we demonstrated that lattice strain could be employed to regulate the defects concentration and then optimize electrical transport performance. Theoretically, the calculated results showed that lattice strain could efficiently raise the formation energy of Ge vacancies, weakening the carrier scattering and improving the carrier mobility. Calculated band structure revealed that Sb doping and Ge vacancy introduction could promote band convergence and thus efficiently decouple the electrical transport parameters. Experimentally, lattice strain was constructed through high-energy ball milling combined with spark plasma sintering to reduce the concentration of Ge vacancy and relaxation time of phonons, leading to high carrier mobility and low lattice thermal conductivity. Additionally, we carefully modulated the nominal content of Ge, and then a high ZT of 2.0 at 723 K in Ge0.90Sb0.08Te alloy was obtained. This work highlights that the lattice strain can be utilized to simultaneously optimize thermal and electrical transport properties.

Automated summary

This research shows that lattice strain can be used to adjust the defect concentration and optimize the electrical transport performance. Theoretical calculations demonstrate that lattice strain can effectively increase the formation energy of Ge vacancies, reducing carrier scattering and improving carrier mobility. Experimental results confirm that lattice strain obtained through high-energy ball milling combined with spark plasma sintering can reduce the concentration of Ge vacancies, leading to high carrier mobility. Additionally, carefully modulating the nominal content of Ge in Ge0.90Sb0.08Te alloy results in a high ZT of 2.0 at 723 K.