High-pressure induces topology boosting thermoelectric performance of Bi₂Te₃

Abstract

Decoupling conductivity (σ) and Seebeck coefficient (S) by electronic topological transitions (ETT) under high pressure (2-4 GPa) is a promising method for Bi2Te3 to optimize thermoelectric (TE) performance. However, the S cannot dramatically increase with increasing σ when ETT occurs in Bi2Te3, which impedes optimizing TE performance by utilizing ETT in Bi2Te3. A new strategy of enhanced ETT by combining lattice distortions and high pressure is proposed in this work. The lattice distortions in Bi2Te3 were introduced by high pressure and high temperature (HPHT) treatment to generate surplus dislocations. The in-situ measurements of σ and S at HPHT in Bi2Te3 with lattice distortions show an enhanced ETT effect at 2 GPa, which causes decouple σ and S with an anomalous increase in its |S| about 22 %. The ETT effect causes the figure of merit (ZT) of Bi2Te3 can be improved to 0.275 at 1.50-2.62 GPa, 460 K, it is more than 62 % compared with 0.79 GPa, at 450 K. The excellent TE performance of Bi2Te3 arising from the lattice distortions can result in local non-hydrostatic pressure which enhances ETT under high pressure. This work provides a new strategy to enhance ETT to decouple σ and S, and search for better TE materials from the pressure dimension in the future.