Ga intercalation in van der Waals layers for advancing p-type Bi₂Te₃-based thermoelectrics

Abstract

Tetradymite-structured chalcogenides, such as Bi2Te3 and Sb2Te3, are quasi-two-dimensional (2D) layered compounds, which are significant thermoelectric materials applied near room temperature. The intercalation of guest species in van der Waals (vdW) gap implemented for tunning properties has attracted much attention in recent years. We attempt to insert Ga atoms in the vdW gap between the Te layers in p-type Bi0.3Sb1.7Te3 (BST) for further improving thermoelectrics. The vdW-related defects (including extrinsic interstitial and intrinsic defects) induced by Ga intercalation can not only modulate the carrier concentration but enhance the texture, thereby yielding excellent electrical properties, which is reflected in the power factor PF ~4.43 mW m-1 K-2. Furthermore, the intercalation of Ga produces multi-scale lattice imperfections such as point defects, Te precipitations, and nanopores, realizing the low lattice thermal conductivity in BST-Ga samples. Ultimately, a peak zT ~1.1 at 373 K is achieved in the BST-1%Ga sample and greatly improved by ~22% compared to the pristine BST. The weak bonding of vdW interlayer interaction can boost the synergistic effect for advancing BST-based or other layered thermoelectrics.