Concurrent defects of intrinsic tellurium and extrinsic silver in an n-type Bi2Te2.88Se0.15 thermoelectric material

Abstract

We suggested a defect system consisting of Te- and Ag-related defects in n-type Bi 2 (Te,Se) 3 . We prepared the Te-rich Bi 2 Te 2.88 Se 0.15 compound, which is expected to have Te antisite defects, via a conventional pulverization process. We devised a one-pot chemical process in which Ag nanoparticles were synthesized and instantly deposited onto the Bi 2 Te 2.88 Se 0.15 , followed by spark plasma sintering; thus, Ag atoms were inserted into the lattice structure of the Bi 2 Te 2.88 Se 0.15 during the sintering process. Atomic layers of the Bi 2 Te 2.88 Se 0.15 were resolved by transmission electron microscopy and dark-field scanning electron microscopy imaging with energy dispersive X-ray spectroscopy; the Ag atoms were thereby proven to occupy the interstitial sites in the Bi 2 Te 2.88 Se 0.15 (i.e., Ag interstitial defects). The defect system composed of the Te antisites and Ag interstitials decoupled the electrical properties of the Bi 2 Te 2.88 Se 0.15 from its thermal properties. We endeavored to adjust the defect system to maximize the decoupling effect, which resulted in the preeminent average figures of merit for operation below 150 °C (ZT ave = 1.22 at 25–100 °C and 1.18 at 25–150 °C) among n-type Bi 2 (Te,Se) 3 materials. © 2019 Elsevier Ltd