Dense dislocation arrays embedded in grain boundaries for high-performance bulk thermoelectrics

TLDR

Thermoelectric technology is limited by low bulk alloy efficiency measured by zT, which can be improved by reducing lattice thermal conductivity through grain boundary and point‑defect scattering that target low‑ and high‑frequency phonons. Dense dislocation arrays formed at low‑energy grain boundaries by liquid‑phase compaction in Bi₀.₅Sb₁.₅Te₃ effectively scatter mid‑frequency phonons, substantially lowering lattice thermal conductivity. Full‑spectrum phonon scattering with minimal charge‑carrier scattering raised zT to 1.86 ± 0.15 at 320 K, and a thermoelectric cooler achieved a maximum temperature difference of 81 K, surpassing current commercial Peltier devices.

Abstract

The widespread use of thermoelectric technology is constrained by a relatively low conversion efficiency of the bulk alloys, which is evaluated in terms of a dimensionless figure of merit (zT). The zT of bulk alloys can be improved by reducing lattice thermal conductivity through grain boundary and point-defect scattering, which target low- and high-frequency phonons. Dense dislocation arrays formed at low-energy grain boundaries by liquid-phase compaction in Bi(0.5)Sb(1.5)Te3 (bismuth antimony telluride) effectively scatter midfrequency phonons, leading to a substantially lower lattice thermal conductivity. Full-spectrum phonon scattering with minimal charge-carrier scattering dramatically improved the zT to 1.86 ± 0.15 at 320 kelvin (K). Further, a thermoelectric cooler confirmed the performance with a maximum temperature difference of 81 K, which is much higher than current commercial Peltier cooling devices.