Atomic-defect-suppressed pristine p-type Bi0.3Sb1.7Te3 as robust high-performance thermoelectrics for power generation and cooling

Abstract

High-strength high-performance p-type (Bi,Sb)₂Te₃ are of pivotal importance for near-room-temperature thermoelectric conversions, the reliable synthesis and fabrication has been viewed of imperative priority. It is known that the energy-favorable formation of anti-site Sb_Te^’ and vacancy v_Sb^''' acceptor defects from high-temperature syntheses results in additional charge carriers and scattering centers for electrical and phonon transport. However, how p-type (Bi,Sb)₂Te₃ with minimal lattice defects function remains to be scrutinized. Herein, we present the synergistic enhancements of mechanical robustness and thermoelectric property in crystallographic-defect-suppressed pristine (Bi,Sb)₂Te₃ through a simple mechanical alloying combined with spark-plasma-sintering (SPS) process. The Sb_Te^’ and v_Sb^''' acceptor defects were efficiently restrained, contributing to markedly increased charge carrier mobilities. A slightly enlarged band gap of 0.24 eV underpinned enhanced thermoelectric performance for pristine Bi_0.3Sb_1.7Te₃ over a wide temperature range, delivering high zT_{300 K} of 1.16 and zT_ave of 1.21 over 300–473 K. Interestingly, the confined in-situ grain coarsening during SPS with uniform dispersive nanopores readily endowed an ultra-high compressive strength of 206 MPa, surpassing that of reported (Bi,Sb)₂Te₃ so far. A 7-pair module (coupled with n-Bi₂Te₃) was fabricated, demonstrating a competitive ΔT over 70 K at T_hot = 300 K. Furthermore, a power-generation module coupled with n-Mg₃SbBi registered a cutting-edge thermoelectric conversion efficiency of 9.5% at a temperature gradient of 250 K. The strategy eliminates the need of complex processing nor extrinsic doping for pristine (Bi,Sb)₂Te₃, demonstrating great potentials in thermoelectric power generation and cooling applications.