Enhancement of thermoelectric performance in Mg3(Sb,Bi)2 through engineered lattice strain and controlled carrier scattering

Abstract

Mg3(Sb,Bi)2 emerges as a promising thermoelectric (TE) material due to its rich elemental composition and high TE performance, offering potential for industrial applications. In this study, we found out that the elevated sintering temperatures can introduce dislocations, vacancies, and nanoscale precipitates in the lattice, inducing desirable lattice strain. Higher lattice strain broadens the phonon dispersion, effectively reducing lattice thermal conductivity. Simultaneously, high-temperature sintering increases grain size, significantly mitigating grain boundary carrier scattering and enhancing carrier mobility. As a result, we observe a 31.4 % increase in lattice strain, a 30 % reduction in lattice thermal conductivity, a 200 % rise in room temperature mobility, ultimately achieving an outstanding figure of merit (zT) of 1.7 at 750 K for Mg3.22Ho0.03Sb1.5Bi0.5. The synergistic effect of engineering lattice strain to minimize lattice thermal conductivity and controlling carrier scattering mechanisms to enhance mobility significantly provides a novel strategy to improve TE performance of Mg3(Sb,Bi)2-based materials.