Enhancing Near-Room-Temperature Thermoelectric Performance of n-Type Mg₃(Sb, Bi)₂-Based Materials via ZrB₂...

Mg₃(Sb, Bi)₂-based thermoelectric materials have shown considerable potential for low-grade waste-heat recovery near room temperature. However, their thermoelectric performance remains limited by the strong coupling among electrical conductivity, Seebeck coefficient, and thermal conductivity. Here, a conductive ceramic composite strategy based on ZrB₂ is proposed to construct stable heterointerfaces within an Mg_3.4Bi_1.29Sb_0.7Te_0.01 matrix, thereby enabling the synergistic regulation of interfacial charge distribution, carrier transport, and phonon scattering. First-principles calculations reveal that the work-function difference between Mg₃(Sb, Bi)₂ and ZrB₂ drive interfacial charge redistribution and generate a localized built-in electric field at the contact region. Experimental results demonstrate that appropriate incorporation of ZrB₂ significantly increases carrier concentration and electrical conductivity while maintaining relatively high carrier mobility. Compared with the pristine matrix, the 1.0 wt.% ZrB₂ composite sample exhibits substantially enhanced room-temperature thermoelectric performance. Specifically, the room-temperature power factor increases from 19.11 to 28.51 µW cm^-1 K^-2 and reaches 30.82 µW cm^-1 K^-2 at 373 K. Meanwhile, a maximum ZT value of 1.22 is achieved at 573 K, and the corresponding single-leg theoretical maximum conversion efficiency reaches 12.92% under a temperature difference of 470 K, demonstrating conductive ceramic heterointerface engineering as an effective strategy for enhancing the thermoelectric performance of Mg₃(Sb, Bi)₂-based materials.