Enhancing Near‐Room‐Temperature Thermoelectric Performance of n‐Type Mg ₃ (Sb, Bi) ₂ ‐Based Materials via ZrB ₂ Heterointerface Engineering

Mg 3 (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 ZrB 2 is proposed to construct stable heterointerfaces within an Mg 3.4 Bi 1.29 Sb 0.7 Te 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 Mg 3 (Sb, Bi) 2 and ZrB 2 drive interfacial charge redistribution and generate a localized built‐in electric field at the contact region. Experimental results demonstrate that appropriate incorporation of ZrB 2 significantly increases carrier concentration and electrical conductivity while maintaining relatively high carrier mobility. Compared with the pristine matrix, the 1.0 wt.% ZrB 2 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 Mg 3 (Sb, Bi) 2 ‐based materials.