Atomic-scale regulation of ion motion and phonon scattering: ALD-driven interface engineering for stabilizing β-Zn 4 Sb 3

has high TE performance but suffers from severe zinc (Zn) ion migration under an external field. This work uses powder atomic layer deposition (pALD) to engineer atomic-scale zinc oxide (ZnO) interfaces that simultaneously suppress Zn ion migration and enhance phonon scattering. Through precise ZnO coatings (50 to 200 cycles), we create continuous barriers that immobilize interstitial Zn ions, eliminating Zn motion and inhibiting phase decomposition. Optimized 100 ALD cycle coatings reduce lattice thermal conductivity by >20% through intensified boundary-phonon scattering, yielding a stabilized, nondegrading figure of merit compared to uncoated performance. Crucially, the thermal stability of 100-ALD-cycle-coated sample persists through 39,260 thermal cycles under gradients of 220 kelvin, and Seebeck coefficient mapping exhibits a uniform distribution along temperature difference. Our approach establishes pALD as a promising atomic-level interface design in migration-prone TE materials, bridging high performance with long-term operational reliability.