Reduced Lattice Thermal Conductivity in Thermoelectric α-MgAgSb via Sb2Te3 Powder Atomic Layer Deposition.

α-MgAgSb is an environmentally friendly alternative to traditional tellurium-based thermoelectric materials for near room temperature applications. In this study, we enhance the thermoelectric properties of α-MgAgSb by introducing a secondary Sb2Te3 phase using powder atomic layer deposition (powder ALD), with the aim to modify phonon scattering mechanisms and reduce the lattice thermal conductivity. Powder ALD is a thin-film deposition technique that allows for the deposition of self-limiting monolayers on high aspect ratio surfaces, enabling the conformal coating of nanopowder regardless of particle morphology. Sb2Te3 was selected as the coating material due to its oxygen-free synthesis route and its potential for good interfacial compatibility with the α-MgAgSb powders. Our results reveal a 10% decrease in lattice thermal conductivity of bulk α-MgAgSb as the powder ALD coating thickness increases from pristine to 20 cycles of Sb2Te3, without affecting the primary phase purity. Our findings highlight the effectiveness of nonoxide powder ALD coatings in suppressing lattice thermal transport, offering a promising pathway for interface-engineered, low-toxicity thermoelectric materials.