Interface-engineered Bi₂Te₃ powders via atomic layer deposited TiO₂-ZnO multilayer for improved thermoelectric performance

Tailoring the interfacial properties at the nanoscale is essential for improving the performance of thermoelectric materials, where the simultaneous optimization of electronic and phononic transport remains a key challenge. We used atomic layer deposition (ALD) to conformally coat Bi₂Te₃Se_0.3 (BTS) powders with TiO₂–ZnO multilayer oxides. Two configurations were fabricated: ZnO/TiO₂ bilayers (2 nm thick) and ZnO/TiO₂/ZnO/TiO₂ multilayers (1 nm thick). The coated powders were consolidated by spark plasma sintering (SPS). The ALD-grown multilayers uniformly coated the powder and remained highly dense after sintering. Consequently, the multilayer-coated structure showed improved carrier concentration and mobility owing to interfacial electron donation and diffusion doping, enhancing electrical conductivity. Their high-density and continuous layers effectively reduce lattice thermal conductivity, resulting in a zT of 0.8 at 460 K, a 27% increase over uncoated BTS. The controlled interface design enabled effective tuning of both charge carrier and phonon transport. This study demonstrates that conformal interfacial engineering via ALD is a promising strategy for enhancing thermoelectric performance by simultaneously tuning the electronic and phononic transport properties through nanoscale interface design.