Bi₂Te₃-based thermoelectric materials are attractive near room temperature, but their performance is constrained by sensitive carrier-concentration control, strong crystallographic anisotropy, and compositional instability from volatile Te. Here, a multilayer core-shell structure was fabricated by conformally coating Bi₂Te₂.₇Se₀.₃ (BTS) powders with ZnO–TiO₂ layers using rotary-type powder atomic layer deposition (pALD), followed by spark plasma sintering. Two configurations with the same ~4 nm total oxide thickness were prepared: a ZnO/TiO₂ bilayer (ZT) and a ZnO/TiO₂/ZnO/TiO₂ multilayer (DZT), where multilayer denotes the deposition scheme rather than a directly imaged layered architecture. Electron microscopy confirmed uniform amorphous shells that were retained as continuous interfacial films after sintering. The oxide interfaces donated electrons to the matrix, raising the carrier concentration and effective mass while preserving mobility and thereby enhancing the electrical conductivity and power factor; simultaneously they scattered phonons and suppressed bipolar conduction, lowering the lattice thermal conductivity. DZT achieved the highest power factor, attributed to its different deposition configuration, whereas ZT exhibited the lowest thermal conductivity; the two coated specimens reached comparable figures of merit (zT) within the measurement uncertainty, both markedly exceeding uncoated BTS. ALD-based interface engineering thus decouples electronic and phononic transport in n-type Bi₂Te₃.

1. Introduction 
2. Experimental Section 
    2.1 Fabrication of the core-shell structure and sintered body 
    2.2 Characterization 
3. Results and Discussion 
    3.1 Microstructure of the core-shell powders 
    3.2 Microstructure of the sintered green body 
    3.3 Thermoelectric properties 
4. Conclusion 
Funding
Conflict of Interest 
Data Availability Statement 
Author Information and Contribution 
Acknowledgments
References

• 은수민(서울과학기술대학교 신소재공학과) | Su Min Eun (Department of Materials Science and Engineering, Seoul National University of Science and Technology, Seoul 01811, Republic of Korea)
• 신진경(서울과학기술대학교 신소재공학과) | Jin Kyeong Shin (Department of Materials Science and Engineering, Seoul National University of Science and Technology, Seoul 01811, Republic of Korea)
• 정세빈(서울과학기술대학교 신소재공학과) | Se Been Jeong (Department of Materials Science and Engineering, Seoul National University of Science and Technology, Seoul 01811, Republic of Korea)
• 이의선(서울과학기술대학교 신소재공학과) | Eui Seon Lee (Department of Materials Science and Engineering, Seoul National University of Science and Technology, Seoul 01811, Republic of Korea)
• 오승탁(서울과학기술대학교 신소재공학과, 서울과학기술대학교 분말기술연구소) | Sung-Tag Oh (Department of Materials Science and Engineering, Seoul National University of Science and Technology, Seoul 01811, Republic of Korea, The Institute of Powder Technology, Seoul National University of Science and Technology, Seoul 01811, Republic of Korea)
• 최병준(서울과학기술대학교 신소재공학과, 서울과학기술대학교 분말기술연구소) | Byung Joon Choi (Department of Materials Science and Engineering, Seoul National University of Science and Technology, Seoul 01811, Republic of Korea, The Institute of Powder Technology, Seoul National University of Science and Technology, Seoul 01811, Republic of Korea) Corresponding author