HSIN-JAY WUWei, Pai-ChunPai-ChunWeiCheng, Hao-YenHao-YenChengDeng, Jie-RuJie-RuDengChen, Yang-YuanYang-YuanChen2024-09-182024-09-182017https://www.scopus.com/record/display.uri?eid=2-s2.0-85029503977&origin=resultslisthttps://scholars.lib.ntu.edu.tw/handle/123456789/721175The n-type I-V-VI2 AgBiSe2 features intrinsically low κ due to the anharmonicity of chemical bonds. Experimentally-determined isothermal section guides the starting compositions for the following AgBiSe2-based alloys. Among the undoped alloys, the Ag25Bi25Se50 exhibits a highest peak of zT∼0.75, and yet the neighboring Ag20Bi27.5Se52.5, which involves a Se-rich liquid phase, has a much lower zT∼0.3 at 748 K, respectively. With the incorporation of Ge, the (GeSe)0.03(AgBiSe2)0.97 exhibits an ultralow κ∼0.3 (W/mK), owing to the formation of Bi2Se3 nano-precipitate in the size of 20–40 nm. Additionally, the moiré fringes with a periodicity of 0.25 nm are observed in the Bi2Se3 nano-precipitate, implying the presence of local mass fluctuation and superlattice, which could further lead to enhancing phonon scattering and reduced κ. As a result, the ultra-low κ∼0.3 (W/mK) boosts the peak of zT up to zT∼1.05 in n-type (GeSe)0.03(AgBiSe2)0.97, which shows a 140% enhancement compared with that of the undoped AgBiSe2. © 2017 Acta Materialia Inc.Bi2 Se3 nano-precipitateIsothermal sectionn-type AgBiSe2Thermoelectric materialjournal article10.1016/j.actamat.2017.09.0292-s2.0-85029503977