N-Type Thermoelectric AgBiPbS<sub>3</sub> with Nanoprecipitates and Low Thermal Conductivity
Jinfeng Dong, Dan Zhang, Jiawei Liu, Yilin Jiang, Xian Yi Tan, Ning Jia, Jing Cao, Ady Suwardi, Qiang Zhu, Jianwei Xu, Jing‐Feng Li, Qingyu Yan
Abstract
Thermoelectric sulfide materials are of particular interest due to the earth-abundant and cost-effective nature of sulfur. Here, we report a new n-type degenerate semiconductor sulfide, AgBiPbS 3, which adopts a Fm 3̅ m structure with a narrow band gap of ∼0.32 eV. Despite the homogeneous distribution of elements at the scale of micrometer, Ag 2 S nanoprecipitates with dimensions of several nanometers were detected throughout the matrix. AgBiPbS 3 exhibits a low room-temperature lattice thermal conductivity of 0.88 W m –1 K –1, owing to the intrinsic low lattice thermal conductivity of Ag 2 S and the effective scattering of phonons at nanoprecipitate boundaries. Moreover, compared to AgBiS 2, AgBiPbS 3 demonstrates a significantly improved weighted mobility of >16 cm 2 V –1 s –1 at 300 K, leading to an enhanced PF of 1.6 μW cm –1 K –2 at 300 K. The superior electrical transport in AgBiPbS 3 can be attributed to the high valley degeneracy of the L point (the conduction band minimum), which is contributed by the Pb s and Pb p orbitals. Further, Ga doping is found to be effective in modulating the Fermi levels of AgBiPbS 3, leading to further enhancement of PF with a PF ave of 2.7 μW cm –1 K –2 in the temperature range of 300–823 K. Consequently, a relatively high ZT ave of 0.22 and a peak ZT of ∼0.4 at 823 K have been achieved in 3% Ga-doped AgBiPbS 3, highlighting the potential of AgBiPbS 3 as an n-type thermoelectric sulfide.