Homo-composition and hetero-structure nanocomposite Pnma Bi(2)SeS(2) - Pnnm Bi(2)SeS(2) with high thermoelectric performance

Nanocomposite engineering decouples the transport of phonons and electrons. This usually involves the in-situ formation or ex-situ addition of nanoparticles to a material matrix with hetero-composition and hetero-structure (heC-heS) interfaces or hetero-composition and homo-structure (heC-hoS) interfaces. Herein, a quasi homo-composition and hetero-structure (hoC-heS) nanocomposite consisting of Pnma Bi(2)SeS(2) - Pnnm Bi(2)SeS(2) is obtained through a Br dopant-induced phase transition, providing a coherent interface between the Pnma matrix and Pnnm second phase due to the slight structural difference between the two phases. This hoC-heS nanocomposite demonstrates a significant reduction in lattice thermal conductivity (~0.40 W m(−1) K(−1)) and an enhanced power factor (7.39 μW cm(−1) K(−2)). Consequently, a record high figure-of-merit ZT(max) = 1.12 (at 773 K) and a high average figure-of-merit ZT(ave) = 0.72 (in the range of 323–773 K) are achieved. This work provides a general strategy for synergistically tuning electrical and thermal transport properties by designing hoC-heS nanocomposites through a dopant-induced phase transition.