Homo-composition and Hetero-Structure Nanocomposite Pnma Bi2SeS2 - Pnnm Bi2SeS2 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 ( he C- he S) interfaces or hetero-composition and homo-structure ( he C- ho S) interfaces. Herein, a quasi homo-composition and hetero-structure ( ho C- he S) 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 ho C- he S 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 ho C- he S nanocomposites through a dopant-induced phase transition.