From microstructure evolution to thermoelectric and mechanical properties enhancement of SnSe

Defect existing form and its evolution play an important role in the thermoelectric transport process. Here different forms of Pb into the SnSe system were introduced in order to improve the thermoelectric and mechanical properties of SnSe. Pb/SnSe samples were fabricated by vacuum melting, solid phase diffusion, spark plasma sintering and annealing treatment. The element valence mapping diagram and the X-ray photoelectron spectra (XPS) characteristic peaks of Pb show that a certain amount of elemental Pb exists in the initial state, and evolves into Pb2+ ion after annealing treatment. The micro-structure evolution leads to significant enhancement of the power factor and the ZT value. The power factor (PF) and the ZT value for Pb/SnSe increases to 623 μW/m/K2 and 1.12 at 773 K after annealing treatment, respectively. Compared with SnSe matrix, the hardness and fracture toughness of Pb/SnSe samples increased by about 40% and 10%, respectively. Reasonable control of microstructure evolution is expected to be a design idea to improve thermoelectric and mechanical properties of SnSe.