In-situ formed nano-pore induced by Ultrasonication boosts the thermoelectric performance of Cu2Se compounds

• Ultrasonic wave breaks SHS Cu 2 Se powders with residual stress into the refined structure. • The refined powders tend to enclose and form pores during SPS process. • In-situ nano-pores intensify the phonon scattering, lowering the thermal conductivity. • Enhancement of thermoelectric performance is achieved in pore-incorporated Cu 2 Se bulk. Herein, we reported an enhanced ZT value of 1.71 is achieved via in-situ formed nano-pore. The nano-pore is mainly in-situ formed by a combination method with self-propagating high temperature synthesis, ultrasonic treatment and spark plasma sintering. The highly non-equilibrium feature of combustion synthesis leads to the large residual stress in the grains. Due to the presence of residual stress in the grains, the ultrasonic treatment breaks the grains into the structure with sub-nanometer scale and high surface energy, which tends to enclose and to form in-situ pores during the fast sintering process. The liquid-like Cu + and the in-situ formed nano-pore intensify the phonon scattering, suppressing the thermal conductivity to 0.40–0.45 Wm −1 K −1 at 873 K for pore-incorporated samples. In comparison with the melting synthesized sample, a remarkable enhancement of ZT value over 16% at 873 K is achieved. In the temperature interval from 473 K to 873 K, the averaged ZT value for Cu 2 Se with in-situ formed nano-pores reaches 1.10, improved by 32.5% when compared to that of the melting synthesized sample. This work demonstrates that the combination of self-propagating high temperature synthesis, ultrasonic treatment and spark plasma sintering is an effective way to synthesize the samples with in-situ nano-pores and paves a new avenue for improving the thermoelectric performance of the Cu 2 Se materials.