Superior multiphase interfaces in AgCuTe-based composite with significantly enhanced thermoelectric properties

It is common sense that phase interface (or grain boundary) could be used to scatter phonons in thermoelectric (TE) materials, resulting in low thermal conductivity. However, a large number of impurity phases are always so harmful for the transport of carriers that poor TE performance is obtained. Here, we demonstrate that numerous superior multiphase (AgCuTe, Ag₂Te, Cu₂Te, Cu_2-xTe and NiTe) interfaces with simultaneous strong phonon scattering and weak electron scattering could be realized in AgCuTe based TE materials. Owing to the similar chemical bonds in these phases, the depletion region at the phase interfaces, which acts as carrier scattering centers, could be ignored. Therefore, the power factor is obviously enhanced from ~ 609 to ~ 832 mW m^-1 K^-2, and the k is simultaneously decreased from ~ 0.52 to ~ 0.43 W m^-1 K^-1 at 636 K. Finally, a peak zT of ~ 1.23 at 636 K and an average zT of ~ 1.12 in the temperature range of 523 to 623 K is achieved, which is one of the best values among AgCuTe based TE materials. This study could provide a new guidance to enhance the performance by designing superior multiphase interfaces in TE materials.