Pavonite Homologous CdAg2.5Sb6.5Se12 as a Promising Thermoelectric Compound

Pavonite compounds with complex and disordered structures are promising thermoelectric materials due to their extremely low lattice thermal conductivity. Herein, we report the pavonite compound CdAg_2.5Sb_6.5Se₁₂ with an extremely low lattice thermal conductivity of 0.36 W m^–1 K^–1 at 773 K. Because of the poor electrical properties, we adjust the ratio of Ag and Cd to populate a large quantity of carriers, thus increasing the carrier concentration. Based on the single parabolic band model, the density of state effective mass increases from 0.3 m_e in the pristine sample to 1.3 m_e in the doped one (m_e is the electron mass) because of the increase in the valence band degeneracy. Ultimately, the extremely low thermal conductivity combined with the enhanced electrical performance results in enhanced ZT ∼ 0.35 at 672 K compared with the pristine sample of ∼0.02.