Synergistically optimized thermoelectric properties of Ag1+xIn5Se8 alloys†
The AgIn5Se8 diamond-like compound with low thermal conductivity is deemed to be a promising thermoelectric material, but its performance is limited by its low electrical conductivity. Herein, we report an effective method to increase the maximum and average zT values of AgIn5Se8-based compounds by adding excess Ag. All the samples exhibit increased carrier concentrations of ∼1018 cm−3 at ambient temperature, leading to considerably enhanced electrical conductivity. Meanwhile, the excess Ag creates numerous point defects, twin boundaries and stacking faults, which serve as the internal-strain field to induce additional phonon scattering and lattice softening to lower the lattice thermal conductivity. The synergistic strategy yields a peak zT value of 0.67 at 883 K and an average zT value of 0.34 from 323 to 883 K for Ag1.03In5Se8.