High Ductility and Excellent Thermoelectric Performance in Te-Stabilized Cubic AgTeS Solid Solutions.

The stabilization at low temperatures of the AgS cubic phase could afford the design of high-performance thermoelectric materials with excellent mechanical behavior, enabling them to withstand prolonged vibrations and thermal stress. In this work, we show that the AgTeS solid solutions, with Te content within the optimal range 0.20 ≤ ≤ 0.30, maintain a stable cubic phase across a wide temperature range from 300 to 773 K, thus avoiding the detrimental phase transition from monoclinic to cubic phase observed in AgS. Notably, the AgTeS (0.20 ≤ ≤ 0.30) samples showed no fractures during bending tests and displayed superior ductility at room temperature compared to AgS, which fractured at a strain of 6.6%. Specifically, the AgTeS sample demonstrated a bending average yield strength of 46.52 MPa at 673 K, significantly higher than that of AgS, whose bending average yield strength dropped from 80.15 MPa at 300 K to 12.66 MPa at 673 K. Furthermore, the thermoelectric performance of the AgTeS (0.20 ≤ ≤ 0.30) samples surpassed that of both InSe and pure AgS, with the AgTeS sample achieving the highest value of 0.59 at 723 K. These results indicate substantial potential for practical applications due to enhanced durability and thermoelectric performance.