Tailoring the phase transition of silver selenide at the atomistic scale

Thermoelectric materials provide promising solutions for energy harvesting from the environment. Silver selenide (Ag₂Se) material attracts much attention due to its excellent thermoelectric properties under superionic phase transition. However, the optimal thermoelectric figure of merit occurs during the phase transition at high temperatures, making low-temperature devices unable to benefit from their best thermoelectric performance. Here, we tailored the phase transition process of Ag₂Se materials with various sizes, and probed the phase transition temperature by in situ transmission electron microscopy. By tuning the motion of the atoms near the surface using size-dependent surface energy, the phase transition-induced process is tailored towards low temperatures. This work paves the way for future phase transition engineering to enhance thermoelectric performance.