Manipulating the intrinsic vacancies for enhanced thermoelectric performance in Eu₂ZnSb₂ Zintl phase

Zintl compounds have caught great attention in thermoelectric applications due to their intrinsic “electron-crystal, phonon-glass” structures. Previous studies suggested that Zintl-phase Eu₂ZnSb₂ was a promising thermoelectric material due to its ultralow thermal conductivity. In this work, we used Ag to regulate the Zn–Sb framework for enhanced electrical properties, and prepared Eu₂Zn_1-0.5xAg_xSb₂ (x = 0.02, 0.06, and 0.1) by ball milling and spark plasma sintering. The additional Ag fills the initial vacancies and causes both increased carrier concentration and mobility. The maximum ZT reaches ~0.92 at 823 K for Eu₂Zn_0.97Ag_0.06Sb₂. By further reducing the Zn content, the carrier concentration increases close to the optimum value, and a peak ZT value of ~1.1 at 823 K was achieved for Eu₂Zn_0.95Ag_0.06Sb₂.