Realizing High Thermoelectric Performance in the CaCd2Sb2 Zintl Phase via Tuning the Carrier Concentration and Anionic Framework
Xinyu Wang, Miao Zhang, Lingmei Zhao, Zhikang Zhang, Hong Tao, Gexia Ruan, Yize Mu, Zuoxu Wu, Fuhua SunAbstract
The “phonon glass-electron crystal” (PGEC) structure of Zintl phase compounds makes them promising candidates for thermoelectric applications. CaCd2Sb2-based materials are characterized by lower carrier concentration, which limits their thermoelectric performance. In this work, K was selected to optimize the carrier concentration, thereby enhancing the electrical conductivity. Mg was alloyed at the Cd site to tune the anionic framework. In synergy with Ba at the Ca site, this dual-alloying strategy introduces intensive point defects, which strengthen phonon scattering, leading to an ultralow lattice thermal conductivity of ∼0.4 W m–1 K–1 at 750 K. Finally, a peak zT value of ∼1.3 was achieved in K0.01Ba0.5Ca0.49Mg0.25Cd1.75Sb2 at 750 K, which is ∼88% enhancement compared with that of CaCd2Sb2.