Thermoelectric Properties of New As-based Compounds Ba_1-xK_xZn₂As

Sb-based 122-systems crystalized in the CaSi₂Al₂-type structure (space group: P-3m1) exhibit high thermoelectric properties. Examining Sb-based 122-systems is now one of hot topics in the development of thermoelectric materials. As-based 122-systems, on the other hand, were not reported as high thermoelectric materials. In this work, we examined thermoelectric properties of As-based Ba_1-xK_xZn₂As₂ compounds crystallized in the α-BaCu₂S₂-type structure (space group Pnma) for x ≤ 0.02 and the ThCr₂Si₂-type structure for x ≥ 0.04 [1]. The κ_L is independent on K concentration with relatively low values of 0.8 - 1.1 W/mK at 773 K. This is almost the same value as Sb based BaZn₂Sb₂ crystallized in the α-BaCu₂S₂-type structure, though Ba_1-xK_xZn₂As₂ consists of As atoms, which are lighter than Sb atoms. The obtained highest value of the dimensionless figure-of-merit ZT is 0.67 at T = 900 K for x = 0.02. The result opens a new class of thermoelectric materials with the As-based 122 Zintl compounds.
[1] K. Kihou, H. Nishiate, A. Yamamoto, and C. H. Lee, Inorg. Chem. 56, 3709 (2017).