High thermoelectric properties of As-based 122-Zintl compounds Ba_1-xK_xCd₂As₂

122-Zintl phase is well known as a high performance thermoelectric (TE) material. For the past decade, Sb-based 122-Zintl compounds have been found that the dimensionless figure-of-merit exceeds the value of 1. In contrast, there are only few studies on As-based Zintl compounds. Lighter atomic mass of As than Sb discourages exploring As-based compounds because the lattice thermal conductivity (k_L) usually becomes higher with lighter atoms. Recently we have found that Ba_1-xK_xZn₂As₂ exhibits low k_L of 0.8 W/mK and high ZT of 0.67 at 900 K [1]. This discovery demonstrates that the As-based 122-Zintl compounds also have a potential for a high performance TE material.
Being based of the first principle calculation, we decided to examine TE properties of As-based 122-Zintl compounds Ba_1-xK_xCd₂As₂. Polycrystalline samples of Ba_1-xK_xCd₂As₂ was synthesized by the solid reaction method. The power factor of Ba_1-xK_xCd₂As₂ reached to 1.3 mW/mK² at T = 773 K. k_L was 0.5 W/mK at T = 773 K. Consequently, ZT reached to 0.81 at 773 K, which is the highest ZT value at As-based 122-Zintl compounds [2].

[1] K. Kihou, H. Nishiate, A. Yamamoto, C. H. Lee, Inorg. Chem. 56, 3709 (2017).
[2] H. Kunioka, K. Kihou, H. Nishiate, A. Yamamoto, H. Usui, K. Kuroki and C. H. Lee, Dalton Trans., (in press).