Increasing the thermoelectric power factor via Ag substitution at Zn site in Ba(Zn1-xAgx)2Sb2

Abstract

Antimony-based Zintl compounds AZn2Sb2 (A = Ca, Sr, Ba, Eu, Yb) have been considered as an appealing thermoelectric system for developing the Zintl structure-property relationship and exploring novel thermoelectric materials. Differing from trigonal layered phases as represented by EuZn2Sb2, BaZn2Sb2 adopts a channel structure (Pnma) constructed by anionic framework [Zn2Sb2]2- and cationic Ba2+. Polycrystalline bulk samples of Ba(Zn1-xAgx)2Sb2 (0 ≤ x ≤ 0.01) were prepared by a solid-state reaction method and subsequent hot press sintering aiming at higher thermoelectric figure of merit. Seebeck coefficient, electrical and thermal conductivities of all the samples were measured in the temperature range 323–760 K. The substitution of Zn by Ag effectively improves the electrical transport properties through optimization of hole concentration. Of all the samples, Ba(Zn0.996Ag0.004)2Sb2 shows the highest thermoelectric power factor (9.45 μW cm−1 K−2@567 K) and figure of merit ZT (0.63@760 K), permitting the substitution strategy in anionic framework of Zintl phase for increasing thermoelectric efficiency.