Enhanced thermoelectric properties of Zintl phase YbMg2Bi1.98 through Bi site substitution with Sb

Benefiting from the unique "Phonon-Glass, Electron-Crystal" (PGEC) characteristic, Zintl phases have been considered as a kind of promising thermoelectric materials. For the typical AM(2)X(2) compounds with the CaAl2Si2-type structure, YbMg2Bi2 has shown competitive thermoelectric performance recently. Nevertheless, the optimization of YbMg2Bi2 compounds is primarily focused on the substitution on Yb or Mg site. Herein, the Bi site is substituted by isoelectric Sb and the effect on the thermoelectric transport behavior is investigated. The partial substitution reduces the carrier concentration and induces the lattice deformation caused by the different atomic radius and mass between Bi and Sb, further leading to the decreased power factor and thermal conductivity. Fortunately, the reduction extent of the thermal conductivity outperforms that of power factor. Finally, the Sb substitution successfully results in a better thermoelectric performance compared with that of the pristine YbMg2Bi1.98. Especially, the calculated energy conversion efficiency (eta) of YbMg2Bi1.88Sb0.1 which also possesses a relatively high output power density reaches the maximum value of 9.8 % when T-h = 873 K, and T-c = 300 K, respectively. This work demonstrates that the idea of substitution on anionic site should be a new strategy to achieve better ZT values for AM(2)X(2) compounds. (C) 2020 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.