  Experimental results have shown that the quaternary compound Cu2ZnSnSe4 is an
excellent thermoelectric material. This inspires us to seek the other
quaternary compounds with similar chemical formula to Cu2ZnSnSe4 as
thermoelectric materials. In this paper, we use the first-principle method to
systematically explore the electronic and phonon structures, mechanical,
thermal and thermoelectric properties of p- and n-type Ag2XYSe4 (X=Ba, Sr;
Y=Sn, Ge). It is found that the ZT maximum for n-type Ag2SrGeSe4 can reach up
to 1.22 at 900 K, and those for p-type Ag2SrSnSe4, Ag2SrGeSe4 and Ag2BaSnSe4
can reach up to 1.20, 1.13 and 1.12, respectively. Our work not only shows that
Ag2XYSe4 (X=Ba, Sr; Y=Sn, Ge) are a kind of potential thermoelectric materials,
but also can inspire more theoretical and experimental researches on
thermoelectric properties of quaternary compounds.
