A thermoelectric material of the general formula Ag.sub.1-XM.sub.mM'Q.sub.2+m, wherein M is selected from the group consisting of Pb, Sn, Ca, Sr, Ba, divalent transition metals, and combinations thereof; M' is selected from the group consisting of Bi, Sb, and combinations thereof; Q is selected from the group consisting of Se, Te, S, and combinations thereof; 8.ltoreq.m.ltoreq.24; and 0.01.ltoreq.x.ltoreq.0.7. In embodiments of the invention, the compositions exhibit n-type semiconductor properties. In preferred embodiments, x is from 0.1 to 0.3, and m is from 10 to 18. The compositions may be synthesized by adding stoichiometric amounts of starting materials comprising Ag, M, M', and Q to a reaction vessel, heating the starting materials to a temperature and for a period of time sufficient to melt the materials, and cooling the reaction product at a controlled rate of cooling.