New Ternary Arsenides for High-Temperature Thermoelectric Applications

Two isostructural materials Mo 3 (Sb,Te) 7 and Re 3 (Ge,As) 7 were synthesized and characterized in our laboratories during the past decade. Both crystallize in the Ir 3 Ge 7 type, possessing the space group Im3̅m . They show excellent potential for thermoelectric energy conversion at high temperatures. Our recent physical properties measurements revealed a higher Seebeck coefficient for the new ternary Re 3 Sn 0.2 As 6.8 , as compared with Re 3 (Ge,As) 7 , while the power factors are comparable. Rietveld refinements indicate an increasing unit cell volume with increasing Sn content. It has also been found that intercalation of an additional transition-metal atom (Co, Ni) into the cubic void of Re 3 (Ge,As) 7 can significantly alter the Seebeck coefficient.