Tin telluride (SnTe) has received extensive attention as a substitute for conventional toxic PbTe for mid temperature range (500-800K). The intrinsic Sn vacancies in SnTe leads to very high hole concentration and thus exhibit very poor Seebeck coefficient along with high thermal conductivity, resulting in very low figure-of-merit (ZT～0.2 at 773K). In SnTe by substitution Sb and Ge at Sn site as Sn_(0.57)Sb_(0.13)Ge_(0.3)Te, we could achieve an enhanced ZT of 1.7 at 773K. The enhanced ZT of the doped SnTe compound is attributed to strong suppression of lattice thermal conductivity and improved Seebeck coefficient due to optimization of carrier concentration. With the optimized Sn_(0.57)Sb_(0.13)Ge_(0.3)Te composition a single thermoelement device was fabricated using Ni as contact layer at both ends. The fabricated device exhibited the conversion efficiency of ～4.8% for temperature difference of 473K.
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