Cu 1.5 Se y Te 1- y ( y = 0.2-0.7): A Series of Narrow Band Gap Semiconductors with Low Thermal Conductivity at Ambient Temperature.

Coinage metal chalcogenides offer ideal prerequisites for high thermoelectric performance and sensor applications, with their usually low lattice thermal and high electrical conductivity, as well as small band gaps. In the solid solution Cu 1.5 Se y Te 1- y we synthesized phase pure materials with y = 0.2-0.7 and characterized them concerning selected physical properties. X-ray crystal structure determination was performed for two representatives of the solid solution, Cu 1.5 Se 0.3 Te 0.7 and Cu 1.5 Se 0.5 Te 0.5 . The entire series crystallizes cubically, in space group Pm 3̅ n . No structural changes are observed between room temperature and the synthesis temperature of 723 K. The conductivity measurements and Seebeck coefficients of Cu 1.5 Se 0.3 Te 0.7 and Cu 1.5 Se 0.5 Te 0.5 indicate that the two representatives are narrow band gap semiconductors ( E g 0.06-0.08 eV). Both compounds show positive Seebeck coefficients and reasonably low thermal conductivities at moderate temperatures. Cu 1.5 Se 0.5 Te 0.5 is characterized by a bulk modulus of 40.9 GPa.