Thermoelectric properties of n-type polycrystalline Bi/sub x/Sb/sub 2-x/Te/sub 3/ alloys

(Bi/sub x/Sb/sub 1-x/)/sub 2/Te/sub 3/ (.5/spl les/x/spl les/.7) polycrystalline samples were synthesized using a combination of melting and powder metallurgy techniques. The samples were hot pressed in graphite dies and cut perpendicular and parallel to the pressing direction. Samples were examined by microprobe analysis to determine their atomic composition. The thermoelectric properties were measured at room temperature in both directions. These properties include Seebeck coefficient, thermal conductivity, electrical resistivity, and Hall effect. The thermoelectric figure-of-merit, ZT, was calculated from these properties. The best ZT was /spl sim/.5, given by annealed (Bi/sub .7/Sb/sub .3/)/sub 2/Te/sub 3/. Selected samples were also annealed at various temperatures in an attempt to optimize ZT. The annealing substantially impacted the thermoelectric properties due to a combination of improved crystallinity and changes in defect concentration. These materials could potentially be incorporated into advanced thermoelectric unicouples for a variety of power generation applications.