Thermoelectric properties of bismuth-tellurium based compounds prepared by particulate processing

The influence of grain size and oxygen content on thermoelectric properties of sintered bismuth-tellurium based compounds has been investigated. Milling time and sintering atmosphere are the processing parameters that change grain size and oxygen content. Bismuth, tellurium, antimony and selenium powders were mixed to the composition of (Bi/sub 2/Te/sub 3/)/sub 0.2/(Sb/sub 2/Te/sub 3/)/sub 0.8/ for p-type and that of (Bi/sub 2/Te/sub 3/)/sub 0.975/(Bi/sub 2/Se/sub 3/)/sub 0.025/ -0.05 mass% SbI/sub 3/ for n-type, respectively. The powder mixtures were ball milled in acetone and consolidated by hot pressing at 460/spl deg/C for p-type and 500/spl deg/C for n-type in an argon or hydrogen atmosphere. The sintered samples exhibited a fine polycrystalline structure and the grain size was 0.1-10 /spl mu/m. The Seebeck coefficient, the resistivity and the thermal conductivity were measured at room temperature. The oxygen contents of the ball-milled powders and sintered samples were measured by the infrared absorption method. Sintering in a reducing atmosphere provided a lower oxygen content, yielding higher Z values. The obtained maximum Z values were 2.6/spl times/10/sup -3//K for the p-type and 2.5/spl times/10/sup -3//K for the n-type compound, respectively.