A new n-type and improved p-type pseudo-ternary (Bi/sub 2/Te/sub 3/)(Sb/sub 2/Te/sub 3/)(Sb/sub 2/Se/sub 3/) alloy for Peltier cooling

Abstract

The pseudo-ternary alloy of (Bi/sub 2/Te/sub 3/)(Sb/sub 2/Te/sub 3/)(Sb/sub 2/Se/sub 3/) has been explored for over twenty-five years with little progress in the figure of merit, p-type 3.4/spl times/10/sup -3//K and n-type 3.2/spl times/10/sup -3//K. Using multiple dopants, Te and SbI/sub 3/, higher figure of merit material can be achieved without creating more of the deleterious pure Te commonly found as a second phase in the p-type alloy, (Bi/sub 2/Te/sub 3/)/sub 25/(Sb/sub 2/Te/sub 3/)/sub 72/(Sb/sub 2/Se/sub 3/)/sub 3/. Using a combination of the two dopants figures of merit as high as 3.7/spl times/10/sup -3//K have been achieved. Using two dopants has also permitted the creation of an n-type alloy with a composition of (Bi/sub 2/Te/sub 3/)/sub 70/(Sb/sub 2/Te/sub 3/)/sub 25/(Sb/sub 2/Se/sub 3/)/sub 5/. Previously n-type doping could not be achieved with a single dopant because the alloy as grown always exhibits p-type conductivity. Using Te and SbI/sub 3/ together as dopants, or SbI/sub 3/ by itself in this alloy produces n-type material with a figure of merit of 3.4/spl times/10/sup -3//K.