The objective of this program is the development of a materials process technology which will reliably provide a high yield of materials for constructing Peltier thermo-elements with a high materials figure of merit over the temperature range 250-350k. The study,, in cooperation with the university of Virginia, will focus on the materials system consisting of (Bi, Sb)2(Te, Se)3 alloys for both p- and n-type thermo elements for two reasons: (1) the literature shows that specific compositions in this alloy system have provided exceptionally high figures of merit (3.2-3.4 x 10-3/k deg at 300k) and a maximum Peltier fooling of 77 deg k; and (2) investigators at the university of Virginia have recently obtained the highest reported figure of merit of 3.7 x 10-3/deg k for a p-type (Bi, Sb)2(Te, Sb)3 alloy. Based on the university of Virginia results, the process selected for fabricating these alloys will involve a combination of rf induction melting and horizontal bridgman growth in order to achieve high chemical homogeneity and minimum internal strains. Such material should exhibit a higher charge carrier mobility and hence an improvement in the electrical component to the figure of merit.
