Radiation Effects in Thermoelectrics. 2. Permanent and Quasi-Permanent Effects of Pile Bombardment on Several Compound Semiconductors

摘要

The effects of reactor bombardment on the thermoelectric properties of several compound semiconductors have been observed experimentally for exposure doses up to 2.3 x 10 to the 19th power fast (E > 1 MeV) neutrons/sq cm. Results are reported for the following materials: PbTe; Ge.95Bi.05T3; Ag2Se; n- and p-types of a Ge-Si alloy whose exact composition is classified; (GeTe)90%(AgSbTe2)10%; CoSi; n- and p-types of commercial grade Bi2Te3; and single-crystal, stoichiometric Bi2Te3. Properties measured were Seebeck coefficient, electrical resistivity, and thermal diffusivity. The effects observed ranged from an apparently simple case of change in majority charge carrier concentration due to transmutations, to rather complicated cases in which the behavior of the variables was strongly influenced, both for the better and for the worse, by post-irradiation, thermally activated processes, e.g., annealing. In some cases, no effects at all were found. Some indications that substantial improvements in the thermoelectric figure of merit for the Ge-Si alloys may be possible through appropriate sequences of irradiation and post-irradiation thermal treatment, were seen.