IRRADIATION EFFECTS ON THERMOELECTRIC MATERIALS

Abstract

Abstract The effects of neutron irradiation on the thermoelectric properties, i.e., electrical resistivity Seebeck coefficient, and relative thermal conductivity, were determined for lead telluride (PbTe), germanium telluride (GeTe), bismuth-germanium telluride (Bi0.05Ge0.95Te), and lithium-nickel oxide (Li0.06Ni0.94O). Two types of experiments were performed: (1) Using the same apparatus for both pre- and post-irradiation measurements, thermoelectric properties were measured over a range of temperatures, and (2) in situ measurements were made of electrical resistivity and Seebeck coefficient at elevated temperatures. Pre-post- experiments were made on thermoelectric materials irradiated to the total integrated neutron flux (nvt) levels as noted in the following table: Materials Total integrated neutron flux (nvt calculated) 1. GeTe 4 · 5 × 10 18 thermal 2. GeTe 1 · 5 × 10 20 fast 3. Bi0.05Ge0.95Te 9 · 4 × 10 18 thermal 4. Bi0.05Ge0.95Te 2 · 7 × 10 19 thermal 5. Bi0.05Ge0.95Te 1 · 5 × 10 20 fast 6. PbTe -n- type 1 · 4 × 10 19 thermal 7. PbTe -n- type 1 · 5 × 10 20 fast 8. PbTe -n- type 1 · 5 × 10 29 fast|none All of the materials irradiated in a thermal flux showed evidence of radiation damage; however, essentially complete recovery of the electrical resistivity, Seebeck coefficient, and thermal conductivity occurred after annealing at average temperatures up to 300°C. Irradiation in a fast flux resulted in damage which was not completely removed by annealing to an average temperature of up to 300°C. In-pile measurements of electrical resitivity and Seebeck coefficient were made on p-type PbTe and Li0.06Ni0.94O irradiated to a total integrated thermal neutron flux of 9 × 1018 at a temperature of approximately 400°C. Measurements made on Li0.06Ni0.94O revealed no change in electrical resistivity and Seebeck coefficient as a function of integrated neutron flux. For the PbTe sample, the Seebeck coefficient increased slightly while the electrical resistivity increased by a factor of two. This change is attributed to a loss of sodium volatilization.