Influence of fast neutron and gamma irradiation on the thermoelectric properties of n-type and p-type SiGe alloy

Abstract

The thermoelectric materials that work in radioisotope thermoelectric generators or space reactor power sources will be exposed to neutron irradiation and gamma irradiation for a long time. Herein, the influences of neutron irradiation doses between 1013 n/cm2 and 1015 n/cm2, and gamma irradiation of 104 Gy, on the transport properties of n- and p-type SiGe alloys were investigated. It was found that, neutron irradiation causes defects, and leads to a dramatic decrease in carrier mobility for both n- and p-type SiGe. As a result, the thermoelectric properties of both n- and p-type SiGe decline steeply after neutron irradiation. However, the thermoelectric properties of SiGe alloys can be restored by heat treatment at proper temperature. The n-type SiGe is more sensitive to neutron irradiation than p-type SiGe. After 1015 n/cm2 neutron irradiation, the electrical conductivity, power factor and ZT of n-type SiGe decrease to 0.014%, 5% and 3.8% that of an un-irradiated sample; while the electrical conductivity, power factor, and ZT of p-type SiGe decrease to 0.14%, 12% and 5.2% that of an un-irradiated sample. The healing temperature is 1273 K for n-type SiGe, while 623 K for p-type SiGe. Gamma irradiation has no obvious effect on the transport properties of SiGe alloys.