Unconventional Electronic Properties of Mg2Si Thermoelectrics Revealed by Fast-Neutron-Irradiation Doping

In this work, we systematically investigated the electrical resistivity, Hall, and magnetoresistance effects of Al-doped Mg2Si thermoelectrics, irradiated with a fluence of fast neutrons and consequently isochronally annealed at moderate high temperatures up to 500 °C. We found that the fast-neutron bombardment itself only slightly modified the electronic properties. Meanwhile, a series of the postirradiation high-temperature anneals affected the properties dramatically. Thus, after annealing at temperatures of 275–325 °C, Mg2Si:Al showed pronounced jumps in both the electrical resistivity and the Hall constant values by several orders of magnitude. This unexpected electronic transition corresponded to a significant variation in the carrier concentration. We proposed that this unusual electronic transition may be related to temperature-assisted chemical bonding of the radiation defects that can involve free charge carriers in the sample, thereby tuning dramatically its transport properties. We proposed a ...