ICT2014 Abstracts

A series of Sb-doped Mg₂Si compounds were synthesized by self-propagating high-temperature synthesis (SHS) method combined with plasma activated sintering (PAS), which totally takes less than 20 minutes. The thermodynamic and kinetic parameters of SHS process, such as adiabatic temperature, ignition temperature, combustion temperature, as well as propagation speed of combustion wave were determined. Nano-precipitates is observed for the samples with Sb doping, playing great roles in electrical and thermal transport properties. Thermoelectric properties were measured in the temperature range of 300-875K. With the increase of Sb content, electrical conductivity s rises monotonously and markedly while Seebeck coefficient a varies with the opposite tendency compared with electrical conductivity s, due to the increase of the carrier concentration. Carrier mobility m_H declines slightly with n_H increasing, but is still larger than that of Sb-doped sample prepared by other methods, which could be ascribed to the purification during SHS processing. The thermal conductivity k rises with increasing x due to the enhanced carrier conductivity, since the lattice thermal conductivity k_L obviously drops on account of the strengthened point scattering induced by the doping of Sb and possible interface scattering by the nano-precipitates. As a result, the sample with x= 0.02 achieves the thermoelectric figure of merit ZT~0.65, one of the highest in doped binary Mg₂Si compounds investigated so far.