Nanotructured high thermoelectric figure-of-merit in n-type bulk SiGe alloys

Silicon germanium alloys (SiGe) have been the exclusice choice for radiosotope thermoelectric generators (RTGs) because of its reliability and high operating temperatures. In this paper, by using mechanical alloying method, nano-sized phosphorous-doped (n-type) SiGe alloy powders were produced, followed by direct current induced hot press technique, bulk samples were obtained with $\sim $100{\%} density. The thermoelectric properties, including electrical conductivity, Seebeck coefficient, and thermal conductivity, were measured in the temperature range from 25 to 900 $^{\circ}$C. A maximum ZT of around 1.3 at 900$^{\circ}$C was obtained under certain doping concentration and hot press conditions, mainly due to thermal conductivity reduction from nano-structured SiGe grains of 20 nm.