Effect of Silicon and Sodium on Thermoelectric Properties of Thallium-Doped Lead Telluride-Based Materials

Thallium (Tl)-doped lead telluride (Tl0.02Pb0.98Te) thermoelectric materials fabricated by ball milling and hot pressing have decent thermoelectric properties but weak mechanical strength. Addition of silicon (Si) nanoparticles strengthened the mechanical property by reducing the grain size and defect density but resulted in low electrical conductivity that was not desired for any thermoelectric materials. Fortunately, doping of sodium (Na) into the Si added Tl0.02Pb0.98Te brings back the high electrical conductivity and yields higher figure-of-merit ZT values of similar to 1.7 at 770 K. The ZT improvement by Si addition and Na doping in Tl0.02Pb0.98Te sample is the direct result of concurrent electron and phonon engineering by improving the power factor and lowering the thermal conductivity, respectively.