Spacer strategy for exceptionally low thermal conductivity and high zT in antimony-doped bulk silicon. (June 2019) - Gayner, Chhatrasal
Abstract: In this study, the effects of inserting mica into bulk silicon for thermoelectric use on the alloying, nanosize, and spacer effects that are mainly used to suppress thermal conductivity are examined. Results revealed that nanocrystallinity as well as the extremely high doping amount of antimony in the grains drastically enhance the power factor. Dislocations or vacancies can be induced at the nanoscopic level by performing multiple heat treatments and by inserting spacer materials at the bulk level, which in turn can inhibit the heat transport in high thermally conductive materials. Furthermore, a record and reliable figure-of-merit of ∼0.6 at 1173 K is obtained for mica-inserted SiSb0.02, in addition to reduced thermal conductivity (∼6.5 W/m-K). These observations open avenues for silicon and can further lead to the formation of intermetallic, half-Heusler, and other chalcogenide materials. Graphical abstract: The high thermal conductivity of silicon (Si, ∼140 W/m-K) at room temperature exhibits an adverse effect on thermoelectricity. For Si to become a promising thermoelectric material, it is imperative to attain a thermal conductivity of 5–7 W/m-K. The thermoelectric figure-of-merit, zT, can be achieved either by enhancing the power factor or by suppressing the thermal conductivity. In this study, a method is proposed to reduce the thermal conductivity by the insertion of mica to examine the spacer effect.Image 1 Highlights: Sb as a new dopant is explored to enhance the thermoelectric performance of Si. Addition of a spacer in Sb-doped Si leading to the large reduction in thermal conductivity. Nanocrystallinity and extremely high doping amount of Sb in the grains drastically enhance the power factor. Reliable figure-of-merit of ∼0.6 at 1173 K is obtained for mica-inserted SiSb0.02.