Ultra-low thermal conductivity in B2O3 composited SiGe bulk with enhanced thermoelectric performance at medium temperature region

Abstract

Commonly, SiGe is considered as a typical thermoelectric material with a favorable performance in the high temperature region. Here, we report a new strategy through the addition of the nano-second-phase B₂O₃ into SiGe via ball milling and spark plasma sintering technique, aiming to realize high thermoelectric performance in the medium temperature region. By controlling the amount of B₂O₃ added to the SiGe matrix, the thermal conductivity is greatly reduced because of the compound effects of the nano-second-phase and beneficial microstructure. Simultaneously, the power factors are also enhanced, resulting in a high ZT of 1.47 of the p-type B₂O₃/SiGe bulk composite at 873 K. Our ZT values are 116% higher than the typical materials used in radio-isotope thermoelectric generators (RTGs), and show 104% enhancement over the p-type SiGe alloys in the present study. This study opens a new way to widen and improve the thermoelectric performance for narrow temperature region materials, and is especially highly effective for the environmentally friendly SiGe materials.