Thermoelectric Properties of Sb-Doped Mg 2 Si Prepared Using Different Silicon Sources

Magnesium silicide (Mg 2 Si) compounds doped with 8000 ppm Sb were prepared using different Si sources via liquid–solid reaction synthesis and hot pressing. The Si sources were solar-grade Si, metal-grade Si, and sludge Si. The Si sludge generated during the cutting of Si wafers was recycled as a Si source. The x-ray diffraction (XRD) patterns of the Si sludge corresponded to Si, silicon dioxide (SiO 2 ), and C, whereas the solar-grade Si and metal-grade Si were indexed as a single Si phase. For the sintered compact samples, the Mg 2 Si phase was predominant in all the samples. However, small amounts of impurity phases, MgO and SiC, were identified in the sintered Mg 2 Si that used sludge Si. The thermoelectric properties of the Mg 2 Si produced using solar-grade Si or metal-grade Si were almost the same at the measured temperature. The efficacy of the low-purity metal-grade Si was demonstrated. However, the power factor and thermal conductivity of the Mg 2 Si produced using sludge Si were smaller than those of the other samples over the entire measured temperature range. However, the maximum value of ZT was almost the same.