Thermoelectric Properties of Sb-Doped Mg2Si Prepared Using Different Silicon Sources

Magnesium silicide (Mg2Si) 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 (SiO2), and C, whereas the solar-grade Si and metal-grade Si were indexed as a single Si phase. For the sintered compact samples, the Mg2Si phase was predominant in all the samples. However, small amounts of impurity phases, MgO and SiC, were identified in the sintered Mg2Si that used sludge Si. The thermoelectric properties of the Mg2Si 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 Mg2Si 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.