Spark Plasma Sintering and Thermoelectric Evaluation of nanostructured Magnesium Silicide (Mg2Si)

Recently magnesium silicide (Mg2Si) has received great interest from thermoelectric (TE) society because it is non-toxicity, environmental friendliness, comparatively abundance and low production cost material as compared to other TE systems. Also it has exhibited promising TE properties such as: high electrical conductivity and low thermal conductivity, which improved the overall performance (ZT). In this work Mg2Si powder was obtained through ball milling under inert atmosphere, starting from commercial magnesium silicide pieces (99,99%, Alfa Aesar). The Mg2Si powder was filled in the graphite die to perform spark plasma sintering (SPS) and the process parameters like temperature, heating rate, holding time and applied pressure were studied in details. The aim of this study is to optimize SPS consolidation parameters in order to achieve high density of compacts with improved mechanical properties and to maintain the nanostructured grains. X Ray diffraction (XRD) was utilized to investigate the crystalline phase of compacted samples and Scanning Electron Microscopy (SEM) coupled with Energy Dispersive Spectroscopy (EDS) used to evaluate the detailed microstructural and chemical composition respectively. All compacted samples have shown the compaction density up to 99%. Temperature dependent TE characteristics of compacted Mg2Si such as thermal conductivity, electrical conductivity and Seebeck coefficient were measured over temperature range of 300 - 900 K.