Fabrication of MnSi1.73 thermoelectric material by mechanical alloying.

The effect of mechanical alloying (MA) on the formation of MnSi1.73 thermoelectric compound was investigated. Due to the observed larger loss of Si relative to Mn during MA, the starting composition of Mn-Si was modified to MnSi1.83 and MnSi1.88. Sintering was performed in a spark plasma sintering (SPS) machine up to 600-800 degrees C under 50 MPa. The single phase MnSi1.73 has been obtained by MA of MnSi1.88 mixture powders for 200 h. It is also found that the grain size of MnSi1.73 compound analyzed by Hall plot method is reduced to 40 nm after 200 h of milling. Additionally, X-ray diffraction data shows that the SPS compact from 200 h MA powders consolidated at 600 degrees C consists of only nanocrystalline MnSi1.73 compound with a grain size of 90 nm.