Fabrication of Mg2Si thermoelectric materials by mechanical alloying and spark-plasma sintering process
Chung-Hyo Lee1, Seong-Hee Lee, Sung-Yong Chun
1Department of Advanced Materials Science and Engineering, Mokpo National University, Muan-gun, Chonnam, 534-729, Korea.
Abstract:
A mixture of pure Mg and Si powders with an atomic ratio 2:1 has been subjected to mechanical alloying (MA) at room temperature to prepare the Mg2Si thermoelectric material. Mg2Si intermetallic compound with a grain size of 50 nm can be obtained by MA of Mg66.7Si33.3 powders for 60 hours and subsequently annealed at 620 degrees C. Consolidation of the MA powders was performed in a spark plasma sintering (SPS) machine using graphite dies up to 800-900 degrees C under 50 MPa. The shrinkage of consolidated samples during SPS was significant at about 250 degrees and 620 degrees C. X-ray diffraction data shows that the SPS compact from 60 h MA powders consolidated up to 800 degrees C consists of only nanocrystalline Mg2Si compound with a grain size of 100 nm.
