Non-wetting crystal growth of Mg2Si by vertical Bridgman method and thermoelectric characteristics

• Published in: Journal of crystal growth Vol. 304; no. 1; pp. 196 - 201
• Main Authors: AKASAKA, Masayasu, IIDA, Tsutomu, NEMOTO, Takashi, SOGA, Junichi, SATO, Junichi, MAKINO, Kenichiro, FUKANO, Masataka, TAKANASHI, Yoshifumi
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier 01.06.2007
• Subjects: Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Growth from melts; zone melting and refining; Materials science; Methods of crystal growth; physics of crystal growth; Physics; Solid-fluid interfaces; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Theory and models of crystal growth; physics of crystal growth, crystal morphology and orientation; Wetting; Crystal growth; Electrical conductivity; B2. Semiconducting silicon compounds; Polycrystals; N type conductivity; XRD; Coatings; Silicon compounds; Thermoelectric materials; Wettability; Energy conversion; A2. Growth from melt; Thermal conductivity; Magnesium; Bridgman method; X-ray topography; Temperature dependence; Semiconductor materials; A1. X-ray topography; Mechanical properties; Mass spectroscopy; Seebeck effect; Adhesion; A1. X-ray diffraction; A2. Bridgman technique; Monocrystals; Residual impurity; B2. Thermoelectrics; Growth mechanism; Growth from melt; Figure of merit; Crystal growth from melts; Tribology
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/j.jcrysgro.2006.10.270

Magnesium siliside (Mg2Si) crystals have been grown using the vertical Bridgman method in a non-wetting growth environment, achieved by the use of an anti-adhesion coating on the crucible wall. The minimized adhesion of highly reactive molten magnesium (Mg), silicon (Si) and Mg2Si permitted easy removal of the grown ingot from the crucible, and the external shape of the grown ingot followed the shape of inner wall of the crucible. The grown crystals were a single phase of polycrystalline Mg2Si. X-ray analysis, such as Laue back-reflection and Lang transmission topographs revealed that grains obtained were single crystal in nature. Process induced contaminants were investigated by using grow discharge mass spectrometry (GDMS). The grown crystals exhibited n-type conductivity, which could result from the residual impurities in the Mg source material used and unintentional impurity incorporation during growth. Since Mg2Si is a material candidate for thermal-to-electric energy-conversion, the thermoelectric properties such as Seebeck coefficient, S, electrical conductivity, sigma, and thermal conductivity, kappa, were measured as a function of temperature up to 873K. Die-casting process induced characteristics of such thermoelectric properties are discussed. The maximum dimensionless figure-of-merit was estimated to be 0.17 at 656K.