Sticking-free growth of bulk Mg/sub 2/Si crystals by the vertical bridgman method and their thermoelectric properties

Abstract

Melt growth of Mg 2 Si was conducted using the vertical Bridgman growth method. Because magnesium is highly reactive at the growth temperature (1358 K), crucible materials were chosen to avoid chemical reactions and sticking between the crucibles, the molten Mg 2 Si and magnesium vapor. Crucibles made of alumina, pyrolytic boron nitride (pBN), and hexagonal boron nitride (hBN) were examined. The use of a pBN crucible enabled in the suppression of chemical reactions involving molten Mg 2 Si and vaporized magnesium at elevated growth temperatures, resulting in no sticking of the grown crystal to the inner wall of the crucible. While the measured conductivity for samples grown using an alumina crucible was n-type for all of the temperatures that were investigated, the samples that were grown using a pBN crucible exhibited p-type conductivity. This correlates closely with unintentional boron incorporation during the growth process.

Theoretical analysis of structure and formation energy of impurity-doped Mg2Si: Comparison of first-principles codes for material properties

“…1; it belongs to the Fm " 3m space group where Si and Mg atoms are located at the 4a and 8c sites, respectively. 9) The atomic positions in the conventional unit cell, in units of the lattice constant, are given by the following coordinates:…”

“…In recent years, much attention has been focusing on Mg 2 Si [1][2][3][4][5][6][7][8][9] as a promising candidate for mid-temperature (600-900 K) thermoelectric applications, and it is therefore expected to be suitable for use in a waste heat recovery system in the automotive industry. This material also possesses advantageous attributes for practical use in terms of cost and environmental protection: it is cheap, lightweight, nontoxic, and composed of elements abundant in the Earth's crust.…”

Influence of native defects on structural and electronic properties of magnesium silicide

“…Mg 2 Si has an antifluorite crystal structure of the Fm " 3m space group, in which the Si and Mg atoms are located at the 4a and 8c sites, respectively, 22) as shown in Fig. 1(a).…”