Synthesis and crystal growth of Mg2Si by the liquid encapsulated vertical gradient freezing method. (24th July 2015)

• Record Type: Journal Article
• Authors: Nakagawa, Reo; Katsumata, Hiroshi; Hashimoto, Satoshi; Sakuragi, Shiro
• Is Part Of: Japanese journal of applied physics. Volume 54:Number 8(2015:Aug.)
• Publication Date: 2015-07-24
• Subjects: Physics -- Periodicals; 621.05
• DOI: 10.7567/JJAP.54.085503
• Languages: English
• ISSNs: 0021-4922

Abstract

Abstract: The synthesis of Mg2 Si bulk crystals was performed by the vertical gradient freezing method using a KCl–MgCl2 eutectic liquid encapsulant. Stoichiometric polycrystalline Mg2 Si bulk crystals were successfully grown by changing the composition ratio of starting Mg and Si powders (Mg/Si) from 2.0 to 3.5. A chemical reaction between Mg2 Si and the crucible materials was inhibited using encapsulant materials, and the contamination by K or Cl originating from the encapsulant materials was not detected in almost all the samples. However, Mg evaporation could not be prevented completely during the synthesis and crystal growth. The optical band-gap energy of Mg2 Si bulk crystals became minimal (0.79 eV) at a Mg/Si ratio of 2.5, at which the maximum electron mobility of 202 cm 2 ·V −1 ·s −1 was obtained. These results indicate that the composition ratio of Mg/Si = 2.5 for starting Mg and Si powders was optimal for synthesizing Mg2 Si bulk crystals with high crystalline quality.