Thermoelectric Hexagonal A-Mg-Si with A = Sr and Ba Zintl Phases

• Published in: Journal of electronic materials Vol. 45; no. 10; pp. 5238 - 5245
• Main Authors: Kajitani, T., Takahashi, K., Saito, M., Suzuki, H., Kikuchi, S., Kubouchi, M., Hayashi, K.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.10.2016; Springer Nature B.V
• Subjects: Aluminum magnesium silicon alloys; Characterization and Evaluation of Materials; Chemistry and Materials Science; Electronics and Microelectronics; Heat conductivity; Instrumentation; Materials Science; Optical and Electronic Materials; Semiconductors; Solid State Physics; structure refinement; Alkaline earth metal; type magnesium silicon semiconductor; Zintl phase
• ISSN: 0361-5235; 1543-186X
• DOI: 10.1007/s11664-016-4658-3

Hexagonal A-Mg-Si with A = Sr and Ba Zintl phases are promising candidates for p -type magnesium silicides usable with n -Mg 2 Si under 900 K. We synthesized p -type A-Mg-Si Zintl phases by the spark plasma synthesis procedure. Mg 2 Si and Mg 2 A powders were mixed at the ratio of 1− x / x with x  = 0.3–0.4. Two-step synthesis was performed at 850 K for 20 min and 1100 K for 20 min under uniaxial pressure at 30 MPa. Sintered pellets exhibited a stable p -type thermoelectric property. These pellets consisted of several unknown phases. We found two semiconductor phases, namely A 2 Mg 4 Si 3 and A 2 Mg 12 Si 7 . The crystal structures of the 2/4/3- and 2/12/7-phases were P 6 ¯ 2 m (No. 189)- and P 6 3 / m (No. 176)-types, respectively. Sr 0.70 Mg 2 Si, Ba 3 Mg 10 Si 7 and Sr 3 Mg 10 Si 7 phases are newly found and characterized by a single crystal diffraction study. Previously found Sr 2 Mg 4 Si 3 single phase polycrystalline 30φ × 10 mm pellets were successfully synthesized. The thermoelectric performance of the Sr 2 Mg 4 Si 3 single phase sample was tested. The pellets exhibit p -type behavior from room temperature to 700 K. The thermal conductivity, κ , was almost constant at 1.1 W/mK from 350 K to 700 K.