Synthesis of ternary Zintl compounds including alkali metal elements and characterization of their thermoelectric properties

2016 Fiscal Year Final Research Report

• Project/Area Number: 26288105
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Partial Multi-year Fund
• Section: 一般
• Research Field: Inorganic industrial materials
• Research Institution: Tohoku University
• Principal Investigator: Yamada Takahiro 東北大学, 多元物質科学研究所, 准教授 (10358260)
• Co-Investigator(Renkei-kenkyūsha): YAMANE Hisanori 東北大学, 多元物質科学研究所, 教授 (20191364)
• Project Period (FY): 2014-04-01 – 2017-03-31
• Keywords: 熱電材料 / ジントル化合物 / トンネル構造

Outline of Final Research Achievements

Ternary Zintl phases in the Na-Tr-Sn system (Tr=Al, Ga, In, Zn) were synthesized, and their thermoelectric properties were characterized. It is revealed that the sintered compacts or ingots of Na2+xTr2+xSn4-x (Tr = Al, Ga, In) and Na2ZnSn5 dimorphs, which have similar crystal structures, showed relatively high thermoelectric figures of merit with low thermal conductivities close to or less than 1 W m-1 K-1. A sintered compact of Na2+xGa2+xSn4-x, (x = 0.19) with a relative density of 73% showed highest dimensionless figure of merit, ZT, of 0.98 at 295 K, which is comparable to the performance of the Bi2Te3-based practical materials. In the crystal structures of the ternary Zintl phases in this study, helical tunnels are formed in a framework structure composed of Tr and Sn atoms, and a Na site with an occupancy of around 1/3 to 1 is located in the tunnels. The low thermal conductivities were probably due to disorder arrangement and large thermal vibration of Na atoms in the tunnels.

Free Research Field

無機固体材料化学