La 도핑된 n형 Mg3SbBi 열전소재의 합성 및 열전특성 = Synthesis and Thermoelectric Properties of La-doped n-type Mg3SbBi Materials

다국어 초록 (Multilingual Abstract)

Mg3Sb2-based materials are very promising for thermoelectric applications at low temperatures,and are strong candidates to replace n-type Bi2Te3 for cooling and power generation. Substituting Sb atomswith chalcogen elements (S, Se, Te) is a typical method of n-type doping, while doping the Mg site with Group3 elements (Y, Sc) and Lanthanides has also been studied. Unique advantages have been recently reported.
In this study, a La-containing compound, LaSb, was used to fabricate n-type Mg3SbBi. The thermoelectricproperties of polycrystalline Mg3LaxSbBi (0 ≤ x ≤ 0.02) were investigated after synthesis by sequentialprocesses of arc melting, ball milling, and spark plasma sintering. Undoped Mg3SbBi is p-type with poorthermoelectric performance, and switched to n-type with La doping. The electron concentration of Mg3LaxSbBiincreased linearly with La content x, reaching up to 9.4 × 1019 cm-3 at x = 0.02. The power factor and the figureof merit were also maximized in Mg3La0.02SbBi, reaching 1.8 mW m-1K-2 (573 K) and 0.89 (623 K), respectively.
The lattice thermal conductivity decreased with increasing La content above ~500 K, and the minimum valueof 0.73 W m-1K-1 was obtained in Mg3La0.02SbBi. This study shows that La doping using LaSb provides areliable method for n-type doping of Mg3Sb2-based materials.