State Key Laboratory of Crystal Materials, Institute of Crystal Materials, Shandong University, Jinan, Shandong 250100, People's Republic of China.
J Am Chem Soc. 2013 Aug 14;135(32):11840-8. doi: 10.1021/ja403653m. Epub 2013 Aug 6.
For materials used in high-temperature thermoelectric power generation, the choices are still quite limited. Here we demonstrate the design and synthesis of a new class of complex Zintl compounds, Ca(1-x)RE(x)Ag(1-y)Sb (RE = La, Ce, Pr, Nd, Sm) (P63mc, No. 186, LiGaGe-type), which exhibit a high figure of merit in the high-temperature region. Compared with the parent structure that is based on CaAgSb (Pnma, No. 62, TiNiSi-type), an interesting structural relationship is established which suggests that important size and electronic effects govern the formation of these multinary phases. According to theoretical calculations, such a structural transformation from the orthorhombic TiNiSi-type to the hexagonal LiGaGe-type also corresponds to an obvious modification in the electronic band structure, which explains the observed significant enhancement of the related thermoelectric properties. For an optimized p-type material, Ca(0.84)Ce(0.16)Ag(0.87)Sb, a figure of merit of ~0.7 can be achieved at 1079 K, which is comparable to that of Yb14MnSb11 at the same temperature. In addition, due to the excellent thermal stability and high electrical conductivity, these materials are very promising candidates for high-temperature thermoelectric power generation.
对于高温热电发电中使用的材料，选择仍然相当有限。在这里，我们展示了一类新的复杂 Zintl 化合物的设计和合成，Ca(1-x)RE(x)Ag(1-y)Sb（RE=La、Ce、Pr、Nd、Sm）（P63mc，No.186，LiGaGe 型），它们在高温区表现出高的品质因数。与基于 CaAgSb（Pnma，No.62，TiNiSi 型）的母体结构相比，建立了一种有趣的结构关系，表明重要的尺寸和电子效应控制着这些多元相的形成。根据理论计算，这种从正交 TiNiSi 型到六方 LiGaGe 型的结构转变也对应于电子能带结构的明显修饰，这解释了观察到的相关热电性能的显著增强。对于优化的 p 型材料 Ca(0.84)Ce(0.16)Ag(0.87)Sb，在 1079 K 时可以实现约 0.7 的品质因数，与相同温度下的 Yb14MnSb11 相当。此外，由于出色的热稳定性和高导电性，这些材料是高温热电发电的很有前途的候选材料。
