Two new Zintl antimonides, Ca₁₀MSb₉ (M = Al and Cd), have been synthesized and characterized for the first time and their thermoelectric performance has been evaluated without additional optimization. The two phases can be readily synthesized either by Sn-flux or direct solid-state reactions. The compounds are isotypic and crystallize in a tetragonal crystal system with the space group P4₂/mnm (no. 136). The crystal structure is highly complex with significant structural disorder—both occupational and positional. For its careful elucidation, both single-crystal X-ray diffraction methods and Rietveld refinements of powder X-ray diffraction data for polycrystalline bulk samples were required. Despite the significant disorder, the structures retain their charge balance and these new Zintl phases are shown to be intrinsic semiconductors with a bandgap of about 0.5 eV. High-temperature transport measurements reveal remarkably low thermal conductivity (0.6–0.7 W m⁻¹ K⁻¹) in the temperature range 323 K to 573 K, which is even lower than that of the well-known thermoelectric Zintl material Yb₁₄MnSb₁₁. Additionally, Seebeck coefficient measurements showed a very high value for Ca₁₀AlSb₉, approaching 350 μV K⁻¹ at 573 K. Therefore, we speculate that with proper systematic work and further optimization, these and potentially other Zintl compounds from this extended family can show excellent thermoelectric performance.

中文翻译：

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超低导热率热电 Zintl 相：Ca10AlSb9 和 Ca10CdSb9 的合成、结构表征和输运特性


首次合成并表征了两种新的 Zintl 锑化物 Ca ₁₀ MSb ₉ （M = Al 和 Cd），并且在无需额外优化的情况下评估了它们的热电性能。这两相可以通过锡助焊剂或直接固态反应轻松合成。这些化合物是同型的，并在具有空间群P 4 ₂ / mnm （编号136）的四方晶系中结晶。晶体结构非常复杂，具有明显的结构无序性——无论是位置还是位置。为了仔细阐明，需要单晶 X 射线衍射方法和多晶块状样品的粉末 X 射线衍射数据的 Rietveld 改进。尽管存在明显的无序性，但结构仍保持其电荷平衡，并且这些新的 Zintl 相被证明是带隙约为 0.5 eV 的本征半导体。高温输运测量表明，在323 K至573 K的温度范围内，其热导率非常低（0.6–0.7 W m ^-1 K ^-1 ），甚至低于著名的热电Zintl材料Yb ₁₄ MnSb ₁₁ 。此外，塞贝克系数测量显示 Ca ₁₀ AlSb ₉的值非常高，在 573 K 时接近 350 μV K ^-1 。 因此，我们推测，通过适当的系统工作和进一步优化，这些以及来自这个大家族的其他潜在 Zintl 化合物可以表现出优异的热电性能。