Four quaternary Zintl phase solid-solutions in the Ca₉Cd_3+x–yM_x+ySb₉ (M = Cu, Zn) system were successfully synthesized, and their crystal structures were characterized by using both powder X-ray and single-crystal X-ray diffractions. All title compounds adopted the Ca₉Zn_3.1In_0.9Sb₉-type phase, featuring three-dimensional anionic frameworks composed of tetrahedral [MSb₄] and tricoordinated [MSb₃] moieties interconnected via vertex-sharing. Detailed structural analyses revealed that various types of partial and mixed occupations existed at the M sites, and the Zn2 site in Ca₉Cd_2.65(1)Zn_1.84(2)Sb₉ exhibited a trigonal pyramid geometry, distinct from the simple planar geometry observed in parental Ca₉Zn_3.1In_0.9Sb₉. The density of states (DOS) analyses revealed successful p-type doping in the Cu-containing compound, indicated by a shift in the Fermi level and an increase in the hole carrier concentration. Crystal orbital Hamilton population curves displayed optimized interatomic interactions between neighboring anionic elements, maintaining structural stability despite a slight increase in the DOS level. Thermoelectric property measurements were conducted for the first time on the Ca₉Zn_3.1In_0.9Sb₉-type phase. The results demonstrated that the Zn-containing compounds exhibited higher Seebeck coefficients and lower thermal conductivities, resulting in larger ZT values compared to the Cu-containing compounds. The highest ZT value of 0.70 at 775 K was observed for Ca₉Cd_4.05Zn_0.45Sb₉.

中文翻译：

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深入了解 Zintl 相 Ca9Cd3+x–yMx+ySb9 （M = Cu， Zn） 系统的晶体结构和热电性能


在 Ca ₉ Cd _3+x–y M _x+y Sb ₉ （M = Cu， Zn） 体系中成功合成了 4 种季 Zintl 相固溶体，并使用粉末 X 射线和单晶 X 射线衍射对它们的晶体结构进行了表征。所有标题化合物均采用 Ca ₉ Zn _3.1 In _0.9 Sb ₉ 型相，具有由四面体 [MSb ₄ ] 和三配位 [MSb ₃ ] 部分组成的三维阴离子框架，通过顶点共享互连。详细的结构分析表明，M 位点存在各种类型的部分和混合职业，Ca ₉ Cd _2.65(1) Zn _1.84(2) Sb ₉ 中的 Zn2 位点表现出三角金字塔几何形状，不同于在 Sb ₉ 中的 _0.9 亲本 Ca ₉ Zn _3.1 中观察到的简单平面几何形状.态密度 （DOS） 分析显示，在含铜化合物中成功实现了 p 型掺杂，费米能级的变化和空穴载流子浓度的增加表明了这一点。晶体轨道 Hamilton 种群曲线显示相邻阴离子元素之间的原子间相互作用得到优化，尽管 DOS 水平略有增加，但仍保持结构稳定性。首次在 Ca ₉ Zn _3.1 In _0.9 Sb ₉ 型相上进行了热电性能测量。结果表明，与含 Cu 化合物相比，含 Zn 化合物表现出更高的 Seebeck 系数和较低的热导率，导致 ZT 值更大。在 775 K 处观察到 Ca ₉ Cd _4.05 Zn _0.45 Sb ₉ 的最高 ZT 值为 0.70。