Shim Daewon, Lee Junsu, Ahmed Aziz, Pi Ji Hee, Choi Myung-Ho, Ok Kang Min, Lee Kyu Hyoung, You Tae-Soo
Department of Chemistry, Chungbuk National University, Cheongju 28644, Chungbuk, Republic of Korea.
Department of Materials Science and Engineering, Yonsei University, Seoul 03722, Republic of Korea.
Molecules. 2025 Jan 14;30(2):310. doi: 10.3390/molecules30020310.
Four quaternary Zintl phase thermoelectric (TE) materials belonging to the BaEuZnSb ( = 0.02(1), 0.04(1), 0.08(1), 0.15(1)) system were successfully synthesized using the molten Pb-flux or the conventional high-temperature reaction methods. Their crystal structures were characterized by both powder and single-crystal X-ray diffraction analyses, and all four isotypic title compounds adopted the orthorhombic BaCuS-type (, = 4, Pearson code 20) structure. The radius ratio criterion, based on the cationic and anionic elements (i.e., /), was successfully verified in the title system, as in our previous reports, where / > 1 for the BaCuS-type structure. A series of density functional theory calculations were performed using a hypothetical model with the idealized compositions of BaEuZnSb, and the results were compared with the ternary parental compound BaZnSb to understand the influence of Eu substituents in the BaEuZnSb system. A similar overall shape of the density of states (DOS) curves and the near-constant DOS values at before and after the cationic substitution suggest only marginal changes in the carrier concentration. Therefore, carrier mobility has a dominant role in rationalizing the observed variations in the electrical transport properties of the title system. Temperature-dependent TE property measurements proved that an increase in the Seebeck coefficient and a decrease in electrical conductivity were observed as the Eu substituents gradually increased in the BaEuZnSb system, although the overall and values were lower than those in the parental compound BaZnSb. The thermal conductivities of these title compounds were successfully lowered by phonon scattering, but due to the overall smaller electrical transport properties, the observed maximum was 0.49 at 773 K for BaEuZnSb.
采用熔融铅助熔剂法或传统高温反应法成功合成了四种属于BaEuZnSb（ = 0.02(1)、0.04(1)、0.08(1)、0.15(1)）体系的四元津特相热电（TE）材料。通过粉末和单晶X射线衍射分析对它们的晶体结构进行了表征，所有四种同型标题化合物均采用正交晶系的BaCuS型（， = 4，皮尔逊编码20）结构。与我们之前的报道一样，基于阳离子和阴离子元素（即 /）的半径比准则在标题体系中得到了成功验证，其中对于BaCuS型结构， / > 1。使用具有理想化组成BaEuZnSb的假设模型进行了一系列密度泛函理论计算，并将结果与三元母体化合物BaZnSb进行比较，以了解Eu取代基在BaEuZnSb体系中的影响。阳离子取代前后态密度（DOS）曲线的总体形状相似且在 处的DOS值近乎恒定，这表明载流子浓度仅发生了微小变化。因此，载流子迁移率在解释标题体系中观察到的电输运性质变化方面起主导作用。温度依赖性热电性能测量表明，在BaEuZnSb体系中，随着Eu取代基逐渐增加，塞贝克系数 增大而电导率 降低，尽管总体 和 值低于母体化合物BaZnSb中的值。这些标题化合物的热导率通过声子散射成功降低，但由于整体电输运性质较小，在773 K时观察到的BaEuZnSb的最大 为0.49。
