Large dimensionless figure of merit (ZT) and high thermoelectric conversion efficiency (η) are key factors to achieve practical application for the semiconductor materials. Here, two semiconductor materials of BeMF₃ (M = Al, Y) with excellent thermoelectric performance are reported. In particular, the ZT and η of BeMF₃ reach 4.76 and 48%, respectively, which are larger than those of all the reported thermoelectric materials in the literature. The electronic properties of BeMF₃ with first‐principles calculations based on density functional theory are carried out. The geometrical structures of BeMF₃ are fully relaxed and stabilities are confirmed by phonon dispersions. Transport properties are determined by the semiclassical Boltzmann transport theory with accurate band structures. The results show that the regions of the large Seebeck coefficients and electrical conductivity are overlapped with those of the small electronic thermal conductivity for the n‐ and p‐type systems and especially true for BeYF₃, which brings about the enhanced ZT values. Moreover, the small lattice thermal conductivities also contribute to the large ZT values.

中文翻译：

---

BeMF3的卓越高热电转换效率材料（M = Al，Y）

大的无量纲品质因数（ZT）和高的热电转换效率（η）是实现半导体材料实际应用的关键因素。在此，报道了两种具有优良热电性能的BeMF ₃（M = Al，Y）半导体材料。特别地，BeMF ₃的ZT和η分别达到4.76％和48％，比文献中所有已报道的热电材料的ZT和η大。利用基于密度泛函理论的第一性原理计算了BeMF ₃的电子性质。BeMF ₃的几何结构完全放松，并且通过声子分散证实了稳定性。传输性质由具有精确带结构的半经典玻尔兹曼传输理论确定。结果表明，对于n型和p型系统，大的塞贝克系数和电导率区域与较小的电子热导率区域重叠，对于BeYF ₃尤其如此，这带来了更高的ZT值。此外，小的晶格热导率也有助于大的ZT值。