标题： 稀土掺杂钙钛矿结构材料中低能光学声子在晶格热导率中的作用：第一性原理研究 显示英文标题

标题： The Role of Low-lying Optical Phonons in Lattice Thermal Conductance of Rare-earth Pyrochlores: A First-principle Study

摘要： 稀土焦绿石通常表现出异常低的晶格热导率，被认为是热障涂层的有前途的顶层材料。 然而，它们低热导率的结构来源仍然不清楚。 在本研究中，我们采用密度泛函理论和准谐近似方法，研究了两组稀土焦绿石，Ln2Zr2O7 (Ln = La, Nd, Sm, Gd) 和 Gd2T2O7 (T = Zr, Hf, Sn, Pb) 的声子特性。 通过与德拜模型结合的弛豫时间近似（RTA），预测了这些稀土焦绿石的热导率，结果与实验测量结果相符。 显示稀土焦绿石的低热导率主要来源于低能光学支与声学支之间的干涉。 然后明确了低能光学支的结构来源，并讨论了横波和纵波声学支中散射过程的竞争。 显示英文摘要

摘要： Rare-earth pyrochlores, commonly exhibiting anomalously low lattice thermal conductivities, are considered as promising topcoat materials for thermal barrier coatings. However the structural origin underlying their low thermal conductivities remain unclear. In the present study, we investigated the phonon properties of two groups of RE pyrochlores, Ln2Zr2O7 (Ln = La, Nd, Sm, Gd) and Gd2T2O7 (T = Zr, Hf, Sn, Pb) employing density functional theory and quasi harmonic approximation. Through the relaxation time approximation (RTA) with Debye model, the thermal conductivities of those RE pyrochlores were predicted, showing good agreement with experimental measurements. The low thermal conductivities of RE pyrochlores were shown to largely come from the interference between the low-lying optical branches and acoustic branches. The structural origin underlying the low-lying optical branches was then clarified and the competition between scattering processes in transverse and longitude acoustic branches was discussed.