Rare‐earth pyrochlore materials are promising thermal barrier coatings materials and fundamental understanding of their thermal transport is crucial for further improving its performance. In this work, using density functional theory (DFT) method, we calculated the intrinsic lattice thermal conductivities of Ln₂Sn₂O₇ (Ln = La, Gd) and conducted a comprehensive analysis on the mode thermal conductivity, relaxation time, Grüneisen parameters, group velocity, and specific heat, respectively. It is shown that in pyrochlore‐type materials the number of the optical phonons is much larger than that of the acoustic phonon, and the thermal conductivity of acoustic phonons are suppressed, both of which increase the contribution ratio of optical phonons. Especially, through cumulative analysis, we found that the contribution of optical phonons is significant: the ratio of optical contribution is more than 50% and 64% in La₂Sn₂O₇ and Gd₂Sn₂O₇. This work provides a comprehensive picture illustrating the significant role of the optical phonons in the lattice thermal conduction in rare‐earth pyrochlore materials, and points out an avenue to obtain low thermal conductivity in complex structural thermal insulation materials.

中文翻译：

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烧绿石相关的Ln2Sn2O7（Ln = La，Gd）中晶格热导率对声子模的依赖

稀土烧绿石材料是很有前途的隔热涂层材料，对其热传递的基本了解对于进一步提高其性能至关重要。在这项工作中，我们使用密度泛函理论（DFT）方法，计算了Ln ₂ Sn ₂ O ₇的固有晶格热导率（Ln = La，Gd）并分别对模式热导率，弛豫时间，Grüneisen参数，组速度和比热进行了综合分析。结果表明，在烧绿石型材料中，光子的数量比声子的数量大得多，并且声子的导热系数受到抑制，这两者都增加了光子的贡献率。特别是，通过累积分析，我们发现光学声子的贡献显着：La ₂ Sn ₂ O ₇和Gd ₂ Sn ₂ O ₇中光学贡献的比率大于50％和64％。这项工作提供了全面的图像，说明了光学声子在稀土烧绿石材料中的晶格热传导中的重要作用，并指出了在复杂的结构绝热材料中获得低热导率的途径。