The dependence of lattice thermal conductivity on phonon modes in pyrochlore-related Ln2Sn2O7 (Ln = La,Gd) |
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Authors: | Zheng Li Jun Yang Yan Xing Chunlei Wan Satoshi Watanabe Wei Pan |
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Affiliation: | 1. State Key Lab of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing, P. R. China;2. Department of general education, Army Engineering University of PLA, Nanjing, P. R. China;3. New Energy Technology Engineering Lab of Jiangsu Province, School of Science, Nanjing University of Posts & Telecommunications, Nanjing, P. R. China;4. Department of Materials Engineering, Graduate School of Engineering, The University of Tokyo, Tokyo, Japan |
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Abstract: | 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. |
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Keywords: | lattice thermal conductivity phonons pyrochlore stannate |
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