Abnormal thermal expansion coefficients in (Nd1−xDyx)2Zr2O7 pyrochlore: The effect of low-lying optical phonons
Chemical doping is a normal strategy to tune thermal expansion coefficient (TEC) of ceramics in engineering applications, but the resultant TEC values usually follow Vegard’s law, as doping does not modify the nature of chemical bonding in ceramics and its anharmonicity. In this paper, we report abn...
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| Format: | Article |
| Language: | English |
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Tsinghua University Press
2023-05-01
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| Series: | Journal of Advanced Ceramics |
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| Online Access: | https://www.sciopen.com/article/10.26599/JAC.2023.9220734 |
| _version_ | 1797801039115583488 |
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| author | Zesheng Yang Yi Li Wei Pan Chunlei Wan |
| author_facet | Zesheng Yang Yi Li Wei Pan Chunlei Wan |
| author_sort | Zesheng Yang |
| collection | DOAJ |
| description | Chemical doping is a normal strategy to tune thermal expansion coefficient (TEC) of ceramics in engineering applications, but the resultant TEC values usually follow Vegard’s law, as doping does not modify the nature of chemical bonding in ceramics and its anharmonicity. In this paper, we report abnormal TEC behavior in (Nd1−xDyx)2Zr2O7 ceramics, where the TEC values remarkably exceed the values predicted by Vegard’s law and even exceed the values obtained for two constituents Nd2Zr2O7 and Dy2Zr2O7. In addition to a reduction in lattice energy with an increasing molar fraction of Dy (x) value, we attribute the additional increase in the TEC to the high concentration of Dy dopants in a pyrochlore (P) region, which can soften low-lying optical phonon modes and induce strongly avoided crossing with acoustic phonon branches and enhanced anharmonicity. We believe that this finding can provide a new route to break through the restriction imposed by the conventional Vegard’s law on the TEC values and bring new opportunities for thermal barrier coatings (TBCs) or ceramic/metal composites towards realizing minimized thermal mismatch and prolonged service life during thermal cycling. |
| first_indexed | 2024-03-13T04:44:21Z |
| format | Article |
| id | doaj.art-52ea1d5995b34575be38012d87140974 |
| institution | Directory Open Access Journal |
| issn | 2226-4108 2227-8508 |
| language | English |
| last_indexed | 2024-03-13T04:44:21Z |
| publishDate | 2023-05-01 |
| publisher | Tsinghua University Press |
| record_format | Article |
| series | Journal of Advanced Ceramics |
| spelling | doaj.art-52ea1d5995b34575be38012d871409742023-06-19T03:59:28ZengTsinghua University PressJournal of Advanced Ceramics2226-41082227-85082023-05-011251001101410.26599/JAC.2023.9220734Abnormal thermal expansion coefficients in (Nd1−xDyx)2Zr2O7 pyrochlore: The effect of low-lying optical phononsZesheng Yang0Yi Li1Wei Pan2Chunlei Wan3State Key Laboratory of New Ceramics & Fine Processing, Tsinghua University, Beijing 100084, ChinaState Key Laboratory of New Ceramics & Fine Processing, Tsinghua University, Beijing 100084, ChinaState Key Laboratory of New Ceramics & Fine Processing, Tsinghua University, Beijing 100084, ChinaState Key Laboratory of New Ceramics & Fine Processing, Tsinghua University, Beijing 100084, ChinaChemical doping is a normal strategy to tune thermal expansion coefficient (TEC) of ceramics in engineering applications, but the resultant TEC values usually follow Vegard’s law, as doping does not modify the nature of chemical bonding in ceramics and its anharmonicity. In this paper, we report abnormal TEC behavior in (Nd1−xDyx)2Zr2O7 ceramics, where the TEC values remarkably exceed the values predicted by Vegard’s law and even exceed the values obtained for two constituents Nd2Zr2O7 and Dy2Zr2O7. In addition to a reduction in lattice energy with an increasing molar fraction of Dy (x) value, we attribute the additional increase in the TEC to the high concentration of Dy dopants in a pyrochlore (P) region, which can soften low-lying optical phonon modes and induce strongly avoided crossing with acoustic phonon branches and enhanced anharmonicity. We believe that this finding can provide a new route to break through the restriction imposed by the conventional Vegard’s law on the TEC values and bring new opportunities for thermal barrier coatings (TBCs) or ceramic/metal composites towards realizing minimized thermal mismatch and prolonged service life during thermal cycling.https://www.sciopen.com/article/10.26599/JAC.2023.9220734thermal barrier coating (tbc)thermal expansionfirst-principles calculationsavoided crossing |
| spellingShingle | Zesheng Yang Yi Li Wei Pan Chunlei Wan Abnormal thermal expansion coefficients in (Nd1−xDyx)2Zr2O7 pyrochlore: The effect of low-lying optical phonons Journal of Advanced Ceramics thermal barrier coating (tbc) thermal expansion first-principles calculations avoided crossing |
| title | Abnormal thermal expansion coefficients in (Nd1−xDyx)2Zr2O7 pyrochlore: The effect of low-lying optical phonons |
| title_full | Abnormal thermal expansion coefficients in (Nd1−xDyx)2Zr2O7 pyrochlore: The effect of low-lying optical phonons |
| title_fullStr | Abnormal thermal expansion coefficients in (Nd1−xDyx)2Zr2O7 pyrochlore: The effect of low-lying optical phonons |
| title_full_unstemmed | Abnormal thermal expansion coefficients in (Nd1−xDyx)2Zr2O7 pyrochlore: The effect of low-lying optical phonons |
| title_short | Abnormal thermal expansion coefficients in (Nd1−xDyx)2Zr2O7 pyrochlore: The effect of low-lying optical phonons |
| title_sort | abnormal thermal expansion coefficients in nd1 xdyx 2zr2o7 pyrochlore the effect of low lying optical phonons |
| topic | thermal barrier coating (tbc) thermal expansion first-principles calculations avoided crossing |
| url | https://www.sciopen.com/article/10.26599/JAC.2023.9220734 |
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