Material-genome perspective towards tunable thermal expansion of rare-earth di-silicates. Issue 10 (August 2018)

• Record Type: Journal Article
• Authors: Luo, Yixiu; Sun, Luchao; Wang, Jiemin; Wu, Zhen; Lv, Xirui; Wang, Jingyang
• Is Part Of: Journal of the European Ceramic Society. Volume 38:Issue 10(2018)
• Page Start: 3547
• Page End: 3554
• Publication Date: 2018-08
• Subjects: Rare-earth disilicates -- Thermal/environmental barrier coating -- Thermal expansion -- Phonon anharmonicity -- Density functional theory; Ceramic materials -- Periodicals; Composite materials -- Periodicals; Matériaux céramiques -- Périodiques; Composites -- Périodiques; Ceramic materials; Composite materials; Periodicals; Electronic journals; 666.05
• DOI: 10.1016/j.jeurceramsoc.2018.04.021
• Languages: English
• ISSNs: 0955-2219

Abstract

Abstract: Optimization of thermal expansion coefficient (CTE) mismatch among constituent rare-earth silicate layers is a critical challenge for the optimal multilayer thermal/environmental barrier coating (T/EBC) architecture for SiCf /SiCm CMCs. In this study, thermal expansion properties for β-, γ- and δ-RE2 Si2 O7 polymorphs are investigated via DFT calculations. The interaction between rare-earth (RE) atoms and neighboring bridging oxygen (OB ) atoms, as well as the structure of [O3 SiOB SiO3 ] pyrosilicate units are the characteristic "gene" that controls the positive or negative contribution from low-frequency vibration patterns to the overall phonon anharmonicity, and eventually determine the significantly different CTE of RE2 Si2 O7 polymorphs. Inspired by the concept of "genome modification", γ-(Dy0.15 Y0.85 )2 Si2 O7 solid solution is designed and synthesized, which shows notable enhancements of CTE as compared with γ-Y2 Si2 O7 . Such tunable CTE could presumably be explained by doping-induced localized lattice distortion around [O3 SiOB SiO3 ] pyrosilicate units, leading to switchable magnitude of negative contribution from low-frequency phonons to thermal expansion.