Theoretical Study on the Relationship Between Crystal Chemistry and Properties of Quaternary Y-Si-O-N Oxynitrides

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• 作者：Luchao Sun ; Bin Liu ; Jiemin Wang ; Zhen Li and Jingyang Wang
• 刊名：Journal of the American Ceramic Society
• 出版年：2016
• 出版时间：July 2016
• 年：2016
• 卷：99
• 期：7
• 页码：2442-2450
• 全文大小：989K
• ISSN：1551-2916

文摘

Y–Si–O–N quaternary oxynitrides (Y₅Si₃O₁₂N, Y₄Si₂O₇N₂, YSiO₂N, Y₂Si₃O₃N₄, and Y₃Si₅ON₉) are recognized as important secondary grain-boundary phases in silicon nitride and believed to have important impacts on the high-temperature mechanical properties and thermal conductivity of Si₃N₄ ceramic. In this work, equilibrium crystal structures, theoretical mechanical properties (second-order elastic constants, polycrystalline bulk modulus, shear modulus, Young's modulus, and Vickers hardness) of the five quaternary phases are calculated using first-principle total energy calculations. Meanwhile, temperature dependence of thermal conductivities of all five compounds is obtained based on Debye–Clarke model and Slack equation. On the basis of theoretical prediction, we establish the relationship between the componential (cation/anion or cation/cation ratios) and structural characteristics (bonding configurations) and mechanical/thermal properties. Our results are expected to provide helpful guidelines to improve the performances of Y–Si–O–N ceramics, and further guide the optimization of mechanical and thermal properties of Si₃N₄ by properly tailoring the secondary grain-boundary phases.