Publication Date:
2016-04-06
Description:
Y–Si–O–N quaternary oxynitrides (Y 5 Si 3 O 12 N, Y 4 Si 2 O 7 N 2 , YSiO 2 N, Y 2 Si 3 O 3 N 4 , and Y 3 Si 5 ON 9 ) 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 Si 3 N 4 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 Si 3 N 4 by properly tailoring the secondary grain-boundary phases.
Print ISSN:
0002-7820
Electronic ISSN:
1551-2916
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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