The Effects of Impurities on the Physical Properties of Beta-Phase Silicon Nitride: A First-Principles Study
Abstract
Point defects play an important role in the physical properties of materials. In this work, the effects of impurities on the stability, mechanical properties, thermal conductivity and thermodynamics of β-Si3N4 have been investigated by first-principles calculations in combination with the Debye model. The results show that, for intrinsic defects, the order of defective formation energy Ef is VN < NSi < VSi < SiN in the N-rich side, while in the N-poor side the formation of antisite SiN becomes facile than the two types before it. The Ef of substitutional defect ON is always far smaller than that of OSi, while the Ef of group defects ON-OSi and ON-VSi are much lower than that of group OSi-VN in N-rich side. Furthermore, the point defects have a significant effect on mechanical properties, thermal conductivity (TC)κ and Gibbs free energy Eg. Interestingly, the incorporation of substitutional defects YSi, (Ce-Pr)Si, and (Tb-Ho)Si would improve the ductility of β-Si3N4 based on the acquired G/B results. On the other hand, intrinsic defects VN, NSi, SiN and substitutional defects of (H, C, O)N, (Sc, Y, La, Nd-Lu)Si have the minimal impact on reducing the κ of β-Si3N4 and can maintain it up to 200 W/(m·K). These findings are helpful for further investigation of improving the ability of heat transfer and service life for β-Si3N4 electronic devices.