Effect of La2O3 on the oxidation resistance of SiC ceramic at 1973 K: Experimental and theoretical study. Issue 1 (2nd August 2019)

• Record Type: Journal Article
• Authors: Xie, Wei; Fu, Qiangang; Cheng, Chunyu; Zhang, Guangpeng; Yan, Ningning; Wang, Zhaowei
• Is Part Of: Journal of the American Ceramic Society. Volume 103:Issue 1(2020)
• Page Start: 614
• Page End: 621
• Publication Date: 2019-08-02
• Subjects: first‐principles calculations -- La2O3 -- oxidation resistance -- SiO2; Ceramics -- Periodicals; 620.1405
• DOI: 10.1111/jace.16708
• Languages: English
• ISSNs: 0002-7820

Abstract

Abstract: The effect of La2 O3 on the oxidation resistance of SiC ceramic at 1973 K was investigated using isothermal oxidation test and first‐principles calculations. The SiC ceramic with La2 O3 shows a better oxidation resistance compared with that without La2 O3 due to the in situ formed La2 Si2 O7 in SiO2 glass layer after oxidation at 1973 K. First‐principles calculations based on density functional theory were applied to analyze the solution behaviors of La atom in the surface of SiO2 and La2 Si2 O7 . The solution energy of La atom in SiO2 (0 1 1) is −19.05 eV, which is far less than −4.19 eV in La2 Si2 O7 (2 0 1) with a La vacancy, thus resulting in that La atom in La2 Si2 O7 (2 0 1) diffuses into SiO2 (0 1 1). The SiO2 lattice with an interstitial La atom is more stable than that with a substitutional La atom and the interstitial La breaks the nearest Si–O bond to form La–O and La–Si bonds, which is beneficial to improving the high‐temperature stability of SiO2 . Experimental and theoretical results indicate that the formation of refractory La2 Si2 O7 phase enhances the stability of SiO2 glass layer, so as to protect SiC ceramic from further oxidation at 1973 K.