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Effect of La 2 O 3 on the oxidation resistance of SiC ceramic at 1973 K: Experimental and theoretical study
Author(s) -
Xie Wei,
Fu Qiangang,
Cheng Chunyu,
Zhang Guangpeng,
Yan Ningning,
Wang Zhaowei
Publication year - 2020
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.16708
Subject(s) - ceramic , vacancy defect , atom (system on chip) , materials science , isothermal process , activation energy , chemistry , analytical chemistry (journal) , crystallography , thermodynamics , metallurgy , physics , chromatography , computer science , embedded system
The effect of La 2 O 3 on the oxidation resistance of SiC ceramic at 1973 K was investigated using isothermal oxidation test and first‐principles calculations. The SiC ceramic with La 2 O 3 shows a better oxidation resistance compared with that without La 2 O 3 due to the in situ formed La 2 Si 2 O 7 in SiO 2 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 SiO 2 and La 2 Si 2 O 7 . The solution energy of La atom in SiO 2 (0 1 1) is −19.05 eV, which is far less than −4.19 eV in La 2 Si 2 O 7 (2 0 1) with a La vacancy, thus resulting in that La atom in La 2 Si 2 O 7 (2 0 1) diffuses into SiO 2 (0 1 1). The SiO 2 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 SiO 2 . Experimental and theoretical results indicate that the formation of refractory La 2 Si 2 O 7 phase enhances the stability of SiO 2 glass layer, so as to protect SiC ceramic from further oxidation at 1973 K.