Enhanced thermal stability of pressureless liquid-phase sintered SiC ceramics via (Hf, Zr, Ta, Nb, Ti)B2 addition

• Published in: Ceramics international 2024-04, Vol.50 (7), p.12637-12644
• Main Authors: Liu, Yang, Liang, Jia-Ji, Guo, Wei-Ming, Chang, Chao, Duan, Xiao-Ming, Jia, De-Chang, Lin, Hua-Tay
• Format: Article
• Language: English
• Subjects: High-entropy diboride; Pressureless liquid-phase sintering; SiC; Thermal stability
• ISSN: 0272-8842; 1873-3956
• DOI: 10.1016/j.ceramint.2024.01.107

High-temperature thermal stability plays a crucial role in the structural application of pressureless liquid-phase sintered SiC (PLS-SiC) ceramics. In this paper, a PLS-SiC ceramic processed with CeO2–Al2O3 as sintering additives with excellent high-temperature thermal stability was achieved by incorporating (Hf, Zr, Ta, Nb, Ti)B2 (HEB) particles. Results showed that PLS-SiC ceramics with HEB-free underwent a structural change from dense to porous microstructure after annealing at 1800 °C/1 h. Conversely, PLS-SiC ceramics with the addition of 10 vol% HEB exhibited excellent thermal stability, as evidenced by the retention of their dense microstructure after exposure to annealing at 1800 °C/1 h. The possible primary reasons for this significantly different response to the thermal stability could be probably attributed to fact that HEB reacted with CeAlO3 and SiC to form solid-phase products, subsequently inhibiting the formation of gas-phase products after decomposition of CeAlO3 alone in a high-temperature vacuum environment. In addition, the formation of a compact protective outer layer containing Hf–Ta containing diboride in PLS-SiC ceramics during the annealing process could effectively hinder the volatilization of volatile substances at a high temperature.