In situ synthesis and properties of self-reinforced $\hbox {Si}_{3} \hbox {N}_{4}\textendash \hbox {SiO}_{2}\textendash \hbox {Al}_{2} \hbox {O}_{3}\textendash \hbox {Y}_{2}\hbox {O}_{3} \ (\hbox {La}_{2}\hbox {O}_{3}$) glass–ceramic composites

Abstract

In-situ-grown $\upbeta \!\hbox {-Si}_{3}\hbox {N}_{4}$-reinforced $\hbox {SiO}_{2}\textendash \hbox {Al}_{2}\hbox {O}_{3}\textendash \hbox {Y}_{2}\hbox {O}_{3}$ $(\hbox {La}_{2}\hbox {O}_{3})$ self-reinforced glass–ceramic composites were obtained without any $\upbeta \!\hbox {-Si}_{3}\hbox {N}_{4}$ seed crystal. These composites with different compositions were prepared in a nitrogen atmosphere for comparison of phase transformation and mechanical properties. The results showed that $\hbox {SiO}_{2}\textendash \hbox {Al}_{2}\hbox {O}_{3}\textendash \hbox {Y}_{2}\hbox {O}_{3}$ $(\hbox {La}_{2}\hbox {O}_{3})$ glass can effectively promote $\upalpha$- to $\upbeta \!\hbox {-Si}_{3}\hbox {N}_{4}$ phase transformation. The crystallized $\hbox {Y}_{2}\hbox {Si}_{2}\hbox {O}_{7}\textendash \hbox {La}_{4.67}\hbox {Si}_{3}\hbox {O}_{13}$ phases with a high melting point significantly benefited the high-temperature mechanical properties of the composites. The $\hbox {Si}_{3}\hbox {N}_{4}\textendash \hbox {SiO}_{2}\textendash \hbox {Al}_{2} \hbox {O}_{3}\textendash \hbox {Y}_{2}\hbox {O}_{3}$ $(\hbox {La}_{2}\hbox {O}_{3})$ glass–ceramic composites exhibit excellent mechanical properties compared with unreinforced glass–ceramic matrix, which is undoubtedly attributed to the elongated $\upbeta \!\hbox {-Si}_{3}\hbox {N}_{4}$ grains. These glass–ceramic $\hbox {Si}_{3}\hbox {N}_{4}$ composites with excellent comprehensive properties might be a promising material for high-temperature applications.