Shuba, RomanChen, I-Wei2023-05-232023-05-232006-04-262006-10-05https://repository.upenn.edu/handle/20.500.14332/40944Refractory Y-α-SiAlON with elongated grain morphology was obtained by utilizing La2O3 as a densification aid, which resulted in excellent room-temperature and high-temperature strength. Room-temperature strength of 1000 MPa was achieved when La2O3 was augmented by adding Y2O3 or removing AlN. With only La2O3, a temperature-independent strength of 800–950 MPa was maintained up to 1100°C, then gradually decreasing by 25% when reaching 1300°C. The R-curve measurements of fracture toughness showed relatively little dependence on microstructure, consistent with a strong interface that suppresses grain boundary decohesion. Compared with other densification aids such as SiO2, Al2O3, Sc2O3, Y2O3, and Lu2O3, a finer microstructure was obtained by using La2O3. High nitrogen content in the residual La–Si–Al–O–N glass in equilibrium with the nitrogen-rich α-SiAlON is suggested to be the cause of these findings.Article