Refractory α-SiAlON Containing La2O3

Refractory 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. Comments Copyright The American Ceramic Society. Reprinted from Journal of the American Ceramic Society, Volume 89, Issue 9, 2006, pages 2860-2868. This journal article is available at ScholarlyCommons: http://repository.upenn.edu/mse_papers/105 Refractory a-SiAlON Containing La2O3 Roman Shuba and I.-Wei Chen Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6272 Refractory Y-a-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 11001C, then gradually decreasing by 25% when reaching 13001C. 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 a-SiAlON is suggested to be the cause of these findings.