Effect of Oxynitride Grain Boundary Phase on Toughening of Silicon Nitride Ceramics

摘要

The Si_3N_4/YSiO_2N composite in which crystalline YSiO_2N was formed as grain boundary phase was fabricated by hot-pressing the mixture of SiO_2, Si_3N_4 and Y_2O_3. The fracture toughness of this composite was significantly improved, compared to the Si_3N_4 composites containing Y_5Si_3O_(12)N or Y_2Si_3O_3N_4 as a grain boundary phases. To clarify the toughening mechanism, the microstructure and the crack propagation profiles were observed.