Reaction Synthesis And Mechanical Properties Of Lu_4Si_2O_7N_2

摘要

Crystallized Lu-Si-O-N phases were believed to be the grain-boundary (GB) phases that might provide Si_3N_4 with excellent high-temperature mechanical properties. However, little is known about the intrinsic properties, as well as the synthesis, of the Lu-Si-O-N ceramics. This work reveals the reaction paths of heating LU_2O_3, SiO_2, and Si_3N_4 powder mixtures (with the stoichiometry of 4:0.96:1) from room temperature to 1600℃. Thereafter, dense Lu_4Si_2O_7N_2 samples are synthesized by in situ reaction/hot-pressing method, and the mechanical properties at room temperature and elevated temperatures are reported for the first time. The Lu_4Si_2O_7N_2 samples show significant high-temperature mechanical properties, such as the elastic stiffness remains 77% from room temperature to 1500℃; and bending strength keeps 93% from room temperature to 1400℃. The present results shine a light on Lu_4Si_2O_7N_2 as a promising target GB phase for the optimization of high-temperature mechanical properties of Si_3N_4.