Improvement of the high temperature properties of the LiYO2–Si3N4 system by removing residual Li

Effects of the vaporization of residual Li on the microstructure, oxidation behavior and high temperature properties of a low-temperature pressureless sintered Si3N4 using LiYO2 additive were investigated. The oxidation and creep resistance of the Si3N4 was improved after an annealing at 1650 °C because residual Li, which deteriorated the high temperature properties of the Si3N4, could be mostly removed. The high temperature deformation of the Si3N4 was strongly suppressed after the annealing treatment. The annealed specimens retained 64% of the room temperature strength at 1300 °C in air. The present investigation reports a method to improve the high temperature properties of Si3N4.