Effect of different ternary lithium oxides on the properties of pressureless sintered porous Si3N4

Porous Si3N4 ceramics were fabricated via pressureless sintering employing ternary lithium oxides (LiScO2, LiYO2, LiYbO2) derived from various Re2O3 as sintering additives under nitrogen atmosphere at the temperature of 1400-1700 degrees C. The study studied how sintering temperatures andternary lithium oxide additives affect the phase, microstructure, and material properties of Si3N4. The results show that as the amount of sintering aids increases, the bulk density of samples increases. At the same time, the apparent porosity diminishes, leading to enhancements in flexure strength and dielectric constant. The Si3N4-based porous ceramic sample containing 5 wt% LiYbO2 sintered at 1600 degrees C exhibits a volumetric weight of 1.828 g/cm(3), an apparent porosity of 35.14 %, an average flexure strength of 114.8 MPa, a dielectric constant of 3.95, a loss tangent of 5.457 x 10(-3), and a low thermal conductivity of 8.241, offering insights into the preparation of radome materials.