A multifunctional Mg2Si5Al4O18/Y2Si2O7 glass-ceramic coating for porous Si3N4 ceramic

In order to enhance the oxidation and moisture resistance of porous Si3N4 ceramics, here we design a novel Y2O3-MgO-Al2O3-SiO2 glass-ceramic coating through a straightforward scraping process followed by sintering method. The crystalline phase, water absorption, dielectric properties and high temperature resistance of the coating are evaluated systematically. The result shows that the coating obtained by sintering at 1200 degrees C for 30 min exhibits high density, with an approximate thickness of 88 +/- 5 mu m. The crystalline phases present in the coating are composed of Mg2Si5Al4O18 and Y2Si2O7. The water absorption rate of the coating is only 0.59 %, and its dielectric constant ranges from 3.3 to 3.4 in the frequency range of 2-20 GHz, with a low dielectric loss tangent below 4 x 10(-3). After exposure to high-temperature (1000 degrees C for 30 min), no significant changes are observed in the microstructure or water absorption rate of the coating. Therefore, this study has successfully developed a multifunctional glass-ceramic coating that is moisture-proof, high-temperature resistant, and exhibits low dielectric loss.