Fabrication and properties of dense α-cordierite glass-ceramic coating on porous BN/Si2N2O ceramic

alpha-Cordierite glass-ceramic coating was fabricated on the porous BN/Si2N2O ceramic by glass-ceramic method. The effect of the heating temperature on the phase composition, microstructure, mechanical properties, water resistance and dielectric properties of the coatings was investigated. A large amount of alpha-cordierite precipitated from the glass phase when the heating temperature was 1050 degrees C and the content of alpha-cordierite in the coating increased with increasing the heating temperature. The resulting alpha-cordierite glass-ceramic coatings had a good wettability and adhesion with the porous ceramic substrate. The coating/substrate interface was continuous without defects. When the heating temperature was 1050-1200 degrees C, the resulting coatings possessed positive mechanical properties and good water resistance due to the high densification. And the dielectric constant and loss tangent of the coated samples prepared at 1050-1200 degrees C were 4.1-4.3 and 0.005-0.01 respectively in the frequency of 21-36 GHz.