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

α-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 α-cordierite precipitated from the glass phase when the heating temperature was 1050 °C and the content of α-cordierite in the coating increased with increasing the heating temperature. The resulting α-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 °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 °C were 4.1-4.3 and 0.005-0.01 respectively in the frequency of 21-36 GHz.