Porous Si2N2O/Si3N4 composite ceramics were fabricated by gas pressure sintering of Si3N4 and SiO2 with Sm2O3 as sintering additive under N2 atmosphere. Porosity and β-Si3N4 phase of the composites are increased with the increasing α-Si3N4 content in starting materials. The composite ceramics show high flexural strength (223 ~ 288 MPa at room temperature) and good thermal shock resistance and the critical thermal shock temperature (ΔTc) could be up to 1100 oC. The dielectric properties are mainly influenced by the sample porosity and phase composition. The as-prepared Si2N2O / Si3N4 composite ceramics possess both low dielectric constant (ε = 4.8-5.2) and loss tangent (tanδ = 0.0014-0.0063), combined with excellent mechanical performance and thermal shock resistance, showing Si2N2O/Si3N4 composite ceramics could be promising high-temperature wave transparent materials.

Keywords: Si2N2O/Si3N4 composite ceramics, Mechanical properties, Thermal shock resistance, Dielectric properties.