Mechanical, dielectric properties and thermal shock resistance of porous Si2N2O/Si3N4 composite ceramics

摘要

Porous Si2N2O/Si3N4 composite ceramics were fabricated by gas pressure sintering of Si3N4 and SiO2 with Sm2O3 as sintering additive under N-2 atmosphere. Porosity and beta-Si3N4 phase of the composites are increased with the increasing alpha-Si3N4 content in starting materials. The composite ceramics show high flexural strength (223 similar to 288 MPa at room temperature) and good thermal shock resistance and the critical thermal shock temperature (Delta T-c) could be up to 1100 degrees C. 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 (epsilon = 4.8-5.2) and loss tangent (tan delta = 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.