中文摘要：

通过添加成孔剂，采用反应烧结工艺制备出具有不同气孔率的氮化硅多孔陶瓷。采用阿基米德法、三点弯曲法测试了材料的密度、气孔率及抗弯强度。用XRD及扫描电镜对相组成和显微结构进行了研究，用谐振腔法测试了该氮化硅陶瓷在9360MHz频率的微波介电特性。结果表明，随着试样中气孔率的增加，试样的介电常数下降；在Si粉中添加α-Si3N4粉后，虽能提高氮化率，改善组织结构，但外加Si3N4和基体生产的Si3N4存在活性差异，两者结合不紧密，使强度降低；加入α-Si3N4粉使晶相组成中Si2ON2的含量降低，能够改善试样的介电性能。

英文摘要：

This paper presents the microwave dielectric property of porous silicon nitride ceramics at a frequency of 9360 MHz, which were fabricated by the nitridation of silicon powder. The porous ceramics with different volume fractions of porosity from 18.6% to 56.2% were produced by adding different amounts of the pore-forming agent into the initial silicon powder. Microstructural analysis revealed a dense matrix containing large pores with needle-shaped and flaky β-Si3N4 grains distributing in it. The results showed that the dielectric constant of the ceramics decreases with increasing of the porosity. Adding α-Si3N4 powder in the raw silicon powder, the nitridation rate raises, and the dielectric constant and the dielectric loss of the ceramics decrease notablely.