中文摘要：

采用反应烧结工艺，通过添加成孔剂的方法，制备出具有球形宏观孔的低密度多孔氮化硅陶瓷，研究了球形宏观孔和烧结工艺对多孔氮化硅陶瓷性能的影响。实验结果表明，与未添加成孔剂的样品相比，成孔剂的添加有效降低了材料的气孔率，使材料的介电常数e’和介电损耗tanδ下降。孔的加入能促进针状氮化硅的生成，降低单位体积中产生的热量，防止局部过热从而避免硅熔现象的出现。缓慢的升温速率可促进a-Si_3。的生成，减少针状物，降低试样中游离硅的含量。烧结后的试样经过热处理可以使氧原子扩散进入材料内部，和试样中的游离Si结合成SiO_2，降低试样的介电性能。

英文摘要：

The low-density silicon nitride ceramics with global macro-pores were prepared by adding pore-form- ing agent through reactive sintering technique. The effects of pore and processing of reaction on the properties of porous silicon nitride ceramics were investigated. The experimental results show that the porosity of samples with 40wt% pore-forming agent increase visibly compared to the samples with no pore-forming agent, which leads to the decrease in the dielectric constant and loss in the sample. Adding of the global macro-pores can pro- mote the formation of needle-like phase and decrease the partial overheating of green compacts to avoid silicon fusion. The a-Si_3N_4 phase increases and the needle-like phase decrease with the decrease of heating-rate. It is found that the free silicon in the ceramics is oxidized and leads to the decrease in the dielectric constant and loss when the sintered compacts are heat-treated in air.