孔隙率和孔径对反应烧结多孔氮化硅陶瓷介电性能的影响

研究添加成孔剂法制备的有球形宏观孔的多孔氮化硅陶瓷在不同孔隙率和孔径下的介电性能.通过控制成孔剂苯甲酸的加入量和调节成孔剂的粒径可达到烧结体的气孔率和孔径可控的目的.结果表明:随着成孔剂量的增加,样品气孔率变大,反应烧结后烧结体中的α-Si3N4相增多,样品的介电常数ε'和介电损耗tanδ降低.在成孔剂加入的质量分数为30%时,随着成孔剂的粒径变大,反应烧结后烧结体中气孔的直径变大而气孔率不变,样品的ε'和tan δ也相应降低.得到的样品中最低的ε'值为2.4297.

EFFECTS OF POROSITY AND PORE SIZE ON THE DIELECTRIC PROPERTIES OF REACTION BONDED POROUS SILICON NITRIDE CERAMICS

The dielectric properties of reaction bonded porous silicon nitride ceramics with global macro-pores which were prepared by adding pore-forming agent benzoic acid into silicon powders were investigated under varied porosity and pore size. The porosity and pore size of the powder compact can be controlled by changing the size and amount of pore-forming agent added. The experimental results show that the porosity of samples increases with the amount of pore-forming agent added, and the phase of a-Si3N4 in the sintered compact also increases, but the dielectric constant and the dielectric loss of the samples decrease. When the mass fraction of pore-forming agent added is 30%, with the increase of the size of the pore-forming agent, the pore size in the sample increases but the porosity has no change, the dielectric constant and the dielectric loss of the ceramics decrease too. Among all the obtained samples, the minimum dielectric constant is about 2.429 7.