制备工艺对多孔Si_3N_4陶瓷介电性能的影响(英文)

采用添加成孔剂和冰冻-干燥法制备具有不同气孔率(30%～60%)的多孔Si3N4陶瓷,研究了不同制备工艺对多孔Si3N4陶瓷介电性能的影响.结果表明:不同的成型工艺制备出具有不同孔分布的氮化硅多孔陶瓷,添加成孔剂制备的多孔陶瓷具有较大的孔,洞分布在致密的基体上:冰冻-干燥法制备的多孔陶瓷具有复合孔分布.对样品的介电特性的研究表明,随着样品的气孔率增加,其介电常数和介电损耗减小;添加成孔剂制各样品的介电常数小于冰冻-干燥法制备样品,而其介电损耗较大,多孔Si3N4陶瓷的介电常数和介电损耗分别在5.21～2.91和9.6×10-3～2.92×10-3范围内变化.

INFLUENCES OF FABRICATION PROCESS ON DIELECTRIC PROPERTIES OF POROUS SILICON NITRIDE CERAMICS

Two different series of porous silicon nitride (Si3N4) ceramics with different porosities from 30% to 60% were fabricated using two different preparation routes: the addition of pore-forming agent and freeze--drying. The microstruetures of the samples were observed in detail. The results show that there is a big difference in the porous structure of the samples prepared by the different fab-rication routes. The samples prepared using the pore-forming agent have a dense matrix containing close pores and cavities with some needle-shaped and flaky β-Si3N4 grains, while those prepared by the freeze-drying process contain open and connective pores with a fiat shape scattered almost uniformly in the Si3N4 matrix. The porosity, pore structure and dielectric properties were measured sepa-rately. The results show that with the increase of porosity, the electric constant and dielectric loss of the ceramic decrease, and the pore distribution of the ceramic is also a major factor that influences its dielectric properties. The ε of the samples prepared by the addition of pore-forming agent is lower than that by freeze-drying, while its tan δ is higher under the same porosity. The ε and tan δ of the porous Si3N4 ceramics typically are in the range of 5.21-2.91 and 9.6×10-3?-2.92×10-3, respectively.