金属Mo对AlN基复相材料性能的影响

以氮化铝、金属Mo为原料,Y2O3为烧结助剂,氮气氛下、1800~1900℃热压烧结制备Mo/AlN复相材料。利用XRD、SEM对材料的相组成、显微结构进行表征,四探针法测试复相材料的电阻率,微带线法测试2~20 GHz频率范围内材料的微波衰减特性,探讨了渗流现象与衰减特性之间的内在联系。结果表明:当Mo添加量为4.56 vol%~15.03 vol%,材料呈现宽频衰减特性,且随着Mo含量和烧结温度的增加衰减量增大;当Mo添加量为16.18 vol%~24.88 vol%,材料仅在6、10、14、18 GHz 4个频率点出现了明显的谐振峰。根据渗流模型对电阻率数据进行拟合,得到导电相渗流阈值Vc和相应电阻率分别为14.87 vol%和11.59Ω.m。当Mo体积分数VVc时,复相材料的衰减特性由宽频向选频转变。

Effect of Mo content on the performance of Mo/AlN composites

Aluminium nitride-molybdenum ceramics with Y_2O_3 additive were prepared via hot-pressing in N_2 atmosphere at 1800～ 1900℃. The phase constitution and microstructure were detected by XRD and SEM. The electrical resistivity and microwave attenuation property were characterized by the four point valves technique and microstrip line method. The results show that, in the 2～20 GHz frequency region, when the content of Mo is between 4. 56 vol% ～ 15.03 vol%, the composites present wide- band attenuation and with the increase of Mo content and sintering temperature, the attenuation increases; when Mo content is between 16.18vol%～24. 88 vol%, the materials show narrow-band attenuation under 6, 10, 14, 18 GHz. According to the percolation model, the fitting curve of electrical resistivity indicates that the percolation threshold V_c of Mo is 14.87 vol% and to narrow-band as the volume fraction of Mo is above V_c.