Microwave characteristics and thermal conductivity of aluminium nitride-molybdenum lossy ceramics

Mumimum nitride-molybdenum lossy ceramics were manufactured by hot pressing a mixture of A1N and Mo powders with Y₂O₃ as sintering aid. The microwave attenuation characteristic was evaluated by network analyzer, and thermal conductivities were measured by laser-flash technique. The results indicate that all samples show densification (open porosity < 0.5%) in the range of sintering temperature. The main crystalline phases of the composites are A1N and Mo as well as small amount of yttrium aluminum garnet (Y₃AI₅O₁₂). With the increase of Mo content, the microwave attenuation characteristic of AIN-Mo composites transfers from wideband attenuation to narrowband attenuation. The sample (AM3), which contained 33wt% metallic phase dispersed in the A1N matrix and was sintered at 1850degC, possesses the best wideband attenuation property with the maximum attenuation up to 4.5 dB. Thermal conductivities improve to over 100 W ldrm^-1 ldrK^-1 with the sintering temperature increasing from 1800degC to 1900degC. The high thermal conductivity is related closely to sintering temperature.