Impact of carbon material (carbon powder/graphene) on thermal and electrical properties of AlN ceramics

The influence of adding carbon powder/graphene on the microstructure, thermal and electrical properties of AlN ceramic were studied. Carbon powder/graphene was beneficial for removing oxygen impurities in AlN samples and purifying grain boundaries. Thermal conductivities of samples with added carbon powder or graphene increased to 194.6 W/(m·K) and 235.9 W/(m·K), respectively. Graphene phase residues appeared in the samples with added graphene, that owned higher thermal conductivity. Meanwhile some electronic defects were introduced, reducing the resistivity of the sample and altering the defect mechanism. Impedance spectroscopy and dielectric temperature spectroscopy revealed the changes in the defect mechanism in the sample. And the AlN sample with 0.25 wt% graphene added had higher electrical conductivity, dielectric constant and dielectric loss than the AlN sample with 0.25 wt% carbon powder added. Therefore, appropriately adding carbon material could enhance the thermal conductivity of AlN ceramics. When added graphene, thermal conductivity was significantly enhanced and the electrical properties were also synergistically regulated.