The Microstructure and Thermal Conductivity of Aluminum Nitride Ceramics Sintered at High Pressure with CaC_(2)

Aluminum nitride (AIN) ceramics are sintered by high-pressure technology at 5 GPa/30min/1500-1800℃,using aluminum nitride powder produced by direct nitriding methods and CaC_(2) (3wt%) powder as the starting material and sintering additive,respectively.The sample sintered at 1800℃ shows relatively high density (99.09%) and thermal conductivity (113.7 W/(m.K).XRD patterns indicate that there are no obvious impurity phases in the sintered AIN sample.Observation of the microstruct ure by SEM shows that the AlN powder grows into full crystal grains with uniform size,the crystal particles are in a regular hexagonal structure,and the grain boundary phases are clean without gas phase.The results suggest that AIN ceramics sintered with CaC_(2) can achieve the desired microstructure and high thermal conductivity.