Effect of hot-pressing sintering on thermal and electrical properties of AlN ceramics with impedance spectroscopy and dielectric relaxations analysis

Abstract The effects of hot-pressing sintering on the phase composition, microstructure, thermal and electrical properties of AlN ceramics with CeO2–CeF3 additives were studied. During hot-pressing sintering, high pressure reduced the grain boundary phase CeAlO3 and decreased the concentration of oxygen in AlN ceramics. The hot-pressing sintered AlN samples had a much higher thermal conductivity of 191.9 W/m·K than pressureless sintered ones because of the great reduction of grain boundary phases and oxygen impurities in AlN ceramic. As the carbon content in hot-pressing sintered sample was very high, carbon contamination led to the decrease in electrical resistivity and changes in polarization mechanisms for AlN ceramics. The relaxation peak in the dielectric temperature spectrum with an activation energy of 0.64 eV for hot-pressing sintered samples was caused by electrons from free carbon at low temperature. Overall, hot-pressing sintering can effectively increase the thermal conductivity and change the electrical properties of AlN ceramics.