Microstructure and thermal conductivity of spark plasma sintering AlN ceramics

AlN ceramics without sintering aids were fabricated by spark plasma sintering (SPS). The as-received sample sintered at 1600 °C has a relative density up to 99.5%, which indicates a very high densification by this method. Microstructure observation by SEM shows that the grains have a very small size. The thermal conductivity of sintered AlN was measured using laser flash method and the effect of microstructure on the thermal conductivity was discussed based on the phonon scattering mechanism. The result shows that the very small grains limit the increase of the thermal conductivity of AlN ceramics densified by SPS.