Densification and structural development in the sintering of AlN ceramics with CaCN2 additives

The effect of CaCN2 addition on the densification and structural development for sintered AlN ceramics was investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and electron diffraction (ED). Dense sintered specimens (bulk density >3.16 g cm−3) with 0.5–3.0 wt.% CaCN2 additives were obtained depending on sintering temperature and time. When added with CaCN2 from 0.50 to 3.0 wt.% and sintered at 1650–1800°C, all of the sintered samples exclusively belonged to the same AlN phase and no other phases were found in the XRD patterns. A large fraction of intergranular fractures was found in the SEM observations of the AlN samples sintered without and with CaCN2 additive. The characterization of the AlN powders sintered with CaCN2 additive was performed with a microstructural analysis using TEM and ED. In the TEM and ED pattern, the minor phase, 3CaO·Al2O3, appeared around the AlN grain boundaries.