Effect of CaCN2 addition on the densification behavior and electric properties of AlN ceramics

Calcium cyanamide (CaCN2) has been used as a sintering aid as well as a dop ant for AlN. The effect of CaCN2 addition on the densification behavior and electric properties of liquid-phase sintered AlN ceramics was investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM) and sca nning electron microscopy (SEM), dielectric and electric resistance measure ments. Dense sintered specimens (relative density > 97.0%) were obtained us ing 1.0 to 2.0 wt% CaCN2 additives. With 0.5 to 3.0 wt% added CaCN2 and sin tering at 1600 to 1700 degreesC, only the AIN phase was observed in the XRD patterns. In the TEM and electron diffraction (ED) patterns, the minor pha se, 3CaO . Al2O3, appeared around the AIN grain boundaries. Based on the SE M observation, the well-faceted grain morphology was considered to be due t o a predominant intergranular fracture. The dielectric constant of the AIN specimens were about 8.6 and 8.2 for 150 kHz to 10 MHz, respectively: when the samples were sintered at 1650 degreesC for 1, 3 and 6 h. The electric r esistance of the AlN specimens approached 3.87 x 10(12) Omega. The trend of the electric resistance variation in the specimens was the same as that of the linear shrinkage and relative density of the specimens.