Effect of CaCN₂ Addition on the Densification Behavior and Electric Properties of AlN Ceramics

Abstract

Calcium cyanamide (CaCN2) has been used as a sintering aid as well as a dopant 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 scanning electron microscopy (SEM), dielectric and electric resistance measurements. Dense sintered specimens (relative density > 97.0%) were obtained using 1.0 to 2.0 wt% CaCN2 additives. With 0.5 to 3.0 wt% added CaCN2 and sintering at 1600 to 1700°C, only the AlN phase was observed in the XRD patterns. In the TEM and electron diffraction (ED) patterns, the minor phase, 3CaO·Al2O3, appeared around the AlN grain boundaries. Based on the SEM observation, the well-faceted grain morphology was considered to be due to a predominant intergranular fracture. The dielectric constant of the AlN specimens were about 8.6 and 8.2 for 150 kHz to 10 MHz, respectively, when the samples were sintered at 1650°C for 1, 3 and 6 h. The electric resistance of the AlN specimens approached 3.87×1012 Ω. 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.

Effect of CaCN2 on the preparation of CaAlSiN3:Eu2+ phosphors

“…In order to investigate the synthetic process of Ca 0.97 AlSiN 3 :Eu 0.03 2+ phosphors by the two‐step calcination procedure, XRD patterns of sample A, which was prepared using CaCN 2 , Si 3 N 4 and AlN at 1000°C for 2 h in nitrogen atmosphere, are shown in Figure . The diffraction peaks of Ca 3 N 2 and carbon indicated that CaCN 2 decomposed into calcium and carbon, leading to the nitridation of calcium in nitrogen atmosphere as shown in equation . …”

Effects of rare earth oxide additives on the thermal behaviors of aluminum nitride ceramics

“…Like most advanced ceramics, AlN does not occur naturally, synthesis of pure AlN is arduous due to its low chemical stability and it is difficult to sinter AlN to full density due to its covalent bonding. There exists oxygen on the grain boundaries and in the AlN lattice, which is responsible for the scattering of the primary heat carrier [4][5]; therefore, rare earth oxides and/or alkaline earth oxides are often added as sintering aids in the fabrication of AlN ceramics. These sintering aids not only contribute to form the liquid phase that promotes the densification by the process of liquid-phase sintering but also improve the thermal conductivity by decreasing the oxygen impurities in the AlN lattice [6][7].…”