The Sintering Technology Of Aluminum Nitride Ceramic

The sintering process of AIN ceramics was studied in this paper. AIN ceramics with high density and high thermal conductivity were obtained by using the AIN powder as material, which was produced in our studio through in-situ synthesis technology.The conventional sintering process of AIN ceramics was studied. Through the analysis of thermodynamic conditions and phase diagrams, some oxides, such as Y2O3, Li2(X CaO> BiOs, were selected as additives. The effects of additives type, sintering temperature, holding time on the density and composition of AIN ceramics were investigated. The results show that the additives can form aluminates (e.g. YAG) with the A^Oa coating on the surface of AIN particles, which density the AIM ceramics by LPS mechanism. It was demonstrated by XRD analysis that the additives do not work adequately at lower temperature. In addition, we made an attempt in selecting low-temperature sintering aids. The results show that the additive system takes a limited effect in sintering process.The Spark Plasma Sintering (SPS) of AIN ceramics was studied. The results show that the SPS was a fast and effective sintering technology. Compared with the conventional sintering process, the SPS process can short consolidation time and lower the sintering temperature. The additives that were used in traditional sintering took a similar effect in SPS process. The consolidation process took place mainly at the stage of elevating temperature. The density of compacts doesn't increase with the holding time. The XRD analysis of the specimen with SPS process shows that with the presence of carbon in atmosphere, the second phase formed in sintering processdecomposes and evaporates from the AlN grain boundary.The relationship between the thermal conductivities of AlN ceramics and their microstructures was studied. The different microstructure characters of AIN samples show that, if grains grow perfectly, and have clear, acute and multilateral morphology, grain boundary phase is little and homogenously distributed, AlN phase is contiguous, the sample would have higher thermal conductivity.