Low-Temperature Synthesis of Aluminum Nitride by Addition of Ammonium Chloride

Aluminum nitride (AlN) is highly insulating and has a high thermal conductivity. AlN also has the advantages of being nontoxic and chemically stable. Therefore, it is a suitable sealing material for electric devices. Previous studies have shown that the addition of NH₄Cl has a large influence on the formation of AlN and can effectively be used in its low-temperature synthesis without the use of special equipment. However, it has not been clarified whether NH₄Cl simply promotes the reaction between Al and nitrogen or directly contributes to the nitridation reaction. In this study, which was part of a series of studies on the development of low-temperature synthesis methods for AlN, the nitridation behaviors of Al in Al-N₂, Al-NH₄Cl-N₂, and Al-NH₄Cl-He systems were determined, and the effects of the heating temperature and amount of NH₄Cl on the nitridation behavior were examined in detail. When NH₄Cl was added, AlN began to form at 600 °C, a formation temperature that was approximately 200 °C lower than that when only Al powder was heated under a nitrogen stream. The fact that the formation of AlN was also observed when the NH₄Cl-added Al powder was heated under a helium gas stream confirmed that nitrogen derived from NH₄Cl contributed to the formation of the AlN. Furthermore, based on the experimental results, the reaction mechanism was clarified, and the kinetic parameters for the nitridation of Al were determined.