Synthesis of Aluminium Nitride Using Urea-Precursors

摘要

We synthesized AlN using aluminium chloride hexahydrate and urea as the starting materials. By directly introducing aluminium chloride into melted urea at 135℃, a urea-precursor was formed under non-aqueous conditions with no γ-Al_2O_3 observed in any calcination steps. As a result, well-crystalline A1N powder was obtained by the pyrolysis of urea-precursor above 900℃ under a stream of N_2 gas for lhour. In this process the urea-precursor decomposed below 400℃, and an A1N skeleton with a layer structure formed above 800℃. The total yield of A1N powder based on the Al atom was only 80% due to production of volatile Al(NH_3)_6AlH_4Cl_2 as a by-product. The AlN powder was characterized by X-ray diffraction, infrared spectroscopy and scanning electron microscopy (SEM). Morphological observation of the AlN powder by mean of SEM revealed large particles of about 30-μm diameter, which consisted of ultrafine particles of less than 1-μm diameter.