We synthesized AN using aluminium chloride hexahydrate and urea as the starting materials. By directly introducing aluminium chloride into melted urea at 135 deg. C, a urea-precursor was formed under non-aqueous conditions with no Y-AlzO, observed in any calcination steps. As a result, well-crystalline AIN powder was obtained by the pyrolysis of urea-precursor above 900 deg C under a stream of N2 gas for l hour. In this process the urea-precursor decomposed below 400 deg C, and an AIN skeleton with a layer structure formed above 800 deg. C. The total yield of AlN powder based on the Ai atom was only 80 due to production of volatile AI(NH3),AlH4CI, as a by-product. The AiN powder was characterized by X-ray diffraction, infrared spectroscopy and scanning electron microscopy (SEM). Morphological observation of the AIN powder by mean of SEM revealed large particles of about 30-mu m diameter, which consisted of ultrafine particles of less than 1-mu m diameter.
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