A bulk layer of aluminum nitride (AlN) polycrystals was synthesized on a boron nitride crucible surface by heating Al chunks with 5 mol% of bismuth at 1273 K for 3 h under NH3 gas flow. The fragments of the layer were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The platelet grains of AlN with a size of 0.1-1.0 mu m and having preferred orientation of the c-axis perpendicular to the layer were formed at the crucible side. Nanotubes 6-15 mu m long and about 20-100 nm thick grew on the gas phase side of the layer.