Preferential orientation of bulk textured AlN by hot pressing

Bulk texture AlN with preferential orientation perpendicular to (0 0 2) plane parallel to c-axis was obtained by hot pressing at 2000 °C for 2 h under 35 MPa. The bulk textured AlN was evaluated by XRD and SEM micrograph. The results indicated the orientation with (0 0 2) plane parallel to the pressing direction was dominant in all diffraction peaks of hexagonal AlN. The same texturing was not found for micron-grade SHS AlN, which might be attributed to different dissolve–precipitate and nuclei growth rate between bulk nanosize and SHS AlN along the direction of c-axis. For bulk nanosize AlN, it is beneficial to increase pressure and soak time for the increment of the oriented crystallinity of bulk AlN. These investigations showed the optimal values of pressure and soak time in our experiment were 35 MPa and 4 h, respectively. The mechanisms of preferential orientation with the normal of c-axis for nanosize bulk AlN were also proposed.