AlON transparent ceramics from powders synthesized by improved direct nitridation

Single-phase aluminum oxynitride (AlON) powders were synthesized by improved direct nitridation (DN). The improved DN method is to obtain high quality powder by adding high nitrogen pressure on the basis of ordinary DN method. Compared with the ordinary DN method, the average particle size of the synthesized powder is reduced by about 20 mu m, the morphology tends to be spherical and the sintering activity is higher. Using different particle size alpha-Al2O3 precursor, a modified DN method was adopted to synthesize spherical, good dispersibility and fine AlON powders. The influence of particle size of raw material alpha-Al2O3 on sintering properties was investigated. Transparent AlON ceramics with dimensions of phi 103mm x 3 mm with in-line transmittance greater than 80%were fabricated by pressureless sintering from above AlON powders. In addition, the effects of different nitrogen pressure on the morphology, particle size distribution and average particle size of synthetic powder were investigated. On this basis, the differences between DN method and improved DN method on synthetic powder and the possible synthesis mechanism were proposed.