EELS Study of Oxygen Diffusion in Aluminum Nitride

The oxygen/nitrogen interdiffusion in AIN ceramics was investigated by electron energy‐loss spectroscopy (EELS) in combination with transmission electron microscopy (TEM). AL2O3/AIN diffusion couples were prepared by oxidation of an AIN ceramic. The samples were annealed for different times in the temperature range from 1500° to 1900°C. The diffusion couples were encapsulated in a tantalum ampoule to guarantee an inert atmosphere. Oxygen concentration profiles across the oxide/nitride interface were measured by EELS. The oxygen/nitrogen interdiffusion coefficient in AIN is given by D= 1.5–1.2+6.0× 10–8 exp[–240 ± 40 (kJ/mol)/(RT)] (cm2/s). The magnitude and temperature dependence of the N/O interdiffusion is comparable to diffusion coefficients reported in the literature for other non‐oxide ceramic materials. At standard AIN sintering conditions the O/N interdiffusion is so slow that it cannot provide an effective means for oxygen removal from the AIN grains.