Single crystals with an initial composition of TiN0.82 or polycrystals with a composition of TiN0.94 were used. The N self-diffusion was investigated using gas-solid isotope exchange at 800 to 1650C. The concentration profiles of 15N were measured using secondary ion mass spectrometry. The profiles exhibited 2 slopes, which corresponded to a fast decrease for short penetration depths (about 100nm) followed by a slower decrease for depths up to a few microns at 1650C. These observations were interpreted in terms of bulk diffusion and short-circuit diffusion. For the bulk diffusion, the solution was an erf profile. For short-circuit diffusion, the Whipple solution was used. For polycrystals, the bulk diffusion coefficients and grain boundary diffusion coefficients were described by:

D(cm2/s) = 6.5 x 10-11exp[-1.79(eV)/kT]

at up to 1500C, and

D(cm2/s) = 1.4 exp[-5.5(eV)/kT]

above 1500C, and

D(cm2/s) =17 exp[-4.2(eV)/kT]

For single crystals, the short-circuit diffusion was estimated to be due to sub-grain boundaries and the diffusion coefficients were described by:

D(cm2/s) = 1.8 x 10-9exp[-1.8(eV)/kT]

and

D(cm2/s) = 1 x 10-3exp[-2.8(eV)/kT]

F.Anglezio-Abautret, B.Pellissier, M.Miloche, P.Eveno: Journal of the European Ceramic Society, 1991, 8[5], 299-304