Self-diffusion coefficients of nitrogen in polycrystalline alpha- and beta-silicon nitride were measured by using a gas-solid isotope exchange technique with 15N as a tracer at 1200 to 1410C. The diffusion coefficients for single-crystal grains could be expressed as:

D(cm2/s) = 1.2 x 10-12 exp[-55700/RT]

for α-Si3N4 and

D(cm2/s) = 5.8 x 10+6 exp[-185700/RT]

for β-Si3N4.

K.Kijima, S.I.Shirasaki: The Journal of Chemical Physics, 1978, 65[7], 2668-71