Nitrogen self-diffusion in silicon nitride

Abstract
Self‐diffusion coefficients of nitrogen in polycrystalline alpha‐ and beta‐silicon nitride were measured by a gas–solid isotope exchange technique using 15N as a tracer at temperatures in the range 1200–1410°C. The diffusion coefficients for single‐crystal grains can be expressed as D (cm2/sec) =1.2×10−12 exp(−55 700/RT) for α‐Si3N4 and D (cm2/sec) =5.8×10+6 exp(−185 700/RT) for β‐Si3N4. The diffusion of nitrogen along grain boundaries in the reaction‐sintered materials was considerably faster than the diffusion through the bulk.