Hot-compaction was carried out, at temperatures of between 900 and 1300C, by applying a pressure of 8.5GPa for a hold-time of 30s. On the basis of these compaction data, it was deduced that the pre-exponential factor for grain boundary diffusion, dDo (where d was the grain-boundary width), was equal to about 6 x 10-18m3/s. The activation energy was equal to 183kJ/mol. The latter energy was close to that (200kJ/mol) for N diffusion in Si3N4.

R.A.Andrievskii, G.M.Voldman, M.A.Leontev: Izvestiya Akademii Nauk SSSR - Neorganicheskie Materialy, 1991, 27[4], 729-32. [Inorganic Materials, 1991, 27[4], 603-6]