It was recalled that AlN, Al2OC and 2H-type SiC were isostructural. The SiC-AlN and AlN-Al2OC systems formed homogeneous solid solutions above 2000 and 1950C, respectively, but the kinetics of phase separation in the systems were very different. Interdiffusion in both systems was studied in the solid-solution regime in order to clarify differences in the kinetics of phase separation in the systems when they were annealed at lower temperatures. Diffusion couples between (SiC)0.3(AlN)0.7/(SiC)0.7(AlN)0.3 and (AlN)0.7(Al2OC)0.3/(AlN)0.3(Al2OC)0.7 were prepared by hot pressing. Interdiffusion coefficients in the former couples were measured at 2373, 2473 and 2573K, and the corresponding activation energy was estimated to be 632kJ/mol. The other couples were annealed at 2273K. It was found that the interdiffusion coefficients in this system were much larger than those in the SiC-AlN system.

Q.Tian, A.V.Virkar: Journal of the American Ceramic Society, 1996, 79[8], 2168-74