Interdiffusion in SiC–AlN and AlN–Al 2 OC Systems

AlN, Al 2 OC, and the 2 H form of SiC are isostructural. Both SiC–AlN and AlN–Al 2 OC form homogeneous solid solutions above 2000° and 1950°C, respectively. The kinetics of phase separation in the two systems, however, are quite different. Interdiffusion in both SiC–AlN and AlN‐Al 2 OC systems was examined in the solid‐solution regime in an attempt to elucidate differences in the kinetics of phase separation that occur in the two systems when annealed at lower temperatures. Diffusion couples of (SiC) 0.3 (AlN) 0.7 /(SiC) 0.7 (AlN) 0.3 and (AlN) 0.7 (Al 2 OC) 0.3 /(AlN) 0.3 (Al 2 OC) 0.7 were fabricated by hot pressing and were annealed at high temperatures by encapsulating them in sealed SiC crucibles to suppress loss due to evaporation. Interdiffusion coefficients in (SiC) 0.3 ‐(AlN) 0.7 /(SiC) 0.7 (AlN) 0.3 diffusion couples were measured at 2373, 2473, and 2573 K, and the corresponding activation energy was determined to be 632 kJ/mol. (AlN) 0.7 (Al 2 OC) 0.3 / (AlN) 0.3 (Al 2 OC) 0.7 samples were annealed at 2273 K. The interdiffusion coefficient measured in the AlN–Al 2 OC system was much larger than that in the SiC–AlN system.