Role of diffusion phenomena in the processing of ceramics

The role of diffusion in ceramic processing is discussed. The utility of secondary ion mass spectroscopy (SIMS) is highlighted for the evaluation of diffusion coefficients in ceramic materials. By comparing diffusion coefficients obtained in this manner with those obtained indirectly from creep measurements, we identified the ion species that govern creep in yttrium aluminum garnet (YAG) ceramics and we showed that diffusion involving metastable defects plays an important role in ceramic processes such as sintering. The oxygen diffusion coefficients of thin films were evaluated, and the defects involved were shown to be metastable, and their origins were clarified. Furthermore, their relationship with reactivity was discussed in thin films.