Ruth Moshe, Rachel Marder, Wayne D. Kaplan

Department of Materials Science and Engineering, Technion - Israel Institute of Technology, Haifa, Israel

The role of dopants in processing materials is an important issue, especially given the contradicting reports of retarded or accelerated grain growth by dopants and impurities.  We have developed a technique to measure dopant solubility limits at the sintering temperature, such that actual dopant levels can be associated with equilibrium grain boundary (GB) segregation (below the solubility limit) or with enrichment (above the solubility limit).  New analysis of the GB mobility of alumina as a function of dopant concentration has shown that some segregating dopants increase the GB mobility, i.e. the opposite of solute-drag. The segregating dopants are associated with 2-D structural and compositional (“complexion”) transitions at the GBs, and possible changes in the mechanism of GB migration.  This presentation will review recent GB mobility measurements and demonstrate how complexion transitions can be used to control particle location and thus the mechanical properties of particle reinforced ceramic matrix nanocomposites.