The literature suggested that there were grain-boundary structures which existed in ceramic systems that were not predicted by bulk thermodynamics. Transitions between the various grain boundary structures were not well understood, either experimentally or theoretically. This revealed 6 different types of grain boundary structure present in the alumina system. These grain boundary structures were directly correlated with significantly different grain boundary mobilities. There was a general trend towards increasing grain boundary disorder, and increasing grain boundary mobility, with increasing temperature. This was the first time that such a broad range of behavior had been observed in a single system. The results had many implications for the understanding of grain-boundary transport phenomena in ceramic systems.

Multiple Grain Boundary Transitions in Ceramics - a Case Study of Alumina. S.J.Dillon, M.P.Harmer: Acta Materialia, 2007, 55[15], 5247-54