Evolution of Average Microstructural Properties in the Final Stage Sintering of Alumina

Models of simultaneous coarsening and densification in final stage sintering commonly assume that the coarsening process results in microstructures that evolve self-similarly from a fixed microstructural geometry, differing only in scale. This assumption is experimentally tested for alumina in the solid volume fraction range of 0.97–1 using nondimensional microstructural parameters. The results clearly show that such models based on assumed geometries often underestimate the pore size relative to the grain size. The largest differences between the model and the experiments occur for lower firing temperatures and higher doping levels. It is concluded that the coarsening reflected in the effect of temperature and dopant level is not a self-similar process from a common microstructural geometry.