New relationships between relative density and grain size during solid-state sintering of ceramic powders

New relationships between grain size and relative density have been established for the case of solid-state sintering of ceramic powders. These new expressions have been used to fit experimental points, obtained during solid-state sintering of a pure submicronic α-alumina powder shaped by slip casting. In contrast to what was established in the past, it is shown that densification is controlled by grain boundary diffusion and grain growth is controlled by the grain boundaries. The quality of the green state (homogeneity of the pore size and homogeneity of the spatial distribution of pores) is used to explain the difference between the results reported here and previous results, where diffusion at the surface of the pores was claimed to control grain growth.