Effect of grain size distribution on sintered density

Abstract

Conditions of pore separation from grain boundaries during sintering are analyzed. It is shown analytically that a minimum intrinsic and solute drag force is required to prevent pore separation. In microstructures with a non-uniform size distribution the minimum dopant concentration is typically 14 times higher than that required in microstructures with a narrow grain size distribution. If the drag force is below the required minimum, pore separation will occur after the compact is sintered to a critical density. In compacts with a narrow grain size distribution, the critical density is about 99.3% of the theoretical density. However, in compacts with a non-uniform size distribution the critical density decreases to about 90.6% of the theoretical density. This analysis shows that it is imperative to maintain a narrow grain size distribution in order to obtain a high sintered density. Sintering data for BaTiO 3, β-Al 2O 3 and ZrO 2 agree with this analysis.