Pore Drag and Pore-Boundary Separation in Alumina

Microdesigned interfacial pore structures were used to study pore drag and pore-boundary separation in Al₂O₃. This approach allows the creation of pore arrays containing pores of controlled size and spacing at well-defined singlecrystal seed/polycrystalline matrix interfaces, and enables experimental determination of the peak pore velocity. From the peak pore velocity, values of the surface diffusion coefficient pertinent to sintering can be extracted. At 1600°C, the surface diffusion coefficient is ～1 × 10^?7 cm²/s for undoped Al₂O₃ and ～4 × 10^?7 cm²/s for MgO-doped Al₂O₃. The values appear to be insensitive to the seed orientation for the two seed orientations studied. The results suggest a strong influence of pore spacing on the separation condition in undoped Al₂O₃, and a diminished influence in MgO-doped Al₂O₃. Quantitative agreement between theoretically predicted and experimentally observed separation/attachment conditions was obtained.