Evaluation of sintering stresses of an Al2O3 powder with a self-loading apparatus

The sintering stress of an Al2O3 powder, σs, is evaluated from an equation σs = Fs/ρSa, where Fs is the uniaxial tensile force necessary to just stop the sintering contraction, ρ is the relative density, and Sa is the cross-sectional area. During densification, σs increases to the maximum at a relative density of 85%, and then abruptly decreases. The variation of σs in the intermediate sintering stage suggests a simple cubic packing of particles. Densification in the final sintering stage is explained by shrinkage of the pores at the corners where four tetrakaidecahedra meet. The present surface tensions of the Al2O3 powder evaluated from the σs roughly equal a reported value.