Densification Behavior in Spark-Plasma-Sintering of MgAl2O4 Spinel

The densification mechanism in park-plasma-sintering (SPS) processing was examined in MgAl(2)O(4) spinel. As the relative density rho(t) increases, that is, as the effective stress sigma(eff) decreases, stress exponent n evaluated from effective stress-densification rate relationship continuously varies from n >= 4 to n approximate to 1. TEM observation shows that significant stacking faults caused by partial dislocations are frequently observed in the low rho(t) region. The results suggest that, for spinel, the predominant densification mechanism in SPS processing changes with rho(t) from plastic flow by a partial dislocation motion in the low rho(t) region (n >= 4) to diffusion-related creep in the high rho(t) region (n approximate to 1)