Journal of the American Ceramic Society, Vol.96, No.3, 852-858, 2013
Estimation of Stress Exponent and Activation Energy for Rapid Densification of 8mol% Yttria-Stabilized Zirconia Powder
The rapid densification behavior of 8mol% Y2O3-stabilized ZrO2 polycrystalline (8Y-SZP) powder compacts at the initial stage of pressure sintering (relative density (center dot) below 0.92) has been investigated using an electric current-activated/assisted sintering (ECAS) system. Data points corresponding to a fixed heating rate were extracted from the densification rate (center dot) versus and center dot versus temperature (T) curves. These curves were obtained experimentally by consolidation at a fixed current. Under fixed current ECAS, the heating rate (T center dot) decreases continuously over sintering time. Using a quasi- constant heating rate (CHR) method, data points were extracted to plot center dot vs. , center dot vs. T, and vs. T curves at a fixed T center dot. The stress exponent (n), estimated from a log-log plot of grain size (d)-corrected center dot/ and effective stress (sigma eff) at 13001400K, shows an almost constant value of 1. In addition, the activation energy (Q) for rapid densification, estimated from an Arrhenius plot of d-corrected center dot/ also shows an almost constant value of 350kJ/mol, which is considerably lower than the previously reported value of the activation energy for Zr4+ lattice diffusion of about 440kJ/mol. These results suggest that rapid densification of 8Y-SZP by ECAS seems to proceed by diffusional creep controlled by grain-boundary diffusion of Zr4+ ions.