Analysis of the Pressure Sintering Kinetics of Ceramic Oxides

Abstract

An analysis of the kinetics of final stage pressure sintering for Al₂O₃ shows that more than one mechanism is normally operative. In this analysis, the effective stress (σ_eff) at constant temperature on the sintering particles is taken as the applied pressure (P_A) divided by the relative density ( ρ), as recently suggested by Coble. A plot of the measured instantaneous true strain-rate (i. e., densification-rate) versus (1/ρ) for a given experiment results in a constant slope over the final ∼20% of densification. This constant slope is the steady-state strain-rate (έ_s) for that experiment and is related to the applied pressure (P_A) by analogy with the power law creep relationship. This same relationship

$$\dot \varepsilon _s = AP_A ^n$$

where A is a constant, is then used to analyze the overall kinetics by a log-log plot of the various (έ_s) values determined by individual (P_A) values from a number of hot pressings. The value of the slope (n) relates to the different kinetic mechanisms: n=1 implies Newtonian flow, a constant n⁠1 implies non-Newtonian flow, and a variable n implies that more than one mechanism is operative (i. e., multi-component kinetics)