Densification of step-graded Al2O3-Al2O3/ZrO2 composites

The preparation of functionally graded materials requires specially adapted shaping techniques and special attention need to be paid to changes in the amount of shrinkage through the cross-section of the graded material during sintering, to avoid high residual stresses leading to crack formation. In this work we report on the results of investigations of FGMs of Al2O3, ZrO2 and ZTA and their densification as a function of the starting suspensions' properties (alumina/zirconia ratio, solids content and dispersion state), with the aim of compensating for the different amount of sintering shrinkage of the outer and inner materials in step-graded Al2O3-ZTA composites. The sintering studies revealed that the green density and hence the densification of the slip-cast ceramic parts are almost independent on the solids content, while significant effect was observed for dispersion state of the suspensions. Hence, different amounts of total sintering shrinkage in step-graded Al2O3-ZTA may be achieved by modification of the zeta-potential by adjusting the pH of well-dispersed suspensions.