Powder processing and densification behaviour of alumina–high zirconia nanocomposites using chloride precursors

Al2O3–ZrO2 composites having nominal equal volume fraction of Al2O3 and ZrO2 were prepared from gel-precipitated powder, precipitated powder and washed precipitated powder. These different processing routes affected the crystallization temperature of the amorphous powder as well as the phase evolution of Al2O3 and ZrO2 during calcination. The agglomerate size was largest for gel-precipitated powder (30 μm) and it was smallest for washed precipitated powder (19 μm). While gel-precipitated powder produce hard agglomerated powder (Pj = 110 MPa), washed precipitated powder produce soft agglomerates with low agglomeration strength (Pj = 70 MPa). Thus, washed precipitated powder could sinter to a high density at lower sintering temperature. The bending strength exhibits a semi logarithmic relationship with porosity. The hardness shows an increasing trend with sintering temperature.