Effects of composition and sintering temperature on the structure and compressive property of the lamellar Al2O3–ZrO2 scaffolds prepared by freeze casting

Using 3 wt% TiO2 nanopowders as sintering aid, we prepared porous lamellar Al2O3–ZrO2 composites with an initial solid loading of 30 vol% and the Al2O3/ZrO2 weight ratios of 1:9, 3:7, 5:5, 7:3, and 9:1 by freeze casting. The viscosity of water-based slurries decreased with increasing Al2O3 content while the porosity and the wavelength of the lamellae in the sintered scaffolds showed first an increase and then decrease with maximum values appearing at Al2O3:ZrO2 = 5:5. A relatively large amount of tetragonal (t) ZrO2 transformed to monoclinic (m) ZrO2 with the increase in the Al2O3 content and sintering temperature, thus reducing stress-induced phase transformation effect during loading. The compressive strength of the sintered scaffolds depended on sintering temperature, porosity, and the phase composition in the composites. A maximum value of 105 ± 10 MPa was achieved in the scaffolds with a composition of Al2O3:ZrO2 = 3:7 after sintering at 1450 °C for 2 h.