Enhanced compressive strength of porous alumina realized by synergy between La-doping and two-step sintering

Abstract

Sintering phenomena, densification, and grain growth are crucial for proper control of the microstructure for good mechanical strength. Here, materials and processing parameters, the addition of La2O3, and two-step sintering (TSS) were combined to lead to higher strength in the porous alumina prepared by freeze-casting. Based on grain growth and densification behaviors with the La2O3 doping, a beneficial thermal profile was designed for the TSS. As a result, higher relative density levels and smaller grain size were obtained compared with the results with conventional sintering (CS): 38.56% and 0.82 µm at 1500°C by CS; 40.78% and 1.78 µm at 1600°C by CS; 41.43% and 0.87 µm by TSS. The microstructural benefits provided ∼1.4 times higher compressive strength (5.46 MPa) from TSS than from the CS sample (3.92 MPa), highlighting the synergetic effect of La2O3 doping and the TSS strategy. © 2024 The American Ceramic Society.