Two-step Sintering Technique for Enhancing Mechanical and Oxygen Permeation Properties of Dual-phase Oxygen Transport Membranes

Abstract The present work involved the application of a two-step sintering (TSS) technique for typical Ce0.9Gd0.1O2−δ–La0.6Sr0.4Co0.2Fe0.8O3–δ (GDC–LSCF) composites and its effect on the microstructure and resultantly mechanical and O2-permeating properties. The samples obtained by conventional sintering (CS) performed at 1100, 1250, and 1400 °C for 3 h exhibited maximum flexural strength and hardness values of 142 MPa and 8.71 GPa, respectively. However, the application of a TSS procedure produced fine-grained microstructures with improved mechanical properties. In particular, with the use of a typical 1250/1200 TSS protocol, increases of approximately 31% and 7% in the flexural strength and hardness values, respectively, were observed compared to those obtained using the CS method. Moreover, thick-film (∼ 60 µm) GDC–LSCF membrane prepared by tape casting and the TSS technique showed remarkably 1.5‒2 times higher oxygen permeation flux than membrane sintered by CS method. The results are discussed and explained in detail.