Role of the sintering atmosphere in the densification and phase composition of asymmetric BCZY-GDC composite membrane

Ceramic hydrogen separation membranes are promising devices to be integrated in industrial hydrogen-based technologies using fossil fuel as feedstock. Among all, BaCe0.65Zr0.20Y0.15O3-δ–Ce0.8Gd0.20O2-δ composite membrane is the most promising ceramic-ceramic system for such application. However, one of the main issues in Ba-containing perovskites is related to Ba loss at the high sintering temperature needed for the complete densification of the material. This work reports the influence of the sintering atmosphere and temperature on the membrane’s densification and phase purity. BaCeO3 (BC), BaCe0.65Zr0.20Y0.15O3-δ (BCZY) and a BaCe0.65Zr0.20Y0.15O3-δ–Ce0.8Gd0.20O2-δ (BCZY-GDC) mixture were used as Ba-sources to modify the sintering atmosphere. The more reactive BC and BCZY systems promoted a solid-state reaction between BCZY and GDC leading to an undesired single mix-phase enriched in barium on the membrane’s surface. The desired asymmetric architecture with the correct stoichiometry was obtained using BCZY-GDC as Ba-source and sintering the membrane at 1550 °C.