Highly Stable Dual-Phase Y0.8Ca0.2Cr0.8Co0.2O3 - Sm0.2Ce0.8O1.9 ceramic Composite Membrane for Oxygen Separation

Abstract

High-temperature oxygen transport membranes based on mixed ionic- and electronic-conducting (MIEC) ceramics are receiving increasing attention due to their potential applications for high-purity oxygen production, oxyfuel combustion, hydrogen/syngas production, coal gasification, and waste recovery. Dense MIEC membranes exclusively allow the permeation of oxygen ions in the presence of an oxygen partial pressure gradient because the oxygen ionic flux is counterbalanced by the flux of electrons to form an internal short circuit. In this work, a highly stable ceramic composite membrane composed of Ca- and Co-doped yttrium chromite, Y0.8Ca0.2Cr0.8Co0.2O3 (YCCC), and samaria-doped ceria, Sm0.2Ce0.8O1.9 (SDC), is demonstrated for oxygen separation. Homogeneously dispersed nano-scale composite powders were synthesized by a single-step combustion process based on the glycine-nitrate method. Dense composite membranes were achieved having submicron grain sizes and well-percolated electronic and ionic conduction pathways. Densification of the composite membrane was assisted by liquid phase sintering caused by cobalt-doping in yttrium chromite, and gas-tight membranes are fabricated at 1400oC. The YCCC and SDC phases were chemically and thermo-mechanically compatible at both processing and operating temperatures. The composite membrane exhibited an oxygen permeation flux comparable to those of the state-of-the-art single-phase membrane materials and excellent stability in harsh operating conditions under a H2-CO2 environment for long-term operation, which suggests potential application in various combustion and fuel production processes.