Creep behaviour of membrane and substrate materials for oxygen separation units

Advanced oxygen separation units are based on thin mixed ionic–electronic conducting ceramic layers that are mechanically supported by a porous substrate. One of the most important aspects for the long-term stability at elevated temperatures is the creep behaviour, which was assessed in the current study for various potential membrane and substrate materials. Systematic creep tests were carried out in air in the temperature range 700–1200 °C, under compressive loads of 20–120 MPa. The steady-state strain rates were described by a standard creep equation. LSCF38, MgO and all investigated cerium oxides (CeO2−δ and its three Gd-/Pr-doped variations: Ce0.8Gd0.2−xPrxO2−0.5(0.2−x)−δ, with x = 0, 0.1 and 0.2) satisfied at around 800 °C a creep limit criterion, suggested to be necessary to warrant reliable long-term stability for membrane systems, but only ceria materials and MgO fulfilled this requirement also at higher temperatures.