Room and elevated temperature strength of perovskite membrane tubes

Lanthanum-based perovskite oxides are promising materials as membranes for oxygen separation and for direct oxidation of gaseous hydrocarbons. The physical and mechanical properties of these oxide membranes are however dependent on the temperature and environment. In the present study, two differing sets of oxide membrane tubes were evaluated for their fracture strength in a C-ring geometry in three different conditions: room temperature in air and at 1000 degreesC in air and nitrogen. The strength of the oxide tubes in ambient conditions was observed to be dependent on the processing route (initial composition, surface and volume flaws). With a change in temperature and environment from ambient to reducing condition, the strength degraded to nearly half its initial value. The strength degradation was accompanied by decomposition of the membranes and changes in fracture mode and morphology. The strength degradation as measured by mean strength and Weibull parameters and changes in fracture characterized by Scanning Electron Microscopy (SEM) and X-ray diffractometry (XRD) are reported. (C) 2003 Elsevier Science Ltd. All rights reserved.