PHASE-STABILITY OF SRFECO0.5OX IN REDUCING ENVIRONMENTS

The mixed-conducting SrFeCo0.5Ox is a potential material for use in de nse ceramic membranes for gas separation at elevated temperatures. Its outstanding oxygen transport properties reveal the feasibility of usi ng oxide ceramic membrane in large-scale oxygen separation. The stabil ity of this material under low oxygen partial pressure is an important issue. To investigate phase and structural stability, SrFeCo0.5Ox sam ples were annealed in various reducing gaseous environments. The annea led samples were characterized by room-temperature X-ray powder diffra ction and scanning electron microscopy analyses. In situ conductivity of the samples was measured in various atmospheres. Reversible phase t ransition related to the change of oxygen partial pressure in the surr ounding atmosphere was observed at elevated temperatures. Our results show that mechanical failure of dense ceramic membranes made of this m aterial may occur when it is cooled in a moisturized reducing atmosphe re, such as hydrogen, and then reheated in an oxidizing atmosphere, su ch as air. (C) 1998 Elsevier Science Ltd.