Oxygen permeability through the tubular La0.7Ca0.3Fe0.85Co0.15O3-delta perovskite membrane prepared by thermoplastic extrusion was measured in the temperature range from 800 degrees to 1040 degrees C in an air/argon gradient, and compared with the oxygen permeability of planar membranes prepared, by injection molding and cold isostatic pressing. Oxygen flux through the perovskite membranes was controlled by bulk diffusion of oxygen and was not limited by surface exchange reactions. The oxygen flux through perovskite membranes normalized to 1 mm wall thickness at 900 degrees C was 0.064 mu mol (cm(2) s)(-1). The activation energy of oxygen diffusion was 128 kJ mol(-1). The tubular membrane was tested in a reactor for partial oxidation of methane for more than 1900 h. The oxygen flux decreased gradually during the test from 1.5 to 1 mu mol (cm s)(-1). The methane conversion could be adjusted to 83%-88%, with the CO selectivity in the same range. After the test, a degradation of the perovskite structure of the membrane was observed. A possible mechanism for the phase degradation and segregation was proposed.