Kinetics of the oxidation of Ba sub 2 YCu sub 3 O sub x ceramics.

The kinetics of the oxidation of dense and porous samples of Ba sub 2 YCu sub 3 O sub x ceramic have been determined by gravimetric analysis at 400 to 700C. At 600C and above the rate is parabolic which indicates that the fully oxidized layer is continuous. At 500C and below the kinetics show a linear relation which indicates that the fully oxidized layer does not protect the ceramic. Dilatometric, microscopic and high temperature x-ray data suggest that fractures in the oxide layer at the lower temperatures are caused by the large volume decrease which accompanies the change in oxygen stoichiometry.