Oxygen diffusion in YBCO: an isothermal thermogravimetric study

The kinetics of oxygenation/deoxygenation in YBa ₂Cu ₃O _7-δ has been studied with thermogravimetry. Experiments were conducted at various constatn temperatures on powder samples subjected to an abrupt change in ambient oxygen partial pressure. The processes are found to be diffusion-controlled, with an activation energy of 1.3 eV for samples with oxygen deficiencies δ near 0.1. The chemical diffusion coefficient at 500°C is determined as 10 ^-10 cm ²/s, two to three orders of magnitude smaller than values measured from sintered samples.