Study on the oxygenation process during the heat treatment of TFA-MOD YBCO thin films by in situ resistance measurement

• In situ resistance measurement (ISM) was carried out on MOD-YBCO thin films.
• Thermodynamic behaviors of the oxygenation process were studied by using ISM.
• A defect reaction was found to control the mechanism of the oxygenation process.
• Porosity accelerated diffusion mechanism was proposed for the MOD thin film system.

The oxygen content is one key factor to determine the properties of YBa2Cu3O6+y (YBCO) high temperature superconductors. In this study, YBCO thin films were produced by TFA-MOD method. The oxygenation process was carried out at 450 °C for 40 min, in various oxygen partial pressures from 0.01 to 1 atm. An in situ resistance measurement system was built up to record the resistance evolution during the whole heat treatment process. It was found that the resistance decreased exponentially and reached a saturate value in a few minutes during oxygen annealing. It was also found both the balanced resistance and the c-axis length of YBCO decreased with increasing oxygen partial pressure. A defect reaction was found to control the mechanism of the oxygenation process. A porosity assisted oxygen diffusion mechanism was proposed to explain the fast diffusion kinetics of oxygen in MOD YBCO thin films.